plugins.go

// Copyright 2016-2021, Pulumi Corporation.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package workspace

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"hash"
	"io"
	"io/fs"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"runtime"
	"sort"
	"strings"
	"time"

	"github.com/blang/semver"
	"github.com/cheggaaa/pb"
	"github.com/djherbis/times"
	"github.com/pkg/errors"

	"github.com/pulumi/pulumi/sdk/v3/go/common/diag"
	"github.com/pulumi/pulumi/sdk/v3/go/common/diag/colors"
	"github.com/pulumi/pulumi/sdk/v3/go/common/util/archive"
	"github.com/pulumi/pulumi/sdk/v3/go/common/util/cmdutil"
	"github.com/pulumi/pulumi/sdk/v3/go/common/util/contract"
	"github.com/pulumi/pulumi/sdk/v3/go/common/util/fsutil"
	"github.com/pulumi/pulumi/sdk/v3/go/common/util/httputil"
	"github.com/pulumi/pulumi/sdk/v3/go/common/util/logging"
	"github.com/pulumi/pulumi/sdk/v3/go/common/version"
	"github.com/pulumi/pulumi/sdk/v3/nodejs/npm"
	"github.com/pulumi/pulumi/sdk/v3/python"
)

const (
	windowsGOOS = "windows"
)

var (
	enableLegacyPluginBehavior = os.Getenv("PULUMI_ENABLE_LEGACY_PLUGIN_SEARCH") != ""
)

// pluginDownloadURLOverrides is a variable instead of a constant so it can be set using the `-X` `ldflag` at build
// time, if necessary. When non-empty, it's parsed into `pluginDownloadURLOverridesParsed` in `init()`. The expected
// format is `regexp=URL`, and multiple pairs can be specified separated by commas, e.g. `regexp1=URL1,regexp2=URL2`.
//
// For example, when set to "^foo.*=https://foo,^bar.*=https://bar", plugin names that start with "foo" will use
// https://foo as the download URL and names that start with "bar" will use https://bar.
var pluginDownloadURLOverrides string

// pluginDownloadURLOverridesParsed is the parsed array from `pluginDownloadURLOverrides`.
var pluginDownloadURLOverridesParsed pluginDownloadOverrideArray

// pluginDownloadURLOverride represents a plugin download URL override, parsed from `pluginDownloadURLOverrides`.
type pluginDownloadURLOverride struct {
	reg *regexp.Regexp // The regex used to match against the plugin's name.
	url string         // The URL to use for the matched plugin.
}

// pluginDownloadOverrideArray represents an array of overrides.
type pluginDownloadOverrideArray []pluginDownloadURLOverride

// get returns the URL and true if name matches an override's regular expression,
// otherwise an empty string and false.
func (overrides pluginDownloadOverrideArray) get(name string) (string, bool) {
	for _, override := range overrides {
		if override.reg.MatchString(name) {
			return override.url, true
		}
	}
	return "", false
}

func init() {
	var err error
	if pluginDownloadURLOverridesParsed, err = parsePluginDownloadURLOverrides(pluginDownloadURLOverrides); err != nil {
		panic(fmt.Errorf("error parsing `pluginDownloadURLOverrides`: %w", err))
	}
}

// parsePluginDownloadURLOverrides parses an overrides string with the expected format `regexp1=URL1,regexp2=URL2`.
func parsePluginDownloadURLOverrides(overrides string) (pluginDownloadOverrideArray, error) {
	var result pluginDownloadOverrideArray
	if overrides == "" {
		return result, nil
	}
	for _, pair := range strings.Split(overrides, ",") {
		split := strings.Split(pair, "=")
		if len(split) != 2 || split[0] == "" || split[1] == "" {
			return nil, fmt.Errorf("expected format to be \"regexp1=URL1,regexp2=URL2\"; got %q", overrides)
		}
		reg, err := regexp.Compile(split[0])
		if err != nil {
			return nil, err
		}
		result = append(result, pluginDownloadURLOverride{
			reg: reg,
			url: split[1],
		})
	}
	return result, nil
}

// InstallPluginError is returned by functions that are unable to download and install a plugin
type InstallPluginError struct {
	// The name of the plugin
	Name string
	// The kind of the plugin
	Kind PluginKind
	// The requested version of the plugin, if any.
	Version *semver.Version
	// the underlying error that occurred during the download or install
	UnderlyingError error
}

func (err *InstallPluginError) Error() string {
	if err.Version != nil {
		return fmt.Sprintf("Could not automatically download and install %[1]s plugin 'pulumi-%[1]s-%[2]s'"+
			"at version v%[3]s, "+
			"install the plugin using `pulumi plugin install %[1]s %[2]s v%[3]s`.\n"+
			"Underlying error: %[4]s",
			err.Kind, err.Name, err.Version.String(), err.UnderlyingError.Error())
	}

	return fmt.Sprintf("Could not automatically download and install %[1]s plugin 'pulumi-%[1]s-%[2]s', "+
		"install the plugin using `pulumi plugin install %[1]s %[2]s`.\n"+
		"Underlying error: %[3]s",
		err.Kind, err.Name, err.UnderlyingError.Error())
}

// PluginSource deals with downloading a specific version of a plugin, or looking up the latest version of it.
type PluginSource interface {
	// Download fetches an io.ReadCloser for this plugin and also returns the size of the response (if known).
	Download(
		version semver.Version, opSy string, arch string,
		getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (io.ReadCloser, int64, error)
	// GetLatestVersion tries to find the latest version for this plugin. This is currently only supported for
	// plugins we can get from github releases.
	GetLatestVersion(getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (*semver.Version, error)
}

// getPulumiSource can download a plugin from get.pulumi.com
type getPulumiSource struct {
	name string
	kind PluginKind
}

func newGetPulumiSource(name string, kind PluginKind) *getPulumiSource {
	return &getPulumiSource{name: name, kind: kind}
}

func (source *getPulumiSource) GetLatestVersion(
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (*semver.Version, error) {
	return nil, errors.New("GetLatestVersion is not supported for plugins from get.pulumi.com")
}

func (source *getPulumiSource) Download(
	version semver.Version, opSy string, arch string,
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (io.ReadCloser, int64, error) {
	serverURL := "https://get.pulumi.com/releases/plugins"

	logging.V(1).Infof("%s downloading from %s", source.name, serverURL)

	serverURL = interpolateURL(serverURL, version, opSy, arch)
	serverURL = strings.TrimSuffix(serverURL, "/")

	logging.V(1).Infof("%s downloading from %s", source.name, serverURL)
	endpoint := fmt.Sprintf("%s/%s",
		serverURL,
		url.QueryEscape(fmt.Sprintf("pulumi-%s-%s-v%s-%s-%s.tar.gz", source.kind, source.name, version.String(), opSy, arch)))

	req, err := buildHTTPRequest(endpoint, "")
	if err != nil {
		return nil, -1, err
	}
	return getHTTPResponse(req)
}

// githubSource can download a plugin from github releases
type githubSource struct {
	host         string
	organization string
	repository   string
	name         string
	kind         PluginKind

	token string
}

// Creates a new github source adding authentication data in the environment, if it exists
func newGithubSource(url *url.URL, name string, kind PluginKind) (*githubSource, error) {
	contract.Assert(url.Scheme == "github")

	// 14-03-2022 we stopped looking at GITHUB_PERSONAL_ACCESS_TOKEN and sending basic auth for github and
	// instead just look at GITHUB_TOKEN and send in a header. Given GITHUB_PERSONAL_ACCESS_TOKEN was an
	// envvar we made up we check to see if it's set here and log a warning. This can be removed after a few
	// releases.
	if os.Getenv("GITHUB_PERSONAL_ACCESS_TOKEN") != "" {
		logging.Warningf("GITHUB_PERSONAL_ACCESS_TOKEN is no longer used for Github authentication, set GITHUB_TOKEN instead")
	}

	host := url.Host
	parts := strings.Split(strings.Trim(url.Path, "/"), "/")

	if host == "" {
		return nil, fmt.Errorf("github:// url must have a host part, was: %s", url.String())
	}

	if len(parts) != 1 && len(parts) != 2 {
		return nil, fmt.Errorf(
			"github:// url must have the format <host>/<organization>[/<repository>], was: %s",
			url.String())
	}

	organization := parts[0]
	repository := "pulumi-" + name
	if len(parts) == 2 {
		repository = parts[1]
	}

	return &githubSource{
		host:         host,
		organization: organization,
		repository:   repository,
		name:         name,
		kind:         kind,

		token: os.Getenv("GITHUB_TOKEN"),
	}, nil
}

func (source *githubSource) HasAuthentication() bool {
	return source.token != ""
}

func (source *githubSource) GetLatestVersion(
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (*semver.Version, error) {
	releaseURL := fmt.Sprintf(
		"https://%s/repos/%s/%s/releases/latest",
		source.host, source.organization, source.repository)
	logging.V(9).Infof("plugin GitHub releases url: %s", releaseURL)
	req, err := buildHTTPRequest(releaseURL, source.token)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/json")
	resp, length, err := getHTTPResponse(req)
	if err != nil {
		return nil, err
	}
	jsonBody, err := ioutil.ReadAll(resp)
	if err != nil {
		return nil, fmt.Errorf("cannot unmarshal github response len(%d): %s", length, err.Error())
	}
	release := struct {
		TagName string `json:"tag_name"`
	}{}
	err = json.Unmarshal(jsonBody, &release)
	if err != nil {
		return nil, err
	}
	parsedVersion, err := semver.ParseTolerant(release.TagName)
	if err != nil {
		return nil, fmt.Errorf("invalid plugin semver: %w", err)
	}
	return &parsedVersion, nil
}

func (source *githubSource) Download(
	version semver.Version, opSy string, arch string,
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (io.ReadCloser, int64, error) {

	assetName := fmt.Sprintf("pulumi-%s-%s-v%s-%s-%s.tar.gz", source.kind, source.name, version.String(), opSy, arch)

	releaseURL := fmt.Sprintf(
		"https://%s/repos/%s/%s/releases/tags/v%s",
		source.host, source.organization, source.repository, version.String())
	logging.V(9).Infof("plugin GitHub releases url: %s", releaseURL)

	req, err := buildHTTPRequest(releaseURL, source.token)
	if err != nil {
		return nil, -1, err
	}
	req.Header.Set("Accept", "application/json")
	resp, length, err := getHTTPResponse(req)
	if err != nil {
		return nil, -1, err
	}
	jsonBody, err := ioutil.ReadAll(resp)
	if err != nil {
		logging.V(9).Infof("cannot unmarshal github response len(%d): %s", length, err.Error())
		return nil, -1, err
	}
	release := struct {
		Assets []struct {
			Name string `json:"name"`
			URL  string `json:"url"`
		} `json:"assets"`
	}{}
	err = json.Unmarshal(jsonBody, &release)
	if err != nil {
		logging.V(9).Infof("github json response: %s", jsonBody)
		logging.V(9).Infof("cannot unmarshal github response: %s", err.Error())
		return nil, -1, err
	}
	assetURL := ""
	for _, asset := range release.Assets {
		if asset.Name == assetName {
			assetURL = asset.URL
		}
	}
	if assetURL == "" {
		logging.V(9).Infof("github json response: %s", jsonBody)
		logging.V(9).Infof("plugin asset '%s' not found", assetName)
		return nil, -1, errors.Errorf("plugin asset '%s' not found", assetName)
	}

	logging.V(1).Infof("%s downloading from %s", source.name, assetURL)

	req, err = buildHTTPRequest(assetURL, source.token)
	if err != nil {
		return nil, -1, err
	}
	req.Header.Set("Accept", "application/octet-stream")
	return getHTTPResponse(req)
}

// pluginURLSource can download a plugin from a given PluginDownloadURL, it doesn't support GetLatestVersion
type pluginURLSource struct {
	name              string
	kind              PluginKind
	pluginDownloadURL string
}

func newPluginURLSource(name string, kind PluginKind, pluginDownloadURL string) *pluginURLSource {
	return &pluginURLSource{
		name:              name,
		kind:              kind,
		pluginDownloadURL: pluginDownloadURL,
	}
}

func (source *pluginURLSource) GetLatestVersion(
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (*semver.Version, error) {
	return nil, errors.New("GetLatestVersion is not supported for plugins using PluginDownloadURL")
}

func (source *pluginURLSource) Download(
	version semver.Version, opSy string, arch string,
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (io.ReadCloser, int64, error) {
	serverURL := source.pluginDownloadURL
	logging.V(1).Infof("%s downloading from %s", source.name, serverURL)

	serverURL = interpolateURL(serverURL, version, opSy, arch)
	serverURL = strings.TrimSuffix(serverURL, "/")

	logging.V(1).Infof("%s downloading from %s", source.name, serverURL)
	endpoint := fmt.Sprintf("%s/%s",
		serverURL,
		url.QueryEscape(fmt.Sprintf("pulumi-%s-%s-v%s-%s-%s.tar.gz", source.kind, source.name, version.String(), opSy, arch)))

	req, err := buildHTTPRequest(endpoint, "")
	if err != nil {
		return nil, -1, err
	}
	return getHTTPResponse(req)
}

// fallbackSource handles our current complicated default logic of trying the pulumi public github, then maybe
// the users private github, then get.pulumi.com
type fallbackSource struct {
	name string
	kind PluginKind
}

func newFallbackSource(name string, kind PluginKind) *fallbackSource {
	return &fallbackSource{
		name: name,
		kind: kind,
	}
}

func urlMustParse(rawURL string) *url.URL {
	url, err := url.Parse(rawURL)
	contract.AssertNoError(err)
	return url
}

func (source *fallbackSource) GetLatestVersion(
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (*semver.Version, error) {

	// Try and get this package from our public pulumi github
	public, err := newGithubSource(urlMustParse("github://api.github.com/pulumi"), source.name, source.kind)
	if err != nil {
		return nil, err
	}
	version, err := public.GetLatestVersion(getHTTPResponse)
	if err != nil {
		return nil, err
	}

	return version, nil
}

func (source *fallbackSource) Download(
	version semver.Version, opSy string, arch string,
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (io.ReadCloser, int64, error) {
	// Try and get this package from public pulumi github
	public, err := newGithubSource(urlMustParse("github://api.github.com/pulumi"), source.name, source.kind)
	if err != nil {
		return nil, -1, err
	}
	resp, length, err := public.Download(version, opSy, arch, getHTTPResponse)
	if err == nil {
		return resp, length, nil
	}

	// Fallback to get.pulumi.com
	pulumi := newGetPulumiSource(source.name, source.kind)
	return pulumi.Download(version, opSy, arch, getHTTPResponse)
}

type checksumError struct {
	expected []byte
	actual   []byte
}

func (err *checksumError) Error() string {
	return fmt.Sprintf("invalid checksum, expected %x, actual %x", err.expected, err.actual)
}

// checksumSource will validate that the archive downloaded from the inner source matches a checksum
type checksumSource struct {
	source   PluginSource
	checksum map[string][]byte
}

func newChecksumSource(source PluginSource, checksum map[string][]byte) *checksumSource {
	return &checksumSource{
		source:   source,
		checksum: checksum,
	}
}

func (source *checksumSource) GetLatestVersion(
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (*semver.Version, error) {
	return source.source.GetLatestVersion(getHTTPResponse)
}

type checksumReader struct {
	checksum []byte
	io       io.ReadCloser
	hasher   hash.Hash
}

func (reader *checksumReader) Read(p []byte) (int, error) {
	n, err := reader.io.Read(p)
	if err != nil {
		if err == io.EOF {
			// Check the checksum matches
			actualChecksum := reader.hasher.Sum(nil)
			if !bytes.Equal(reader.checksum, actualChecksum) {
				return n, &checksumError{expected: reader.checksum, actual: actualChecksum}
			}
		}
		return n, err
	}

	m, err := reader.hasher.Write(p[0:n])
	contract.AssertNoError(err)
	contract.Assert(m == n)

	return n, nil
}

func (reader *checksumReader) Close() error {
	return reader.io.Close()
}

func (source *checksumSource) Download(
	version semver.Version, opSy string, arch string,
	getHTTPResponse func(*http.Request) (io.ReadCloser, int64, error)) (io.ReadCloser, int64, error) {

	checksum := source.checksum[fmt.Sprintf("%s-%s", opSy, arch)]
	response, length, err := source.source.Download(version, opSy, arch, getHTTPResponse)
	if err != nil {
		return nil, -1, err
	}

	return &checksumReader{
		checksum: checksum,
		hasher:   sha256.New(),
		io:       response,
	}, length, nil
}

// ProjectPlugin Information about a locally installed plugin specified by the project.
type ProjectPlugin struct {
	Name    string          // the simple name of the plugin.
	Kind    PluginKind      // the kind of the plugin (language, resource, etc).
	Version *semver.Version // the plugin's semantic version, if present.
	Path    string          // the path that a plugin is to be loaded from (this will always be a directory)
}

// Spec Return a PluginSpec object for this project plugin.
func (pp ProjectPlugin) Spec() PluginSpec {
	return PluginSpec{
		Name:    pp.Name,
		Kind:    pp.Kind,
		Version: pp.Version,
	}
}

// PluginSpec provides basic specification for a plugin.
type PluginSpec struct {
	Name              string          // the simple name of the plugin.
	Kind              PluginKind      // the kind of the plugin (language, resource, etc).
	Version           *semver.Version // the plugin's semantic version, if present.
	PluginDownloadURL string          // an optional server to use when downloading this plugin.
	PluginDir         string          // if set, will be used as the root plugin dir instead of ~/.pulumi/plugins.

	// if set will be used to validate the plugin downloaded matches. This is keyed by "$os-$arch", e.g. "linux-x64".
	Checksums map[string][]byte
}

// Dir gets the expected plugin directory for this plugin.
func (spec PluginSpec) Dir() string {
	dir := fmt.Sprintf("%s-%s", spec.Kind, spec.Name)
	if spec.Version != nil {
		dir = fmt.Sprintf("%s-v%s", dir, spec.Version.String())
	}
	return dir
}

// File gets the expected filename for this plugin, excluding any platform specific suffixes (e.g. ".exe" on
// windows).
func (spec PluginSpec) File() string {
	return fmt.Sprintf("pulumi-%s-%s", spec.Kind, spec.Name)
}

// DirPath returns the directory where this plugin should be installed.
func (spec PluginSpec) DirPath() (string, error) {
	var err error
	dir := spec.PluginDir
	if dir == "" {
		dir, err = GetPluginDir()
		if err != nil {
			return "", err
		}
	}

	return filepath.Join(dir, spec.Dir()), nil
}

// LockFilePath returns the full path to the plugin's lock file used during installation
// to prevent concurrent installs.
func (spec PluginSpec) LockFilePath() (string, error) {
	dir, err := spec.DirPath()
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("%s.lock", dir), nil
}

// PartialFilePath returns the full path to the plugin's partial file used during installation
// to indicate installation of the plugin hasn't completed yet.
func (spec PluginSpec) PartialFilePath() (string, error) {
	dir, err := spec.DirPath()
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("%s.partial", dir), nil
}

func (spec PluginSpec) String() string {
	var version string
	if v := spec.Version; v != nil {
		version = fmt.Sprintf("-%s", v)
	}
	return spec.Name + version
}

// PluginInfo provides basic information about a plugin.  Each plugin gets installed into a system-wide
// location, by default `~/.pulumi/plugins/<kind>-<name>-<version>/`.  A plugin may contain multiple files,
// however the primary loadable executable must be named `pulumi-<kind>-<name>`.
type PluginInfo struct {
	Name         string          // the simple name of the plugin.
	Path         string          // the path that a plugin was loaded from (this will always be a directory)
	Kind         PluginKind      // the kind of the plugin (language, resource, etc).
	Version      *semver.Version // the plugin's semantic version, if present.
	Size         int64           // the size of the plugin, in bytes.
	InstallTime  time.Time       // the time the plugin was installed.
	LastUsedTime time.Time       // the last time the plugin was used.
	SchemaPath   string          // if set, used as the path for loading and caching the schema
	SchemaTime   time.Time       // if set and newer than the file at SchemaPath, used to invalidate a cached schema
}

// Spec returns the PluginSpec for this PluginInfo
func (info *PluginInfo) Spec() PluginSpec {
	return PluginSpec{Name: info.Name, Kind: info.Kind, Version: info.Version}
}

func (info PluginInfo) String() string {
	var version string
	if v := info.Version; v != nil {
		version = fmt.Sprintf("-%s", v)
	}
	return info.Name + version
}

// Delete removes the plugin from the cache.  It also deletes any supporting files in the cache, which includes
// any files that contain the same prefix as the plugin itself.
func (info *PluginInfo) Delete() error {
	dir := info.Path
	if err := os.RemoveAll(dir); err != nil {
		return err
	}
	// Attempt to delete any leftover .partial or .lock files.
	// Don't fail the operation if we can't delete these.
	contract.IgnoreError(os.Remove(fmt.Sprintf("%s.partial", dir)))
	contract.IgnoreError(os.Remove(fmt.Sprintf("%s.lock", dir)))
	return nil
}

// SetFileMetadata adds extra metadata from the given file, representing this plugin's directory.
func (info *PluginInfo) SetFileMetadata(path string) error {
	// Get the file info.
	file, err := os.Stat(path)
	if err != nil {
		return err
	}

	// Next, get the size from the directory (or, if there is none, just the file).
	size, err := getPluginSize(path)
	if err == nil {
		info.Size = size
	} else {
		logging.V(6).Infof("unable to get plugin dir size for %s: %v", path, err)
	}

	// Next get the access times from the plugin binary itself.
	tinfo := times.Get(file)

	if tinfo.HasChangeTime() {
		info.InstallTime = tinfo.ChangeTime()
	} else {
		info.InstallTime = tinfo.ModTime()
	}

	info.LastUsedTime = tinfo.AccessTime()

	if info.Kind == ResourcePlugin {
		var v string
		if info.Version != nil {
			v = "-" + info.Version.String() + "-"
		}
		info.SchemaPath = filepath.Join(filepath.Dir(path), "schema-"+info.Name+v+".json")
		info.SchemaTime = tinfo.ModTime()
	}

	return nil
}

func interpolateURL(serverURL string, version semver.Version, os, arch string) string {
	replacer := strings.NewReplacer(
		"${VERSION}", url.QueryEscape(version.String()),
		"${OS}", url.QueryEscape(os),
		"${ARCH}", url.QueryEscape(arch))
	return replacer.Replace(serverURL)
}

func (spec PluginSpec) GetSource() (PluginSource, error) {
	baseSource, err := func() (PluginSource, error) {
		// The plugin has a set URL use that.
		if spec.PluginDownloadURL != "" {
			// Support schematised URLS if the URL has a "schema" part we recognize
			url, err := url.Parse(spec.PluginDownloadURL)
			if err != nil {
				return nil, err
			}

			if url.Scheme == "github" {
				return newGithubSource(url, spec.Name, spec.Kind)
			}

			return newPluginURLSource(spec.Name, spec.Kind, spec.PluginDownloadURL), nil
		}

		// If the plugin name matches an override, download the plugin from the override URL.
		if url, ok := pluginDownloadURLOverridesParsed.get(spec.Name); ok {
			return newPluginURLSource(spec.Name, spec.Kind, url), nil
		}

		// Use our default fallback behaviour of github then get.pulumi.com
		return newFallbackSource(spec.Name, spec.Kind), nil
	}()

	if err != nil {
		return nil, err
	}

	if len(spec.Checksums) != 0 {
		return newChecksumSource(baseSource, spec.Checksums), nil
	}
	return baseSource, nil
}

// GetLatestVersion tries to find the latest version for this plugin. This is currently only supported for
// plugins we can get from github releases.
func (spec PluginSpec) GetLatestVersion() (*semver.Version, error) {
	source, err := spec.GetSource()
	if err != nil {
		return nil, err
	}
	return source.GetLatestVersion(getHTTPResponse)
}

// Download fetches an io.ReadCloser for this plugin and also returns the size of the response (if known).
func (spec PluginSpec) Download() (io.ReadCloser, int64, error) {
	// Figure out the OS/ARCH pair for the download URL.
	var opSy string
	switch runtime.GOOS {
	case "darwin", "linux", "windows":
		opSy = runtime.GOOS
	default:
		return nil, -1, errors.Errorf("unsupported plugin OS: %s", runtime.GOOS)
	}
	var arch string
	switch runtime.GOARCH {
	case "amd64", "arm64":
		arch = runtime.GOARCH
	default:
		return nil, -1, errors.Errorf("unsupported plugin architecture: %s", runtime.GOARCH)
	}

	// The plugin version is necessary for the endpoint. If it's not present, return an error.
	if spec.Version == nil {
		return nil, -1, errors.Errorf("unknown version for plugin %s", spec.Name)
	}

	source, err := spec.GetSource()
	if err != nil {
		return nil, -1, err
	}
	return source.Download(*spec.Version, opSy, arch, getHTTPResponse)
}

func buildHTTPRequest(pluginEndpoint string, token string) (*http.Request, error) {
	req, err := http.NewRequest("GET", pluginEndpoint, nil)
	if err != nil {
		return nil, err
	}

	userAgent := fmt.Sprintf("pulumi-cli/1 (%s; %s)", version.Version, runtime.GOOS)
	req.Header.Set("User-Agent", userAgent)

	if token != "" {
		req.Header.Set("Authorization", fmt.Sprintf("token %s", token))
	}

	return req, nil
}

func getHTTPResponse(req *http.Request) (io.ReadCloser, int64, error) {
	logging.V(9).Infof("full plugin download url: %s", req.URL)
	// This logs at level 11 because it could include authentication headers, we reserve log level 11 for
	// detailed api logs that may include credentials.
	logging.V(11).Infof("plugin install request headers: %v", req.Header)

	resp, err := httputil.DoWithRetry(req, http.DefaultClient)
	if err != nil {
		return nil, -1, err
	}

	// As above this might include authentication information, but also to be consistent at what level headers
	// print at.
	logging.V(11).Infof("plugin install response headers: %v", resp.Header)

	if resp.StatusCode < 200 || resp.StatusCode > 299 {
		return nil, -1, newDownloadError(resp.StatusCode, req.URL)
	}

	return resp.Body, resp.ContentLength, nil
}

// downloadError is an error that happened during the HTTP download of a plugin.
type downloadError struct {
	msg  string
	code int
}

func (e *downloadError) Error() string {
	return e.msg
}

func (e *downloadError) Code() int {
	return e.code
}

// Create a new downloadError with a message that indicates GITHUB_TOKEN should be set.
func newGithubPrivateRepoError(statusCode int, url *url.URL) error {
	return &downloadError{
		code: statusCode,
		msg: fmt.Sprintf("%d HTTP error fetching plugin from %s. "+
			"If this is a private GitHub repository, try "+
			"providing a token via the GITHUB_TOKEN environment variable. "+
			"See: https://github.com/settings/tokens",
			statusCode, url),
	}
}

// Create a new downloadError.
func newDownloadError(statusCode int, url *url.URL) error {
	if url.Host == "api.github.com" && statusCode == 404 {
		return newGithubPrivateRepoError(statusCode, url)
	}
	return &downloadError{
		code: statusCode,
		msg:  fmt.Sprintf("%d HTTP error fetching plugin from %s", statusCode, url),
	}
}

// installLock acquires a file lock used to prevent concurrent installs.
func (spec PluginSpec) installLock() (unlock func(), err error) {
	finalDir, err := spec.DirPath()
	if err != nil {
		return nil, err
	}
	lockFilePath := fmt.Sprintf("%s.lock", finalDir)

	if err := os.MkdirAll(filepath.Dir(lockFilePath), 0700); err != nil {
		return nil, errors.Wrap(err, "creating plugin root")
	}

	mutex := fsutil.NewFileMutex(lockFilePath)
	if err := mutex.Lock(); err != nil {
		return nil, err
	}
	return func() {
		contract.IgnoreError(mutex.Unlock())
	}, nil
}

// Install installs a plugin's tarball into the cache. See InstallWithContext for details.
func (spec PluginSpec) Install(tgz io.ReadCloser, reinstall bool) error {
	return spec.InstallWithContext(context.Background(), tarPlugin{tgz}, reinstall)
}

// DownloadToFile downloads the given PluginInfo to a temporary file and returns that temporary file.
// This has some retry logic to re-attempt the download if it errors for any reason.
func DownloadToFile(
	pkgPlugin PluginSpec,
	wrapper func(stream io.ReadCloser, size int64) io.ReadCloser,
	retry func(err error, attempt int, limit int, delay time.Duration)) (*os.File, error) {

	// This is an internal helper that's pretty much just a copy of io.Copy except it returns read and
	// write errors separately. We only want to retry if the read (i.e. download) fails, if the write
	// fails thats probably due to file permissions or space limitations and there's no point retrying.
	copyBuffer := func(dst io.Writer, src io.Reader) (written int64, readErr error, writeErr error) {
		size := 32 * 1024
		if l, ok := src.(*io.LimitedReader); ok && int64(size) > l.N {
			if l.N < 1 {
				size = 1
			} else {
				size = int(l.N)
			}
		}
		buf := make([]byte, size)

		for {
			nr, er := src.Read(buf)
			if nr > 0 {
				nw, ew := dst.Write(buf[0:nr])
				if nw < 0 || nr < nw {
					nw = 0
					if ew == nil {
						ew = errors.New("invalid write result")
					}
				}
				written += int64(nw)
				if ew != nil {
					return written, nil, ew
				}
				if nr != nw {
					return written, nil, io.ErrShortWrite
				}
			}
			if er != nil {
				if er == io.EOF {
					er = nil
				}
				return written, er, nil
			}
		}
	}

	tryDownload := func(dst io.WriteCloser) (error, error) {
		defer dst.Close()
		tarball, expectedByteCount, err := pkgPlugin.Download()
		if err != nil {
			return err, nil
		}
		if wrapper != nil {
			tarball = wrapper(tarball, expectedByteCount)
		}
		defer tarball.Close()
		copiedByteCount, readErr, writerErr := copyBuffer(dst, tarball)
		if readErr != nil || writerErr != nil {
			return readErr, writerErr
		}
		if copiedByteCount != expectedByteCount {
			return nil, fmt.Errorf("expected %d bytes but copied %d when downloading plugin %s",
				expectedByteCount, copiedByteCount, pkgPlugin)
		}
		return nil, nil
	}

	tryDownloadToFile := func() (string, error, error) {
		file, err := ioutil.TempFile("" /* default temp dir */, "pulumi-plugin-tar")
		if err != nil {
			return "", nil, err
		}
		readErr, writeErr := tryDownload(file)
		if readErr != nil || writeErr != nil {
			err2 := os.Remove(file.Name())
			if err2 != nil {
				// only one of readErr or writeErr will be set
				err := readErr
				if err == nil {
					err = writeErr
				}

				return "", nil, fmt.Errorf("error while removing tempfile: %v. Context: %w", err2, err)
			}
			return "", readErr, writeErr
		}
		return file.Name(), nil, nil
	}

	downloadToFileWithRetry := func() (string, error) {
		delay := 80 * time.Millisecond
		for attempt := 0; ; attempt++ {
			tempFile, readErr, writeErr := tryDownloadToFile()
			if readErr == nil && writeErr == nil {
				return tempFile, nil
			}
			if writeErr != nil {
				return "", writeErr
			}

			// If the readErr is a checksum error don't retry
			if _, ok := readErr.(*checksumError); ok {
				return "", readErr
			}

			// Don't retry, since the request was processed and rejected.
			if err, ok := readErr.(*downloadError); ok && (err.Code() == 404 || err.Code() == 403) {
				return "", readErr
			}

			// Don't attempt more than 5 times
			attempts := 5
			if readErr != nil && attempt >= attempts {
				return "", readErr
			}
			if retry != nil {
				retry(readErr, attempt+1, attempts, delay)
			}
			time.Sleep(delay)
			delay = delay * 2
		}
	}

	tarball, err := downloadToFileWithRetry()
	if err != nil {
		return nil, fmt.Errorf("failed to download plugin: %s: %w", pkgPlugin, err)
	}
	reader, err := os.Open(tarball)
	if err != nil {
		return nil, fmt.Errorf("failed to open downloaded plugin: %s: %w", pkgPlugin, err)
	}
	return reader, nil

}

type PluginContent interface {
	io.Closer

	writeToDir(pathToDir string) error
}

func SingleFilePlugin(f *os.File, spec PluginSpec) PluginContent {
	return singleFilePlugin{F: f, Kind: spec.Kind, Name: spec.Name}
}

type singleFilePlugin struct {
	F    *os.File
	Kind PluginKind
	Name string
}

func (p singleFilePlugin) writeToDir(finalDir string) error {
	bytes, err := ioutil.ReadAll(p.F)
	if err != nil {
		return err
	}

	finalPath := filepath.Join(finalDir, fmt.Sprintf("pulumi-%s-%s", p.Kind, p.Name))
	// We are writing an executable.
	return os.WriteFile(finalPath, bytes, 0700) //nolint:gosec
}

func (p singleFilePlugin) Close() error {
	return p.F.Close()
}

func TarPlugin(tgz io.ReadCloser) PluginContent {
	return tarPlugin{Tgz: tgz}
}

type tarPlugin struct {
	Tgz io.ReadCloser
}

func (p tarPlugin) Close() error {
	return p.Tgz.Close()
}

func (p tarPlugin) writeToDir(finalPath string) error {
	return archive.ExtractTGZ(p.Tgz, finalPath)
}

func DirPlugin(rootPath string) PluginContent {
	return dirPlugin{Root: rootPath}
}

type dirPlugin struct {
	Root string
}

func (p dirPlugin) Close() error {
	return nil
}

func (p dirPlugin) writeToDir(dstRoot string) error {
	return filepath.WalkDir(p.Root, func(srcPath string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		relPath := strings.TrimPrefix(srcPath, p.Root)
		dstPath := filepath.Join(dstRoot, relPath)

		if srcPath == p.Root {
			return nil
		}
		if d.IsDir() {
			return os.Mkdir(dstPath, 0700)
		}

		src, err := os.Open(srcPath)
		if err != nil {
			return err
		}

		info, err := d.Info()
		if err != nil {
			return err
		}

		bytes, err := ioutil.ReadAll(src)
		if err != nil {
			return err
		}

		return os.WriteFile(dstPath, bytes, info.Mode())
	})
}

// InstallWithContext installs a plugin's tarball into the cache. It validates that plugin names are in the expected
// format. Previous versions of Pulumi extracted the tarball to a temp directory first, and then renamed the temp
// directory to the final directory. The rename operation fails often enough on Windows due to aggressive virus scanners
// opening files in the temp directory. To address this, we now extract the tarball directly into the final directory,
// and use file locks to prevent concurrent installs.
//
// Each plugin has its own file lock, with the same name as the plugin directory, with a `.lock` suffix.
// During installation an empty file with a `.partial` suffix is created, indicating that installation is in-progress.
// The `.partial` file is deleted when installation is complete, indicating that the plugin has finished installing.
// If a failure occurs during installation, the `.partial` file will remain, indicating the plugin wasn't fully
// installed. The next time the plugin is installed, the old installation directory will be removed and replaced with
// a fresh installation.
func (spec PluginSpec) InstallWithContext(ctx context.Context, content PluginContent, reinstall bool) error {
	defer contract.IgnoreClose(content)

	// Fetch the directory into which we will expand this tarball.
	finalDir, err := spec.DirPath()
	if err != nil {
		return err
	}

	// Create a file lock file at <pluginsdir>/<kind>-<name>-<version>.lock.
	unlock, err := spec.installLock()
	if err != nil {
		return err
	}
	defer unlock()

	// Cleanup any temp dirs from failed installations of this plugin from previous versions of Pulumi.
	if err := cleanupTempDirs(finalDir); err != nil {
		// We don't want to fail the installation if there was an error cleaning up these old temp dirs.
		// Instead, log the error and continue on.
		logging.V(5).Infof("Install: Error cleaning up temp dirs: %s", err.Error())
	}

	// Get the partial file path (e.g. <pluginsdir>/<kind>-<name>-<version>.partial).
	partialFilePath, err := spec.PartialFilePath()
	if err != nil {
		return err
	}

	// Check whether the directory exists while we were waiting on the lock.
	_, finalDirStatErr := os.Stat(finalDir)
	if finalDirStatErr == nil {
		_, partialFileStatErr := os.Stat(partialFilePath)
		if partialFileStatErr != nil {
			if !os.IsNotExist(partialFileStatErr) {
				return partialFileStatErr
			}
			if !reinstall {
				// finalDir exists, there's no partial file, and we're not reinstalling, so the plugin is already
				// installed.
				return nil
			}
		}

		// Either the partial file exists--meaning a previous attempt at installing the plugin failed--or we're
		// deliberately reinstalling the plugin. Delete finalDir so we can try installing again. There's no need to
		// delete the partial file since we'd just be recreating it again below anyway.
		if err := os.RemoveAll(finalDir); err != nil {
			return err
		}
	} else if !os.IsNotExist(finalDirStatErr) {
		return finalDirStatErr
	}

	// Create an empty partial file to indicate installation is in-progress.
	if err := ioutil.WriteFile(partialFilePath, nil, 0600); err != nil {
		return err
	}

	// Create the final directory.
	if err := os.MkdirAll(finalDir, 0700); err != nil {
		return err
	}

	if err := content.writeToDir(finalDir); err != nil {
		return err
	}

	// Even though we deferred closing the tarball at the beginning of this function, go ahead and explicitly close
	// it now since we're finished extracting it, to prevent subsequent output from being displayed oddly with
	// the progress bar.
	contract.IgnoreClose(content)

	// Install dependencies, if needed.
	proj, err := LoadPluginProject(filepath.Join(finalDir, "PulumiPlugin.yaml"))
	if err != nil && !os.IsNotExist(err) {
		return errors.Wrap(err, "loading PulumiPlugin.yaml")
	}
	if proj != nil {
		runtime := strings.ToLower(proj.Runtime.Name())
		// For now, we only do this for Node.js and Python. For Go, the expectation is the binary is
		// already built. For .NET, similarly, a single self-contained binary could be used, but
		// otherwise `dotnet run` will implicitly run `dotnet restore`.
		// TODO[pulumi/pulumi#1334]: move to the language plugins so we don't have to hard code here.
		switch runtime {
		case "nodejs":
			var b bytes.Buffer
			if _, err := npm.Install(ctx, finalDir, true /* production */, &b, &b); err != nil {
				os.Stderr.Write(b.Bytes())
				return errors.Wrap(err, "installing plugin dependencies")
			}
		case "python":
			if err := python.InstallDependencies(ctx, finalDir, "venv", false /*showOutput*/); err != nil {
				return errors.Wrap(err, "installing plugin dependencies")
			}
		}
	}

	// Installation is complete. Remove the partial file.
	return os.Remove(partialFilePath)
}

// cleanupTempDirs cleans up leftover temp dirs from failed installs with previous versions of Pulumi.
func cleanupTempDirs(finalDir string) error {
	dir := filepath.Dir(finalDir)

	infos, err := os.ReadDir(dir)
	if err != nil {
		return err
	}

	for _, info := range infos {
		// Temp dirs have a suffix of `.tmpXXXXXX` (where `XXXXXX`) is a random number,
		// from ioutil.TempFile.
		if info.IsDir() && installingPluginRegexp.MatchString(info.Name()) {
			path := filepath.Join(dir, info.Name())
			if err := os.RemoveAll(path); err != nil {
				return errors.Wrapf(err, "cleaning up temp dir %s", path)
			}
		}
	}

	return nil
}

// PluginKind represents a kind of a plugin that may be dynamically loaded and used by Pulumi.
type PluginKind string

const (
	// AnalyzerPlugin is a plugin that can be used as a resource analyzer.
	AnalyzerPlugin PluginKind = "analyzer"
	// LanguagePlugin is a plugin that can be used as a language host.
	LanguagePlugin PluginKind = "language"
	// ResourcePlugin is a plugin that can be used as a resource provider for custom CRUD operations.
	ResourcePlugin PluginKind = "resource"
)

// IsPluginKind returns true if k is a valid plugin kind, and false otherwise.
func IsPluginKind(k string) bool {
	switch PluginKind(k) {
	case AnalyzerPlugin, LanguagePlugin, ResourcePlugin:
		return true
	default:
		return false
	}
}

// HasPlugin returns true if the given plugin exists.
func HasPlugin(spec PluginSpec) bool {
	dir, err := spec.DirPath()
	if err == nil {
		_, err := os.Stat(dir)
		if err == nil {
			partialFilePath, err := spec.PartialFilePath()
			if err == nil {
				if _, err := os.Stat(partialFilePath); os.IsNotExist(err) {
					return true
				}
			}
		}
	}
	return false
}

// HasPluginGTE returns true if the given plugin exists at the given version number or greater.
func HasPluginGTE(spec PluginSpec) (bool, error) {
	// If an exact match, return true right away.
	if HasPlugin(spec) {
		return true, nil
	}

	// Otherwise, load up the list of plugins and find one with the same name/type and >= version.
	plugs, err := GetPlugins()
	if err != nil {
		return false, err
	}

	// If we're not doing the legacy plugin behavior and we've been asked for a specific version, do the same plugin
	// search that we'd do at runtime. This ensures that `pulumi plugin install` works the same way that the runtime
	// loader does, to minimize confusion when a user has to install new plugins.
	if !enableLegacyPluginBehavior && spec.Version != nil {
		requestedVersion := semver.MustParseRange(spec.Version.String())
		_, err := SelectCompatiblePlugin(plugs, spec.Kind, spec.Name, requestedVersion)
		return err == nil, err
	}

	for _, p := range plugs {
		if p.Name == spec.Name &&
			p.Kind == spec.Kind &&
			(p.Version != nil && spec.Version != nil && p.Version.GTE(*spec.Version)) {
			return true, nil
		}
	}
	return false, nil
}

// GetPolicyDir returns the directory in which an organization's Policy Packs on the current machine are managed.
func GetPolicyDir(orgName string) (string, error) {
	return GetPulumiPath(PolicyDir, orgName)
}

// GetPolicyPath finds a PolicyPack by its name version, as well as a bool marked true if the path
// already exists and is a directory.
func GetPolicyPath(orgName, name, version string) (string, bool, error) {
	policiesDir, err := GetPolicyDir(orgName)
	if err != nil {
		return "", false, err
	}

	policyPackPath := path.Join(policiesDir, fmt.Sprintf("pulumi-analyzer-%s-v%s", name, version))

	file, err := os.Stat(policyPackPath)
	if err == nil && file.IsDir() {
		// PolicyPack exists. Return.
		return policyPackPath, true, nil
	} else if err != nil && !os.IsNotExist(err) {
		// Error trying to inspect PolicyPack FS entry. Return error.
		return "", false, err
	}

	// Not found. Return empty path.
	return policyPackPath, false, nil
}

// GetPluginDir returns the directory in which plugins on the current machine are managed.
func GetPluginDir() (string, error) {
	return GetPulumiPath(PluginDir)
}

// GetPlugins returns a list of installed plugins without size info and last accessed metadata.
// Plugin size requires recursively traversing the plugin directory, which can be extremely
// expensive with the introduction of nodejs multilang components that have
// deeply nested node_modules folders.
func GetPlugins() ([]PluginInfo, error) {
	// To get the list of plugins, simply scan the directory in the usual place.
	dir, err := GetPluginDir()
	if err != nil {
		return nil, err
	}
	return getPlugins(dir, true /* skipMetadata */)
}

// GetPluginsWithMetadata returns a list of installed plugins with metadata about size,
// and last access (POOR RUNTIME PERF). Plugin size requires recursively traversing the
// plugin directory, which can be extremely expensive with the introduction of
// nodejs multilang components that have deeply nested node_modules folders.
func GetPluginsWithMetadata() ([]PluginInfo, error) {
	// To get the list of plugins, simply scan the directory in the usual place.
	dir, err := GetPluginDir()
	if err != nil {
		return nil, err
	}
	return getPlugins(dir, false /* skipMetadata */)
}

func getPlugins(dir string, skipMetadata bool) ([]PluginInfo, error) {
	files, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}

	// Now read the file infos and create the plugin infos.
	var plugins []PluginInfo
	for _, file := range files {
		// Skip anything that doesn't look like a plugin.
		if kind, name, version, ok := tryPlugin(file); ok {
			path := filepath.Join(dir, file.Name())
			plugin := PluginInfo{
				Name:    name,
				Kind:    kind,
				Version: &version,
				Path:    path,
			}
			if _, err := os.Stat(fmt.Sprintf("%s.partial", path)); err == nil {
				// Skip it if the partial file exists, meaning the plugin is not fully installed.
				continue
			} else if !os.IsNotExist(err) {
				return nil, err
			}
			// computing plugin sizes can be very expensive (nested node_modules)
			if !skipMetadata {
				if err = plugin.SetFileMetadata(path); err != nil {
					return nil, err
				}
			}
			plugins = append(plugins, plugin)
		}
	}
	return plugins, nil
}

// GetPluginPath finds a plugin's path by its kind, name, and optional version.  It will match the latest version that
// is >= the version specified.  If no version is supplied, the latest plugin for that given kind/name pair is loaded,
// using standard semver sorting rules.  A plugin may be overridden entirely by placing it on your $PATH, though it is
// possible to opt out of this behavior by setting PULUMI_IGNORE_AMBIENT_PLUGINS to any non-empty value.
func GetPluginPath(kind PluginKind, name string, version *semver.Version,
	projectPlugins []ProjectPlugin) (string, error) {
	info, path, err := getPluginInfoAndPath(kind, name, version, true /* skipMetadata */, projectPlugins)
	if err != nil {
		return "", err
	}

	contract.Assert(info.Path == filepath.Dir(path))
	return path, err
}

func GetPluginInfo(kind PluginKind, name string, version *semver.Version,
	projectPlugins []ProjectPlugin) (*PluginInfo, error) {
	info, path, err := getPluginInfoAndPath(kind, name, version, false, projectPlugins)
	if err != nil {
		return nil, err
	}

	contract.Assert(info.Path == filepath.Dir(path))
	return info, nil
}

func attemptToDownloadAndInstallPlugin(kind PluginKind, name string, version *semver.Version) error {
	pluginSpec := PluginSpec{
		Kind: kind,
		Name: name,
	}

	if version == nil {
		latestVersion, err := pluginSpec.GetLatestVersion()
		if err != nil {
			return &InstallPluginError{
				Name:            name,
				Kind:            kind,
				UnderlyingError: err,
			}
		}

		version = latestVersion
	}

	pluginSpec.Version = version

	withProgress := func(stream io.ReadCloser, size int64) io.ReadCloser {
		header := fmt.Sprintf("Downloading plugin %s v%s", pluginSpec.Name, version.String())
		return ReadCloserProgressBar(stream, size, header, colors.Always)
	}

	retry := func(err error, attempt int, limit int, delay time.Duration) {
		cmdutil.Diag().Warningf(
			diag.Message("", "Error downloading plugin: %s\nWill retry in %v [%d/%d]"), err, delay, attempt, limit)
	}

	downloadedFile, err := DownloadToFile(pluginSpec, withProgress, retry)
	if err != nil {
		downloadError := fmt.Errorf("error downloading plugin %s to file: %w", pluginSpec.Name, err)
		return &InstallPluginError{
			Name:            name,
			Kind:            kind,
			Version:         version,
			UnderlyingError: downloadError,
		}
	}

	logging.V(1).Infof("installing plugin %s", pluginSpec.Name)
	pluginInstallError := pluginSpec.Install(downloadedFile, false)
	if pluginInstallError != nil {
		return &InstallPluginError{
			Name:            name,
			Kind:            kind,
			Version:         version,
			UnderlyingError: pluginInstallError,
		}
	}

	return nil
}

// Given a PluginInfo try to find the executable file that corresponds to it
func getPluginPath(info *PluginInfo) string {
	var path string
	exts := getCandidateExtensions()
	for _, ext := range exts {
		path = filepath.Join(info.Path, info.Spec().File()) + ext
		_, err := os.Stat(path)
		if err == nil {
			return path
		}
	}

	// We didn't actually find a file for this plugin, so just use the old behaviour of assuming the first
	// extension.
	return filepath.Join(info.Path, info.Spec().File()) + exts[0]
}

// getPluginInfoAndPath searches for a compatible plugin kind, name, and version and returns either:
//   - if found as an ambient plugin, nil and the path to the executable
//   - if found in the pulumi dir's installed plugins, a PluginInfo and path to the executable
//   - an error in all other cases.
func getPluginInfoAndPath(
	kind PluginKind, name string, version *semver.Version, skipMetadata bool,
	projectPlugins []ProjectPlugin) (*PluginInfo, string, error) {
	var filename string

	for i, p1 := range projectPlugins {
		for j, p2 := range projectPlugins {
			if j < i {
				if p2.Kind == p1.Kind && p2.Name == p1.Name {
					if p1.Version != nil && p2.Version != nil && p2.Version.Equals(*p1.Version) {
						return nil, "", fmt.Errorf(
							"multiple project plugins with kind %s, name %s, version %s",
							p1.Kind, p1.Name, p1.Version)
					}
				}
			}
		}
	}

	for _, plugin := range projectPlugins {
		if plugin.Kind != kind {
			continue
		}
		if plugin.Name != name {
			continue
		}
		if plugin.Version != nil && version != nil {
			if !plugin.Version.Equals(*version) {
				logging.Warningf(
					"Project plugin %s with version %s is incompatible with requested version %s.\n",
					name, plugin.Version, version)
				continue
			}
		}

		spec := plugin.Spec()
		info := &PluginInfo{
			Name:    spec.Name,
			Kind:    spec.Kind,
			Version: spec.Version,
			Path:    plugin.Path,
		}
		path := getPluginPath(info)
		// computing plugin sizes can be very expensive (nested node_modules)
		if !skipMetadata && path != "" {
			if err := info.SetFileMetadata(path); err != nil {
				return nil, "", err
			}
		}
		return info, path, nil
	}

	// We currently bundle some plugins with "pulumi" and thus expect them to be next to the pulumi binary. We
	// also always allow these plugins to be picked up from PATH even if PULUMI_IGNORE_AMBIENT_PLUGINS is set.
	// Eventually we want to fix this so new plugins are true plugins in the plugin cache.
	isBundled := kind == LanguagePlugin ||
		(kind == ResourcePlugin && name == "pulumi-nodejs") ||
		(kind == ResourcePlugin && name == "pulumi-python") ||
		(kind == AnalyzerPlugin && name == "policy") ||
		(kind == AnalyzerPlugin && name == "policy-python")

	// If we have a version of the plugin on its $PATH, use it, unless we have opted out of this behavior explicitly.
	// This supports development scenarios.
	optOut, isFound := os.LookupEnv("PULUMI_IGNORE_AMBIENT_PLUGINS")
	includeAmbient := !(isFound && cmdutil.IsTruthy(optOut)) || isBundled
	if includeAmbient {
		filename = (&PluginSpec{Kind: kind, Name: name}).File()
		if path, err := exec.LookPath(filename); err == nil {
			logging.V(6).Infof("GetPluginPath(%s, %s, %v): found on $PATH %s", kind, name, version, path)
			return &PluginInfo{
				Kind: kind,
				Name: name,
				Path: filepath.Dir(path),
			}, path, nil
		}
	}

	// At some point in the future, bundled plugins will be located in the plugin cache, just like regular
	// plugins (see pulumi/pulumi#956 for some of the reasons why this isn't the case today). For now, they
	// ship next to the `pulumi` binary. While we encourage this folder to be on the $PATH (and so the check
	// above would have found the plugin) it's possible someone is running `pulumi` with an explicit path on
	// the command line or has done symlink magic such that `pulumi` is on the path, but the bundled plugins
	// are not. So, if possible, look next to the instance of `pulumi` that is running to find this bundled
	// plugin.
	if isBundled {
		exePath, exeErr := os.Executable()
		if exeErr == nil {
			fullPath, fullErr := filepath.EvalSymlinks(exePath)
			if fullErr == nil {
				for _, ext := range getCandidateExtensions() {
					candidate := filepath.Join(filepath.Dir(fullPath), filename+ext)
					// Let's see if the file is executable. On Windows, os.Stat() returns a mode of "-rw-rw-rw" so on
					// on windows we just trust the fact that the .exe can actually be launched.
					if stat, err := os.Stat(candidate); err == nil &&
						(stat.Mode()&0100 != 0 || runtime.GOOS == windowsGOOS) {
						logging.V(6).Infof("GetPluginPath(%s, %s, %v): found next to current executable %s",
							kind, name, version, candidate)

						return &PluginInfo{
							Kind: kind,
							Name: name,
							Path: filepath.Dir(candidate),
						}, candidate, nil
					}
				}
			}
		}
	}

	// Otherwise, check the plugin cache.
	var plugins []PluginInfo
	var err error
	if skipMetadata {
		plugins, err = GetPlugins()
	} else {
		plugins, err = GetPluginsWithMetadata()
	}
	if err != nil {
		return nil, "", errors.Wrapf(err, "loading plugin list")
	}

	var match *PluginInfo
	if !enableLegacyPluginBehavior && version != nil {
		logging.V(6).Infof("GetPluginPath(%s, %s, %s): enabling new plugin behavior", kind, name, version)
		candidate, err := SelectCompatiblePlugin(plugins, kind, name, semver.MustParseRange(version.String()))
		if err != nil {
			// could not find a compatible plugin
			// this could be due to the fact that a transitive version of a plugin is required
			// which are not picked up by initial pass of required plugin installations
			// so instead of reporting an error, we just install that required plugin
			if err = attemptToDownloadAndInstallPlugin(kind, name, version); err != nil {
				return nil, "", err
			}

			// downloaded the missing plugin successfully
			// restart the plugin retrieval
			return getPluginInfoAndPath(kind, name, version, skipMetadata, projectPlugins)
		}
		match = &candidate
	} else {
		for _, cur := range plugins {
			// Since the value of cur changes as we iterate, we can't save a pointer to it. So let's have a local that
			// we can take a pointer to if this plugin is the best match yet.
			plugin := cur
			if plugin.Kind == kind && plugin.Name == name {
				// Always pick the most recent version of the plugin available.  Even if this is an exact match, we
				// keep on searching just in case there's a newer version available.
				var m *PluginInfo
				if match == nil && version == nil {
					m = &plugin // no existing match, no version spec, take it.
				} else if match != nil &&
					(match.Version == nil || (plugin.Version != nil && plugin.Version.GT(*match.Version))) {
					m = &plugin // existing match, but this plugin is newer, prefer it.
				} else if version != nil && plugin.Version != nil && plugin.Version.GTE(*version) {
					m = &plugin // this plugin is >= the version being requested, use it.
				}

				if m != nil {
					match = m
					logging.V(6).Infof("GetPluginPath(%s, %s, %s): found candidate (#%s)",
						kind, name, version, match.Version)
				}
			}
		}
	}

	if match != nil {
		matchPath := getPluginPath(match)
		logging.V(6).Infof("GetPluginPath(%s, %s, %v): found in cache at %s", kind, name, version, matchPath)
		return match, matchPath, nil
	}

	if err := attemptToDownloadAndInstallPlugin(kind, name, version); err != nil {
		return nil, "", err
	}

	// downloaded the missing plugin successfully
	// restart the plugin retrieval
	return getPluginInfoAndPath(kind, name, version, skipMetadata, projectPlugins)
}

// SortedPluginInfo is a wrapper around PluginInfo that allows for sorting by version.
type SortedPluginInfo []PluginInfo

func (sp SortedPluginInfo) Len() int { return len(sp) }
func (sp SortedPluginInfo) Less(i, j int) bool {
	iVersion := sp[i].Version
	jVersion := sp[j].Version
	switch {
	case iVersion == nil && jVersion == nil:
		return false
	case iVersion == nil:
		return true
	case jVersion == nil:
		return false
	case iVersion.EQ(*jVersion):
		return iVersion.String() < jVersion.String()
	default:
		return iVersion.LT(*jVersion)
	}
}
func (sp SortedPluginInfo) Swap(i, j int) { sp[i], sp[j] = sp[j], sp[i] }

// SortedPluginSpec is a wrapper around PluginSpec that allows for sorting by version.
type SortedPluginSpec []PluginSpec

func (sp SortedPluginSpec) Len() int { return len(sp) }
func (sp SortedPluginSpec) Less(i, j int) bool {
	iVersion := sp[i].Version
	jVersion := sp[j].Version
	switch {
	case iVersion == nil && jVersion == nil:
		return false
	case iVersion == nil:
		return true
	case jVersion == nil:
		return false
	case iVersion.EQ(*jVersion):
		return iVersion.String() < jVersion.String()
	default:
		return iVersion.LT(*jVersion)
	}
}
func (sp SortedPluginSpec) Swap(i, j int) { sp[i], sp[j] = sp[j], sp[i] }

// SelectCompatiblePlugin selects a plugin from the list of plugins with the given kind and name that sastisfies the
// requested semver range. It returns the highest version plugin that satisfies the requested constraints, or an error
// if no such plugin could be found.
//
// If there exist plugins in the plugin list that don't have a version, SelectCompatiblePlugin will select them if there
// are no other compatible plugins available.
func SelectCompatiblePlugin(
	plugins []PluginInfo, kind PluginKind, name string, requested semver.Range) (PluginInfo, error) {
	logging.V(7).Infof("SelectCompatiblePlugin(..., %s): beginning", name)
	var bestMatch PluginInfo
	var hasMatch bool

	// Before iterating over the list of plugins, sort the list of plugins by version in ascending order. This ensures
	// that we can do a single pass over the plugin list, from lowest version to greatest version, and be confident that
	// the best match that we find at the end is the greatest possible compatible version for the requested plugin.
	//
	// Plugins without versions are treated as having the lowest version. Ties between plugins without versions are
	// resolved arbitrarily.
	sort.Sort(SortedPluginInfo(plugins))
	for _, plugin := range plugins {
		switch {
		case plugin.Kind != kind || plugin.Name != name:
			// Not the plugin we're looking for.
		case !hasMatch && plugin.Version == nil:
			// This is the plugin we're looking for, but it doesn't have a version. We haven't seen anything better yet,
			// so take it.
			logging.V(7).Infof(
				"SelectCompatiblePlugin(..., %s): best plugin %s: no version and no other candidates",
				name, plugin.String())
			hasMatch = true
			bestMatch = plugin
		case plugin.Version == nil:
			// This is a rare case - we've already seen a version-less plugin and we're seeing another here. Ignore this
			// one and defer to the one we previously selected.
			logging.V(7).Infof("SelectCompatiblePlugin(..., %s): skipping plugin %s: no version", name, plugin.String())
		case requested(*plugin.Version):
			// This plugin is compatible with the requested semver range. Save it as the best match and continue.
			logging.V(7).Infof("SelectCompatiblePlugin(..., %s): best plugin %s: semver match", name, plugin.String())
			hasMatch = true
			bestMatch = plugin
		default:
			logging.V(7).Infof(
				"SelectCompatiblePlugin(..., %s): skipping plugin %s: semver mismatch", name, plugin.String())
		}
	}

	if !hasMatch {
		logging.V(7).Infof("SelectCompatiblePlugin(..., %s): failed to find match", name)
		return PluginInfo{}, errors.New("failed to locate compatible plugin")
	}
	logging.V(7).Infof("SelectCompatiblePlugin(..., %s): selecting plugin '%s': best match ", name, bestMatch.String())
	return bestMatch, nil
}

// ReadCloserProgressBar displays a progress bar for the given closer and returns a wrapper closer to manipulate it.
func ReadCloserProgressBar(
	closer io.ReadCloser, size int64, message string, colorization colors.Colorization) io.ReadCloser {
	if size == -1 {
		return closer
	}

	if !cmdutil.Interactive() {
		return closer
	}

	// If we know the length of the download, show a progress bar.
	bar := pb.New(int(size))
	bar.Output = os.Stderr
	bar.Prefix(colorization.Colorize(colors.SpecUnimportant + message + ":"))
	bar.Postfix(colorization.Colorize(colors.Reset))
	bar.SetMaxWidth(80)
	bar.SetUnits(pb.U_BYTES)
	bar.Start()

	return &barCloser{
		bar:        bar,
		readCloser: bar.NewProxyReader(closer),
	}
}

// getCandidateExtensions returns a set of file extensions (including the dot seprator) which should be used when
// probing for an executable file.
func getCandidateExtensions() []string {
	if runtime.GOOS == windowsGOOS {
		return []string{".exe", ".cmd"}
	}

	return []string{""}
}

// pluginRegexp matches plugin directory names: pulumi-KIND-NAME-VERSION.
var pluginRegexp = regexp.MustCompile(
	"^(?P<Kind>[a-z]+)-" + // KIND
		"(?P<Name>[a-zA-Z0-9-]*[a-zA-Z0-9])-" + // NAME
		"v(?P<Version>.*)$") // VERSION

// installingPluginRegexp matches the name of temporary folders. Previous versions of Pulumi first extracted
// plugins to a temporary folder with a suffix of `.tmpXXXXXX` (where `XXXXXX`) is a random number, from
// ioutil.TempFile. We should ignore these folders.
var installingPluginRegexp = regexp.MustCompile(`\.tmp[0-9]+$`)

// tryPlugin returns true if a file is a plugin, and extracts information about it.
func tryPlugin(file os.DirEntry) (PluginKind, string, semver.Version, bool) {
	// Only directories contain plugins.
	if !file.IsDir() {
		logging.V(11).Infof("skipping file in plugin directory: %s", file.Name())
		return "", "", semver.Version{}, false
	}

	// Ignore plugins which are being installed
	if installingPluginRegexp.MatchString(file.Name()) {
		logging.V(11).Infof("skipping plugin %s which is being installed", file.Name())
		return "", "", semver.Version{}, false
	}

	// Filenames must match the plugin regexp.
	match := pluginRegexp.FindStringSubmatch(file.Name())
	if len(match) != len(pluginRegexp.SubexpNames()) {
		logging.V(11).Infof("skipping plugin %s with missing capture groups: expect=%d, actual=%d",
			file.Name(), len(pluginRegexp.SubexpNames()), len(match))
		return "", "", semver.Version{}, false
	}
	var kind PluginKind
	var name string
	var version *semver.Version
	for i, group := range pluginRegexp.SubexpNames() {
		v := match[i]
		switch group {
		case "Kind":
			// Skip invalid kinds.
			if IsPluginKind(v) {
				kind = PluginKind(v)
			} else {
				logging.V(11).Infof("skipping invalid plugin kind: %s", v)
			}
		case "Name":
			name = v
		case "Version":
			// Skip invalid versions.
			ver, err := semver.ParseTolerant(v)
			if err == nil {
				version = &ver
			} else {
				logging.V(11).Infof("skipping invalid plugin version: %s", v)
			}
		}
	}

	// If anything was missing or invalid, skip this plugin.
	if kind == "" || name == "" || version == nil {
		logging.V(11).Infof("skipping plugin with missing information: kind=%s, name=%s, version=%v",
			kind, name, version)
		return "", "", semver.Version{}, false
	}

	return kind, name, *version, true
}

// getPluginSize recursively computes how much space is devoted to a given plugin.
func getPluginSize(path string) (int64, error) {
	file, err := os.Stat(path)
	if err != nil {
		return 0, nil
	}

	size := int64(0)
	if file.IsDir() {
		subs, err := os.ReadDir(path)
		if err != nil {
			return 0, err
		}
		for _, child := range subs {
			add, err := getPluginSize(filepath.Join(path, child.Name()))
			if err != nil {
				return 0, err
			}
			size += add
		}
	} else {
		size += file.Size()
	}
	return size, nil
}

type barCloser struct {
	bar        *pb.ProgressBar
	readCloser io.ReadCloser
}

func (bc *barCloser) Read(dest []byte) (int, error) {
	return bc.readCloser.Read(dest)
}

func (bc *barCloser) Close() error {
	bc.bar.Finish()
	return bc.readCloser.Close()
}