Introduce providerserver package, deprecate tfsdk server functionality

Reference: #215
Reference: #294
Reference: #296

This change represents the first half of the work necessary to extract the `tfprotov6.ProviderServer` implementation and helper functions out of the `tfsdk` package and into separate packages. The `providerserver` package will be the provider developer facing functionality, while the next iteration of this refactoring will move the actual server implementation into a separate internal package. Once in that separate internal package, efforts can be made to make that code handle terraform-plugin-go type conversions "at the edge" better.

.changelog/pending.txt

@@ -0,0 +1,19 @@
+```release-note:note
+tfsdk: The `NewProtocol6Server()` function has been deprecated in preference of `providerserver.NewProtocol6()` and `providerserver.NewProtocol6WithError()` functions, which will simplify muxing and testing implementations. The `tfsdk.NewProtocol6Server()` function will be removed in the next minor version.
+```
+
+```release-note:note
+tfsdk: The `Serve()` function has been deprecated in preference of the `providerserver.Serve()` function. The `tfsdk.Serve()` function will be removed in the next minor version.
+```
+
+```release-note:note
+tfsdk: The `ServeOpts` type has been deprecated in preference of the `providerserver.ServeOpts` type. When migrating, the `Name` field has been replaced with `Address`. The `tfsdk.ServeOpts` type will be removed in the next minor version.
+```
+
+```release-note:note
+tfsdk: The previously unexported `server` type has been temporarily exported to aid in the migration to the new `providerserver` package. It is not intended for provider developer usage and will be moved into an internal package in the next minor version.
+```
+
+```release-note:feature
+Introduced `providerserver` package, which contains all functions and types necessary for serving a provider in production or acceptance testing.
+```

providerserver/provider_test.go

@@ -0,0 +1,31 @@
+package providerserver
+
+import (
+	"context"
+
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/hashicorp/terraform-plugin-framework/tfsdk"
+)
+
+var _ tfsdk.Provider = &testProvider{}
+
+// Provider type for testing package functionality.
+//
+// This is separate from tfsdk.testServeProvider to avoid changing that.
+type testProvider struct{}
+
+func (t *testProvider) GetSchema(_ context.Context) (tfsdk.Schema, diag.Diagnostics) {
+	return tfsdk.Schema{}, nil
+}
+
+func (t *testProvider) Configure(_ context.Context, _ tfsdk.ConfigureProviderRequest, _ *tfsdk.ConfigureProviderResponse) {
+	// intentionally empty
+}
+
+func (t *testProvider) GetDataSources(_ context.Context) (map[string]tfsdk.DataSourceType, diag.Diagnostics) {
+	return map[string]tfsdk.DataSourceType{}, nil
+}
+
+func (t *testProvider) GetResources(_ context.Context) (map[string]tfsdk.ResourceType, diag.Diagnostics) {
+	return map[string]tfsdk.ResourceType{}, nil
+}

providerserver/providerserver.go

@@ -0,0 +1,59 @@
+package providerserver
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/terraform-plugin-framework/tfsdk"
+	"github.com/hashicorp/terraform-plugin-go/tfprotov6"
+	"github.com/hashicorp/terraform-plugin-go/tfprotov6/tf6server"
+)
+
+// Returns a protocol version 6 ProviderServer implementation based on the
+// given Provider and suitable for usage with the terraform-plugin-go
+// tf6server.Serve() function and various terraform-plugin-mux functions.
+func NewProtocol6(p tfsdk.Provider) func() tfprotov6.ProviderServer {
+	return func() tfprotov6.ProviderServer {
+		return &tfsdk.Server{
+			Provider: p,
+		}
+	}
+}
+
+// Returns a protocol version 6 ProviderServer implementation based on the
+// given Provider and suitable for usage with the terraform-plugin-sdk
+// acceptance testing helper/resource.TestCase.ProtoV6ProviderFactories.
+//
+// The error return is not currently used, but it may be in the future.
+func NewProtocol6WithError(p tfsdk.Provider) func() (tfprotov6.ProviderServer, error) {
+	return func() (tfprotov6.ProviderServer, error) {
+		return &tfsdk.Server{
+			Provider: p,
+		}, nil
+	}
+}
+
+// Serve serves a provider, blocking until the context is canceled.
+func Serve(ctx context.Context, providerFunc func() tfsdk.Provider, opts ServeOpts) error {
+	err := opts.validate(ctx)
+
+	if err != nil {
+		return fmt.Errorf("unable to validate ServeOpts: %w", err)
+	}
+
+	var tf6serverOpts []tf6server.ServeOpt
+
+	if opts.Debug {
+		tf6serverOpts = append(tf6serverOpts, tf6server.WithManagedDebug())
+	}
+
+	return tf6server.Serve(
+		opts.Address,
+		func() tfprotov6.ProviderServer {
+			return &tfsdk.Server{
+				Provider: providerFunc(),
+			}
+		},
+		tf6serverOpts...,
+	)
+}

providerserver/providerserver_test.go

@@ -0,0 +1,39 @@
+package providerserver
+
+import (
+	"context"
+	"testing"
+
+	"github.com/hashicorp/terraform-plugin-go/tfprotov6"
+)
+
+func TestNewProtocol6(t *testing.T) {
+	provider := &testProvider{}
+
+	providerServerFunc := NewProtocol6(provider)
+	providerServer := providerServerFunc()
+
+	// Simple verification
+	_, err := providerServer.GetProviderSchema(context.Background(), &tfprotov6.GetProviderSchemaRequest{})
+
+	if err != nil {
+		t.Fatalf("unexpected error calling ProviderServer: %s", err)
+	}
+}
+
+func TestNewProtocol6WithError(t *testing.T) {
+	provider := &testProvider{}
+
+	providerServer, err := NewProtocol6WithError(provider)()
+
+	if err != nil {
+		t.Fatalf("unexpected error creating ProviderServer: %s", err)
+	}
+
+	// Simple verification
+	_, err = providerServer.GetProviderSchema(context.Background(), &tfprotov6.GetProviderSchemaRequest{})
+
+	if err != nil {
+		t.Fatalf("unexpected error calling ProviderServer: %s", err)
+	}
+}

providerserver/serve_opts.go

@@ -0,0 +1,65 @@
+package providerserver
+
+import (
+	"context"
+	"fmt"
+	"strings"
+)
+
+// ServeOpts are options for serving the provider.
+type ServeOpts struct {
+	// Address is the full address of the provider. Full address form has three
+	// parts separated by forward slashes (/): Hostname, namespace, and
+	// provider type ("name").
+	//
+	// For example: registry.terraform.io/hashicorp/random.
+	Address string
+
+	// Debug runs the provider in a mode acceptable for debugging and testing
+	// processes, such as delve, by managing the process lifecycle. Information
+	// needed for Terraform CLI to connect to the provider is output to stdout.
+	// os.Interrupt (Ctrl-c) can be used to stop the provider.
+	Debug bool
+}
+
+// Validate a given provider address. This is only used for the Address field
+// to preserve backwards compatibility for the Name field.
+//
+// This logic is manually implemented over importing
+// github.com/hashicorp/terraform-registry-address as its functionality such as
+// ParseAndInferProviderSourceString and ParseRawProviderSourceString allow
+// shorter address formats, which would then require post-validation anyways.
+func (opts ServeOpts) validateAddress(_ context.Context) error {
+	addressParts := strings.Split(opts.Address, "/")
+	formatErr := fmt.Errorf("expected hostname/namespace/type format, got: %s", opts.Address)
+
+	if len(addressParts) != 3 {
+		return formatErr
+	}
+
+	if addressParts[0] == "" || addressParts[1] == "" || addressParts[2] == "" {
+		return formatErr
+	}
+
+	return nil
+}
+
+// Validation checks for provider defined ServeOpts.
+//
+// Current checks which return errors:
+//
+//    - If Address is not set
+//    - Address is a valid full provider address
+func (opts ServeOpts) validate(ctx context.Context) error {
+	if opts.Address == "" {
+		return fmt.Errorf("Address must be provided")
+	}
+
+	err := opts.validateAddress(ctx)
+
+	if err != nil {
+		return fmt.Errorf("unable to validate Address: %w", err)
+	}
+
+	return nil
+}

providerserver/serve_opts_test.go

@@ -0,0 +1,114 @@
+package providerserver
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func TestServeOptsValidate(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		serveOpts     ServeOpts
+		expectedError error
+	}{
+		"Address": {
+			serveOpts: ServeOpts{
+				Address: "registry.terraform.io/hashicorp/testing",
+			},
+		},
+		"Address-missing": {
+			serveOpts:     ServeOpts{},
+			expectedError: fmt.Errorf("Address must be provided"),
+		},
+		"Address-invalid-missing-hostname-and-namespace": {
+			serveOpts: ServeOpts{
+				Address: "testing",
+			},
+			expectedError: fmt.Errorf("unable to validate Address: expected hostname/namespace/type format, got: testing"),
+		},
+		"Address-invalid-missing-hostname": {
+			serveOpts: ServeOpts{
+				Address: "hashicorp/testing",
+			},
+			expectedError: fmt.Errorf("unable to validate Address: expected hostname/namespace/type format, got: hashicorp/testing"),
+		},
+	}
+
+	for name, testCase := range testCases {
+		name, testCase := name, testCase
+
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			err := testCase.serveOpts.validate(context.Background())
+
+			if err != nil {
+				if testCase.expectedError == nil {
+					t.Fatalf("expected no error, got: %s", err)
+				}
+
+				if !strings.Contains(err.Error(), testCase.expectedError.Error()) {
+					t.Fatalf("expected error %q, got: %s", testCase.expectedError, err)
+				}
+			}
+
+			if err == nil && testCase.expectedError != nil {
+				t.Fatalf("got no error, expected: %s", testCase.expectedError)
+			}
+		})
+	}
+}
+
+func TestServeOptsValidateAddress(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		serveOpts     ServeOpts
+		expectedError error
+	}{
+		"valid": {
+			serveOpts: ServeOpts{
+				Address: "registry.terraform.io/hashicorp/testing",
+			},
+		},
+		"invalid-missing-hostname-and-namepsace": {
+			serveOpts: ServeOpts{
+				Address: "testing",
+			},
+			expectedError: fmt.Errorf("expected hostname/namespace/type format, got: testing"),
+		},
+		"invalid-missing-hostname": {
+			serveOpts: ServeOpts{
+				Address: "hashicorp/testing",
+			},
+			expectedError: fmt.Errorf("expected hostname/namespace/type format, got: hashicorp/testing"),
+		},
+	}
+
+	for name, testCase := range testCases {
+		name, testCase := name, testCase
+
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			err := testCase.serveOpts.validateAddress(context.Background())
+
+			if err != nil {
+				if testCase.expectedError == nil {
+					t.Fatalf("expected no error, got: %s", err)
+				}
+
+				if !strings.Contains(err.Error(), testCase.expectedError.Error()) {
+					t.Fatalf("expected error %q, got: %s", testCase.expectedError, err)
+				}
+			}
+
+			if err == nil && testCase.expectedError != nil {
+				t.Fatalf("got no error, expected: %s", testCase.expectedError)
+			}
+		})
+	}
+}