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wrapcheck.go
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wrapcheck.go
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package wrapcheck
import (
"fmt"
"go/ast"
"go/token"
"go/types"
"log"
"os"
"regexp"
"strings"
"github.com/gobwas/glob"
"golang.org/x/tools/go/analysis"
)
var DefaultIgnoreSigs = []string{
".Errorf(",
"errors.New(",
"errors.Unwrap(",
".Wrap(",
".Wrapf(",
".WithMessage(",
".WithMessagef(",
".WithStack(",
}
// WrapcheckConfig is the set of configuration values which configure the
// behaviour of the linter.
type WrapcheckConfig struct {
// IgnoreSigs defines a list of substrings which if contained within the
// signature of the function call returning the error, will be ignored. This
// allows you to specify functions that wrapcheck will not report as
// unwrapped.
//
// For example, an ignoreSig of `[]string{"errors.New("}` will ignore errors
// returned from the stdlib package error's function:
//
// `func errors.New(message string) error`
//
// Due to the signature containing the substring `errors.New(`.
//
// Note: Setting this value will intentionally override the default ignored
// sigs. To achieve the same behaviour as default, you should add the default
// list to your config.
IgnoreSigs []string `mapstructure:"ignoreSigs" yaml:"ignoreSigs"`
// IgnoreSigRegexps defines a list of regular expressions which if matched
// to the signature of the function call returning the error, will be ignored. This
// allows you to specify functions that wrapcheck will not report as
// unwrapped.
//
// For example, an ignoreSigRegexp of `[]string{"\.New.*Err\("}`` will ignore errors
// returned from any signture whose method name starts with "New" and ends with "Err"
// due to the signature matching the regular expression `\.New.*Err\(`.
//
// Note that this is similar to the ignoreSigs configuration, but provides
// slightly more flexibility in defining rules by which signtures will be
// ignored.
IgnoreSigRegexps []string `mapstructure:"ignoreSigRegexps" yaml:"ignoreSigRegexps"`
// IgnorePackageGlobs defines a list of globs which, if matching the package
// of the function returning the error, will ignore the error when doing
// wrapcheck analysis.
//
// This is useful for broadly ignoring packages and subpackages from wrapcheck
// analysis. For example, to ignore all errors from all packages and
// subpackages of "encoding" you may include the configuration:
//
// -- .wrapcheck.yaml
// ignorePackageGlobs:
// - encoding/*
IgnorePackageGlobs []string `mapstructure:"ignorePackageGlobs" yaml:"ignorePackageGlobs"`
}
func NewDefaultConfig() WrapcheckConfig {
return WrapcheckConfig{
IgnoreSigs: DefaultIgnoreSigs,
IgnoreSigRegexps: []string{},
IgnorePackageGlobs: []string{},
}
}
func NewAnalyzer(cfg WrapcheckConfig) *analysis.Analyzer {
return &analysis.Analyzer{
Name: "wrapcheck",
Doc: "Checks that errors returned from external packages are wrapped",
Run: run(cfg),
}
}
func run(cfg WrapcheckConfig) func(*analysis.Pass) (interface{}, error) {
// Precompile the regexps, report the error
ignoreSigRegexp, err := compileRegexps(cfg.IgnoreSigRegexps)
return func(pass *analysis.Pass) (interface{}, error) {
if err != nil {
return nil, err
}
for _, file := range pass.Files {
ast.Inspect(file, func(n ast.Node) bool {
ret, ok := n.(*ast.ReturnStmt)
if !ok {
return true
}
if len(ret.Results) < 1 {
return true
}
// Iterate over the values to be returned looking for errors
for _, expr := range ret.Results {
// Check if the return expression is a function call, if it is, we need
// to handle it by checking the return params of the function.
retFn, ok := expr.(*ast.CallExpr)
if ok {
// If the return type of the function is a single error. This will not
// match an error within multiple return values, for that, the below
// tuple check is required.
if isError(pass.TypesInfo.TypeOf(expr)) {
reportUnwrapped(pass, retFn, retFn.Pos(), cfg, ignoreSigRegexp)
return true
}
// Check if one of the return values from the function is an error
tup, ok := pass.TypesInfo.TypeOf(expr).(*types.Tuple)
if !ok {
return true
}
// Iterate over the return values of the function looking for error
// types
for i := 0; i < tup.Len(); i++ {
v := tup.At(i)
if v == nil {
return true
}
if isError(v.Type()) {
reportUnwrapped(pass, retFn, expr.Pos(), cfg, ignoreSigRegexp)
return true
}
}
}
if !isError(pass.TypesInfo.TypeOf(expr)) {
continue
}
ident, ok := expr.(*ast.Ident)
if !ok {
return true
}
var call *ast.CallExpr
// Attempt to find the most recent short assign
if shortAss := prevErrAssign(pass, file, ident); shortAss != nil {
call, ok = shortAss.Rhs[0].(*ast.CallExpr)
if !ok {
return true
}
} else if isUnresolved(file, ident) {
// TODO Check if the identifier is unresolved, and try to resolve it in
// another file.
return true
} else {
// Check for ValueSpec nodes in order to locate a possible var
// declaration.
if ident.Obj == nil {
return true
}
vSpec, ok := ident.Obj.Decl.(*ast.ValueSpec)
if !ok {
// We couldn't find a short or var assign for this error return.
// This is an error. Where did this identifier come from? Possibly a
// function param.
//
// TODO decide how to handle this case, whether to follow function
// param back, or assert wrapping at call site.
return true
}
if len(vSpec.Values) < 1 {
return true
}
call, ok = vSpec.Values[0].(*ast.CallExpr)
if !ok {
return true
}
}
// Make sure there is a call identified as producing the error being
// returned, otherwise just bail
if call == nil {
return true
}
reportUnwrapped(pass, call, ident.NamePos, cfg, ignoreSigRegexp)
}
return true
})
}
return nil, nil
}
}
// Report unwrapped takes a call expression and an identifier and reports
// if the call is unwrapped.
func reportUnwrapped(pass *analysis.Pass, call *ast.CallExpr, tokenPos token.Pos, cfg WrapcheckConfig, regexps []*regexp.Regexp) {
sel, ok := call.Fun.(*ast.SelectorExpr)
if !ok {
return
}
// Check for ignored signatures
fnSig := pass.TypesInfo.ObjectOf(sel.Sel).String()
if contains(cfg.IgnoreSigs, fnSig) {
return
} else if containsMatch(regexps, fnSig) {
return
}
// Check if the underlying type of the "x" in x.y.z is an interface, as
// errors returned from interface types should be wrapped.
if isInterface(pass, sel) {
pass.Reportf(tokenPos, "error returned from interface method should be wrapped: sig: %s", fnSig)
return
}
// Check whether the function being called comes from another package,
// as functions called across package boundaries which returns errors
// should be wrapped
if isFromOtherPkg(pass, sel, cfg) {
pass.Reportf(tokenPos, "error returned from external package is unwrapped: sig: %s", fnSig)
return
}
}
// isInterface returns whether the function call is one defined on an interface.
func isInterface(pass *analysis.Pass, sel *ast.SelectorExpr) bool {
_, ok := pass.TypesInfo.TypeOf(sel.X).Underlying().(*types.Interface)
return ok
}
// isFromotherPkg returns whether the function is defined in the pacakge
// currently under analysis or is considered external. It will ignore packages
// defined in config.IgnorePackageGlobs.
func isFromOtherPkg(pass *analysis.Pass, sel *ast.SelectorExpr, config WrapcheckConfig) bool {
// The package of the function that we are calling which returns the error
fn := pass.TypesInfo.ObjectOf(sel.Sel)
for _, globString := range config.IgnorePackageGlobs {
g, err := glob.Compile(globString)
if err != nil {
log.Printf("unable to parse glob: %s\n", globString)
os.Exit(1)
}
if g.Match(fn.Pkg().Path()) {
return false
}
}
// If it's not a package name, then we should check the selector to make sure
// that it's an identifier from the same package
if pass.Pkg.Path() == fn.Pkg().Path() {
return false
}
return true
}
// prevErrAssign traverses the AST of a file looking for the most recent
// assignment to an error declaration which is specified by the returnIdent
// identifier.
//
// This only returns short form assignments and reassignments, e.g. `:=` and
// `=`. This does not include `var` statements. This function will return nil if
// the only declaration is a `var` (aka ValueSpec) declaration.
func prevErrAssign(pass *analysis.Pass, file *ast.File, returnIdent *ast.Ident) *ast.AssignStmt {
// A slice containing all the assignments which contain an identifer
// referring to the source declaration of the error. This is to catch
// cases where err is defined once, and then reassigned multiple times
// within the same block. In these cases, we should check the method of
// the most recent call.
var assigns []*ast.AssignStmt
// Find all assignments which have the same declaration
ast.Inspect(file, func(n ast.Node) bool {
if ass, ok := n.(*ast.AssignStmt); ok {
for _, expr := range ass.Lhs {
if !isError(pass.TypesInfo.TypeOf(expr)) {
continue
}
if assIdent, ok := expr.(*ast.Ident); ok {
if assIdent.Obj == nil || returnIdent.Obj == nil {
// If we can't find the Obj for one of the identifiers, just skip
// it.
return true
} else if assIdent.Obj.Decl == returnIdent.Obj.Decl {
assigns = append(assigns, ass)
}
}
}
}
return true
})
// Iterate through the assignments, comparing the token positions to
// find the assignment that directly precedes the return position
var mostRecentAssign *ast.AssignStmt
for _, ass := range assigns {
if ass.Pos() > returnIdent.Pos() {
break
}
mostRecentAssign = ass
}
return mostRecentAssign
}
func contains(slice []string, el string) bool {
for _, s := range slice {
if strings.Contains(el, s) {
return true
}
}
return false
}
func containsMatch(regexps []*regexp.Regexp, el string) bool {
for _, re := range regexps {
if re.MatchString(el) {
return true
}
}
return false
}
// isError returns whether or not the provided type interface is an error
func isError(typ types.Type) bool {
if typ == nil {
return false
}
return typ.String() == "error"
}
func isUnresolved(file *ast.File, ident *ast.Ident) bool {
for _, unresolvedIdent := range file.Unresolved {
if unresolvedIdent.Pos() == ident.Pos() {
return true
}
}
return false
}
// compileRegexps compiles a set of regular expressions returning them for use,
// or the first encountered error due to an invalid expression.
func compileRegexps(regexps []string) ([]*regexp.Regexp, error) {
var compiledRegexps []*regexp.Regexp
for _, reg := range regexps {
re, err := regexp.Compile(reg)
if err != nil {
return nil, fmt.Errorf("unable to compile regexp %s: %v\n", reg, err)
}
compiledRegexps = append(compiledRegexps, re)
}
return compiledRegexps, nil
}