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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package embeddirective
import (
_ "embed"
"go/ast"
"go/token"
"go/types"
"strings"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/internal/aliases"
"golang.org/x/tools/internal/analysisinternal"
)
//go:embed doc.go
var doc string
var Analyzer = &analysis.Analyzer{
Name: "embed",
Doc: analysisinternal.MustExtractDoc(doc, "embed"),
Run: run,
RunDespiteErrors: true,
URL: "https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/embeddirective",
}
const FixCategory = "addembedimport" // recognized by gopls ApplyFix
func run(pass *analysis.Pass) (interface{}, error) {
for _, f := range pass.Files {
comments := embedDirectiveComments(f)
if len(comments) == 0 {
continue // nothing to check
}
hasEmbedImport := false
for _, imp := range f.Imports {
if imp.Path.Value == `"embed"` {
hasEmbedImport = true
break
}
}
for _, c := range comments {
pos, end := c.Pos(), c.Pos()+token.Pos(len("//go:embed"))
if !hasEmbedImport {
pass.Report(analysis.Diagnostic{
Pos: pos,
End: end,
Message: `must import "embed" when using go:embed directives`,
Category: FixCategory,
SuggestedFixes: []analysis.SuggestedFix{{
Message: `Add missing "embed" import`,
// No TextEdits => computed by a gopls command.
}},
})
}
var msg string
spec := nextVarSpec(c, f)
switch {
case spec == nil:
msg = `go:embed directives must precede a "var" declaration`
case len(spec.Names) != 1:
msg = "declarations following go:embed directives must define a single variable"
case len(spec.Values) > 0:
msg = "declarations following go:embed directives must not specify a value"
case !embeddableType(pass.TypesInfo.Defs[spec.Names[0]]):
msg = "declarations following go:embed directives must be of type string, []byte or embed.FS"
}
if msg != "" {
pass.Report(analysis.Diagnostic{
Pos: pos,
End: end,
Message: msg,
})
}
}
}
return nil, nil
}
// embedDirectiveComments returns all comments in f that contains a //go:embed directive.
func embedDirectiveComments(f *ast.File) []*ast.Comment {
comments := []*ast.Comment{}
for _, cg := range f.Comments {
for _, c := range cg.List {
if strings.HasPrefix(c.Text, "//go:embed ") {
comments = append(comments, c)
}
}
}
return comments
}
// nextVarSpec returns the ValueSpec for the variable declaration immediately following
// the go:embed comment, or nil if the next declaration is not a variable declaration.
func nextVarSpec(com *ast.Comment, f *ast.File) *ast.ValueSpec {
// Embed directives must be followed by a declaration of one variable with no value.
// There may be comments and empty lines between the directive and the declaration.
var nextDecl ast.Decl
for _, d := range f.Decls {
if com.End() < d.End() {
nextDecl = d
break
}
}
if nextDecl == nil || nextDecl.Pos() == token.NoPos {
return nil
}
decl, ok := nextDecl.(*ast.GenDecl)
if !ok {
return nil
}
if decl.Tok != token.VAR {
return nil
}
// var declarations can be both freestanding and blocks (with parenthesis).
// Only the first variable spec following the directive is interesting.
var nextSpec ast.Spec
for _, s := range decl.Specs {
if com.End() < s.End() {
nextSpec = s
break
}
}
if nextSpec == nil {
return nil
}
spec, ok := nextSpec.(*ast.ValueSpec)
if !ok {
// Invalid AST, but keep going.
return nil
}
return spec
}
// embeddableType in go:embed directives are string, []byte or embed.FS.
func embeddableType(o types.Object) bool {
if o == nil {
return false
}
// For embed.FS the underlying type is an implementation detail.
// As long as the named type resolves to embed.FS, it is OK.
if named, ok := aliases.Unalias(o.Type()).(*types.Named); ok {
obj := named.Obj()
if obj.Pkg() != nil && obj.Pkg().Path() == "embed" && obj.Name() == "FS" {
return true
}
}
switch v := o.Type().Underlying().(type) {
case *types.Basic:
return types.Identical(v, types.Typ[types.String])
case *types.Slice:
return types.Identical(v.Elem(), types.Typ[types.Byte])
}
return false
}
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