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// Copyright 2020 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 undeclaredname defines an Analyzer that applies suggested fixes
// to errors of the type "undeclared name: %s".
package undeclaredname
import (
"bytes"
"fmt"
"go/ast"
"go/token"
"go/types"
"strings"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/internal/analysisinternal"
"golang.org/x/tools/internal/span"
)
const Doc = `suggested fixes for "undeclared name: <>"
This checker provides suggested fixes for type errors of the
type "undeclared name: <>". It will insert a new statement:
"<> := ".`
var Analyzer = &analysis.Analyzer{
Name: string(analysisinternal.UndeclaredName),
Doc: Doc,
Requires: []*analysis.Analyzer{},
Run: run,
RunDespiteErrors: true,
}
const undeclaredNamePrefix = "undeclared name: "
func run(pass *analysis.Pass) (interface{}, error) {
for _, err := range analysisinternal.GetTypeErrors(pass) {
if !FixesError(err.Msg) {
continue
}
name := strings.TrimPrefix(err.Msg, undeclaredNamePrefix)
var file *ast.File
for _, f := range pass.Files {
if f.Pos() <= err.Pos && err.Pos < f.End() {
file = f
break
}
}
if file == nil {
continue
}
// Get the path for the relevant range.
path, _ := astutil.PathEnclosingInterval(file, err.Pos, err.Pos)
if len(path) < 2 {
continue
}
ident, ok := path[0].(*ast.Ident)
if !ok || ident.Name != name {
continue
}
// Skip selector expressions because it might be too complex
// to try and provide a suggested fix for fields and methods.
if _, ok := path[1].(*ast.SelectorExpr); ok {
continue
}
// TODO(golang.org/issue/34644): Handle call expressions with suggested
// fixes to create a function.
if _, ok := path[1].(*ast.CallExpr); ok {
continue
}
tok := pass.Fset.File(file.Pos())
if tok == nil {
continue
}
offset := pass.Fset.Position(err.Pos).Offset
end := tok.Pos(offset + len(name))
pass.Report(analysis.Diagnostic{
Pos: err.Pos,
End: end,
Message: err.Msg,
})
}
return nil, nil
}
func SuggestedFix(fset *token.FileSet, rng span.Range, content []byte, file *ast.File, _ *types.Package, _ *types.Info) (*analysis.SuggestedFix, error) {
pos := rng.Start // don't use the end
path, _ := astutil.PathEnclosingInterval(file, pos, pos)
if len(path) < 2 {
return nil, fmt.Errorf("")
}
ident, ok := path[0].(*ast.Ident)
if !ok {
return nil, fmt.Errorf("")
}
// Get the place to insert the new statement.
insertBeforeStmt := analysisinternal.StmtToInsertVarBefore(path)
if insertBeforeStmt == nil {
return nil, fmt.Errorf("")
}
insertBefore := fset.Position(insertBeforeStmt.Pos()).Offset
// Get the indent to add on the line after the new statement.
// Since this will have a parse error, we can not use format.Source().
contentBeforeStmt, indent := content[:insertBefore], "\n"
if nl := bytes.LastIndex(contentBeforeStmt, []byte("\n")); nl != -1 {
indent = string(contentBeforeStmt[nl:])
}
// Create the new local variable statement.
newStmt := fmt.Sprintf("%s := %s", ident.Name, indent)
return &analysis.SuggestedFix{
Message: fmt.Sprintf("Create variable \"%s\"", ident.Name),
TextEdits: []analysis.TextEdit{{
Pos: insertBeforeStmt.Pos(),
End: insertBeforeStmt.Pos(),
NewText: []byte(newStmt),
}},
}, nil
}
func FixesError(msg string) bool {
return strings.HasPrefix(msg, undeclaredNamePrefix)
}
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