gopls/internal/lsp/analysis/undeclaredname/undeclared.go - tools - Git at Google

 // 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/format"
 	"go/token"
 	"go/types"
 	"strings"
 	"unicode"

 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/gopls/internal/lsp/safetoken"
 	"golang.org/x/tools/internal/analysisinternal"
 )

 const Doc = `suggested fixes for "undeclared name: <>"

 This checker provides suggested fixes for type errors of the
 type "undeclared name: <>". It will either insert a new statement,
 such as:

 "<> := "

 or a new function declaration, such as:

 func <>(inferred parameters) {
 	panic("implement me!")
 }
 `

 var Analyzer = &analysis.Analyzer{
 	Name:             "undeclaredname",
 	Doc:              Doc,
 	Requires:         []*analysis.Analyzer{},
 	Run:              run,
 	RunDespiteErrors: true,
 }

 // The prefix for this error message changed in Go 1.20.
 var undeclaredNamePrefixes = []string{"undeclared name: ", "undefined: "}

 func run(pass *analysis.Pass) (interface{}, error) {
 	for _, err := range pass.TypeErrors {
 		runForError(pass, err)
 	}
 	return nil, nil
 }

 func runForError(pass *analysis.Pass, err types.Error) {
 	var name string
 	for _, prefix := range undeclaredNamePrefixes {
 		if !strings.HasPrefix(err.Msg, prefix) {
 			continue
 		}
 		name = strings.TrimPrefix(err.Msg, prefix)
 	}
 	if name == "" {
 		return
 	}
 	var file *ast.File
 	for _, f := range pass.Files {
 		if f.Pos() <= err.Pos && err.Pos < f.End() {
 			file = f
 			break
 		}
 	}
 	if file == nil {
 		return
 	}

 	// Get the path for the relevant range.
 	path, _ := astutil.PathEnclosingInterval(file, err.Pos, err.Pos)
 	if len(path) < 2 {
 		return
 	}
 	ident, ok := path[0].(*ast.Ident)
 	if !ok || ident.Name != name {
 		return
 	}

 	// Undeclared quick fixes only work in function bodies.
 	inFunc := false
 	for i := range path {
 		if _, inFunc = path[i].(*ast.FuncDecl); inFunc {
 			if i == 0 {
 				return
 			}
 			if _, isBody := path[i-1].(*ast.BlockStmt); !isBody {
 				return
 			}
 			break
 		}
 	}
 	if !inFunc {
 		return
 	}
 	// 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 {
 		return
 	}
 	tok := pass.Fset.File(file.Pos())
 	if tok == nil {
 		return
 	}
 	offset := safetoken.StartPosition(pass.Fset, err.Pos).Offset
 	end := tok.Pos(offset + len(name)) // TODO(adonovan): dubious! err.Pos + len(name)??
 	pass.Report(analysis.Diagnostic{
 		Pos:     err.Pos,
 		End:     end,
 		Message: err.Msg,
 	})
 }

 func SuggestedFix(fset *token.FileSet, start, end token.Pos, content []byte, file *ast.File, pkg *types.Package, info *types.Info) (*analysis.SuggestedFix, error) {
 	pos := start // don't use the end
 	path, _ := astutil.PathEnclosingInterval(file, pos, pos)
 	if len(path) < 2 {
 		return nil, fmt.Errorf("no expression found")
 	}
 	ident, ok := path[0].(*ast.Ident)
 	if !ok {
 		return nil, fmt.Errorf("no identifier found")
 	}

 	// Check for a possible call expression, in which case we should add a
 	// new function declaration.
 	if len(path) > 1 {
 		if _, ok := path[1].(*ast.CallExpr); ok {
 			return newFunctionDeclaration(path, file, pkg, info, fset)
 		}
 	}

 	// Get the place to insert the new statement.
 	insertBeforeStmt := analysisinternal.StmtToInsertVarBefore(path)
 	if insertBeforeStmt == nil {
 		return nil, fmt.Errorf("could not locate insertion point")
 	}

 	insertBefore := safetoken.StartPosition(fset, 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 newFunctionDeclaration(path []ast.Node, file *ast.File, pkg *types.Package, info *types.Info, fset *token.FileSet) (*analysis.SuggestedFix, error) {
 	if len(path) < 3 {
 		return nil, fmt.Errorf("unexpected set of enclosing nodes: %v", path)
 	}
 	ident, ok := path[0].(*ast.Ident)
 	if !ok {
 		return nil, fmt.Errorf("no name for function declaration %v (%T)", path[0], path[0])
 	}
 	call, ok := path[1].(*ast.CallExpr)
 	if !ok {
 		return nil, fmt.Errorf("no call expression found %v (%T)", path[1], path[1])
 	}

 	// Find the enclosing function, so that we can add the new declaration
 	// below.
 	var enclosing *ast.FuncDecl
 	for _, n := range path {
 		if n, ok := n.(*ast.FuncDecl); ok {
 			enclosing = n
 			break
 		}
 	}
 	// TODO(rstambler): Support the situation when there is no enclosing
 	// function.
 	if enclosing == nil {
 		return nil, fmt.Errorf("no enclosing function found: %v", path)
 	}

 	pos := enclosing.End()

 	var paramNames []string
 	var paramTypes []types.Type
 	// keep track of all param names to later ensure uniqueness
 	nameCounts := map[string]int{}
 	for _, arg := range call.Args {
 		typ := info.TypeOf(arg)
 		if typ == nil {
 			return nil, fmt.Errorf("unable to determine type for %s", arg)
 		}

 		switch t := typ.(type) {
 		// this is the case where another function call returning multiple
 		// results is used as an argument
 		case *types.Tuple:
 			n := t.Len()
 			for i := 0; i < n; i++ {
 				name := typeToArgName(t.At(i).Type())
 				nameCounts[name]++

 				paramNames = append(paramNames, name)
 				paramTypes = append(paramTypes, types.Default(t.At(i).Type()))
 			}

 		default:
 			// does the argument have a name we can reuse?
 			// only happens in case of a *ast.Ident
 			var name string
 			if ident, ok := arg.(*ast.Ident); ok {
 				name = ident.Name
 			}

 			if name == "" {
 				name = typeToArgName(typ)
 			}

 			nameCounts[name]++

 			paramNames = append(paramNames, name)
 			paramTypes = append(paramTypes, types.Default(typ))
 		}
 	}

 	for n, c := range nameCounts {
 		// Any names we saw more than once will need a unique suffix added
 		// on. Reset the count to 1 to act as the suffix for the first
 		// occurrence of that name.
 		if c >= 2 {
 			nameCounts[n] = 1
 		} else {
 			delete(nameCounts, n)
 		}
 	}

 	params := &ast.FieldList{}

 	for i, name := range paramNames {
 		if suffix, repeats := nameCounts[name]; repeats {
 			nameCounts[name]++
 			name = fmt.Sprintf("%s%d", name, suffix)
 		}

 		// only worth checking after previous param in the list
 		if i > 0 {
 			// if type of parameter at hand is the same as the previous one,
 			// add it to the previous param list of identifiers so to have:
 			//  (s1, s2 string)
 			// and not
 			//  (s1 string, s2 string)
 			if paramTypes[i] == paramTypes[i-1] {
 				params.List[len(params.List)-1].Names = append(params.List[len(params.List)-1].Names, ast.NewIdent(name))
 				continue
 			}
 		}

 		params.List = append(params.List, &ast.Field{
 			Names: []*ast.Ident{
 				ast.NewIdent(name),
 			},
 			Type: analysisinternal.TypeExpr(file, pkg, paramTypes[i]),
 		})
 	}

 	decl := &ast.FuncDecl{
 		Name: ast.NewIdent(ident.Name),
 		Type: &ast.FuncType{
 			Params: params,
 			// TODO(rstambler): Also handle result parameters here.
 		},
 		Body: &ast.BlockStmt{
 			List: []ast.Stmt{
 				&ast.ExprStmt{
 					X: &ast.CallExpr{
 						Fun: ast.NewIdent("panic"),
 						Args: []ast.Expr{
 							&ast.BasicLit{
 								Value: `"unimplemented"`,
 							},
 						},
 					},
 				},
 			},
 		},
 	}

 	b := bytes.NewBufferString("\n\n")
 	if err := format.Node(b, fset, decl); err != nil {
 		return nil, err
 	}
 	return &analysis.SuggestedFix{
 		Message: fmt.Sprintf("Create function \"%s\"", ident.Name),
 		TextEdits: []analysis.TextEdit{{
 			Pos:     pos,
 			End:     pos,
 			NewText: b.Bytes(),
 		}},
 	}, nil
 }
 func typeToArgName(ty types.Type) string {
 	s := types.Default(ty).String()

 	switch t := ty.(type) {
 	case *types.Basic:
 		// use first letter in type name for basic types
 		return s[0:1]
 	case *types.Slice:
 		// use element type to decide var name for slices
 		return typeToArgName(t.Elem())
 	case *types.Array:
 		// use element type to decide var name for arrays
 		return typeToArgName(t.Elem())
 	case *types.Chan:
 		return "ch"
 	}

 	s = strings.TrimFunc(s, func(r rune) bool {
 		return !unicode.IsLetter(r)
 	})

 	if s == "error" {
 		return "err"
 	}

 	// remove package (if present)
 	// and make first letter lowercase
 	a := []rune(s[strings.LastIndexByte(s, '.')+1:])
 	a[0] = unicode.ToLower(a[0])
 	return string(a)
 }
	// 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/format"
	"go/token"
	"go/types"
	"strings"
	"unicode"

	"golang.org/x/tools/go/analysis"
	"golang.org/x/tools/go/ast/astutil"
	"golang.org/x/tools/gopls/internal/lsp/safetoken"
	"golang.org/x/tools/internal/analysisinternal"
	)

	const Doc = `suggested fixes for "undeclared name: <>"

	This checker provides suggested fixes for type errors of the
	type "undeclared name: <>". It will either insert a new statement,
	such as:

	"<> := "

	or a new function declaration, such as:

	func <>(inferred parameters) {
	panic("implement me!")
	}
	`

	var Analyzer = &analysis.Analyzer{
	Name: "undeclaredname",
	Doc: Doc,
	Requires: []*analysis.Analyzer{},
	Run: run,
	RunDespiteErrors: true,
	}

	// The prefix for this error message changed in Go 1.20.
	var undeclaredNamePrefixes = []string{"undeclared name: ", "undefined: "}

	func run(pass *analysis.Pass) (interface{}, error) {
	for _, err := range pass.TypeErrors {
	runForError(pass, err)
	}
	return nil, nil
	}

	func runForError(pass *analysis.Pass, err types.Error) {
	var name string
	for _, prefix := range undeclaredNamePrefixes {
	if !strings.HasPrefix(err.Msg, prefix) {
	continue
	}
	name = strings.TrimPrefix(err.Msg, prefix)
	}
	if name == "" {
	return
	}
	var file *ast.File
	for _, f := range pass.Files {
	if f.Pos() <= err.Pos && err.Pos < f.End() {
	file = f
	break
	}
	}
	if file == nil {
	return
	}

	// Get the path for the relevant range.
	path, _ := astutil.PathEnclosingInterval(file, err.Pos, err.Pos)
	if len(path) < 2 {
	return
	}
	ident, ok := path[0].(*ast.Ident)
	if !ok \|\| ident.Name != name {
	return
	}

	// Undeclared quick fixes only work in function bodies.
	inFunc := false
	for i := range path {
	if _, inFunc = path[i].(*ast.FuncDecl); inFunc {
	if i == 0 {
	return
	}
	if _, isBody := path[i-1].(*ast.BlockStmt); !isBody {
	return
	}
	break
	}
	}
	if !inFunc {
	return
	}
	// 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 {
	return
	}
	tok := pass.Fset.File(file.Pos())
	if tok == nil {
	return
	}
	offset := safetoken.StartPosition(pass.Fset, err.Pos).Offset
	end := tok.Pos(offset + len(name)) // TODO(adonovan): dubious! err.Pos + len(name)??
	pass.Report(analysis.Diagnostic{
	Pos: err.Pos,
	End: end,
	Message: err.Msg,
	})
	}

	func SuggestedFix(fset token.FileSet, start, end token.Pos, content []byte, file ast.File, pkg types.Package, info types.Info) (*analysis.SuggestedFix, error) {
	pos := start // don't use the end
	path, _ := astutil.PathEnclosingInterval(file, pos, pos)
	if len(path) < 2 {
	return nil, fmt.Errorf("no expression found")
	}
	ident, ok := path[0].(*ast.Ident)
	if !ok {
	return nil, fmt.Errorf("no identifier found")
	}

	// Check for a possible call expression, in which case we should add a
	// new function declaration.
	if len(path) > 1 {
	if _, ok := path[1].(*ast.CallExpr); ok {
	return newFunctionDeclaration(path, file, pkg, info, fset)
	}
	}

	// Get the place to insert the new statement.
	insertBeforeStmt := analysisinternal.StmtToInsertVarBefore(path)
	if insertBeforeStmt == nil {
	return nil, fmt.Errorf("could not locate insertion point")
	}

	insertBefore := safetoken.StartPosition(fset, 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 newFunctionDeclaration(path []ast.Node, file ast.File, pkg types.Package, info types.Info, fset token.FileSet) (*analysis.SuggestedFix, error) {
	if len(path) < 3 {
	return nil, fmt.Errorf("unexpected set of enclosing nodes: %v", path)
	}
	ident, ok := path[0].(*ast.Ident)
	if !ok {
	return nil, fmt.Errorf("no name for function declaration %v (%T)", path[0], path[0])
	}
	call, ok := path[1].(*ast.CallExpr)
	if !ok {
	return nil, fmt.Errorf("no call expression found %v (%T)", path[1], path[1])
	}

	// Find the enclosing function, so that we can add the new declaration
	// below.
	var enclosing *ast.FuncDecl
	for _, n := range path {
	if n, ok := n.(*ast.FuncDecl); ok {
	enclosing = n
	break
	}
	}
	// TODO(rstambler): Support the situation when there is no enclosing
	// function.
	if enclosing == nil {
	return nil, fmt.Errorf("no enclosing function found: %v", path)
	}

	pos := enclosing.End()

	var paramNames []string
	var paramTypes []types.Type
	// keep track of all param names to later ensure uniqueness
	nameCounts := map[string]int{}
	for _, arg := range call.Args {
	typ := info.TypeOf(arg)
	if typ == nil {
	return nil, fmt.Errorf("unable to determine type for %s", arg)
	}

	switch t := typ.(type) {
	// this is the case where another function call returning multiple
	// results is used as an argument
	case *types.Tuple:
	n := t.Len()
	for i := 0; i < n; i++ {
	name := typeToArgName(t.At(i).Type())
	nameCounts[name]++

	paramNames = append(paramNames, name)
	paramTypes = append(paramTypes, types.Default(t.At(i).Type()))
	}

	default:
	// does the argument have a name we can reuse?
	// only happens in case of a *ast.Ident
	var name string
	if ident, ok := arg.(*ast.Ident); ok {
	name = ident.Name
	}

	if name == "" {
	name = typeToArgName(typ)
	}

	nameCounts[name]++

	paramNames = append(paramNames, name)
	paramTypes = append(paramTypes, types.Default(typ))
	}
	}

	for n, c := range nameCounts {
	// Any names we saw more than once will need a unique suffix added
	// on. Reset the count to 1 to act as the suffix for the first
	// occurrence of that name.
	if c >= 2 {
	nameCounts[n] = 1
	} else {
	delete(nameCounts, n)
	}
	}

	params := &ast.FieldList{}

	for i, name := range paramNames {
	if suffix, repeats := nameCounts[name]; repeats {
	nameCounts[name]++
	name = fmt.Sprintf("%s%d", name, suffix)
	}

	// only worth checking after previous param in the list
	if i > 0 {
	// if type of parameter at hand is the same as the previous one,
	// add it to the previous param list of identifiers so to have:
	// (s1, s2 string)
	// and not
	// (s1 string, s2 string)
	if paramTypes[i] == paramTypes[i-1] {
	params.List[len(params.List)-1].Names = append(params.List[len(params.List)-1].Names, ast.NewIdent(name))
	continue
	}
	}

	params.List = append(params.List, &ast.Field{
	Names: []*ast.Ident{
	ast.NewIdent(name),
	},
	Type: analysisinternal.TypeExpr(file, pkg, paramTypes[i]),
	})
	}

	decl := &ast.FuncDecl{
	Name: ast.NewIdent(ident.Name),
	Type: &ast.FuncType{
	Params: params,
	// TODO(rstambler): Also handle result parameters here.
	},
	Body: &ast.BlockStmt{
	List: []ast.Stmt{
	&ast.ExprStmt{
	X: &ast.CallExpr{
	Fun: ast.NewIdent("panic"),
	Args: []ast.Expr{
	&ast.BasicLit{
	Value: `"unimplemented"`,
	},
	},
	},
	},
	},
	},
	}

	b := bytes.NewBufferString("\n\n")
	if err := format.Node(b, fset, decl); err != nil {
	return nil, err
	}
	return &analysis.SuggestedFix{
	Message: fmt.Sprintf("Create function \"%s\"", ident.Name),
	TextEdits: []analysis.TextEdit{{
	Pos: pos,
	End: pos,
	NewText: b.Bytes(),
	}},
	}, nil
	}
	func typeToArgName(ty types.Type) string {
	s := types.Default(ty).String()

	switch t := ty.(type) {
	case *types.Basic:
	// use first letter in type name for basic types
	return s[0:1]
	case *types.Slice:
	// use element type to decide var name for slices
	return typeToArgName(t.Elem())
	case *types.Array:
	// use element type to decide var name for arrays
	return typeToArgName(t.Elem())
	case *types.Chan:
	return "ch"
	}

	s = strings.TrimFunc(s, func(r rune) bool {
	return !unicode.IsLetter(r)
	})

	if s == "error" {
	return "err"
	}

	// remove package (if present)
	// and make first letter lowercase
	a := []rune(s[strings.LastIndexByte(s, '.')+1:])
	a[0] = unicode.ToLower(a[0])
	return string(a)
	}