blob: b7b2292e4e3069421c05ee6f1b7b8d4f783df4ea [file] [log] [blame]
// 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 source
import (
"bytes"
"context"
"fmt"
"go/format"
"go/parser"
"go/token"
"go/types"
"io"
"path"
"strings"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/gopls/internal/bug"
"golang.org/x/tools/gopls/internal/lsp/analysis/stubmethods"
"golang.org/x/tools/gopls/internal/lsp/protocol"
"golang.org/x/tools/gopls/internal/lsp/safetoken"
"golang.org/x/tools/internal/tokeninternal"
"golang.org/x/tools/internal/typeparams"
)
// stubSuggestedFixFunc returns a suggested fix to declare the missing
// methods of the concrete type that is assigned to an interface type
// at the cursor position.
func stubSuggestedFixFunc(ctx context.Context, snapshot Snapshot, fh FileHandle, rng protocol.Range) (*token.FileSet, *analysis.SuggestedFix, error) {
pkg, pgf, err := NarrowestPackageForFile(ctx, snapshot, fh.URI())
if err != nil {
return nil, nil, fmt.Errorf("GetTypedFile: %w", err)
}
start, end, err := pgf.RangePos(rng)
if err != nil {
return nil, nil, err
}
nodes, _ := astutil.PathEnclosingInterval(pgf.File, start, end)
si := stubmethods.GetStubInfo(pkg.FileSet(), pkg.GetTypesInfo(), nodes, start)
if si == nil {
return nil, nil, fmt.Errorf("nil interface request")
}
return stub(ctx, snapshot, si)
}
// stub returns a suggested fix to declare the missing methods of si.Concrete.
func stub(ctx context.Context, snapshot Snapshot, si *stubmethods.StubInfo) (*token.FileSet, *analysis.SuggestedFix, error) {
// A function-local type cannot be stubbed
// since there's nowhere to put the methods.
conc := si.Concrete.Obj()
if conc.Parent() != conc.Pkg().Scope() {
return nil, nil, fmt.Errorf("local type %q cannot be stubbed", conc.Name())
}
// Parse the file declaring the concrete type.
declPGF, _, err := parseFull(ctx, snapshot, si.Fset, conc.Pos())
if err != nil {
return nil, nil, fmt.Errorf("failed to parse file %q declaring implementation type: %w", declPGF.URI, err)
}
if declPGF.Fixed() {
return nil, nil, fmt.Errorf("file contains parse errors: %s", declPGF.URI)
}
// Build import environment for the declaring file.
importEnv := make(map[ImportPath]string) // value is local name
for _, imp := range declPGF.File.Imports {
importPath := UnquoteImportPath(imp)
var name string
if imp.Name != nil {
name = imp.Name.Name
if name == "_" {
continue
} else if name == "." {
name = "" // see types.Qualifier
}
} else {
// TODO(adonovan): may omit a vendor/ prefix; consult the Metadata.
name = path.Base(string(importPath))
}
importEnv[importPath] = name // latest alias wins
}
// Find subset of interface methods that the concrete type lacks.
var missing []*types.Func
ifaceType := si.Interface.Type().Underlying().(*types.Interface)
for i := 0; i < ifaceType.NumMethods(); i++ {
imethod := ifaceType.Method(i)
cmethod, _, _ := types.LookupFieldOrMethod(si.Concrete, si.Pointer, imethod.Pkg(), imethod.Name())
if cmethod == nil {
missing = append(missing, imethod)
continue
}
if _, ok := cmethod.(*types.Var); ok {
// len(LookupFieldOrMethod.index) = 1 => conflict, >1 => shadow.
return nil, nil, fmt.Errorf("adding method %s.%s would conflict with (or shadow) existing field",
conc.Name(), imethod.Name())
}
if !types.Identical(cmethod.Type(), imethod.Type()) {
return nil, nil, fmt.Errorf("method %s.%s already exists but has the wrong type: got %s, want %s",
conc.Name(), imethod.Name(), cmethod.Type(), imethod.Type())
}
}
if len(missing) == 0 {
return nil, nil, fmt.Errorf("no missing methods found")
}
// Create a package name qualifier that uses the
// locally appropriate imported package name.
// It records any needed new imports.
// TODO(adonovan): factor with source.FormatVarType, stubmethods.RelativeToFiles?
//
// Prior to CL 469155 this logic preserved any renaming
// imports from the file that declares the interface
// method--ostensibly the preferred name for imports of
// frequently renamed packages such as protobufs.
// Now we use the package's declared name. If this turns out
// to be a mistake, then use parseHeader(si.iface.Pos()).
//
type newImport struct{ name, importPath string }
var newImports []newImport // for AddNamedImport
qual := func(pkg *types.Package) string {
// TODO(adonovan): don't ignore vendor prefix.
importPath := ImportPath(pkg.Path())
name, ok := importEnv[importPath]
if !ok {
// Insert new import using package's declared name.
//
// TODO(adonovan): resolve conflict between declared
// name and existing file-level (declPGF.File.Imports)
// or package-level (si.Concrete.Pkg.Scope) decls by
// generating a fresh name.
name = pkg.Name()
importEnv[importPath] = name
new := newImport{importPath: string(importPath)}
// For clarity, use a renaming import whenever the
// local name does not match the path's last segment.
if name != path.Base(new.importPath) {
new.name = name
}
newImports = append(newImports, new)
}
return name
}
// Format interface name (used only in a comment).
iface := si.Interface.Name()
if ipkg := si.Interface.Pkg(); ipkg != nil && ipkg != conc.Pkg() {
iface = ipkg.Name() + "." + iface
}
// Pointer receiver?
var star string
if si.Pointer {
star = "*"
}
// Format the new methods.
var newMethods bytes.Buffer
for _, method := range missing {
fmt.Fprintf(&newMethods, `// %s implements %s.
func (%s%s%s) %s%s {
panic("unimplemented")
}
`,
method.Name(),
iface,
star,
si.Concrete.Obj().Name(),
FormatTypeParams(typeparams.ForNamed(si.Concrete)),
method.Name(),
strings.TrimPrefix(types.TypeString(method.Type(), qual), "func"))
}
// Compute insertion point for new methods:
// after the top-level declaration enclosing the (package-level) type.
insertOffset, err := safetoken.Offset(declPGF.Tok, declPGF.File.End())
if err != nil {
return nil, nil, bug.Errorf("internal error: end position outside file bounds: %v", err)
}
concOffset, err := safetoken.Offset(si.Fset.File(conc.Pos()), conc.Pos())
if err != nil {
return nil, nil, bug.Errorf("internal error: finding type decl offset: %v", err)
}
for _, decl := range declPGF.File.Decls {
declEndOffset, err := safetoken.Offset(declPGF.Tok, decl.End())
if err != nil {
return nil, nil, bug.Errorf("internal error: finding decl offset: %v", err)
}
if declEndOffset > concOffset {
insertOffset = declEndOffset
break
}
}
// Splice the new methods into the file content.
var buf bytes.Buffer
input := declPGF.Mapper.Content // unfixed content of file
buf.Write(input[:insertOffset])
buf.WriteByte('\n')
io.Copy(&buf, &newMethods)
buf.Write(input[insertOffset:])
// Re-parse the file.
fset := token.NewFileSet()
newF, err := parser.ParseFile(fset, declPGF.File.Name.Name, buf.Bytes(), parser.ParseComments)
if err != nil {
return nil, nil, fmt.Errorf("could not reparse file: %w", err)
}
// Splice the new imports into the syntax tree.
for _, imp := range newImports {
astutil.AddNamedImport(fset, newF, imp.name, imp.importPath)
}
// Pretty-print.
var output strings.Builder
if err := format.Node(&output, fset, newF); err != nil {
return nil, nil, fmt.Errorf("format.Node: %w", err)
}
// Report the diff.
diffs := snapshot.View().Options().ComputeEdits(string(input), output.String())
var edits []analysis.TextEdit
for _, edit := range diffs {
edits = append(edits, analysis.TextEdit{
Pos: declPGF.Tok.Pos(edit.Start),
End: declPGF.Tok.Pos(edit.End),
NewText: []byte(edit.New),
})
}
return tokeninternal.FileSetFor(declPGF.Tok), // edits use declPGF.Tok
&analysis.SuggestedFix{TextEdits: edits},
nil
}