gopls: remove usage of golang.org/x/xerrors

As of golang/go#50827, gopls no longer supports building at 1.12, and so
usage of golang.org/x/xerrors can be replaced with the native support for
error wrapping introduced in Go 1.13.

Remove this usage as a step toward eliminating the xerrors dependency
from x/tools.

For golang/go#52442

Change-Id: Ibf459cc72402a30a6c2735dc620f76ed8a5e2525
Reviewed-on: https://go-review.googlesource.com/c/tools/+/401097
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

internal/lsp/cache/analysis.go

@@ -21,7 +21,6 @@ import (
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/memoize"
 	"golang.org/x/tools/internal/span"
-	errors "golang.org/x/xerrors"
 )
 
 func (s *snapshot) Analyze(ctx context.Context, id string, analyzers []*source.Analyzer) ([]*source.Diagnostic, error) {
@@ -96,7 +95,7 @@ func (s *snapshot) actionHandle(ctx context.Context, id PackageID, a *analysis.A
 		return act, nil
 	}
 	if len(ph.key) == 0 {
-		return nil, errors.Errorf("actionHandle: no key for package %s", id)
+		return nil, fmt.Errorf("actionHandle: no key for package %s", id)
 	}
 	pkg, err := ph.check(ctx, s)
 	if err != nil {
@@ -162,10 +161,10 @@ func (act *actionHandle) analyze(ctx context.Context, snapshot *snapshot) ([]*so
 	}
 	data, ok := d.(*actionData)
 	if !ok {
-		return nil, nil, errors.Errorf("unexpected type for %s:%s", act.pkg.ID(), act.analyzer.Name)
+		return nil, nil, fmt.Errorf("unexpected type for %s:%s", act.pkg.ID(), act.analyzer.Name)
 	}
 	if data == nil {
-		return nil, nil, errors.Errorf("unexpected nil analysis for %s:%s", act.pkg.ID(), act.analyzer.Name)
+		return nil, nil, fmt.Errorf("unexpected nil analysis for %s:%s", act.pkg.ID(), act.analyzer.Name)
 	}
 	return data.diagnostics, data.result, data.err
 }
@@ -192,7 +191,7 @@ func execAll(ctx context.Context, snapshot *snapshot, actions []*actionHandle) (
 			}
 			data, ok := v.(*actionData)
 			if !ok {
-				return errors.Errorf("unexpected type for %s: %T", act, v)
+				return fmt.Errorf("unexpected type for %s: %T", act, v)
 			}
 
 			mu.Lock()
@@ -212,7 +211,7 @@ func runAnalysis(ctx context.Context, snapshot *snapshot, analyzer *analysis.Ana
 	}
 	defer func() {
 		if r := recover(); r != nil {
-			data.err = errors.Errorf("analysis %s for package %s panicked: %v", analyzer.Name, pkg.PkgPath(), r)
+			data.err = fmt.Errorf("analysis %s for package %s panicked: %v", analyzer.Name, pkg.PkgPath(), r)
 		}
 	}()
 
@@ -327,7 +326,7 @@ func runAnalysis(ctx context.Context, snapshot *snapshot, analyzer *analysis.Ana
 	analysisinternal.SetTypeErrors(pass, pkg.typeErrors)
 
 	if pkg.IsIllTyped() {
-		data.err = errors.Errorf("analysis skipped due to errors in package")
+		data.err = fmt.Errorf("analysis skipped due to errors in package")
 		return data
 	}
 	data.result, data.err = pass.Analyzer.Run(pass)
@@ -336,7 +335,7 @@ func runAnalysis(ctx context.Context, snapshot *snapshot, analyzer *analysis.Ana
 	}
 
 	if got, want := reflect.TypeOf(data.result), pass.Analyzer.ResultType; got != want {
-		data.err = errors.Errorf(
+		data.err = fmt.Errorf(
 			"internal error: on package %s, analyzer %s returned a result of type %v, but declared ResultType %v",
 			pass.Pkg.Path(), pass.Analyzer, got, want)
 		return data

internal/lsp/cache/check.go

@@ -7,6 +7,7 @@ package cache
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"go/ast"
 	"go/types"
@@ -29,7 +30,6 @@ import (
 	"golang.org/x/tools/internal/span"
 	"golang.org/x/tools/internal/typeparams"
 	"golang.org/x/tools/internal/typesinternal"
-	errors "golang.org/x/xerrors"
 )
 
 type packageHandleKey string
@@ -144,7 +144,7 @@ func (s *snapshot) buildPackageHandle(ctx context.Context, id PackageID, mode so
 func (s *snapshot) buildKey(ctx context.Context, id PackageID, mode source.ParseMode) (*packageHandle, map[PackagePath]*packageHandle, error) {
 	m := s.getMetadata(id)
 	if m == nil {
-		return nil, nil, errors.Errorf("no metadata for %s", id)
+		return nil, nil, fmt.Errorf("no metadata for %s", id)
 	}
 	goFiles, err := s.parseGoHandles(ctx, m.GoFiles, mode)
 	if err != nil {
@@ -291,7 +291,7 @@ func (ph *packageHandle) ID() string {
 func (ph *packageHandle) cached(g *memoize.Generation) (*pkg, error) {
 	v := ph.handle.Cached(g)
 	if v == nil {
-		return nil, errors.Errorf("no cached type information for %s", ph.m.PkgPath)
+		return nil, fmt.Errorf("no cached type information for %s", ph.m.PkgPath)
 	}
 	data := v.(*packageData)
 	return data.pkg, data.err
@@ -494,7 +494,7 @@ func doTypeCheck(ctx context.Context, snapshot *snapshot, m *Metadata, mode sour
 		if found {
 			return pkg, nil
 		}
-		return nil, errors.Errorf("no parsed files for package %s, expected: %v, errors: %v", pkg.m.PkgPath, pkg.compiledGoFiles, m.Errors)
+		return nil, fmt.Errorf("no parsed files for package %s, expected: %v, errors: %v", pkg.m.PkgPath, pkg.compiledGoFiles, m.Errors)
 	}
 
 	cfg := &types.Config{
@@ -511,7 +511,7 @@ func doTypeCheck(ctx context.Context, snapshot *snapshot, m *Metadata, mode sour
 				return nil, snapshot.missingPkgError(ctx, pkgPath)
 			}
 			if !source.IsValidImport(string(m.PkgPath), string(dep.m.PkgPath)) {
-				return nil, errors.Errorf("invalid use of internal package %s", pkgPath)
+				return nil, fmt.Errorf("invalid use of internal package %s", pkgPath)
 			}
 			depPkg, err := dep.check(ctx, snapshot)
 			if err != nil {

internal/lsp/cache/errors.go

@@ -21,7 +21,6 @@ import (
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/span"
 	"golang.org/x/tools/internal/typesinternal"
-	errors "golang.org/x/xerrors"
 )
 
 func goPackagesErrorDiagnostics(snapshot *snapshot, pkg *pkg, e packages.Error) ([]*source.Diagnostic, error) {
@@ -75,7 +74,7 @@ func goPackagesErrorDiagnostics(snapshot *snapshot, pkg *pkg, e packages.Error)
 func parseErrorDiagnostics(snapshot *snapshot, pkg *pkg, errList scanner.ErrorList) ([]*source.Diagnostic, error) {
 	// The first parser error is likely the root cause of the problem.
 	if errList.Len() <= 0 {
-		return nil, errors.Errorf("no errors in %v", errList)
+		return nil, fmt.Errorf("no errors in %v", errList)
 	}
 	e := errList[0]
 	pgf, err := pkg.File(span.URIFromPath(e.Pos.Filename))

internal/lsp/cache/load.go

@@ -7,6 +7,7 @@ package cache
 import (
 	"context"
 	"crypto/sha256"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -24,7 +25,6 @@ import (
 	"golang.org/x/tools/internal/memoize"
 	"golang.org/x/tools/internal/packagesinternal"
 	"golang.org/x/tools/internal/span"
-	errors "golang.org/x/xerrors"
 )
 
 // load calls packages.Load for the given scopes, updating package metadata,
@@ -135,7 +135,7 @@ func (s *snapshot) load(ctx context.Context, allowNetwork bool, scopes ...interf
 		if err == nil {
 			err = fmt.Errorf("no packages returned")
 		}
-		return errors.Errorf("%v: %w", err, source.PackagesLoadError)
+		return fmt.Errorf("%v: %w", err, source.PackagesLoadError)
 	}
 	for _, pkg := range pkgs {
 		if !containsDir || s.view.Options().VerboseOutput {
@@ -152,7 +152,7 @@ func (s *snapshot) load(ctx context.Context, allowNetwork bool, scopes ...interf
 		// Special case for the builtin package, as it has no dependencies.
 		if pkg.PkgPath == "builtin" {
 			if len(pkg.GoFiles) != 1 {
-				return errors.Errorf("only expected 1 file for builtin, got %v", len(pkg.GoFiles))
+				return fmt.Errorf("only expected 1 file for builtin, got %v", len(pkg.GoFiles))
 			}
 			s.setBuiltin(pkg.GoFiles[0])
 			continue
@@ -213,7 +213,7 @@ You can work with multiple modules by opening each one as a workspace folder.
 Improvements to this workflow will be coming soon, and you can learn more here:
 https://github.com/golang/tools/blob/master/gopls/doc/workspace.md.`
 		return &source.CriticalError{
-			MainError: errors.Errorf(msg),
+			MainError: fmt.Errorf(msg),
 			DiagList:  s.applyCriticalErrorToFiles(ctx, msg, openFiles),
 		}
 	}
@@ -249,7 +249,7 @@ You can learn more here: https://github.com/golang/tools/blob/master/gopls/doc/w
 		}
 		if len(srcDiags) != 0 {
 			return &source.CriticalError{
-				MainError: errors.Errorf(`You are working in a nested module.
+				MainError: fmt.Errorf(`You are working in a nested module.
 Please open it as a separate workspace folder. Learn more:
 https://github.com/golang/tools/blob/master/gopls/doc/workspace.md.`),
 				DiagList: srcDiags,
@@ -374,7 +374,7 @@ func (s *snapshot) setMetadataLocked(ctx context.Context, pkgPath PackagePath, p
 		pkgPath = PackagePath(string(pkgPath) + suffix)
 	}
 	if _, ok := seen[id]; ok {
-		return nil, errors.Errorf("import cycle detected: %q", id)
+		return nil, fmt.Errorf("import cycle detected: %q", id)
 	}
 	// Recreate the metadata rather than reusing it to avoid locking.
 	m := &Metadata{

internal/lsp/cache/parse.go

@@ -26,7 +26,6 @@ import (
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/memoize"
 	"golang.org/x/tools/internal/span"
-	errors "golang.org/x/xerrors"
 )
 
 // parseKey uniquely identifies a parsed Go file.
@@ -249,7 +248,7 @@ func parseGo(ctx context.Context, fset *token.FileSet, fh source.FileHandle, mod
 
 	ext := filepath.Ext(fh.URI().Filename())
 	if ext != ".go" && ext != "" { // files generated by cgo have no extension
-		return &parseGoData{err: errors.Errorf("cannot parse non-Go file %s", fh.URI())}
+		return &parseGoData{err: fmt.Errorf("cannot parse non-Go file %s", fh.URI())}
 	}
 	src, err := fh.Read()
 	if err != nil {
@@ -686,7 +685,7 @@ func fixAST(ctx context.Context, n ast.Node, tok *token.File, src []byte) (fixed
 				// Recursively fix in our fixed node.
 				_ = fixAST(ctx, parent, tok, src)
 			} else {
-				err = errors.Errorf("unable to parse defer or go from *ast.BadStmt: %v", err)
+				err = fmt.Errorf("unable to parse defer or go from *ast.BadStmt: %v", err)
 			}
 			return false
 		case *ast.BadExpr:
@@ -1339,17 +1338,17 @@ func parseStmt(pos token.Pos, src []byte) (ast.Stmt, error) {
 	// best-effort behavior, whereas ParseExpr fails hard on any error.
 	fakeFile, err := parser.ParseFile(token.NewFileSet(), "", fileSrc, 0)
 	if fakeFile == nil {
-		return nil, errors.Errorf("error reading fake file source: %v", err)
+		return nil, fmt.Errorf("error reading fake file source: %v", err)
 	}
 
 	// Extract our expression node from inside the fake file.
 	if len(fakeFile.Decls) == 0 {
-		return nil, errors.Errorf("error parsing fake file: %v", err)
+		return nil, fmt.Errorf("error parsing fake file: %v", err)
 	}
 
 	fakeDecl, _ := fakeFile.Decls[0].(*ast.FuncDecl)
 	if fakeDecl == nil || len(fakeDecl.Body.List) == 0 {
-		return nil, errors.Errorf("no statement in %s: %v", src, err)
+		return nil, fmt.Errorf("no statement in %s: %v", src, err)
 	}
 
 	stmt := fakeDecl.Body.List[0]
@@ -1371,7 +1370,7 @@ func parseExpr(pos token.Pos, src []byte) (ast.Expr, error) {
 
 	exprStmt, ok := stmt.(*ast.ExprStmt)
 	if !ok {
-		return nil, errors.Errorf("no expr in %s: %v", src, err)
+		return nil, fmt.Errorf("no expr in %s: %v", src, err)
 	}
 
 	return exprStmt.X, nil

internal/lsp/cache/pkg.go

@@ -5,14 +5,14 @@
 package cache
 
 import (
+	"fmt"
 	"go/ast"
 	"go/scanner"
 	"go/types"
 
 	"golang.org/x/mod/module"
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/span"
-	errors "golang.org/x/xerrors"
 )
 
 // pkg contains the type information needed by the source package.
@@ -70,7 +70,7 @@ func (p *pkg) File(uri span.URI) (*source.ParsedGoFile, error) {
 			return gf, nil
 		}
 	}
-	return nil, errors.Errorf("no parsed file for %s in %v", uri, p.m.ID)
+	return nil, fmt.Errorf("no parsed file for %s in %v", uri, p.m.ID)
 }
 
 func (p *pkg) GetSyntax() []*ast.File {
@@ -106,7 +106,7 @@ func (p *pkg) GetImport(pkgPath string) (source.Package, error) {
 		return imp, nil
 	}
 	// Don't return a nil pointer because that still satisfies the interface.
-	return nil, errors.Errorf("no imported package for %s", pkgPath)
+	return nil, fmt.Errorf("no imported package for %s", pkgPath)
 }
 
 func (p *pkg) MissingDependencies() []string {

internal/lsp/cache/session.go

@@ -18,7 +18,6 @@ import (
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/span"
 	"golang.org/x/tools/internal/xcontext"
-	errors "golang.org/x/xerrors"
 )
 
 type Session struct {
@@ -404,7 +403,7 @@ func (s *Session) dropView(ctx context.Context, v *View) (int, error) {
 			return i, nil
 		}
 	}
-	return -1, errors.Errorf("view %s for %v not found", v.Name(), v.Folder())
+	return -1, fmt.Errorf("view %s for %v not found", v.Name(), v.Folder())
 }
 
 func (s *Session) ModifyFiles(ctx context.Context, changes []source.FileModification) error {
@@ -614,7 +613,7 @@ func (s *Session) updateOverlays(ctx context.Context, changes []source.FileModif
 			kind = source.FileKindForLang(c.LanguageID)
 		default:
 			if !ok {
-				return nil, errors.Errorf("updateOverlays: modifying unopened overlay %v", c.URI)
+				return nil, fmt.Errorf("updateOverlays: modifying unopened overlay %v", c.URI)
 			}
 			kind = o.kind
 		}
@@ -648,10 +647,10 @@ func (s *Session) updateOverlays(ctx context.Context, changes []source.FileModif
 		case source.Save:
 			// Make sure the version and content (if present) is the same.
 			if false && o.version != version { // Client no longer sends the version
-				return nil, errors.Errorf("updateOverlays: saving %s at version %v, currently at %v", c.URI, c.Version, o.version)
+				return nil, fmt.Errorf("updateOverlays: saving %s at version %v, currently at %v", c.URI, c.Version, o.version)
 			}
 			if c.Text != nil && o.hash != hash {
-				return nil, errors.Errorf("updateOverlays: overlay %s changed on save", c.URI)
+				return nil, fmt.Errorf("updateOverlays: overlay %s changed on save", c.URI)
 			}
 			sameContentOnDisk = true
 		default:
@@ -676,10 +675,10 @@ func (s *Session) updateOverlays(ctx context.Context, changes []source.FileModif
 		if c.Action == source.Open {
 			view, err := s.ViewOf(o.uri)
 			if err != nil {
-				return nil, errors.Errorf("updateOverlays: finding view for %s: %v", o.uri, err)
+				return nil, fmt.Errorf("updateOverlays: finding view for %s: %v", o.uri, err)
 			}
 			if kind := view.FileKind(o); kind == source.UnknownKind {
-				return nil, errors.Errorf("updateOverlays: unknown file kind for %s", o.uri)
+				return nil, fmt.Errorf("updateOverlays: unknown file kind for %s", o.uri)
 			}
 		}
 

internal/lsp/cache/snapshot.go

@@ -7,6 +7,7 @@ package cache
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"go/ast"
 	"go/token"
@@ -35,7 +36,6 @@ import (
 	"golang.org/x/tools/internal/packagesinternal"
 	"golang.org/x/tools/internal/span"
 	"golang.org/x/tools/internal/typesinternal"
-	errors "golang.org/x/xerrors"
 )
 
 type snapshot struct {
@@ -511,7 +511,7 @@ func (s *snapshot) PackageForFile(ctx context.Context, uri span.URI, mode source
 	}
 
 	if len(phs) < 1 {
-		return nil, errors.Errorf("no packages")
+		return nil, fmt.Errorf("no packages")
 	}
 
 	ph := phs[0]
@@ -528,7 +528,7 @@ func (s *snapshot) PackageForFile(ctx context.Context, uri span.URI, mode source
 		}
 	}
 	if ph == nil {
-		return nil, errors.Errorf("no packages in input")
+		return nil, fmt.Errorf("no packages in input")
 	}
 
 	return ph.check(ctx, s)
@@ -2268,7 +2268,7 @@ func (s *snapshot) BuiltinFile(ctx context.Context) (*source.ParsedGoFile, error
 	s.mu.Unlock()
 
 	if builtin == "" {
-		return nil, errors.Errorf("no builtin package for view %s", s.view.name)
+		return nil, fmt.Errorf("no builtin package for view %s", s.view.name)
 	}
 
 	fh, err := s.GetFile(ctx, builtin)
@@ -2425,7 +2425,7 @@ func buildWorkspaceSumFile(ctx context.Context, modFiles map[span.URI]struct{},
 			continue
 		}
 		if err != nil {
-			return nil, errors.Errorf("reading go sum: %w", err)
+			return nil, fmt.Errorf("reading go sum: %w", err)
 		}
 		if err := readGoSum(allSums, sumURI.Filename(), data); err != nil {
 			return nil, err