gopls/internal/lsp/cache/errors.go - tools - Git at Google

 // Copyright 2019 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 cache

 // This file defines routines to convert diagnostics from go list, go
 // get, go/packages, parsing, type checking, and analysis into
 // source.Diagnostic form, and suggesting quick fixes.

 import (
 	"context"
 	"fmt"
 	"go/parser"
 	"go/scanner"
 	"go/token"
 	"log"
 	"path/filepath"
 	"regexp"
 	"strconv"
 	"strings"

 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/gopls/internal/analysis/embeddirective"
 	"golang.org/x/tools/gopls/internal/file"
 	"golang.org/x/tools/gopls/internal/lsp/cache/metadata"
 	"golang.org/x/tools/gopls/internal/lsp/command"
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/gopls/internal/settings"
 	"golang.org/x/tools/gopls/internal/util/bug"
 	"golang.org/x/tools/internal/typesinternal"
 )

 // goPackagesErrorDiagnostics translates the given go/packages Error into a
 // diagnostic, using the provided metadata and filesource.
 //
 // The slice of diagnostics may be empty.
 func goPackagesErrorDiagnostics(ctx context.Context, e packages.Error, mp *metadata.Package, fs file.Source) ([]*Diagnostic, error) {
 	if diag, err := parseGoListImportCycleError(ctx, e, mp, fs); err != nil {
 		return nil, err
 	} else if diag != nil {
 		return []*Diagnostic{diag}, nil
 	}

 	// Parse error location and attempt to convert to protocol form.
 	loc, err := func() (protocol.Location, error) {
 		filename, line, col8 := parseGoListError(e, mp.LoadDir)
 		uri := protocol.URIFromPath(filename)

 		fh, err := fs.ReadFile(ctx, uri)
 		if err != nil {
 			return protocol.Location{}, err
 		}
 		content, err := fh.Content()
 		if err != nil {
 			return protocol.Location{}, err
 		}
 		mapper := protocol.NewMapper(uri, content)
 		posn, err := mapper.LineCol8Position(line, col8)
 		if err != nil {
 			return protocol.Location{}, err
 		}
 		return protocol.Location{
 			URI: uri,
 			Range: protocol.Range{
 				Start: posn,
 				End:   posn,
 			},
 		}, nil
 	}()

 	// TODO(rfindley): in some cases the go command outputs invalid spans, for
 	// example (from TestGoListErrors):
 	//
 	//   package a
 	//   import
 	//
 	// In this case, the go command will complain about a.go:2:8, which is after
 	// the trailing newline but still considered to be on the second line, most
 	// likely because *token.File lacks information about newline termination.
 	//
 	// We could do better here by handling that case.
 	if err != nil {
 		// Unable to parse a valid position.
 		// Apply the error to all files to be safe.
 		var diags []*Diagnostic
 		for _, uri := range mp.CompiledGoFiles {
 			diags = append(diags, &Diagnostic{
 				URI:      uri,
 				Severity: protocol.SeverityError,
 				Source:   ListError,
 				Message:  e.Msg,
 			})
 		}
 		return diags, nil
 	}
 	return []*Diagnostic{{
 		URI:      loc.URI,
 		Range:    loc.Range,
 		Severity: protocol.SeverityError,
 		Source:   ListError,
 		Message:  e.Msg,
 	}}, nil
 }

 func parseErrorDiagnostics(pkg *syntaxPackage, errList scanner.ErrorList) ([]*Diagnostic, error) {
 	// The first parser error is likely the root cause of the problem.
 	if errList.Len() <= 0 {
 		return nil, fmt.Errorf("no errors in %v", errList)
 	}
 	e := errList[0]
 	pgf, err := pkg.File(protocol.URIFromPath(e.Pos.Filename))
 	if err != nil {
 		return nil, err
 	}
 	rng, err := pgf.Mapper.OffsetRange(e.Pos.Offset, e.Pos.Offset)
 	if err != nil {
 		return nil, err
 	}
 	return []*Diagnostic{{
 		URI:      pgf.URI,
 		Range:    rng,
 		Severity: protocol.SeverityError,
 		Source:   ParseError,
 		Message:  e.Msg,
 	}}, nil
 }

 var importErrorRe = regexp.MustCompile(`could not import ([^\s]+)`)
 var unsupportedFeatureRe = regexp.MustCompile(`.*require.* go(\d+\.\d+) or later`)

 func goGetQuickFixes(moduleMode bool, uri protocol.DocumentURI, pkg string) []SuggestedFix {
 	// Go get only supports module mode for now.
 	if !moduleMode {
 		return nil
 	}
 	title := fmt.Sprintf("go get package %v", pkg)
 	cmd, err := command.NewGoGetPackageCommand(title, command.GoGetPackageArgs{
 		URI:        uri,
 		AddRequire: true,
 		Pkg:        pkg,
 	})
 	if err != nil {
 		bug.Reportf("internal error building 'go get package' fix: %v", err)
 		return nil
 	}
 	return []SuggestedFix{SuggestedFixFromCommand(cmd, protocol.QuickFix)}
 }

 func editGoDirectiveQuickFix(moduleMode bool, uri protocol.DocumentURI, version string) []SuggestedFix {
 	// Go mod edit only supports module mode.
 	if !moduleMode {
 		return nil
 	}
 	title := fmt.Sprintf("go mod edit -go=%s", version)
 	cmd, err := command.NewEditGoDirectiveCommand(title, command.EditGoDirectiveArgs{
 		URI:     uri,
 		Version: version,
 	})
 	if err != nil {
 		bug.Reportf("internal error constructing 'edit go directive' fix: %v", err)
 		return nil
 	}
 	return []SuggestedFix{SuggestedFixFromCommand(cmd, protocol.QuickFix)}
 }

 // encodeDiagnostics gob-encodes the given diagnostics.
 func encodeDiagnostics(srcDiags []*Diagnostic) []byte {
 	var gobDiags []gobDiagnostic
 	for _, srcDiag := range srcDiags {
 		var gobFixes []gobSuggestedFix
 		for _, srcFix := range srcDiag.SuggestedFixes {
 			gobFix := gobSuggestedFix{
 				Message:    srcFix.Title,
 				ActionKind: srcFix.ActionKind,
 			}
 			for uri, srcEdits := range srcFix.Edits {
 				for _, srcEdit := range srcEdits {
 					gobFix.TextEdits = append(gobFix.TextEdits, gobTextEdit{
 						Location: protocol.Location{
 							URI:   uri,
 							Range: srcEdit.Range,
 						},
 						NewText: []byte(srcEdit.NewText),
 					})
 				}
 			}
 			if srcCmd := srcFix.Command; srcCmd != nil {
 				gobFix.Command = &gobCommand{
 					Title:     srcCmd.Title,
 					Command:   srcCmd.Command,
 					Arguments: srcCmd.Arguments,
 				}
 			}
 			gobFixes = append(gobFixes, gobFix)
 		}
 		var gobRelated []gobRelatedInformation
 		for _, srcRel := range srcDiag.Related {
 			gobRel := gobRelatedInformation(srcRel)
 			gobRelated = append(gobRelated, gobRel)
 		}
 		gobDiag := gobDiagnostic{
 			Location: protocol.Location{
 				URI:   srcDiag.URI,
 				Range: srcDiag.Range,
 			},
 			Severity:       srcDiag.Severity,
 			Code:           srcDiag.Code,
 			CodeHref:       srcDiag.CodeHref,
 			Source:         string(srcDiag.Source),
 			Message:        srcDiag.Message,
 			SuggestedFixes: gobFixes,
 			Related:        gobRelated,
 			Tags:           srcDiag.Tags,
 		}
 		gobDiags = append(gobDiags, gobDiag)
 	}
 	return diagnosticsCodec.Encode(gobDiags)
 }

 // decodeDiagnostics decodes the given gob-encoded diagnostics.
 func decodeDiagnostics(data []byte) []*Diagnostic {
 	var gobDiags []gobDiagnostic
 	diagnosticsCodec.Decode(data, &gobDiags)
 	var srcDiags []*Diagnostic
 	for _, gobDiag := range gobDiags {
 		var srcFixes []SuggestedFix
 		for _, gobFix := range gobDiag.SuggestedFixes {
 			srcFix := SuggestedFix{
 				Title:      gobFix.Message,
 				ActionKind: gobFix.ActionKind,
 			}
 			for _, gobEdit := range gobFix.TextEdits {
 				if srcFix.Edits == nil {
 					srcFix.Edits = make(map[protocol.DocumentURI][]protocol.TextEdit)
 				}
 				srcEdit := protocol.TextEdit{
 					Range:   gobEdit.Location.Range,
 					NewText: string(gobEdit.NewText),
 				}
 				uri := gobEdit.Location.URI
 				srcFix.Edits[uri] = append(srcFix.Edits[uri], srcEdit)
 			}
 			if gobCmd := gobFix.Command; gobCmd != nil {
 				srcFix.Command = &protocol.Command{
 					Title:     gobCmd.Title,
 					Command:   gobCmd.Command,
 					Arguments: gobCmd.Arguments,
 				}
 			}
 			srcFixes = append(srcFixes, srcFix)
 		}
 		var srcRelated []protocol.DiagnosticRelatedInformation
 		for _, gobRel := range gobDiag.Related {
 			srcRel := protocol.DiagnosticRelatedInformation(gobRel)
 			srcRelated = append(srcRelated, srcRel)
 		}
 		srcDiag := &Diagnostic{
 			URI:            gobDiag.Location.URI,
 			Range:          gobDiag.Location.Range,
 			Severity:       gobDiag.Severity,
 			Code:           gobDiag.Code,
 			CodeHref:       gobDiag.CodeHref,
 			Source:         DiagnosticSource(gobDiag.Source),
 			Message:        gobDiag.Message,
 			Tags:           gobDiag.Tags,
 			Related:        srcRelated,
 			SuggestedFixes: srcFixes,
 		}
 		srcDiags = append(srcDiags, srcDiag)
 	}
 	return srcDiags
 }

 // toSourceDiagnostic converts a gobDiagnostic to "source" form.
 func toSourceDiagnostic(srcAnalyzer *settings.Analyzer, gobDiag *gobDiagnostic) *Diagnostic {
 	var related []protocol.DiagnosticRelatedInformation
 	for _, gobRelated := range gobDiag.Related {
 		related = append(related, protocol.DiagnosticRelatedInformation(gobRelated))
 	}

 	severity := srcAnalyzer.Severity
 	if severity == 0 {
 		severity = protocol.SeverityWarning
 	}

 	diag := &Diagnostic{
 		URI:      gobDiag.Location.URI,
 		Range:    gobDiag.Location.Range,
 		Severity: severity,
 		Code:     gobDiag.Code,
 		CodeHref: gobDiag.CodeHref,
 		Source:   DiagnosticSource(gobDiag.Source),
 		Message:  gobDiag.Message,
 		Related:  related,
 		Tags:     srcAnalyzer.Tag,
 	}
 	if canFix(srcAnalyzer, diag) {
 		// We cross the set of fixes (whether edit- or command-based)
 		// with the set of kinds, as a single fix may represent more
 		// than one kind of action (e.g. refactor, quickfix, fixall),
 		// each corresponding to a distinct client UI element
 		// or operation.
 		kinds := srcAnalyzer.ActionKind
 		if len(kinds) == 0 {
 			kinds = []protocol.CodeActionKind{protocol.QuickFix}
 		}

 		// Accumulate edit-based fixes supplied by the diagnostic itself.
 		fixes := suggestedAnalysisFixes(gobDiag, kinds)

 		// Accumulate command-based fixes computed on demand by
 		// (logic adjacent to) the analyzer.
 		if srcAnalyzer.Fix != "" {
 			cmd, err := command.NewApplyFixCommand(gobDiag.Message, command.ApplyFixArgs{
 				URI:   gobDiag.Location.URI,
 				Range: gobDiag.Location.Range,
 				Fix:   string(srcAnalyzer.Fix),
 			})
 			if err != nil {
 				// JSON marshalling of these argument values cannot fail.
 				log.Fatalf("internal error in NewApplyFixCommand: %v", err)
 			}
 			for _, kind := range kinds {
 				fixes = append(fixes, SuggestedFixFromCommand(cmd, kind))
 			}
 		}
 		diag.SuggestedFixes = fixes
 	}

 	// If the fixes only delete code, assume that the diagnostic is reporting dead code.
 	if onlyDeletions(diag.SuggestedFixes) {
 		diag.Tags = append(diag.Tags, protocol.Unnecessary)
 	}
 	return diag
 }

 // canFix reports whether the Analyzer can fix the Diagnostic.
 func canFix(a *settings.Analyzer, diag *Diagnostic) bool {
 	if a.Fix == settings.AddEmbedImport {
 		return diag.Message == embeddirective.MissingImportMessage
 	}

 	// This doesn't make sense, but preserves pre-existing semantics.
 	// TODO(rfindley): reconcile the semantics of Fix and suggestedAnalysisFixes.
 	return true
 }

 // onlyDeletions returns true if fixes is non-empty and all of the suggested
 // fixes are deletions.
 func onlyDeletions(fixes []SuggestedFix) bool {
 	for _, fix := range fixes {
 		if fix.Command != nil {
 			return false
 		}
 		for _, edits := range fix.Edits {
 			for _, edit := range edits {
 				if edit.NewText != "" {
 					return false
 				}
 				if protocol.ComparePosition(edit.Range.Start, edit.Range.End) == 0 {
 					return false
 				}
 			}
 		}
 	}
 	return len(fixes) > 0
 }

 func typesCodeHref(linkTarget string, code typesinternal.ErrorCode) string {
 	return BuildLink(linkTarget, "golang.org/x/tools/internal/typesinternal", code.String())
 }

 // BuildLink constructs a URL with the given target, path, and anchor.
 func BuildLink(target, path, anchor string) string {
 	link := fmt.Sprintf("https://%s/%s", target, path)
 	if anchor == "" {
 		return link
 	}
 	return link + "#" + anchor
 }

 // suggestedAnalysisFixes converts edit-based fixes associated
 // with a gobDiagnostic to cache.SuggestedFixes.
 // It returns the cross product of fixes and kinds.
 func suggestedAnalysisFixes(diag *gobDiagnostic, kinds []protocol.CodeActionKind) []SuggestedFix {
 	var fixes []SuggestedFix
 	for _, fix := range diag.SuggestedFixes {
 		edits := make(map[protocol.DocumentURI][]protocol.TextEdit)
 		for _, e := range fix.TextEdits {
 			uri := e.Location.URI
 			edits[uri] = append(edits[uri], protocol.TextEdit{
 				Range:   e.Location.Range,
 				NewText: string(e.NewText),
 			})
 		}
 		for _, kind := range kinds {
 			fixes = append(fixes, SuggestedFix{
 				Title:      fix.Message,
 				Edits:      edits,
 				ActionKind: kind,
 			})
 		}
 	}
 	return fixes
 }

 func parseGoListError(e packages.Error, dir string) (filename string, line, col8 int) {
 	input := e.Pos
 	if input == "" {
 		// No position. Attempt to parse one out of a
 		// go list error of the form "file:line:col:
 		// message" by stripping off the message.
 		input = strings.TrimSpace(e.Msg)
 		if i := strings.Index(input, ": "); i >= 0 {
 			input = input[:i]
 		}
 	}

 	filename, line, col8 = splitFileLineCol(input)
 	if !filepath.IsAbs(filename) {
 		filename = filepath.Join(dir, filename)
 	}
 	return filename, line, col8
 }

 // splitFileLineCol splits s into "filename:line:col",
 // where line and col consist of decimal digits.
 func splitFileLineCol(s string) (file string, line, col8 int) {
 	// Beware that the filename may contain colon on Windows.

 	// stripColonDigits removes a ":%d" suffix, if any.
 	stripColonDigits := func(s string) (rest string, num int) {
 		if i := strings.LastIndex(s, ":"); i >= 0 {
 			if v, err := strconv.ParseInt(s[i+1:], 10, 32); err == nil {
 				return s[:i], int(v)
 			}
 		}
 		return s, -1
 	}

 	// strip col ":%d"
 	s, n1 := stripColonDigits(s)
 	if n1 < 0 {
 		return s, 0, 0 // "filename"
 	}

 	// strip line ":%d"
 	s, n2 := stripColonDigits(s)
 	if n2 < 0 {
 		return s, n1, 0 // "filename:line"
 	}

 	return s, n2, n1 // "filename:line:col"
 }

 // parseGoListImportCycleError attempts to parse the given go/packages error as
 // an import cycle, returning a diagnostic if successful.
 //
 // If the error is not detected as an import cycle error, it returns nil, nil.
 func parseGoListImportCycleError(ctx context.Context, e packages.Error, mp *metadata.Package, fs file.Source) (*Diagnostic, error) {
 	re := regexp.MustCompile(`(.*): import stack: \[(.+)\]`)
 	matches := re.FindStringSubmatch(strings.TrimSpace(e.Msg))
 	if len(matches) < 3 {
 		return nil, nil
 	}
 	msg := matches[1]
 	importList := strings.Split(matches[2], " ")
 	// Since the error is relative to the current package. The import that is causing
 	// the import cycle error is the second one in the list.
 	if len(importList) < 2 {
 		return nil, nil
 	}
 	// Imports have quotation marks around them.
 	circImp := strconv.Quote(importList[1])
 	for _, uri := range mp.CompiledGoFiles {
 		pgf, err := parseGoURI(ctx, fs, uri, ParseHeader)
 		if err != nil {
 			return nil, err
 		}
 		// Search file imports for the import that is causing the import cycle.
 		for _, imp := range pgf.File.Imports {
 			if imp.Path.Value == circImp {
 				rng, err := pgf.NodeMappedRange(imp)
 				if err != nil {
 					return nil, nil
 				}

 				return &Diagnostic{
 					URI:      pgf.URI,
 					Range:    rng.Range(),
 					Severity: protocol.SeverityError,
 					Source:   ListError,
 					Message:  msg,
 				}, nil
 			}
 		}
 	}
 	return nil, nil
 }

 // parseGoURI is a helper to parse the Go file at the given URI from the file
 // source fs. The resulting syntax and token.File belong to an ephemeral,
 // encapsulated FileSet, so this file stands only on its own: it's not suitable
 // to use in a list of file of a package, for example.
 //
 // It returns an error if the file could not be read.
 //
 // TODO(rfindley): eliminate this helper.
 func parseGoURI(ctx context.Context, fs file.Source, uri protocol.DocumentURI, mode parser.Mode) (*ParsedGoFile, error) {
 	fh, err := fs.ReadFile(ctx, uri)
 	if err != nil {
 		return nil, err
 	}
 	return parseGoImpl(ctx, token.NewFileSet(), fh, mode, false)
 }

 // parseModURI is a helper to parse the Mod file at the given URI from the file
 // source fs.
 //
 // It returns an error if the file could not be read.
 func parseModURI(ctx context.Context, fs file.Source, uri protocol.DocumentURI) (*ParsedModule, error) {
 	fh, err := fs.ReadFile(ctx, uri)
 	if err != nil {
 		return nil, err
 	}
 	return parseModImpl(ctx, fh)
 }
	// Copyright 2019 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 cache

	// This file defines routines to convert diagnostics from go list, go
	// get, go/packages, parsing, type checking, and analysis into
	// source.Diagnostic form, and suggesting quick fixes.

	import (
	"context"
	"fmt"
	"go/parser"
	"go/scanner"
	"go/token"
	"log"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"

	"golang.org/x/tools/go/packages"
	"golang.org/x/tools/gopls/internal/analysis/embeddirective"
	"golang.org/x/tools/gopls/internal/file"
	"golang.org/x/tools/gopls/internal/lsp/cache/metadata"
	"golang.org/x/tools/gopls/internal/lsp/command"
	"golang.org/x/tools/gopls/internal/lsp/protocol"
	"golang.org/x/tools/gopls/internal/settings"
	"golang.org/x/tools/gopls/internal/util/bug"
	"golang.org/x/tools/internal/typesinternal"
	)

	// goPackagesErrorDiagnostics translates the given go/packages Error into a
	// diagnostic, using the provided metadata and filesource.
	//
	// The slice of diagnostics may be empty.
	func goPackagesErrorDiagnostics(ctx context.Context, e packages.Error, mp metadata.Package, fs file.Source) ([]Diagnostic, error) {
	if diag, err := parseGoListImportCycleError(ctx, e, mp, fs); err != nil {
	return nil, err
	} else if diag != nil {
	return []*Diagnostic{diag}, nil
	}

	// Parse error location and attempt to convert to protocol form.
	loc, err := func() (protocol.Location, error) {
	filename, line, col8 := parseGoListError(e, mp.LoadDir)
	uri := protocol.URIFromPath(filename)

	fh, err := fs.ReadFile(ctx, uri)
	if err != nil {
	return protocol.Location{}, err
	}
	content, err := fh.Content()
	if err != nil {
	return protocol.Location{}, err
	}
	mapper := protocol.NewMapper(uri, content)
	posn, err := mapper.LineCol8Position(line, col8)
	if err != nil {
	return protocol.Location{}, err
	}
	return protocol.Location{
	URI: uri,
	Range: protocol.Range{
	Start: posn,
	End: posn,
	},
	}, nil
	}()

	// TODO(rfindley): in some cases the go command outputs invalid spans, for
	// example (from TestGoListErrors):
	//
	// package a
	// import
	//
	// In this case, the go command will complain about a.go:2:8, which is after
	// the trailing newline but still considered to be on the second line, most
	// likely because *token.File lacks information about newline termination.
	//
	// We could do better here by handling that case.
	if err != nil {
	// Unable to parse a valid position.
	// Apply the error to all files to be safe.
	var diags []*Diagnostic
	for _, uri := range mp.CompiledGoFiles {
	diags = append(diags, &Diagnostic{
	URI: uri,
	Severity: protocol.SeverityError,
	Source: ListError,
	Message: e.Msg,
	})
	}
	return diags, nil
	}
	return []*Diagnostic{{
	URI: loc.URI,
	Range: loc.Range,
	Severity: protocol.SeverityError,
	Source: ListError,
	Message: e.Msg,
	}}, nil
	}

	func parseErrorDiagnostics(pkg syntaxPackage, errList scanner.ErrorList) ([]Diagnostic, error) {
	// The first parser error is likely the root cause of the problem.
	if errList.Len() <= 0 {
	return nil, fmt.Errorf("no errors in %v", errList)
	}
	e := errList[0]
	pgf, err := pkg.File(protocol.URIFromPath(e.Pos.Filename))
	if err != nil {
	return nil, err
	}
	rng, err := pgf.Mapper.OffsetRange(e.Pos.Offset, e.Pos.Offset)
	if err != nil {
	return nil, err
	}
	return []*Diagnostic{{
	URI: pgf.URI,
	Range: rng,
	Severity: protocol.SeverityError,
	Source: ParseError,
	Message: e.Msg,
	}}, nil
	}

	var importErrorRe = regexp.MustCompile(`could not import ([^\s]+)`)
	var unsupportedFeatureRe = regexp.MustCompile(`.require. go(\d+\.\d+) or later`)

	func goGetQuickFixes(moduleMode bool, uri protocol.DocumentURI, pkg string) []SuggestedFix {
	// Go get only supports module mode for now.
	if !moduleMode {
	return nil
	}
	title := fmt.Sprintf("go get package %v", pkg)
	cmd, err := command.NewGoGetPackageCommand(title, command.GoGetPackageArgs{
	URI: uri,
	AddRequire: true,
	Pkg: pkg,
	})
	if err != nil {
	bug.Reportf("internal error building 'go get package' fix: %v", err)
	return nil
	}
	return []SuggestedFix{SuggestedFixFromCommand(cmd, protocol.QuickFix)}
	}

	func editGoDirectiveQuickFix(moduleMode bool, uri protocol.DocumentURI, version string) []SuggestedFix {
	// Go mod edit only supports module mode.
	if !moduleMode {
	return nil
	}
	title := fmt.Sprintf("go mod edit -go=%s", version)
	cmd, err := command.NewEditGoDirectiveCommand(title, command.EditGoDirectiveArgs{
	URI: uri,
	Version: version,
	})
	if err != nil {
	bug.Reportf("internal error constructing 'edit go directive' fix: %v", err)
	return nil
	}
	return []SuggestedFix{SuggestedFixFromCommand(cmd, protocol.QuickFix)}
	}

	// encodeDiagnostics gob-encodes the given diagnostics.
	func encodeDiagnostics(srcDiags []*Diagnostic) []byte {
	var gobDiags []gobDiagnostic
	for _, srcDiag := range srcDiags {
	var gobFixes []gobSuggestedFix
	for _, srcFix := range srcDiag.SuggestedFixes {
	gobFix := gobSuggestedFix{
	Message: srcFix.Title,
	ActionKind: srcFix.ActionKind,
	}
	for uri, srcEdits := range srcFix.Edits {
	for _, srcEdit := range srcEdits {
	gobFix.TextEdits = append(gobFix.TextEdits, gobTextEdit{
	Location: protocol.Location{
	URI: uri,
	Range: srcEdit.Range,
	},
	NewText: []byte(srcEdit.NewText),
	})
	}
	}
	if srcCmd := srcFix.Command; srcCmd != nil {
	gobFix.Command = &gobCommand{
	Title: srcCmd.Title,
	Command: srcCmd.Command,
	Arguments: srcCmd.Arguments,
	}
	}
	gobFixes = append(gobFixes, gobFix)
	}
	var gobRelated []gobRelatedInformation
	for _, srcRel := range srcDiag.Related {
	gobRel := gobRelatedInformation(srcRel)
	gobRelated = append(gobRelated, gobRel)
	}
	gobDiag := gobDiagnostic{
	Location: protocol.Location{
	URI: srcDiag.URI,
	Range: srcDiag.Range,
	},
	Severity: srcDiag.Severity,
	Code: srcDiag.Code,
	CodeHref: srcDiag.CodeHref,
	Source: string(srcDiag.Source),
	Message: srcDiag.Message,
	SuggestedFixes: gobFixes,
	Related: gobRelated,
	Tags: srcDiag.Tags,
	}
	gobDiags = append(gobDiags, gobDiag)
	}
	return diagnosticsCodec.Encode(gobDiags)
	}

	// decodeDiagnostics decodes the given gob-encoded diagnostics.
	func decodeDiagnostics(data []byte) []*Diagnostic {
	var gobDiags []gobDiagnostic
	diagnosticsCodec.Decode(data, &gobDiags)
	var srcDiags []*Diagnostic
	for _, gobDiag := range gobDiags {
	var srcFixes []SuggestedFix
	for _, gobFix := range gobDiag.SuggestedFixes {
	srcFix := SuggestedFix{
	Title: gobFix.Message,
	ActionKind: gobFix.ActionKind,
	}
	for _, gobEdit := range gobFix.TextEdits {
	if srcFix.Edits == nil {
	srcFix.Edits = make(map[protocol.DocumentURI][]protocol.TextEdit)
	}
	srcEdit := protocol.TextEdit{
	Range: gobEdit.Location.Range,
	NewText: string(gobEdit.NewText),
	}
	uri := gobEdit.Location.URI
	srcFix.Edits[uri] = append(srcFix.Edits[uri], srcEdit)
	}
	if gobCmd := gobFix.Command; gobCmd != nil {
	srcFix.Command = &protocol.Command{
	Title: gobCmd.Title,
	Command: gobCmd.Command,
	Arguments: gobCmd.Arguments,
	}
	}
	srcFixes = append(srcFixes, srcFix)
	}
	var srcRelated []protocol.DiagnosticRelatedInformation
	for _, gobRel := range gobDiag.Related {
	srcRel := protocol.DiagnosticRelatedInformation(gobRel)
	srcRelated = append(srcRelated, srcRel)
	}
	srcDiag := &Diagnostic{
	URI: gobDiag.Location.URI,
	Range: gobDiag.Location.Range,
	Severity: gobDiag.Severity,
	Code: gobDiag.Code,
	CodeHref: gobDiag.CodeHref,
	Source: DiagnosticSource(gobDiag.Source),
	Message: gobDiag.Message,
	Tags: gobDiag.Tags,
	Related: srcRelated,
	SuggestedFixes: srcFixes,
	}
	srcDiags = append(srcDiags, srcDiag)
	}
	return srcDiags
	}

	// toSourceDiagnostic converts a gobDiagnostic to "source" form.
	func toSourceDiagnostic(srcAnalyzer settings.Analyzer, gobDiag gobDiagnostic) *Diagnostic {
	var related []protocol.DiagnosticRelatedInformation
	for _, gobRelated := range gobDiag.Related {
	related = append(related, protocol.DiagnosticRelatedInformation(gobRelated))
	}

	severity := srcAnalyzer.Severity
	if severity == 0 {
	severity = protocol.SeverityWarning
	}

	diag := &Diagnostic{
	URI: gobDiag.Location.URI,
	Range: gobDiag.Location.Range,
	Severity: severity,
	Code: gobDiag.Code,
	CodeHref: gobDiag.CodeHref,
	Source: DiagnosticSource(gobDiag.Source),
	Message: gobDiag.Message,
	Related: related,
	Tags: srcAnalyzer.Tag,
	}
	if canFix(srcAnalyzer, diag) {
	// We cross the set of fixes (whether edit- or command-based)
	// with the set of kinds, as a single fix may represent more
	// than one kind of action (e.g. refactor, quickfix, fixall),
	// each corresponding to a distinct client UI element
	// or operation.
	kinds := srcAnalyzer.ActionKind
	if len(kinds) == 0 {
	kinds = []protocol.CodeActionKind{protocol.QuickFix}
	}

	// Accumulate edit-based fixes supplied by the diagnostic itself.
	fixes := suggestedAnalysisFixes(gobDiag, kinds)

	// Accumulate command-based fixes computed on demand by
	// (logic adjacent to) the analyzer.
	if srcAnalyzer.Fix != "" {
	cmd, err := command.NewApplyFixCommand(gobDiag.Message, command.ApplyFixArgs{
	URI: gobDiag.Location.URI,
	Range: gobDiag.Location.Range,
	Fix: string(srcAnalyzer.Fix),
	})
	if err != nil {
	// JSON marshalling of these argument values cannot fail.
	log.Fatalf("internal error in NewApplyFixCommand: %v", err)
	}
	for _, kind := range kinds {
	fixes = append(fixes, SuggestedFixFromCommand(cmd, kind))
	}
	}
	diag.SuggestedFixes = fixes
	}

	// If the fixes only delete code, assume that the diagnostic is reporting dead code.
	if onlyDeletions(diag.SuggestedFixes) {
	diag.Tags = append(diag.Tags, protocol.Unnecessary)
	}
	return diag
	}

	// canFix reports whether the Analyzer can fix the Diagnostic.
	func canFix(a settings.Analyzer, diag Diagnostic) bool {
	if a.Fix == settings.AddEmbedImport {
	return diag.Message == embeddirective.MissingImportMessage
	}

	// This doesn't make sense, but preserves pre-existing semantics.
	// TODO(rfindley): reconcile the semantics of Fix and suggestedAnalysisFixes.
	return true
	}

	// onlyDeletions returns true if fixes is non-empty and all of the suggested
	// fixes are deletions.
	func onlyDeletions(fixes []SuggestedFix) bool {
	for _, fix := range fixes {
	if fix.Command != nil {
	return false
	}
	for _, edits := range fix.Edits {
	for _, edit := range edits {
	if edit.NewText != "" {
	return false
	}
	if protocol.ComparePosition(edit.Range.Start, edit.Range.End) == 0 {
	return false
	}
	}
	}
	}
	return len(fixes) > 0
	}

	func typesCodeHref(linkTarget string, code typesinternal.ErrorCode) string {
	return BuildLink(linkTarget, "golang.org/x/tools/internal/typesinternal", code.String())
	}

	// BuildLink constructs a URL with the given target, path, and anchor.
	func BuildLink(target, path, anchor string) string {
	link := fmt.Sprintf("https://%s/%s", target, path)
	if anchor == "" {
	return link
	}
	return link + "#" + anchor
	}

	// suggestedAnalysisFixes converts edit-based fixes associated
	// with a gobDiagnostic to cache.SuggestedFixes.
	// It returns the cross product of fixes and kinds.
	func suggestedAnalysisFixes(diag *gobDiagnostic, kinds []protocol.CodeActionKind) []SuggestedFix {
	var fixes []SuggestedFix
	for _, fix := range diag.SuggestedFixes {
	edits := make(map[protocol.DocumentURI][]protocol.TextEdit)
	for _, e := range fix.TextEdits {
	uri := e.Location.URI
	edits[uri] = append(edits[uri], protocol.TextEdit{
	Range: e.Location.Range,
	NewText: string(e.NewText),
	})
	}
	for _, kind := range kinds {
	fixes = append(fixes, SuggestedFix{
	Title: fix.Message,
	Edits: edits,
	ActionKind: kind,
	})
	}
	}
	return fixes
	}

	func parseGoListError(e packages.Error, dir string) (filename string, line, col8 int) {
	input := e.Pos
	if input == "" {
	// No position. Attempt to parse one out of a
	// go list error of the form "file:line:col:
	// message" by stripping off the message.
	input = strings.TrimSpace(e.Msg)
	if i := strings.Index(input, ": "); i >= 0 {
	input = input[:i]
	}
	}

	filename, line, col8 = splitFileLineCol(input)
	if !filepath.IsAbs(filename) {
	filename = filepath.Join(dir, filename)
	}
	return filename, line, col8
	}

	// splitFileLineCol splits s into "filename:line:col",
	// where line and col consist of decimal digits.
	func splitFileLineCol(s string) (file string, line, col8 int) {
	// Beware that the filename may contain colon on Windows.

	// stripColonDigits removes a ":%d" suffix, if any.
	stripColonDigits := func(s string) (rest string, num int) {
	if i := strings.LastIndex(s, ":"); i >= 0 {
	if v, err := strconv.ParseInt(s[i+1:], 10, 32); err == nil {
	return s[:i], int(v)
	}
	}
	return s, -1
	}

	// strip col ":%d"
	s, n1 := stripColonDigits(s)
	if n1 < 0 {
	return s, 0, 0 // "filename"
	}

	// strip line ":%d"
	s, n2 := stripColonDigits(s)
	if n2 < 0 {
	return s, n1, 0 // "filename:line"
	}

	return s, n2, n1 // "filename:line:col"
	}

	// parseGoListImportCycleError attempts to parse the given go/packages error as
	// an import cycle, returning a diagnostic if successful.
	//
	// If the error is not detected as an import cycle error, it returns nil, nil.
	func parseGoListImportCycleError(ctx context.Context, e packages.Error, mp metadata.Package, fs file.Source) (Diagnostic, error) {
	re := regexp.MustCompile(`(.*): import stack: \[(.+)\]`)
	matches := re.FindStringSubmatch(strings.TrimSpace(e.Msg))
	if len(matches) < 3 {
	return nil, nil
	}
	msg := matches[1]
	importList := strings.Split(matches[2], " ")
	// Since the error is relative to the current package. The import that is causing
	// the import cycle error is the second one in the list.
	if len(importList) < 2 {
	return nil, nil
	}
	// Imports have quotation marks around them.
	circImp := strconv.Quote(importList[1])
	for _, uri := range mp.CompiledGoFiles {
	pgf, err := parseGoURI(ctx, fs, uri, ParseHeader)
	if err != nil {
	return nil, err
	}
	// Search file imports for the import that is causing the import cycle.
	for _, imp := range pgf.File.Imports {
	if imp.Path.Value == circImp {
	rng, err := pgf.NodeMappedRange(imp)
	if err != nil {
	return nil, nil
	}

	return &Diagnostic{
	URI: pgf.URI,
	Range: rng.Range(),
	Severity: protocol.SeverityError,
	Source: ListError,
	Message: msg,
	}, nil
	}
	}
	}
	return nil, nil
	}

	// parseGoURI is a helper to parse the Go file at the given URI from the file
	// source fs. The resulting syntax and token.File belong to an ephemeral,
	// encapsulated FileSet, so this file stands only on its own: it's not suitable
	// to use in a list of file of a package, for example.
	//
	// It returns an error if the file could not be read.
	//
	// TODO(rfindley): eliminate this helper.
	func parseGoURI(ctx context.Context, fs file.Source, uri protocol.DocumentURI, mode parser.Mode) (*ParsedGoFile, error) {
	fh, err := fs.ReadFile(ctx, uri)
	if err != nil {
	return nil, err
	}
	return parseGoImpl(ctx, token.NewFileSet(), fh, mode, false)
	}

	// parseModURI is a helper to parse the Mod file at the given URI from the file
	// source fs.
	//
	// It returns an error if the file could not be read.
	func parseModURI(ctx context.Context, fs file.Source, uri protocol.DocumentURI) (*ParsedModule, error) {
	fh, err := fs.ReadFile(ctx, uri)
	if err != nil {
	return nil, err
	}
	return parseModImpl(ctx, fh)
	}