internal/lsp/source/workspace_symbol.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 source

 import (
 	"context"
 	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
 	"sort"
 	"strings"
 	"unicode"
 	"unicode/utf8"

 	"golang.org/x/tools/internal/event"
 	"golang.org/x/tools/internal/lsp/fuzzy"
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/span"
 )

 // maxSymbols defines the maximum number of symbol results that should ever be
 // sent in response to a client.
 const maxSymbols = 100

 // WorkspaceSymbols matches symbols across all views using the given query,
 // according to the match semantics parameterized by matcherType and style.
 //
 // The workspace symbol method is defined in the spec as follows:
 //
 //   The workspace symbol request is sent from the client to the server to
 //   list project-wide symbols matching the query string.
 //
 // It is unclear what "project-wide" means here, but given the parameters of
 // workspace/symbol do not include any workspace identifier, then it has to be
 // assumed that "project-wide" means "across all workspaces".  Hence why
 // WorkspaceSymbols receives the views []View.
 //
 // However, it then becomes unclear what it would mean to call WorkspaceSymbols
 // with a different configured SymbolMatcher per View. Therefore we assume that
 // Session level configuration will define the SymbolMatcher to be used for the
 // WorkspaceSymbols method.
 func WorkspaceSymbols(ctx context.Context, matcherType SymbolMatcher, style SymbolStyle, views []View, query string) ([]protocol.SymbolInformation, error) {
 	ctx, done := event.Start(ctx, "source.WorkspaceSymbols")
 	defer done()
 	if query == "" {
 		return nil, nil
 	}
 	sc := newSymbolCollector(matcherType, style, query)
 	return sc.walk(ctx, views)
 }

 // A matcherFunc determines the matching score of a symbol.
 //
 // See the comment for symbolCollector for more information.
 type matcherFunc func(name string) float64

 // A symbolizer returns the best symbol match for a name with pkg, according to
 // some heuristic. The symbol name is passed as the slice nameParts of logical
 // name pieces. For example, for myType.field the caller can pass either
 // []string{"myType.field"} or []string{"myType.", "field"}.
 //
 // See the comment for symbolCollector for more information.
 type symbolizer func(nameParts []string, pkg Package, m matcherFunc) (string, float64)

 func fullyQualifiedSymbolMatch(nameParts []string, pkg Package, matcher matcherFunc) (string, float64) {
 	_, score := dynamicSymbolMatch(nameParts, pkg, matcher)
 	path := append([]string{pkg.PkgPath() + "."}, nameParts...)
 	if score > 0 {
 		return strings.Join(path, ""), score
 	}
 	return "", 0
 }

 func dynamicSymbolMatch(nameParts []string, pkg Package, matcher matcherFunc) (string, float64) {
 	var best string
 	fullName := strings.Join(nameParts, "")
 	var score float64
 	var name string

 	// Compute the match score by finding the highest scoring suffix. In these
 	// cases the matched symbol is still the full name: it is confusing to match
 	// an unqualified nested field or method.
 	if match := bestMatch("", nameParts, matcher); match > score {
 		best = fullName
 		score = match
 	}

 	// Next: try to match a package-qualified name.
 	name = pkg.Name() + "." + fullName
 	if match := matcher(name); match > score {
 		best = name
 		score = match
 	}

 	// Finally: consider a fully qualified name.
 	prefix := pkg.PkgPath() + "."
 	fullyQualified := prefix + fullName
 	// As with field/method selectors, consider suffixes from right to left, but
 	// always return a fully-qualified symbol.
 	pathParts := strings.SplitAfter(prefix, "/")
 	if match := bestMatch(fullName, pathParts, matcher); match > score {
 		best = fullyQualified
 		score = match
 	}
 	return best, score
 }

 func bestMatch(name string, prefixParts []string, matcher matcherFunc) float64 {
 	var score float64
 	for i := len(prefixParts) - 1; i >= 0; i-- {
 		name = prefixParts[i] + name
 		if match := matcher(name); match > score {
 			score = match
 		}
 	}
 	return score
 }

 func packageSymbolMatch(components []string, pkg Package, matcher matcherFunc) (string, float64) {
 	path := append([]string{pkg.Name() + "."}, components...)
 	qualified := strings.Join(path, "")
 	if matcher(qualified) > 0 {
 		return qualified, 1
 	}
 	return "", 0
 }

 // symbolCollector holds context as we walk Packages, gathering symbols that
 // match a given query.
 //
 // How we match symbols is parameterized by two interfaces:
 //  * A matcherFunc determines how well a string symbol matches a query. It
 //    returns a non-negative score indicating the quality of the match. A score
 //    of zero indicates no match.
 //  * A symbolizer determines how we extract the symbol for an object. This
 //    enables the 'symbolStyle' configuration option.
 type symbolCollector struct {
 	// These types parameterize the symbol-matching pass.
 	matcher    matcherFunc
 	symbolizer symbolizer

 	// current holds metadata for the package we are currently walking.
 	current *pkgView
 	curFile *ParsedGoFile

 	res [maxSymbols]symbolInformation
 }

 func newSymbolCollector(matcher SymbolMatcher, style SymbolStyle, query string) *symbolCollector {
 	var m matcherFunc
 	switch matcher {
 	case SymbolFuzzy:
 		m = parseQuery(query)
 	case SymbolCaseSensitive:
 		m = func(s string) float64 {
 			if strings.Contains(s, query) {
 				return 1
 			}
 			return 0
 		}
 	case SymbolCaseInsensitive:
 		q := strings.ToLower(query)
 		m = func(s string) float64 {
 			if strings.Contains(strings.ToLower(s), q) {
 				return 1
 			}
 			return 0
 		}
 	default:
 		panic(fmt.Errorf("unknown symbol matcher: %v", matcher))
 	}
 	var s symbolizer
 	switch style {
 	case DynamicSymbols:
 		s = dynamicSymbolMatch
 	case FullyQualifiedSymbols:
 		s = fullyQualifiedSymbolMatch
 	case PackageQualifiedSymbols:
 		s = packageSymbolMatch
 	default:
 		panic(fmt.Errorf("unknown symbol style: %v", style))
 	}
 	return &symbolCollector{
 		matcher:    m,
 		symbolizer: s,
 	}
 }

 // parseQuery parses a field-separated symbol query, extracting the special
 // characters listed below, and returns a matcherFunc corresponding to the AND
 // of all field queries.
 //
 // Special characters:
 //   ^  match exact prefix
 //   $  match exact suffix
 //   '  match exact
 //
 // In all three of these special queries, matches are 'smart-cased', meaning
 // they are case sensitive if the symbol query contains any upper-case
 // characters, and case insensitive otherwise.
 func parseQuery(q string) matcherFunc {
 	fields := strings.Fields(q)
 	if len(fields) == 0 {
 		return func(string) float64 { return 0 }
 	}
 	var funcs []matcherFunc
 	for _, field := range fields {
 		var f matcherFunc
 		switch {
 		case strings.HasPrefix(field, "^"):
 			prefix := field[1:]
 			f = smartCase(prefix, func(s string) float64 {
 				if strings.HasPrefix(s, prefix) {
 					return 1
 				}
 				return 0
 			})
 		case strings.HasPrefix(field, "'"):
 			exact := field[1:]
 			f = smartCase(exact, func(s string) float64 {
 				if strings.Contains(s, exact) {
 					return 1
 				}
 				return 0
 			})
 		case strings.HasSuffix(field, "$"):
 			suffix := field[0 : len(field)-1]
 			f = smartCase(suffix, func(s string) float64 {
 				if strings.HasSuffix(s, suffix) {
 					return 1
 				}
 				return 0
 			})
 		default:
 			fm := fuzzy.NewMatcher(field)
 			f = func(s string) float64 {
 				return float64(fm.Score(s))
 			}
 		}
 		funcs = append(funcs, f)
 	}
 	return comboMatcher(funcs).match
 }

 // smartCase returns a matcherFunc that is case-sensitive if q contains any
 // upper-case characters, and case-insensitive otherwise.
 func smartCase(q string, m matcherFunc) matcherFunc {
 	insensitive := strings.ToLower(q) == q
 	return func(s string) float64 {
 		if insensitive {
 			s = strings.ToLower(s)
 		}
 		return m(s)
 	}
 }

 type comboMatcher []matcherFunc

 func (c comboMatcher) match(s string) float64 {
 	score := 1.0
 	for _, f := range c {
 		score *= f(s)
 	}
 	return score
 }

 // walk walks views, gathers symbols, and returns the results.
 func (sc *symbolCollector) walk(ctx context.Context, views []View) (_ []protocol.SymbolInformation, err error) {
 	toWalk, err := sc.collectPackages(ctx, views)
 	if err != nil {
 		return nil, err
 	}
 	// Make sure we only walk files once (we might see them more than once due to
 	// build constraints).
 	seen := make(map[span.URI]bool)
 	for _, pv := range toWalk {
 		sc.current = pv
 		for _, pgf := range pv.pkg.CompiledGoFiles() {
 			if seen[pgf.URI] {
 				continue
 			}
 			seen[pgf.URI] = true
 			sc.curFile = pgf
 			sc.walkFilesDecls(pgf.File.Decls)
 		}
 	}
 	return sc.results(), nil
 }

 func (sc *symbolCollector) results() []protocol.SymbolInformation {
 	var res []protocol.SymbolInformation
 	for _, si := range sc.res {
 		if si.score <= 0 {
 			return res
 		}
 		res = append(res, si.asProtocolSymbolInformation())
 	}
 	return res
 }

 // collectPackages gathers all known packages and sorts for stability.
 func (sc *symbolCollector) collectPackages(ctx context.Context, views []View) ([]*pkgView, error) {
 	var toWalk []*pkgView
 	for _, v := range views {
 		snapshot, release := v.Snapshot(ctx)
 		defer release()
 		knownPkgs, err := snapshot.KnownPackages(ctx)
 		if err != nil {
 			return nil, err
 		}
 		// TODO(rfindley): this can result in incomplete information in degraded
 		// memory mode.
 		workspacePackages, err := snapshot.ActivePackages(ctx)
 		if err != nil {
 			return nil, err
 		}
 		isWorkspacePkg := make(map[Package]bool)
 		for _, wp := range workspacePackages {
 			isWorkspacePkg[wp] = true
 		}
 		for _, pkg := range knownPkgs {
 			toWalk = append(toWalk, &pkgView{
 				pkg:         pkg,
 				isWorkspace: isWorkspacePkg[pkg],
 			})
 		}
 	}
 	// Now sort for stability of results. We order by
 	// (pkgView.isWorkspace, pkgView.p.ID())
 	sort.Slice(toWalk, func(i, j int) bool {
 		lhs := toWalk[i]
 		rhs := toWalk[j]
 		switch {
 		case lhs.isWorkspace == rhs.isWorkspace:
 			return lhs.pkg.ID() < rhs.pkg.ID()
 		case lhs.isWorkspace:
 			return true
 		default:
 			return false
 		}
 	})
 	return toWalk, nil
 }

 func (sc *symbolCollector) walkFilesDecls(decls []ast.Decl) {
 	for _, decl := range decls {
 		switch decl := decl.(type) {
 		case *ast.FuncDecl:
 			kind := protocol.Function
 			var recv *ast.Ident
 			if decl.Recv.NumFields() > 0 {
 				kind = protocol.Method
 				recv = unpackRecv(decl.Recv.List[0].Type)
 			}
 			if recv != nil {
 				sc.match(decl.Name.Name, kind, decl.Name, recv)
 			} else {
 				sc.match(decl.Name.Name, kind, decl.Name)
 			}
 		case *ast.GenDecl:
 			for _, spec := range decl.Specs {
 				switch spec := spec.(type) {
 				case *ast.TypeSpec:
 					sc.match(spec.Name.Name, typeToKind(sc.current.pkg.GetTypesInfo().TypeOf(spec.Type)), spec.Name)
 					sc.walkType(spec.Type, spec.Name)
 				case *ast.ValueSpec:
 					for _, name := range spec.Names {
 						kind := protocol.Variable
 						if decl.Tok == token.CONST {
 							kind = protocol.Constant
 						}
 						sc.match(name.Name, kind, name)
 					}
 				}
 			}
 		}
 	}
 }

 func unpackRecv(rtyp ast.Expr) *ast.Ident {
 	// Extract the receiver identifier. Lifted from go/types/resolver.go
 L:
 	for {
 		switch t := rtyp.(type) {
 		case *ast.ParenExpr:
 			rtyp = t.X
 		case *ast.StarExpr:
 			rtyp = t.X
 		default:
 			break L
 		}
 	}
 	if name, _ := rtyp.(*ast.Ident); name != nil {
 		return name
 	}
 	return nil
 }

 // walkType processes symbols related to a type expression. path is path of
 // nested type identifiers to the type expression.
 func (sc *symbolCollector) walkType(typ ast.Expr, path ...*ast.Ident) {
 	switch st := typ.(type) {
 	case *ast.StructType:
 		for _, field := range st.Fields.List {
 			sc.walkField(field, protocol.Field, protocol.Field, path...)
 		}
 	case *ast.InterfaceType:
 		for _, field := range st.Methods.List {
 			sc.walkField(field, protocol.Interface, protocol.Method, path...)
 		}
 	}
 }

 // walkField processes symbols related to the struct field or interface method.
 //
 // unnamedKind and namedKind are the symbol kinds if the field is resp. unnamed
 // or named. path is the path of nested identifiers containing the field.
 func (sc *symbolCollector) walkField(field *ast.Field, unnamedKind, namedKind protocol.SymbolKind, path ...*ast.Ident) {
 	if len(field.Names) == 0 {
 		switch typ := field.Type.(type) {
 		case *ast.SelectorExpr:
 			// embedded qualified type
 			sc.match(typ.Sel.Name, unnamedKind, field, path...)
 		default:
 			sc.match(types.ExprString(field.Type), unnamedKind, field, path...)
 		}
 	}
 	for _, name := range field.Names {
 		sc.match(name.Name, namedKind, name, path...)
 		sc.walkType(field.Type, append(path, name)...)
 	}
 }

 func typeToKind(typ types.Type) protocol.SymbolKind {
 	switch typ := typ.Underlying().(type) {
 	case *types.Interface:
 		return protocol.Interface
 	case *types.Struct:
 		return protocol.Struct
 	case *types.Signature:
 		if typ.Recv() != nil {
 			return protocol.Method
 		}
 		return protocol.Function
 	case *types.Named:
 		return typeToKind(typ.Underlying())
 	case *types.Basic:
 		i := typ.Info()
 		switch {
 		case i&types.IsNumeric != 0:
 			return protocol.Number
 		case i&types.IsBoolean != 0:
 			return protocol.Boolean
 		case i&types.IsString != 0:
 			return protocol.String
 		}
 	}
 	return protocol.Variable
 }

 // match finds matches and gathers the symbol identified by name, kind and node
 // via the symbolCollector's matcher after first de-duping against previously
 // seen symbols.
 //
 // path specifies the identifier path to a nested field or interface method.
 func (sc *symbolCollector) match(name string, kind protocol.SymbolKind, node ast.Node, path ...*ast.Ident) {
 	if !node.Pos().IsValid() || !node.End().IsValid() {
 		return
 	}

 	isExported := isExported(name)
 	var names []string
 	for _, ident := range path {
 		names = append(names, ident.Name+".")
 		if !ident.IsExported() {
 			isExported = false
 		}
 	}
 	names = append(names, name)

 	// Factors to apply to the match score for the purpose of downranking
 	// results.
 	//
 	// These numbers were crudely calibrated based on trial-and-error using a
 	// small number of sample queries. Adjust as necessary.
 	//
 	// All factors are multiplicative, meaning if more than one applies they are
 	// multiplied together.
 	const (
 		// nonWorkspaceFactor is applied to symbols outside of any active
 		// workspace. Developers are less likely to want to jump to code that they
 		// are not actively working on.
 		nonWorkspaceFactor = 0.5
 		// nonWorkspaceUnexportedFactor is applied to unexported symbols outside of
 		// any active workspace. Since one wouldn't usually jump to unexported
 		// symbols to understand a package API, they are particularly irrelevant.
 		nonWorkspaceUnexportedFactor = 0.5
 		// fieldFactor is applied to fields and interface methods. One would
 		// typically jump to the type definition first, so ranking fields highly
 		// can be noisy.
 		fieldFactor = 0.5
 	)
 	symbol, score := sc.symbolizer(names, sc.current.pkg, sc.matcher)

 	// Downrank symbols outside of the workspace.
 	if !sc.current.isWorkspace {
 		score *= nonWorkspaceFactor
 		if !isExported {
 			score *= nonWorkspaceUnexportedFactor
 		}
 	}

 	// Downrank fields.
 	if len(path) > 0 {
 		score *= fieldFactor
 	}

 	// Avoid the work below if we know this score will not be sorted into the
 	// results.
 	if score <= sc.res[len(sc.res)-1].score {
 		return
 	}

 	rng, err := fileRange(sc.curFile, node.Pos(), node.End())
 	if err != nil {
 		return
 	}
 	si := symbolInformation{
 		score:     score,
 		name:      name,
 		symbol:    symbol,
 		container: sc.current.pkg.PkgPath(),
 		kind:      kind,
 		location: protocol.Location{
 			URI:   protocol.URIFromSpanURI(sc.curFile.URI),
 			Range: rng,
 		},
 	}
 	insertAt := sort.Search(len(sc.res), func(i int) bool {
 		return sc.res[i].score < score
 	})
 	if insertAt < len(sc.res)-1 {
 		copy(sc.res[insertAt+1:], sc.res[insertAt:len(sc.res)-1])
 	}
 	sc.res[insertAt] = si
 }

 func fileRange(pgf *ParsedGoFile, start, end token.Pos) (protocol.Range, error) {
 	s, err := span.FileSpan(pgf.Tok, pgf.Mapper.Converter, start, end)
 	if err != nil {
 		return protocol.Range{}, nil
 	}
 	return pgf.Mapper.Range(s)
 }

 // isExported reports if a token is exported. Copied from
 // token.IsExported (go1.13+).
 //
 // TODO: replace usage with token.IsExported once go1.12 is no longer
 // supported.
 func isExported(name string) bool {
 	ch, _ := utf8.DecodeRuneInString(name)
 	return unicode.IsUpper(ch)
 }

 // pkgView holds information related to a package that we are going to walk.
 type pkgView struct {
 	pkg         Package
 	isWorkspace bool
 }

 // symbolInformation is a cut-down version of protocol.SymbolInformation that
 // allows struct values of this type to be used as map keys.
 type symbolInformation struct {
 	score     float64
 	name      string
 	symbol    string
 	container string
 	kind      protocol.SymbolKind
 	location  protocol.Location
 }

 // asProtocolSymbolInformation converts s to a protocol.SymbolInformation value.
 //
 // TODO: work out how to handle tags if/when they are needed.
 func (s symbolInformation) asProtocolSymbolInformation() protocol.SymbolInformation {
 	return protocol.SymbolInformation{
 		Name:          s.symbol,
 		Kind:          s.kind,
 		Location:      s.location,
 		ContainerName: s.container,
 	}
 }
	// 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 source

	import (
	"context"
	"fmt"
	"go/ast"
	"go/token"
	"go/types"
	"sort"
	"strings"
	"unicode"
	"unicode/utf8"

	"golang.org/x/tools/internal/event"
	"golang.org/x/tools/internal/lsp/fuzzy"
	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/span"
	)

	// maxSymbols defines the maximum number of symbol results that should ever be
	// sent in response to a client.
	const maxSymbols = 100

	// WorkspaceSymbols matches symbols across all views using the given query,
	// according to the match semantics parameterized by matcherType and style.
	//
	// The workspace symbol method is defined in the spec as follows:
	//
	// The workspace symbol request is sent from the client to the server to
	// list project-wide symbols matching the query string.
	//
	// It is unclear what "project-wide" means here, but given the parameters of
	// workspace/symbol do not include any workspace identifier, then it has to be
	// assumed that "project-wide" means "across all workspaces". Hence why
	// WorkspaceSymbols receives the views []View.
	//
	// However, it then becomes unclear what it would mean to call WorkspaceSymbols
	// with a different configured SymbolMatcher per View. Therefore we assume that
	// Session level configuration will define the SymbolMatcher to be used for the
	// WorkspaceSymbols method.
	func WorkspaceSymbols(ctx context.Context, matcherType SymbolMatcher, style SymbolStyle, views []View, query string) ([]protocol.SymbolInformation, error) {
	ctx, done := event.Start(ctx, "source.WorkspaceSymbols")
	defer done()
	if query == "" {
	return nil, nil
	}
	sc := newSymbolCollector(matcherType, style, query)
	return sc.walk(ctx, views)
	}

	// A matcherFunc determines the matching score of a symbol.
	//
	// See the comment for symbolCollector for more information.
	type matcherFunc func(name string) float64

	// A symbolizer returns the best symbol match for a name with pkg, according to
	// some heuristic. The symbol name is passed as the slice nameParts of logical
	// name pieces. For example, for myType.field the caller can pass either
	// []string{"myType.field"} or []string{"myType.", "field"}.
	//
	// See the comment for symbolCollector for more information.
	type symbolizer func(nameParts []string, pkg Package, m matcherFunc) (string, float64)

	func fullyQualifiedSymbolMatch(nameParts []string, pkg Package, matcher matcherFunc) (string, float64) {
	_, score := dynamicSymbolMatch(nameParts, pkg, matcher)
	path := append([]string{pkg.PkgPath() + "."}, nameParts...)
	if score > 0 {
	return strings.Join(path, ""), score
	}
	return "", 0
	}

	func dynamicSymbolMatch(nameParts []string, pkg Package, matcher matcherFunc) (string, float64) {
	var best string
	fullName := strings.Join(nameParts, "")
	var score float64
	var name string

	// Compute the match score by finding the highest scoring suffix. In these
	// cases the matched symbol is still the full name: it is confusing to match
	// an unqualified nested field or method.
	if match := bestMatch("", nameParts, matcher); match > score {
	best = fullName
	score = match
	}

	// Next: try to match a package-qualified name.
	name = pkg.Name() + "." + fullName
	if match := matcher(name); match > score {
	best = name
	score = match
	}

	// Finally: consider a fully qualified name.
	prefix := pkg.PkgPath() + "."
	fullyQualified := prefix + fullName
	// As with field/method selectors, consider suffixes from right to left, but
	// always return a fully-qualified symbol.
	pathParts := strings.SplitAfter(prefix, "/")
	if match := bestMatch(fullName, pathParts, matcher); match > score {
	best = fullyQualified
	score = match
	}
	return best, score
	}

	func bestMatch(name string, prefixParts []string, matcher matcherFunc) float64 {
	var score float64
	for i := len(prefixParts) - 1; i >= 0; i-- {
	name = prefixParts[i] + name
	if match := matcher(name); match > score {
	score = match
	}
	}
	return score
	}

	func packageSymbolMatch(components []string, pkg Package, matcher matcherFunc) (string, float64) {
	path := append([]string{pkg.Name() + "."}, components...)
	qualified := strings.Join(path, "")
	if matcher(qualified) > 0 {
	return qualified, 1
	}
	return "", 0
	}

	// symbolCollector holds context as we walk Packages, gathering symbols that
	// match a given query.
	//
	// How we match symbols is parameterized by two interfaces:
	// * A matcherFunc determines how well a string symbol matches a query. It
	// returns a non-negative score indicating the quality of the match. A score
	// of zero indicates no match.
	// * A symbolizer determines how we extract the symbol for an object. This
	// enables the 'symbolStyle' configuration option.
	type symbolCollector struct {
	// These types parameterize the symbol-matching pass.
	matcher matcherFunc
	symbolizer symbolizer

	// current holds metadata for the package we are currently walking.
	current *pkgView
	curFile *ParsedGoFile

	res [maxSymbols]symbolInformation
	}

	func newSymbolCollector(matcher SymbolMatcher, style SymbolStyle, query string) *symbolCollector {
	var m matcherFunc
	switch matcher {
	case SymbolFuzzy:
	m = parseQuery(query)
	case SymbolCaseSensitive:
	m = func(s string) float64 {
	if strings.Contains(s, query) {
	return 1
	}
	return 0
	}
	case SymbolCaseInsensitive:
	q := strings.ToLower(query)
	m = func(s string) float64 {
	if strings.Contains(strings.ToLower(s), q) {
	return 1
	}
	return 0
	}
	default:
	panic(fmt.Errorf("unknown symbol matcher: %v", matcher))
	}
	var s symbolizer
	switch style {
	case DynamicSymbols:
	s = dynamicSymbolMatch
	case FullyQualifiedSymbols:
	s = fullyQualifiedSymbolMatch
	case PackageQualifiedSymbols:
	s = packageSymbolMatch
	default:
	panic(fmt.Errorf("unknown symbol style: %v", style))
	}
	return &symbolCollector{
	matcher: m,
	symbolizer: s,
	}
	}

	// parseQuery parses a field-separated symbol query, extracting the special
	// characters listed below, and returns a matcherFunc corresponding to the AND
	// of all field queries.
	//
	// Special characters:
	// ^ match exact prefix
	// $ match exact suffix
	// ' match exact
	//
	// In all three of these special queries, matches are 'smart-cased', meaning
	// they are case sensitive if the symbol query contains any upper-case
	// characters, and case insensitive otherwise.
	func parseQuery(q string) matcherFunc {
	fields := strings.Fields(q)
	if len(fields) == 0 {
	return func(string) float64 { return 0 }
	}
	var funcs []matcherFunc
	for _, field := range fields {
	var f matcherFunc
	switch {
	case strings.HasPrefix(field, "^"):
	prefix := field[1:]
	f = smartCase(prefix, func(s string) float64 {
	if strings.HasPrefix(s, prefix) {
	return 1
	}
	return 0
	})
	case strings.HasPrefix(field, "'"):
	exact := field[1:]
	f = smartCase(exact, func(s string) float64 {
	if strings.Contains(s, exact) {
	return 1
	}
	return 0
	})
	case strings.HasSuffix(field, "$"):
	suffix := field[0 : len(field)-1]
	f = smartCase(suffix, func(s string) float64 {
	if strings.HasSuffix(s, suffix) {
	return 1
	}
	return 0
	})
	default:
	fm := fuzzy.NewMatcher(field)
	f = func(s string) float64 {
	return float64(fm.Score(s))
	}
	}
	funcs = append(funcs, f)
	}
	return comboMatcher(funcs).match
	}

	// smartCase returns a matcherFunc that is case-sensitive if q contains any
	// upper-case characters, and case-insensitive otherwise.
	func smartCase(q string, m matcherFunc) matcherFunc {
	insensitive := strings.ToLower(q) == q
	return func(s string) float64 {
	if insensitive {
	s = strings.ToLower(s)
	}
	return m(s)
	}
	}

	type comboMatcher []matcherFunc

	func (c comboMatcher) match(s string) float64 {
	score := 1.0
	for _, f := range c {
	score *= f(s)
	}
	return score
	}

	// walk walks views, gathers symbols, and returns the results.
	func (sc *symbolCollector) walk(ctx context.Context, views []View) (_ []protocol.SymbolInformation, err error) {
	toWalk, err := sc.collectPackages(ctx, views)
	if err != nil {
	return nil, err
	}
	// Make sure we only walk files once (we might see them more than once due to
	// build constraints).
	seen := make(map[span.URI]bool)
	for _, pv := range toWalk {
	sc.current = pv
	for _, pgf := range pv.pkg.CompiledGoFiles() {
	if seen[pgf.URI] {
	continue
	}
	seen[pgf.URI] = true
	sc.curFile = pgf
	sc.walkFilesDecls(pgf.File.Decls)
	}
	}
	return sc.results(), nil
	}

	func (sc *symbolCollector) results() []protocol.SymbolInformation {
	var res []protocol.SymbolInformation
	for _, si := range sc.res {
	if si.score <= 0 {
	return res
	}
	res = append(res, si.asProtocolSymbolInformation())
	}
	return res
	}

	// collectPackages gathers all known packages and sorts for stability.
	func (sc symbolCollector) collectPackages(ctx context.Context, views []View) ([]pkgView, error) {
	var toWalk []*pkgView
	for _, v := range views {
	snapshot, release := v.Snapshot(ctx)
	defer release()
	knownPkgs, err := snapshot.KnownPackages(ctx)
	if err != nil {
	return nil, err
	}
	// TODO(rfindley): this can result in incomplete information in degraded
	// memory mode.
	workspacePackages, err := snapshot.ActivePackages(ctx)
	if err != nil {
	return nil, err
	}
	isWorkspacePkg := make(map[Package]bool)
	for _, wp := range workspacePackages {
	isWorkspacePkg[wp] = true
	}
	for _, pkg := range knownPkgs {
	toWalk = append(toWalk, &pkgView{
	pkg: pkg,
	isWorkspace: isWorkspacePkg[pkg],
	})
	}
	}
	// Now sort for stability of results. We order by
	// (pkgView.isWorkspace, pkgView.p.ID())
	sort.Slice(toWalk, func(i, j int) bool {
	lhs := toWalk[i]
	rhs := toWalk[j]
	switch {
	case lhs.isWorkspace == rhs.isWorkspace:
	return lhs.pkg.ID() < rhs.pkg.ID()
	case lhs.isWorkspace:
	return true
	default:
	return false
	}
	})
	return toWalk, nil
	}

	func (sc *symbolCollector) walkFilesDecls(decls []ast.Decl) {
	for _, decl := range decls {
	switch decl := decl.(type) {
	case *ast.FuncDecl:
	kind := protocol.Function
	var recv *ast.Ident
	if decl.Recv.NumFields() > 0 {
	kind = protocol.Method
	recv = unpackRecv(decl.Recv.List[0].Type)
	}
	if recv != nil {
	sc.match(decl.Name.Name, kind, decl.Name, recv)
	} else {
	sc.match(decl.Name.Name, kind, decl.Name)
	}
	case *ast.GenDecl:
	for _, spec := range decl.Specs {
	switch spec := spec.(type) {
	case *ast.TypeSpec:
	sc.match(spec.Name.Name, typeToKind(sc.current.pkg.GetTypesInfo().TypeOf(spec.Type)), spec.Name)
	sc.walkType(spec.Type, spec.Name)
	case *ast.ValueSpec:
	for _, name := range spec.Names {
	kind := protocol.Variable
	if decl.Tok == token.CONST {
	kind = protocol.Constant
	}
	sc.match(name.Name, kind, name)
	}
	}
	}
	}
	}
	}

	func unpackRecv(rtyp ast.Expr) *ast.Ident {
	// Extract the receiver identifier. Lifted from go/types/resolver.go
	L:
	for {
	switch t := rtyp.(type) {
	case *ast.ParenExpr:
	rtyp = t.X
	case *ast.StarExpr:
	rtyp = t.X
	default:
	break L
	}
	}
	if name, _ := rtyp.(*ast.Ident); name != nil {
	return name
	}
	return nil
	}

	// walkType processes symbols related to a type expression. path is path of
	// nested type identifiers to the type expression.
	func (sc symbolCollector) walkType(typ ast.Expr, path ...ast.Ident) {
	switch st := typ.(type) {
	case *ast.StructType:
	for _, field := range st.Fields.List {
	sc.walkField(field, protocol.Field, protocol.Field, path...)
	}
	case *ast.InterfaceType:
	for _, field := range st.Methods.List {
	sc.walkField(field, protocol.Interface, protocol.Method, path...)
	}
	}
	}

	// walkField processes symbols related to the struct field or interface method.
	//
	// unnamedKind and namedKind are the symbol kinds if the field is resp. unnamed
	// or named. path is the path of nested identifiers containing the field.
	func (sc symbolCollector) walkField(field ast.Field, unnamedKind, namedKind protocol.SymbolKind, path ...*ast.Ident) {
	if len(field.Names) == 0 {
	switch typ := field.Type.(type) {
	case *ast.SelectorExpr:
	// embedded qualified type
	sc.match(typ.Sel.Name, unnamedKind, field, path...)
	default:
	sc.match(types.ExprString(field.Type), unnamedKind, field, path...)
	}
	}
	for _, name := range field.Names {
	sc.match(name.Name, namedKind, name, path...)
	sc.walkType(field.Type, append(path, name)...)
	}
	}

	func typeToKind(typ types.Type) protocol.SymbolKind {
	switch typ := typ.Underlying().(type) {
	case *types.Interface:
	return protocol.Interface
	case *types.Struct:
	return protocol.Struct
	case *types.Signature:
	if typ.Recv() != nil {
	return protocol.Method
	}
	return protocol.Function
	case *types.Named:
	return typeToKind(typ.Underlying())
	case *types.Basic:
	i := typ.Info()
	switch {
	case i&types.IsNumeric != 0:
	return protocol.Number
	case i&types.IsBoolean != 0:
	return protocol.Boolean
	case i&types.IsString != 0:
	return protocol.String
	}
	}
	return protocol.Variable
	}

	// match finds matches and gathers the symbol identified by name, kind and node
	// via the symbolCollector's matcher after first de-duping against previously
	// seen symbols.
	//
	// path specifies the identifier path to a nested field or interface method.
	func (sc symbolCollector) match(name string, kind protocol.SymbolKind, node ast.Node, path ...ast.Ident) {
	if !node.Pos().IsValid() \|\| !node.End().IsValid() {
	return
	}

	isExported := isExported(name)
	var names []string
	for _, ident := range path {
	names = append(names, ident.Name+".")
	if !ident.IsExported() {
	isExported = false
	}
	}
	names = append(names, name)

	// Factors to apply to the match score for the purpose of downranking
	// results.
	//
	// These numbers were crudely calibrated based on trial-and-error using a
	// small number of sample queries. Adjust as necessary.
	//
	// All factors are multiplicative, meaning if more than one applies they are
	// multiplied together.
	const (
	// nonWorkspaceFactor is applied to symbols outside of any active
	// workspace. Developers are less likely to want to jump to code that they
	// are not actively working on.
	nonWorkspaceFactor = 0.5
	// nonWorkspaceUnexportedFactor is applied to unexported symbols outside of
	// any active workspace. Since one wouldn't usually jump to unexported
	// symbols to understand a package API, they are particularly irrelevant.
	nonWorkspaceUnexportedFactor = 0.5
	// fieldFactor is applied to fields and interface methods. One would
	// typically jump to the type definition first, so ranking fields highly
	// can be noisy.
	fieldFactor = 0.5
	)
	symbol, score := sc.symbolizer(names, sc.current.pkg, sc.matcher)

	// Downrank symbols outside of the workspace.
	if !sc.current.isWorkspace {
	score *= nonWorkspaceFactor
	if !isExported {
	score *= nonWorkspaceUnexportedFactor
	}
	}

	// Downrank fields.
	if len(path) > 0 {
	score *= fieldFactor
	}

	// Avoid the work below if we know this score will not be sorted into the
	// results.
	if score <= sc.res[len(sc.res)-1].score {
	return
	}

	rng, err := fileRange(sc.curFile, node.Pos(), node.End())
	if err != nil {
	return
	}
	si := symbolInformation{
	score: score,
	name: name,
	symbol: symbol,
	container: sc.current.pkg.PkgPath(),
	kind: kind,
	location: protocol.Location{
	URI: protocol.URIFromSpanURI(sc.curFile.URI),
	Range: rng,
	},
	}
	insertAt := sort.Search(len(sc.res), func(i int) bool {
	return sc.res[i].score < score
	})
	if insertAt < len(sc.res)-1 {
	copy(sc.res[insertAt+1:], sc.res[insertAt:len(sc.res)-1])
	}
	sc.res[insertAt] = si
	}

	func fileRange(pgf *ParsedGoFile, start, end token.Pos) (protocol.Range, error) {
	s, err := span.FileSpan(pgf.Tok, pgf.Mapper.Converter, start, end)
	if err != nil {
	return protocol.Range{}, nil
	}
	return pgf.Mapper.Range(s)
	}

	// isExported reports if a token is exported. Copied from
	// token.IsExported (go1.13+).
	//
	// TODO: replace usage with token.IsExported once go1.12 is no longer
	// supported.
	func isExported(name string) bool {
	ch, _ := utf8.DecodeRuneInString(name)
	return unicode.IsUpper(ch)
	}

	// pkgView holds information related to a package that we are going to walk.
	type pkgView struct {
	pkg Package
	isWorkspace bool
	}

	// symbolInformation is a cut-down version of protocol.SymbolInformation that
	// allows struct values of this type to be used as map keys.
	type symbolInformation struct {
	score float64
	name string
	symbol string
	container string
	kind protocol.SymbolKind
	location protocol.Location
	}

	// asProtocolSymbolInformation converts s to a protocol.SymbolInformation value.
	//
	// TODO: work out how to handle tags if/when they are needed.
	func (s symbolInformation) asProtocolSymbolInformation() protocol.SymbolInformation {
	return protocol.SymbolInformation{
	Name: s.symbol,
	Kind: s.kind,
	Location: s.location,
	ContainerName: s.container,
	}
	}