internal/lsp/source/completion/deep_completion.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 completion

 import (
 	"context"
 	"go/types"
 	"strings"
 	"time"
 )

 // MaxDeepCompletions limits deep completion results because in most cases
 // there are too many to be useful.
 const MaxDeepCompletions = 3

 // deepCompletionState stores our state as we search for deep completions.
 // "deep completion" refers to searching into objects' fields and methods to
 // find more completion candidates.
 type deepCompletionState struct {
 	// enabled indicates wether deep completion is permitted.
 	enabled bool

 	// queueClosed is used to disable adding new sub-fields to search queue
 	// once we're running out of our time budget.
 	queueClosed bool

 	// searchQueue holds the current breadth first search queue.
 	searchQueue []candidate

 	// highScores tracks the highest deep candidate scores we have found
 	// so far. This is used to avoid work for low scoring deep candidates.
 	highScores [MaxDeepCompletions]float64

 	// candidateCount is the count of unique deep candidates encountered
 	// so far.
 	candidateCount int
 }

 // enqueue adds a candidate to the search queue.
 func (s *deepCompletionState) enqueue(cand candidate) {
 	s.searchQueue = append(s.searchQueue, cand)
 }

 // dequeue removes and returns the leftmost element from the search queue.
 func (s *deepCompletionState) dequeue() *candidate {
 	var cand *candidate
 	cand, s.searchQueue = &s.searchQueue[0], s.searchQueue[1:]
 	return cand
 }

 // scorePenalty computes a deep candidate score penalty. A candidate is
 // penalized based on depth to favor shallower candidates. We also give a
 // slight bonus to unexported objects and a slight additional penalty to
 // function objects.
 func (s *deepCompletionState) scorePenalty(cand *candidate) float64 {
 	var deepPenalty float64
 	for _, dc := range cand.path {
 		deepPenalty++

 		if !dc.Exported() {
 			deepPenalty -= 0.1
 		}

 		if _, isSig := dc.Type().Underlying().(*types.Signature); isSig {
 			deepPenalty += 0.1
 		}
 	}

 	// Normalize penalty to a max depth of 10.
 	return deepPenalty / 10
 }

 // isHighScore returns whether score is among the top MaxDeepCompletions deep
 // candidate scores encountered so far. If so, it adds score to highScores,
 // possibly displacing an existing high score.
 func (s *deepCompletionState) isHighScore(score float64) bool {
 	// Invariant: s.highScores is sorted with highest score first. Unclaimed
 	// positions are trailing zeros.

 	// If we beat an existing score then take its spot.
 	for i, deepScore := range s.highScores {
 		if score <= deepScore {
 			continue
 		}

 		if deepScore != 0 && i != len(s.highScores)-1 {
 			// If this wasn't an empty slot then we need to scooch everyone
 			// down one spot.
 			copy(s.highScores[i+1:], s.highScores[i:])
 		}
 		s.highScores[i] = score
 		return true
 	}

 	return false
 }

 // newPath returns path from search root for an object following a given
 // candidate.
 func (s *deepCompletionState) newPath(cand *candidate, obj types.Object, invoke bool) ([]types.Object, []string) {
 	name := obj.Name()
 	if invoke {
 		name += "()"
 	}

 	// copy the slice since we don't want to overwrite the original slice.
 	path := append([]types.Object{}, cand.path...)
 	names := append([]string{}, cand.names...)

 	return append(path, obj), append(names, name)
 }

 // deepSearch searches a candidate and its subordinate objects for completion
 // items if deep completion is enabled and adds the valid candidates to
 // completion items.
 func (c *completer) deepSearch(ctx context.Context) {
 outer:
 	for len(c.deepState.searchQueue) > 0 {
 		cand := c.deepState.dequeue()
 		obj := cand.obj

 		if obj == nil {
 			continue
 		}

 		// At the top level, dedupe by object.
 		if len(cand.path) == 0 {
 			if c.seen[obj] {
 				continue
 			}
 			c.seen[obj] = true
 		}

 		// If obj is not accessible because it lives in another package and is
 		// not exported, don't treat it as a completion candidate unless it's
 		// a package completion candidate.
 		if !c.completionContext.packageCompletion &&
 			obj.Pkg() != nil && obj.Pkg() != c.pkg.GetTypes() && !obj.Exported() {
 			continue
 		}

 		// If we want a type name, don't offer non-type name candidates.
 		// However, do offer package names since they can contain type names,
 		// and do offer any candidate without a type since we aren't sure if it
 		// is a type name or not (i.e. unimported candidate).
 		if c.wantTypeName() && obj.Type() != nil && !isTypeName(obj) && !isPkgName(obj) {
 			continue
 		}

 		// When searching deep, make sure we don't have a cycle in our chain.
 		// We don't dedupe by object because we want to allow both "foo.Baz"
 		// and "bar.Baz" even though "Baz" is represented the same types.Object
 		// in both.
 		for _, seenObj := range cand.path {
 			if seenObj == obj {
 				continue outer
 			}
 		}

 		c.addCandidate(ctx, cand)

 		c.deepState.candidateCount++
 		if c.opts.budget > 0 && c.deepState.candidateCount%100 == 0 {
 			spent := float64(time.Since(c.startTime)) / float64(c.opts.budget)
 			select {
 			case <-ctx.Done():
 				return
 			default:
 				// If we are almost out of budgeted time, no further elements
 				// should be added to the queue. This ensures remaining time is
 				// used for processing current queue.
 				if !c.deepState.queueClosed && spent >= 0.85 {
 					c.deepState.queueClosed = true
 				}
 			}
 		}

 		// if deep search is disabled, don't add any more candidates.
 		if !c.deepState.enabled || c.deepState.queueClosed {
 			continue
 		}

 		// Searching members for a type name doesn't make sense.
 		if isTypeName(obj) {
 			continue
 		}
 		if obj.Type() == nil {
 			continue
 		}

 		// Don't search embedded fields because they were already included in their
 		// parent's fields.
 		if v, ok := obj.(*types.Var); ok && v.Embedded() {
 			continue
 		}

 		if sig, ok := obj.Type().Underlying().(*types.Signature); ok {
 			// If obj is a function that takes no arguments and returns one
 			// value, keep searching across the function call.
 			if sig.Params().Len() == 0 && sig.Results().Len() == 1 {
 				path, names := c.deepState.newPath(cand, obj, true)
 				// The result of a function call is not addressable.
 				candidates := c.methodsAndFields(sig.Results().At(0).Type(), false, cand.imp)
 				for _, newCand := range candidates {
 					newCand.path, newCand.names = path, names
 					c.deepState.enqueue(newCand)
 				}
 			}
 		}

 		path, names := c.deepState.newPath(cand, obj, false)
 		switch obj := obj.(type) {
 		case *types.PkgName:
 			candidates := c.packageMembers(obj.Imported(), stdScore, cand.imp)
 			for _, newCand := range candidates {
 				newCand.path, newCand.names = path, names
 				c.deepState.enqueue(newCand)
 			}
 		default:
 			candidates := c.methodsAndFields(obj.Type(), cand.addressable, cand.imp)
 			for _, newCand := range candidates {
 				newCand.path, newCand.names = path, names
 				c.deepState.enqueue(newCand)
 			}
 		}
 	}
 }

 // addCandidate adds a completion candidate to suggestions, without searching
 // its members for more candidates.
 func (c *completer) addCandidate(ctx context.Context, cand *candidate) {
 	obj := cand.obj
 	if c.matchingCandidate(cand) {
 		cand.score *= highScore

 		if p := c.penalty(cand); p > 0 {
 			cand.score *= (1 - p)
 		}
 	} else if isTypeName(obj) {
 		// If obj is a *types.TypeName that didn't otherwise match, check
 		// if a literal object of this type makes a good candidate.

 		// We only care about named types (i.e. don't want builtin types).
 		if _, isNamed := obj.Type().(*types.Named); isNamed {
 			c.literal(ctx, obj.Type(), cand.imp)
 		}
 	}

 	// Lower score of method calls so we prefer fields and vars over calls.
 	if cand.expandFuncCall {
 		if sig, ok := obj.Type().Underlying().(*types.Signature); ok && sig.Recv() != nil {
 			cand.score *= 0.9
 		}
 	}

 	// Prefer private objects over public ones.
 	if !obj.Exported() && obj.Parent() != types.Universe {
 		cand.score *= 1.1
 	}

 	// Favor shallow matches by lowering score according to depth.
 	cand.score -= cand.score * c.deepState.scorePenalty(cand)

 	if cand.score < 0 {
 		cand.score = 0
 	}

 	cand.name = strings.Join(append(cand.names, cand.obj.Name()), ".")
 	if item, err := c.item(ctx, *cand); err == nil {
 		c.items = append(c.items, item)
 	}
 }

 // penalty reports a score penalty for cand in the range (0, 1).
 // For example, a candidate is penalized if it has already been used
 // in another switch case statement.
 func (c *completer) penalty(cand *candidate) float64 {
 	for _, p := range c.inference.penalized {
 		if c.objChainMatches(cand, p.objChain) {
 			return p.penalty
 		}
 	}

 	return 0
 }

 // objChainMatches reports whether cand combined with the surrounding
 // object prefix matches chain.
 func (c *completer) objChainMatches(cand *candidate, chain []types.Object) bool {
 	// For example, when completing:
 	//
 	//   foo.ba<>
 	//
 	// If we are considering the deep candidate "bar.baz", cand is baz,
 	// objChain is [foo] and deepChain is [bar]. We would match the
 	// chain [foo, bar, baz].
 	if len(chain) != len(c.inference.objChain)+len(cand.path)+1 {
 		return false
 	}

 	if chain[len(chain)-1] != cand.obj {
 		return false
 	}

 	for i, o := range c.inference.objChain {
 		if chain[i] != o {
 			return false
 		}
 	}

 	for i, o := range cand.path {
 		if chain[i+len(c.inference.objChain)] != o {
 			return false
 		}
 	}

 	return true
 }
	// 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 completion

	import (
	"context"
	"go/types"
	"strings"
	"time"
	)

	// MaxDeepCompletions limits deep completion results because in most cases
	// there are too many to be useful.
	const MaxDeepCompletions = 3

	// deepCompletionState stores our state as we search for deep completions.
	// "deep completion" refers to searching into objects' fields and methods to
	// find more completion candidates.
	type deepCompletionState struct {
	// enabled indicates wether deep completion is permitted.
	enabled bool

	// queueClosed is used to disable adding new sub-fields to search queue
	// once we're running out of our time budget.
	queueClosed bool

	// searchQueue holds the current breadth first search queue.
	searchQueue []candidate

	// highScores tracks the highest deep candidate scores we have found
	// so far. This is used to avoid work for low scoring deep candidates.
	highScores [MaxDeepCompletions]float64

	// candidateCount is the count of unique deep candidates encountered
	// so far.
	candidateCount int
	}

	// enqueue adds a candidate to the search queue.
	func (s *deepCompletionState) enqueue(cand candidate) {
	s.searchQueue = append(s.searchQueue, cand)
	}

	// dequeue removes and returns the leftmost element from the search queue.
	func (s deepCompletionState) dequeue() candidate {
	var cand *candidate
	cand, s.searchQueue = &s.searchQueue[0], s.searchQueue[1:]
	return cand
	}

	// scorePenalty computes a deep candidate score penalty. A candidate is
	// penalized based on depth to favor shallower candidates. We also give a
	// slight bonus to unexported objects and a slight additional penalty to
	// function objects.
	func (s deepCompletionState) scorePenalty(cand candidate) float64 {
	var deepPenalty float64
	for _, dc := range cand.path {
	deepPenalty++

	if !dc.Exported() {
	deepPenalty -= 0.1
	}

	if _, isSig := dc.Type().Underlying().(*types.Signature); isSig {
	deepPenalty += 0.1
	}
	}

	// Normalize penalty to a max depth of 10.
	return deepPenalty / 10
	}

	// isHighScore returns whether score is among the top MaxDeepCompletions deep
	// candidate scores encountered so far. If so, it adds score to highScores,
	// possibly displacing an existing high score.
	func (s *deepCompletionState) isHighScore(score float64) bool {
	// Invariant: s.highScores is sorted with highest score first. Unclaimed
	// positions are trailing zeros.

	// If we beat an existing score then take its spot.
	for i, deepScore := range s.highScores {
	if score <= deepScore {
	continue
	}

	if deepScore != 0 && i != len(s.highScores)-1 {
	// If this wasn't an empty slot then we need to scooch everyone
	// down one spot.
	copy(s.highScores[i+1:], s.highScores[i:])
	}
	s.highScores[i] = score
	return true
	}

	return false
	}

	// newPath returns path from search root for an object following a given
	// candidate.
	func (s deepCompletionState) newPath(cand candidate, obj types.Object, invoke bool) ([]types.Object, []string) {
	name := obj.Name()
	if invoke {
	name += "()"
	}

	// copy the slice since we don't want to overwrite the original slice.
	path := append([]types.Object{}, cand.path...)
	names := append([]string{}, cand.names...)

	return append(path, obj), append(names, name)
	}

	// deepSearch searches a candidate and its subordinate objects for completion
	// items if deep completion is enabled and adds the valid candidates to
	// completion items.
	func (c *completer) deepSearch(ctx context.Context) {
	outer:
	for len(c.deepState.searchQueue) > 0 {
	cand := c.deepState.dequeue()
	obj := cand.obj

	if obj == nil {
	continue
	}

	// At the top level, dedupe by object.
	if len(cand.path) == 0 {
	if c.seen[obj] {
	continue
	}
	c.seen[obj] = true
	}

	// If obj is not accessible because it lives in another package and is
	// not exported, don't treat it as a completion candidate unless it's
	// a package completion candidate.
	if !c.completionContext.packageCompletion &&
	obj.Pkg() != nil && obj.Pkg() != c.pkg.GetTypes() && !obj.Exported() {
	continue
	}

	// If we want a type name, don't offer non-type name candidates.
	// However, do offer package names since they can contain type names,
	// and do offer any candidate without a type since we aren't sure if it
	// is a type name or not (i.e. unimported candidate).
	if c.wantTypeName() && obj.Type() != nil && !isTypeName(obj) && !isPkgName(obj) {
	continue
	}

	// When searching deep, make sure we don't have a cycle in our chain.
	// We don't dedupe by object because we want to allow both "foo.Baz"
	// and "bar.Baz" even though "Baz" is represented the same types.Object
	// in both.
	for _, seenObj := range cand.path {
	if seenObj == obj {
	continue outer
	}
	}

	c.addCandidate(ctx, cand)

	c.deepState.candidateCount++
	if c.opts.budget > 0 && c.deepState.candidateCount%100 == 0 {
	spent := float64(time.Since(c.startTime)) / float64(c.opts.budget)
	select {
	case <-ctx.Done():
	return
	default:
	// If we are almost out of budgeted time, no further elements
	// should be added to the queue. This ensures remaining time is
	// used for processing current queue.
	if !c.deepState.queueClosed && spent >= 0.85 {
	c.deepState.queueClosed = true
	}
	}
	}

	// if deep search is disabled, don't add any more candidates.
	if !c.deepState.enabled \|\| c.deepState.queueClosed {
	continue
	}

	// Searching members for a type name doesn't make sense.
	if isTypeName(obj) {
	continue
	}
	if obj.Type() == nil {
	continue
	}

	// Don't search embedded fields because they were already included in their
	// parent's fields.
	if v, ok := obj.(*types.Var); ok && v.Embedded() {
	continue
	}

	if sig, ok := obj.Type().Underlying().(*types.Signature); ok {
	// If obj is a function that takes no arguments and returns one
	// value, keep searching across the function call.
	if sig.Params().Len() == 0 && sig.Results().Len() == 1 {
	path, names := c.deepState.newPath(cand, obj, true)
	// The result of a function call is not addressable.
	candidates := c.methodsAndFields(sig.Results().At(0).Type(), false, cand.imp)
	for _, newCand := range candidates {
	newCand.path, newCand.names = path, names
	c.deepState.enqueue(newCand)
	}
	}
	}

	path, names := c.deepState.newPath(cand, obj, false)
	switch obj := obj.(type) {
	case *types.PkgName:
	candidates := c.packageMembers(obj.Imported(), stdScore, cand.imp)
	for _, newCand := range candidates {
	newCand.path, newCand.names = path, names
	c.deepState.enqueue(newCand)
	}
	default:
	candidates := c.methodsAndFields(obj.Type(), cand.addressable, cand.imp)
	for _, newCand := range candidates {
	newCand.path, newCand.names = path, names
	c.deepState.enqueue(newCand)
	}
	}
	}
	}

	// addCandidate adds a completion candidate to suggestions, without searching
	// its members for more candidates.
	func (c completer) addCandidate(ctx context.Context, cand candidate) {
	obj := cand.obj
	if c.matchingCandidate(cand) {
	cand.score *= highScore

	if p := c.penalty(cand); p > 0 {
	cand.score *= (1 - p)
	}
	} else if isTypeName(obj) {
	// If obj is a *types.TypeName that didn't otherwise match, check
	// if a literal object of this type makes a good candidate.

	// We only care about named types (i.e. don't want builtin types).
	if _, isNamed := obj.Type().(*types.Named); isNamed {
	c.literal(ctx, obj.Type(), cand.imp)
	}
	}

	// Lower score of method calls so we prefer fields and vars over calls.
	if cand.expandFuncCall {
	if sig, ok := obj.Type().Underlying().(*types.Signature); ok && sig.Recv() != nil {
	cand.score *= 0.9
	}
	}

	// Prefer private objects over public ones.
	if !obj.Exported() && obj.Parent() != types.Universe {
	cand.score *= 1.1
	}

	// Favor shallow matches by lowering score according to depth.
	cand.score -= cand.score * c.deepState.scorePenalty(cand)

	if cand.score < 0 {
	cand.score = 0
	}

	cand.name = strings.Join(append(cand.names, cand.obj.Name()), ".")
	if item, err := c.item(ctx, *cand); err == nil {
	c.items = append(c.items, item)
	}
	}

	// penalty reports a score penalty for cand in the range (0, 1).
	// For example, a candidate is penalized if it has already been used
	// in another switch case statement.
	func (c completer) penalty(cand candidate) float64 {
	for _, p := range c.inference.penalized {
	if c.objChainMatches(cand, p.objChain) {
	return p.penalty
	}
	}

	return 0
	}

	// objChainMatches reports whether cand combined with the surrounding
	// object prefix matches chain.
	func (c completer) objChainMatches(cand candidate, chain []types.Object) bool {
	// For example, when completing:
	//
	// foo.ba<>
	//
	// If we are considering the deep candidate "bar.baz", cand is baz,
	// objChain is [foo] and deepChain is [bar]. We would match the
	// chain [foo, bar, baz].
	if len(chain) != len(c.inference.objChain)+len(cand.path)+1 {
	return false
	}

	if chain[len(chain)-1] != cand.obj {
	return false
	}

	for i, o := range c.inference.objChain {
	if chain[i] != o {
	return false
	}
	}

	for i, o := range cand.path {
	if chain[i+len(c.inference.objChain)] != o {
	return false
	}
	}

	return true
	}