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"
 )

 // searchItem represents a candidate in deep completion search queue.
 type searchItem struct {
 	*searchPath
 	cand candidate
 }

 // searchPath holds the path from search root (excluding the item itself) for
 // a searchItem.
 type searchPath struct {
 	path  []types.Object
 	names []string
 }

 // 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. It should be
 	// reset to original value if manually disabled for an individual case.
 	enabled bool

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

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

 	// curPath tracks the current deep completion search path.
 	curPath *searchPath

 	// 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 candidates to the search queue.
 func (s *deepCompletionState) enqueue(path *searchPath, candidates ...candidate) {
 	for _, cand := range candidates {
 		s.searchQueue = append(s.searchQueue, searchItem{path, cand})
 	}
 }

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

 // 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() float64 {
 	var deepPenalty float64
 	for _, dc := range s.curPath.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
 }

 // inDeepCompletion returns if we're currently searching an object's members.
 func (s *deepCompletionState) inDeepCompletion() bool {
 	return len(s.curPath.path) > 0
 }

 // reset resets deepCompletionState since found might be called multiple times.
 // We don't reset high scores since multiple calls to found still respect the
 // same MaxDeepCompletions count.
 func (s *deepCompletionState) reset() {
 	s.searchQueue = nil
 	s.curPath = &searchPath{}
 }

 // appendToSearchPath appends an object to a given searchPath.
 func appendToSearchPath(oldPath searchPath, obj types.Object, invoke bool) *searchPath {
 	name := obj.Name()
 	if invoke {
 		name += "()"
 	}

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

 	return &searchPath{
 		path:  append(path, obj),
 		names: append(names, name),
 	}
 }

 // found adds a candidate to completion items if it's a valid suggestion and
 // searches the candidate's subordinate objects for more completion items if
 // deep completion is enabled.
 func (c *completer) found(ctx context.Context, cand candidate) {
 	// reset state at the end so current state doesn't affect completions done
 	// outside c.found.
 	defer c.deepState.reset()

 	// At the top level, dedupe by object.
 	if c.seen[cand.obj] {
 		return
 	}
 	c.seen[cand.obj] = true

 	c.deepState.enqueue(&searchPath{}, cand)
 outer:
 	for len(c.deepState.searchQueue) > 0 {
 		item := c.deepState.dequeue()
 		curCand := item.cand
 		obj := curCand.obj

 		// If obj is not accessible because it lives in another package and is
 		// not exported, don't treat it as a completion candidate.
 		if 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 item.path {
 			if seenObj == obj {
 				continue outer
 			}
 		}

 		// update tracked current path since other functions might check it.
 		c.deepState.curPath = item.searchPath

 		c.addCandidate(ctx, curCand)

 		c.deepState.candidateCount++
 		if c.opts.budget > 0 && c.deepState.candidateCount%100 == 0 {
 			spent := float64(time.Since(c.startTime)) / float64(c.opts.budget)
 			if spent > 1.0 {
 				return
 			}
 			// 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 {
 				newSearchPath := appendToSearchPath(*item.searchPath, obj, true)
 				// The result of a function call is not addressable.
 				candidates := c.methodsAndFields(ctx, sig.Results().At(0).Type(), false, curCand.imp)
 				c.deepState.enqueue(newSearchPath, candidates...)
 			}
 		}

 		newSearchPath := appendToSearchPath(*item.searchPath, obj, false)
 		switch obj := obj.(type) {
 		case *types.PkgName:
 			candidates := c.packageMembers(ctx, obj.Imported(), stdScore, curCand.imp)
 			c.deepState.enqueue(newSearchPath, candidates...)
 		default:
 			candidates := c.methodsAndFields(ctx, obj.Type(), curCand.addressable, curCand.imp)
 			c.deepState.enqueue(newSearchPath, candidates...)
 		}
 	}
 }

 // 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()

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

 	cand.name = strings.Join(append(c.deepState.curPath.names, cand.obj.Name()), ".")
 	matchScore := c.matcher.Score(cand.name)
 	if matchScore > 0 {
 		cand.score *= float64(matchScore)

 		// Avoid calling c.item() for deep candidates that wouldn't be in the top
 		// MaxDeepCompletions anyway.
 		if !c.deepState.inDeepCompletion() || c.deepState.isHighScore(cand.score) {
 			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.obj, p.objChain) {
 			return p.penalty
 		}
 	}

 	return 0
 }

 // objChainMatches reports whether cand combined with the surrounding
 // object prefix matches chain.
 func (c *completer) objChainMatches(cand types.Object, 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(c.deepState.curPath.path)+1 {
 		return false
 	}

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

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

 	for i, o := range c.deepState.curPath.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"
	)

	// searchItem represents a candidate in deep completion search queue.
	type searchItem struct {
	*searchPath
	cand candidate
	}

	// searchPath holds the path from search root (excluding the item itself) for
	// a searchItem.
	type searchPath struct {
	path []types.Object
	names []string
	}

	// 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. It should be
	// reset to original value if manually disabled for an individual case.
	enabled bool

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

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

	// curPath tracks the current deep completion search path.
	curPath *searchPath

	// 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 candidates to the search queue.
	func (s deepCompletionState) enqueue(path searchPath, candidates ...candidate) {
	for _, cand := range candidates {
	s.searchQueue = append(s.searchQueue, searchItem{path, cand})
	}
	}

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

	// 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() float64 {
	var deepPenalty float64
	for _, dc := range s.curPath.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
	}

	// inDeepCompletion returns if we're currently searching an object's members.
	func (s *deepCompletionState) inDeepCompletion() bool {
	return len(s.curPath.path) > 0
	}

	// reset resets deepCompletionState since found might be called multiple times.
	// We don't reset high scores since multiple calls to found still respect the
	// same MaxDeepCompletions count.
	func (s *deepCompletionState) reset() {
	s.searchQueue = nil
	s.curPath = &searchPath{}
	}

	// appendToSearchPath appends an object to a given searchPath.
	func appendToSearchPath(oldPath searchPath, obj types.Object, invoke bool) *searchPath {
	name := obj.Name()
	if invoke {
	name += "()"
	}

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

	return &searchPath{
	path: append(path, obj),
	names: append(names, name),
	}
	}

	// found adds a candidate to completion items if it's a valid suggestion and
	// searches the candidate's subordinate objects for more completion items if
	// deep completion is enabled.
	func (c *completer) found(ctx context.Context, cand candidate) {
	// reset state at the end so current state doesn't affect completions done
	// outside c.found.
	defer c.deepState.reset()

	// At the top level, dedupe by object.
	if c.seen[cand.obj] {
	return
	}
	c.seen[cand.obj] = true

	c.deepState.enqueue(&searchPath{}, cand)
	outer:
	for len(c.deepState.searchQueue) > 0 {
	item := c.deepState.dequeue()
	curCand := item.cand
	obj := curCand.obj

	// If obj is not accessible because it lives in another package and is
	// not exported, don't treat it as a completion candidate.
	if 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 item.path {
	if seenObj == obj {
	continue outer
	}
	}

	// update tracked current path since other functions might check it.
	c.deepState.curPath = item.searchPath

	c.addCandidate(ctx, curCand)

	c.deepState.candidateCount++
	if c.opts.budget > 0 && c.deepState.candidateCount%100 == 0 {
	spent := float64(time.Since(c.startTime)) / float64(c.opts.budget)
	if spent > 1.0 {
	return
	}
	// 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 {
	newSearchPath := appendToSearchPath(*item.searchPath, obj, true)
	// The result of a function call is not addressable.
	candidates := c.methodsAndFields(ctx, sig.Results().At(0).Type(), false, curCand.imp)
	c.deepState.enqueue(newSearchPath, candidates...)
	}
	}

	newSearchPath := appendToSearchPath(*item.searchPath, obj, false)
	switch obj := obj.(type) {
	case *types.PkgName:
	candidates := c.packageMembers(ctx, obj.Imported(), stdScore, curCand.imp)
	c.deepState.enqueue(newSearchPath, candidates...)
	default:
	candidates := c.methodsAndFields(ctx, obj.Type(), curCand.addressable, curCand.imp)
	c.deepState.enqueue(newSearchPath, candidates...)
	}
	}
	}

	// 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()

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

	cand.name = strings.Join(append(c.deepState.curPath.names, cand.obj.Name()), ".")
	matchScore := c.matcher.Score(cand.name)
	if matchScore > 0 {
	cand.score *= float64(matchScore)

	// Avoid calling c.item() for deep candidates that wouldn't be in the top
	// MaxDeepCompletions anyway.
	if !c.deepState.inDeepCompletion() \|\| c.deepState.isHighScore(cand.score) {
	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.obj, p.objChain) {
	return p.penalty
	}
	}

	return 0
	}

	// objChainMatches reports whether cand combined with the surrounding
	// object prefix matches chain.
	func (c *completer) objChainMatches(cand types.Object, 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(c.deepState.curPath.path)+1 {
	return false
	}

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

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

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

	return true
	}