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// 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
// thisQueue holds the current breadth first search queue.
thisQueue []candidate
// nextQueue holds the next breadth first search iteration's queue.
nextQueue []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.nextQueue = append(s.nextQueue, cand)
}
// dequeue removes and returns the leftmost element from the search queue.
func (s *deepCompletionState) dequeue() *candidate {
var cand *candidate
cand, s.thisQueue = &s.thisQueue[len(s.thisQueue)-1], s.thisQueue[:len(s.thisQueue)-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) []types.Object {
path := make([]types.Object, len(cand.path)+1)
copy(path, cand.path)
path[len(path)-1] = obj
return path
}
// 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) {
defer func() {
// We can return early before completing the search, so be sure to
// clear out our queues to not impact any further invocations.
c.deepState.thisQueue = c.deepState.thisQueue[:0]
c.deepState.nextQueue = c.deepState.nextQueue[:0]
}()
for len(c.deepState.nextQueue) > 0 {
c.deepState.thisQueue, c.deepState.nextQueue = c.deepState.nextQueue, c.deepState.thisQueue[:0]
outer:
for _, cand := range c.deepState.thisQueue {
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 := c.deepState.newPath(cand, obj)
// The result of a function call is not addressable.
c.methodsAndFields(sig.Results().At(0).Type(), false, cand.imp, func(newCand candidate) {
newCand.pathInvokeMask = cand.pathInvokeMask | (1 << uint64(len(cand.path)))
newCand.path = path
c.deepState.enqueue(newCand)
})
}
}
path := c.deepState.newPath(cand, obj)
switch obj := obj.(type) {
case *types.PkgName:
c.packageMembers(obj.Imported(), stdScore, cand.imp, func(newCand candidate) {
newCand.pathInvokeMask = cand.pathInvokeMask
newCand.path = path
c.deepState.enqueue(newCand)
})
default:
c.methodsAndFields(obj.Type(), cand.addressable, cand.imp, func(newCand candidate) {
newCand.pathInvokeMask = cand.pathInvokeMask
newCand.path = path
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.hasMod(invoke) {
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
}
// Slight penalty for index modifier (e.g. changing "foo" to
// "foo[]") to curb false positives.
if cand.hasMod(index) {
cand.score *= 0.9
}
// 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 = deepCandName(cand)
if item, err := c.item(ctx, *cand); err == nil {
c.items = append(c.items, item)
}
}
// deepCandName produces the full candidate name including any
// ancestor objects. For example, "foo.bar().baz" for candidate "baz".
func deepCandName(cand *candidate) string {
totalLen := len(cand.obj.Name())
for i, obj := range cand.path {
totalLen += len(obj.Name()) + 1
if cand.pathInvokeMask&(1<<uint16(i)) > 0 {
totalLen += 2
}
}
var buf strings.Builder
buf.Grow(totalLen)
for i, obj := range cand.path {
buf.WriteString(obj.Name())
if cand.pathInvokeMask&(1<<uint16(i)) > 0 {
buf.WriteByte('(')
buf.WriteByte(')')
}
buf.WriteByte('.')
}
buf.WriteString(cand.obj.Name())
return buf.String()
}
// 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
}