internal/lsp: add completion for use directives

For golang/go#50930

Change-Id: I9def58e9406ee735c93e988de336dbfee37e6c95
Reviewed-on: https://go-review.googlesource.com/c/tools/+/390054
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

gopls/internal/regtest/completion/completion_test.go

@@ -599,3 +599,48 @@ func BenchmarkFoo()
 		}
 	})
 }
+
+func TestGoWorkCompletion(t *testing.T) {
+	const files = `
+-- go.work --
+go 1.18
+
+use ./a
+use ./a/ba
+use ./a/b/
+use ./dir/foo
+use ./dir/foobar/
+-- a/go.mod --
+-- go.mod --
+-- a/bar/go.mod --
+-- a/b/c/d/e/f/go.mod --
+-- dir/bar --
+-- dir/foobar/go.mod --
+`
+
+	Run(t, files, func(t *testing.T, env *Env) {
+		env.OpenFile("go.work")
+
+		tests := []struct {
+			re   string
+			want []string
+		}{
+			{`use ()\.`, []string{".", "./a", "./a/bar", "./dir/foobar"}},
+			{`use \.()`, []string{"", "/a", "/a/bar", "/dir/foobar"}},
+			{`use \./()`, []string{"a", "a/bar", "dir/foobar"}},
+			{`use ./a()`, []string{"", "/b/c/d/e/f", "/bar"}},
+			{`use ./a/b()`, []string{"/c/d/e/f", "ar"}},
+			{`use ./a/b/()`, []string{`c/d/e/f`}},
+			{`use ./a/ba()`, []string{"r"}},
+			{`use ./dir/foo()`, []string{"bar"}},
+			{`use ./dir/foobar/()`, []string{}},
+		}
+		for _, tt := range tests {
+			completions := env.Completion("go.work", env.RegexpSearch("go.work", tt.re))
+			diff := compareCompletionResults(tt.want, completions.Items)
+			if diff != "" {
+				t.Errorf("%s: %s", tt.re, diff)
+			}
+		}
+	})
+}

internal/lsp/completion.go

@@ -16,6 +16,7 @@ import (
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/lsp/source/completion"
 	"golang.org/x/tools/internal/lsp/template"
+	"golang.org/x/tools/internal/lsp/work"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -32,6 +33,12 @@ func (s *Server) completion(ctx context.Context, params *protocol.CompletionPara
 		candidates, surrounding, err = completion.Completion(ctx, snapshot, fh, params.Position, params.Context)
 	case source.Mod:
 		candidates, surrounding = nil, nil
+	case source.Work:
+		cl, err := work.Completion(ctx, snapshot, fh, params.Position)
+		if err != nil {
+			break
+		}
+		return cl, nil
 	case source.Tmpl:
 		var cl *protocol.CompletionList
 		cl, err = template.Completion(ctx, snapshot, fh, params.Position, params.Context)

internal/lsp/work/completion.go

@@ -0,0 +1,159 @@
+// Copyright 2022 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 work
+
+import (
+	"context"
+	"go/token"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"golang.org/x/tools/internal/event"
+	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/lsp/source"
+	errors "golang.org/x/xerrors"
+)
+
+func Completion(ctx context.Context, snapshot source.Snapshot, fh source.VersionedFileHandle, position protocol.Position) (*protocol.CompletionList, error) {
+	ctx, done := event.Start(ctx, "work.Completion")
+	defer done()
+
+	// Get the position of the cursor.
+	pw, err := snapshot.ParseWork(ctx, fh)
+	if err != nil {
+		return nil, errors.Errorf("getting go.work file handle: %w", err)
+	}
+	spn, err := pw.Mapper.PointSpan(position)
+	if err != nil {
+		return nil, errors.Errorf("computing cursor position: %w", err)
+	}
+	rng, err := spn.Range(pw.Mapper.Converter)
+	if err != nil {
+		return nil, errors.Errorf("computing range: %w", err)
+	}
+
+	// Find the use statement the user is in.
+	cursor := rng.Start - 1
+	use, pathStart, _ := usePath(pw, cursor)
+	if use == nil {
+		return &protocol.CompletionList{}, nil
+	}
+	completingFrom := use.Path[:cursor-token.Pos(pathStart)]
+
+	// We're going to find the completions of the user input
+	// (completingFrom) by doing a walk on the innermost directory
+	// of the given path, and comparing the found paths to make sure
+	// that they match the component of the path after the
+	// innermost directory.
+	//
+	// We'll maintain two paths when doing this: pathPrefixSlash
+	// is essentially the path the user typed in, and pathPrefixAbs
+	// is the path made absolute from the go.work directory.
+
+	pathPrefixSlash := completingFrom
+	pathPrefixAbs := filepath.FromSlash(pathPrefixSlash)
+	if !filepath.IsAbs(pathPrefixAbs) {
+		pathPrefixAbs = filepath.Join(filepath.Dir(pw.URI.Filename()), pathPrefixAbs)
+	}
+
+	// pathPrefixDir is the directory that will be walked to find matches.
+	// If pathPrefixSlash is not explicitly a directory boundary (is either equivalent to "." or
+	// ends in a separator) we need to examine its parent directory to find sibling files that
+	// match.
+	depthBound := 5
+	pathPrefixDir, pathPrefixBase := pathPrefixAbs, ""
+	pathPrefixSlashDir := pathPrefixSlash
+	if filepath.Clean(pathPrefixSlash) != "." && !strings.HasSuffix(pathPrefixSlash, "/") {
+		depthBound++
+		pathPrefixDir, pathPrefixBase = filepath.Split(pathPrefixAbs)
+		pathPrefixSlashDir = dirNonClean(pathPrefixSlash)
+	}
+
+	var completions []string
+	// Stop traversing deeper once we've hit 10k files to try to stay generally under 100ms.
+	const numSeenBound = 10000
+	var numSeen int
+	stopWalking := errors.New("hit numSeenBound")
+	err = filepath.Walk(pathPrefixDir, func(wpath string, info os.FileInfo, err error) error {
+		if numSeen > numSeenBound {
+			// Stop traversing if we hit bound.
+			return stopWalking
+		}
+		numSeen++
+
+		// rel is the path relative to pathPrefixDir.
+		// Make sure that it has pathPrefixBase as a prefix
+		// otherwise it won't match the beginning of the
+		// base component of the path the user typed in.
+		rel := strings.TrimPrefix(wpath[len(pathPrefixDir):], string(filepath.Separator))
+		if info.IsDir() && wpath != pathPrefixDir && !strings.HasPrefix(rel, pathPrefixBase) {
+			return filepath.SkipDir
+		}
+
+		// Check for a match (a module directory).
+		if filepath.Base(rel) == "go.mod" {
+			relDir := strings.TrimSuffix(dirNonClean(rel), string(os.PathSeparator))
+			completionPath := join(pathPrefixSlashDir, filepath.ToSlash(relDir))
+
+			if !strings.HasPrefix(completionPath, completingFrom) {
+				return nil
+			}
+			if strings.HasSuffix(completionPath, "/") {
+				// Don't suggest paths that end in "/". This happens
+				// when the input is a path that ends in "/" and
+				// the completion is empty.
+				return nil
+			}
+			completion := completionPath[len(completingFrom):]
+			if completingFrom == "" && !strings.HasPrefix(completion, "./") {
+				// Bias towards "./" prefixes.
+				completion = join(".", completion)
+			}
+
+			completions = append(completions, completion)
+		}
+
+		if depth := strings.Count(rel, string(filepath.Separator)); depth >= depthBound {
+			return filepath.SkipDir
+		}
+		return nil
+	})
+	if err != nil && !errors.Is(err, stopWalking) {
+		return nil, errors.Errorf("walking to find completions: %w", err)
+	}
+
+	sort.Strings(completions)
+
+	var items []protocol.CompletionItem
+	for _, c := range completions {
+		items = append(items, protocol.CompletionItem{
+			Label:      c,
+			InsertText: c,
+		})
+	}
+	return &protocol.CompletionList{Items: items}, nil
+}
+
+// dirNonClean is filepath.Dir, without the Clean at the end.
+func dirNonClean(path string) string {
+	vol := filepath.VolumeName(path)
+	i := len(path) - 1
+	for i >= len(vol) && !os.IsPathSeparator(path[i]) {
+		i--
+	}
+	return path[len(vol) : i+1]
+}
+
+func join(a, b string) string {
+	if a == "" {
+		return b
+	}
+	if b == "" {
+		return a
+	}
+	return strings.TrimSuffix(a, "/") + "/" + b
+}

internal/lsp/work/hover.go

@@ -41,24 +41,7 @@ func Hover(ctx context.Context, snapshot source.Snapshot, fh source.FileHandle,
 
 	// Confirm that the cursor is inside a use statement, and then find
 	// the position of the use statement's directory path.
-	var use *modfile.Use
-	var pathStart, pathEnd int
-	for _, u := range pw.File.Use {
-		dep := []byte(u.Path)
-		s, e := u.Syntax.Start.Byte, u.Syntax.End.Byte
-		i := bytes.Index(pw.Mapper.Content[s:e], dep)
-		if i == -1 {
-			// This should not happen.
-			continue
-		}
-		// Shift the start position to the location of the
-		// module directory within the use statement.
-		pathStart, pathEnd = s+i, s+i+len(dep)
-		if token.Pos(pathStart) <= hoverRng.Start && hoverRng.Start <= token.Pos(pathEnd) {
-			use = u
-			break
-		}
-	}
+	use, pathStart, pathEnd := usePath(pw, hoverRng.Start)
 
 	// The cursor position is not on a use statement.
 	if use == nil {
@@ -87,3 +70,22 @@ func Hover(ctx context.Context, snapshot source.Snapshot, fh source.FileHandle,
 		Range: rng,
 	}, nil
 }
+
+func usePath(pw *source.ParsedWorkFile, pos token.Pos) (use *modfile.Use, pathStart, pathEnd int) {
+	for _, u := range pw.File.Use {
+		path := []byte(u.Path)
+		s, e := u.Syntax.Start.Byte, u.Syntax.End.Byte
+		i := bytes.Index(pw.Mapper.Content[s:e], path)
+		if i == -1 {
+			// This should not happen.
+			continue
+		}
+		// Shift the start position to the location of the
+		// module directory within the use statement.
+		pathStart, pathEnd = s+i, s+i+len(path)
+		if token.Pos(pathStart) <= pos && pos <= token.Pos(pathEnd) {
+			return u, pathStart, pathEnd
+		}
+	}
+	return nil, 0, 0
+}