gopls/internal/lsp: go to definition from embed directive

Enable jump to definition on //go:embed directive arguments.
If multiple files match the pattern one is picked at random.

Improve the pattern matching for both definition and hover to
exclude directories since they are not embeddable in themselves.

Updates golang/go#50262

Change-Id: I09da40f195e8edfe661acaacd99f62d9f577e9ea
Reviewed-on: https://go-review.googlesource.com/c/tools/+/531775
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

gopls/internal/lsp/definition.go

@@ -6,7 +6,6 @@ package lsp
 
 import (
 	"context"
-	"errors"
 	"fmt"
 
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
@@ -36,11 +35,6 @@ func (s *Server) definition(ctx context.Context, params *protocol.DefinitionPara
 	case source.Tmpl:
 		return template.Definition(snapshot, fh, params.Position)
 	case source.Go:
-		// Partial support for jumping from linkname directive (position at 2nd argument).
-		locations, err := source.LinknameDefinition(ctx, snapshot, fh, params.Position)
-		if !errors.Is(err, source.ErrNoLinkname) {
-			return locations, err
-		}
 		return source.Definition(ctx, snapshot, fh, params.Position)
 	default:
 		return nil, fmt.Errorf("can't find definitions for file type %s", kind)

gopls/internal/lsp/source/definition.go

@@ -6,6 +6,7 @@ package source
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"go/ast"
 	"go/token"
@@ -58,6 +59,18 @@ func Definition(ctx context.Context, snapshot Snapshot, fh FileHandle, position
 		return []protocol.Location{loc}, nil
 	}
 
+	// Handle the case where the cursor is in a linkname directive.
+	locations, err := LinknameDefinition(ctx, snapshot, fh, position)
+	if !errors.Is(err, ErrNoLinkname) {
+		return locations, err
+	}
+
+	// Handle the case where the cursor is in an embed directive.
+	locations, err = EmbedDefinition(pgf.Mapper, position)
+	if !errors.Is(err, ErrNoEmbed) {
+		return locations, err
+	}
+
 	// The general case: the cursor is on an identifier.
 	_, obj, _ := referencedObject(pkg, pgf, pos)
 	if obj == nil {

gopls/internal/lsp/source/embeddirective.go

@@ -5,7 +5,10 @@
 package source
 
 import (
+	"errors"
 	"fmt"
+	"io/fs"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"unicode"
@@ -14,6 +17,59 @@ import (
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 )
 
+// ErrNoEmbed is returned by EmbedDefinition when no embed
+// directive is found at a particular position.
+// As such it indicates that other definitions could be worth checking.
+var ErrNoEmbed = errors.New("no embed directive found")
+
+var errStopWalk = errors.New("stop walk")
+
+// EmbedDefinition finds a file matching the embed directive at pos in the mapped file.
+// If there is no embed directive at pos, returns ErrNoEmbed.
+// If multiple files match the embed pattern, one is picked at random.
+func EmbedDefinition(m *protocol.Mapper, pos protocol.Position) ([]protocol.Location, error) {
+	pattern, _ := parseEmbedDirective(m, pos)
+	if pattern == "" {
+		return nil, ErrNoEmbed
+	}
+
+	// Find the first matching file.
+	var match string
+	dir := filepath.Dir(m.URI.Filename())
+	err := filepath.WalkDir(dir, func(abs string, d fs.DirEntry, e error) error {
+		if e != nil {
+			return e
+		}
+		rel, err := filepath.Rel(dir, abs)
+		if err != nil {
+			return err
+		}
+		ok, err := filepath.Match(pattern, rel)
+		if err != nil {
+			return err
+		}
+		if ok && !d.IsDir() {
+			match = abs
+			return errStopWalk
+		}
+		return nil
+	})
+	if err != nil && !errors.Is(err, errStopWalk) {
+		return nil, err
+	}
+	if match == "" {
+		return nil, fmt.Errorf("%q does not match any files in %q", pattern, dir)
+	}
+
+	loc := protocol.Location{
+		URI: protocol.URIFromPath(match),
+		Range: protocol.Range{
+			Start: protocol.Position{Line: 0, Character: 0},
+		},
+	}
+	return []protocol.Location{loc}, nil
+}
+
 // parseEmbedDirective attempts to parse a go:embed directive argument at pos.
 // If successful it return the directive argument and its range, else zero values are returned.
 func parseEmbedDirective(m *protocol.Mapper, pos protocol.Position) (string, protocol.Range) {

gopls/internal/lsp/source/hover.go

@@ -640,7 +640,7 @@ func hoverEmbed(fh FileHandle, rng protocol.Range, pattern string) (protocol.Ran
 
 	dir := filepath.Dir(fh.URI().Filename())
 	var matches []string
-	err := filepath.WalkDir(dir, func(abs string, _ fs.DirEntry, e error) error {
+	err := filepath.WalkDir(dir, func(abs string, d fs.DirEntry, e error) error {
 		if e != nil {
 			return e
 		}
@@ -652,7 +652,7 @@ func hoverEmbed(fh FileHandle, rng protocol.Range, pattern string) (protocol.Ran
 		if err != nil {
 			return err
 		}
-		if ok {
+		if ok && !d.IsDir() {
 			matches = append(matches, rel)
 		}
 		return nil

gopls/internal/regtest/misc/definition_test.go

@@ -529,3 +529,43 @@ const _ = b.K
 		}
 	})
 }
+
+const embedDefinition = `
+-- go.mod --
+module mod.com
+
+-- main.go --
+package main
+
+import (
+	"embed"
+)
+
+//go:embed *.txt
+var foo embed.FS
+
+func main() {}
+
+-- skip.sql --
+SKIP
+
+-- foo.txt --
+FOO
+
+-- skip.bat --
+SKIP
+`
+
+func TestGoToEmbedDefinition(t *testing.T) {
+	Run(t, embedDefinition, func(t *testing.T, env *Env) {
+		env.OpenFile("main.go")
+
+		start := env.RegexpSearch("main.go", `\*.txt`)
+		loc := env.GoToDefinition(start)
+
+		name := env.Sandbox.Workdir.URIToPath(loc.URI)
+		if want := "foo.txt"; name != want {
+			t.Errorf("GoToDefinition: got file %q, want %q", name, want)
+		}
+	})
+}

gopls/internal/regtest/misc/hover_test.go

@@ -458,6 +458,8 @@ BAR
 BAZ
 -- other.sql --
 SKIPPED
+-- dir.txt/skip.txt --
+SKIPPED
 `
 
 func TestHoverEmbedDirective(t *testing.T) {
@@ -478,5 +480,14 @@ func TestHoverEmbedDirective(t *testing.T) {
 				t.Errorf("hover: %q does not contain: %q", content, want)
 			}
 		}
+
+		// A directory should never be matched, even if it happens to have a matching name.
+		// Content in subdirectories should not match on only one asterisk.
+		skips := []string{"other.sql", "dir.txt", "skip.txt"}
+		for _, skip := range skips {
+			if strings.Contains(content, skip) {
+				t.Errorf("hover: %q should not contain: %q", content, skip)
+			}
+		}
 	})
 }