gopls/internal/golang: avoid PackageSymbols errors with missing packages

As reported in golang/vscode-go#3681, spurious errors from
gopls.package_symbols can cause very distracting popups in VS Code.

For now, err on the side of silence. In the future, we may want to
revisit this behavior.

For golang/vscode-go#3681

Change-Id: I67f8b8e1e299ef88dabbb284a151aada131652f8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/649257
Reviewed-by: Hongxiang Jiang <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: findleyr

gopls/internal/golang/symbols.go

@@ -86,17 +86,22 @@ func PackageSymbols(ctx context.Context, snapshot *cache.Snapshot, uri protocol.
 	ctx, done := event.Start(ctx, "source.PackageSymbols")
 	defer done()
 
-	mp, err := NarrowestMetadataForFile(ctx, snapshot, uri)
-	if err != nil {
-		return command.PackageSymbolsResult{}, err
+	pkgFiles := []protocol.DocumentURI{uri}
+
+	// golang/vscode-go#3681: do our best if the file is not in a package.
+	// TODO(rfindley): revisit this in the future once there is more graceful
+	// handling in VS Code.
+	if mp, err := NarrowestMetadataForFile(ctx, snapshot, uri); err == nil {
+		pkgFiles = mp.CompiledGoFiles
 	}
-	pkgfiles := mp.CompiledGoFiles
-	// Maps receiver name to the methods that use it
-	receiverToMethods := make(map[string][]command.PackageSymbol)
-	// Maps type symbol name to its index in symbols
-	typeSymbolToIdx := make(map[string]int)
-	var symbols []command.PackageSymbol
-	for fidx, f := range pkgfiles {
+
+	var (
+		pkgName           string
+		symbols           []command.PackageSymbol
+		receiverToMethods = make(map[string][]command.PackageSymbol) // receiver name -> methods
+		typeSymbolToIdx   = make(map[string]int)                     // type name -> index in symbols
+	)
+	for fidx, f := range pkgFiles {
 		fh, err := snapshot.ReadFile(ctx, f)
 		if err != nil {
 			return command.PackageSymbolsResult{}, err
@@ -105,6 +110,9 @@ func PackageSymbols(ctx context.Context, snapshot *cache.Snapshot, uri protocol.
 		if err != nil {
 			return command.PackageSymbolsResult{}, err
 		}
+		if pkgName == "" && pgf.File != nil && pgf.File.Name != nil {
+			pkgName = pgf.File.Name.Name
+		}
 		for _, decl := range pgf.File.Decls {
 			switch decl := decl.(type) {
 			case *ast.FuncDecl:
@@ -154,8 +162,8 @@ func PackageSymbols(ctx context.Context, snapshot *cache.Snapshot, uri protocol.
 		}
 	}
 	return command.PackageSymbolsResult{
-		PackageName: string(mp.Name),
-		Files:       pkgfiles,
+		PackageName: pkgName,
+		Files:       pkgFiles,
 		Symbols:     symbols,
 	}, nil
 

gopls/internal/server/command.go

@@ -1741,6 +1741,10 @@ func (c *commandHandler) PackageSymbols(ctx context.Context, args command.Packag
 	err := c.run(ctx, commandConfig{
 		forURI: args.URI,
 	}, func(ctx context.Context, deps commandDeps) error {
+		if deps.snapshot.FileKind(deps.fh) != file.Go {
+			// golang/vscode-go#3681: fail silently, to avoid spurious error popups.
+			return nil
+		}
 		res, err := golang.PackageSymbols(ctx, deps.snapshot, args.URI)
 		if err != nil {
 			return err

gopls/internal/test/integration/misc/package_symbols_test.go

@@ -16,6 +16,11 @@ import (
 
 func TestPackageSymbols(t *testing.T) {
 	const files = `
+-- go.mod --
+module example.com
+
+go 1.20
+
 -- a.go --
 package a
 
@@ -33,68 +38,74 @@ func (s *S) M2() {}
 func (s *S) M3() {}
 
 func F() {}
+-- unloaded.go --
+//go:build unloaded
+
+package a
+
+var Unloaded int
 `
 	integration.Run(t, files, func(t *testing.T, env *integration.Env) {
-		a_uri := env.Sandbox.Workdir.URI("a.go")
-		b_uri := env.Sandbox.Workdir.URI("b.go")
+		aURI := env.Sandbox.Workdir.URI("a.go")
+		bURI := env.Sandbox.Workdir.URI("b.go")
 		args, err := command.MarshalArgs(command.PackageSymbolsArgs{
-			URI: a_uri,
+			URI: aURI,
 		})
 		if err != nil {
-			t.Fatalf("failed to MarshalArgs: %v", err)
+			t.Fatal(err)
 		}
 
 		var res command.PackageSymbolsResult
 		env.ExecuteCommand(&protocol.ExecuteCommandParams{
-			Command:   "gopls.package_symbols",
+			Command:   command.PackageSymbols.String(),
 			Arguments: args,
 		}, &res)
 
 		want := command.PackageSymbolsResult{
 			PackageName: "a",
-			Files:       []protocol.DocumentURI{a_uri, b_uri},
+			Files:       []protocol.DocumentURI{aURI, bURI},
 			Symbols: []command.PackageSymbol{
-				{
-					Name: "A",
-					Kind: protocol.Variable,
-					File: 0,
-				},
-				{
-					Name: "F",
-					Kind: protocol.Function,
-					File: 1,
-				},
-				{
-					Name: "S",
-					Kind: protocol.Struct,
-					File: 0,
-					Children: []command.PackageSymbol{
-						{
-							Name: "M1",
-							Kind: protocol.Method,
-							File: 0,
-						},
-						{
-							Name: "M2",
-							Kind: protocol.Method,
-							File: 1,
-						},
-						{
-							Name: "M3",
-							Kind: protocol.Method,
-							File: 1,
-						},
-					},
-				},
-				{
-					Name: "b",
-					Kind: protocol.Variable,
-					File: 1,
-				},
+				{Name: "A", Kind: protocol.Variable, File: 0},
+				{Name: "F", Kind: protocol.Function, File: 1},
+				{Name: "S", Kind: protocol.Struct, File: 0, Children: []command.PackageSymbol{
+					{Name: "M1", Kind: protocol.Method, File: 0},
+					{Name: "M2", Kind: protocol.Method, File: 1},
+					{Name: "M3", Kind: protocol.Method, File: 1},
+				}},
+				{Name: "b", Kind: protocol.Variable, File: 1},
 			},
 		}
-		if diff := cmp.Diff(want, res, cmpopts.IgnoreFields(command.PackageSymbol{}, "Range", "SelectionRange", "Detail")); diff != "" {
-			t.Errorf("gopls.package_symbols returned unexpected diff (-want +got):\n%s", diff)
+		ignore := cmpopts.IgnoreFields(command.PackageSymbol{}, "Range", "SelectionRange", "Detail")
+		if diff := cmp.Diff(want, res, ignore); diff != "" {
+			t.Errorf("package_symbols returned unexpected diff (-want +got):\n%s", diff)
+		}
+
+		for file, want := range map[string]command.PackageSymbolsResult{
+			"go.mod": {},
+			"unloaded.go": {
+				PackageName: "a",
+				Files:       []protocol.DocumentURI{env.Sandbox.Workdir.URI("unloaded.go")},
+				Symbols: []command.PackageSymbol{
+					{Name: "Unloaded", Kind: protocol.Variable, File: 0},
+				},
+			},
+		} {
+			uri := env.Sandbox.Workdir.URI(file)
+			args, err := command.MarshalArgs(command.PackageSymbolsArgs{
+				URI: uri,
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+			var res command.PackageSymbolsResult
+			env.ExecuteCommand(&protocol.ExecuteCommandParams{
+				Command:   command.PackageSymbols.String(),
+				Arguments: args,
+			}, &res)
+
+			if diff := cmp.Diff(want, res, ignore); diff != "" {
+				t.Errorf("package_symbols returned unexpected diff (-want +got):\n%s", diff)
+			}
 		}
 	})
 }