internal/lsp: don't keep track of closed overlays

getFile still returns a FileHandle, even if the file doesn't exist on
disk. Work-around this by checking if the file exists before adding
the file handle to the map.

Fixes golang/go#38498

Change-Id: Ie02679068b37bf4f3d19966c6cfcf2361086b1de
Reviewed-on: https://go-review.googlesource.com/c/tools/+/242924
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

internal/lsp/cache/cache.go

@@ -60,6 +60,10 @@ type fileHandle struct {
 	err   error
 }
 
+func (c *Cache) GetFile(ctx context.Context, uri span.URI) (source.FileHandle, error) {
+	return c.getFile(ctx, uri)
+}
+
 func (c *Cache) getFile(ctx context.Context, uri span.URI) (*fileHandle, error) {
 	var modTime time.Time
 	if fi, err := os.Stat(uri.Filename()); err == nil {

internal/lsp/regtest/diagnostics_test.go

@@ -211,6 +211,7 @@ func TestRmTest38878Close(t *testing.T) {
 		env.Await(EmptyDiagnostics("a_test.go"))
 	})
 }
+
 func TestRmTest38878(t *testing.T) {
 	log.SetFlags(log.Lshortfile)
 	runner.Run(t, test38878, func(t *testing.T, env *Env) {
@@ -1009,3 +1010,32 @@ func main() {
 		)
 	})
 }
+
+func TestClosingBuffer(t *testing.T) {
+	const basic = `
+-- go.mod --
+module mod.com
+
+go 1.14
+-- main.go --
+package main
+
+func main() {}
+`
+	runner.Run(t, basic, func(t *testing.T, env *Env) {
+		env.Await(
+			CompletedWork(lsp.DiagnosticWorkTitle(lsp.FromInitialWorkspaceLoad), 1),
+		)
+		env.Editor.OpenFileWithContent(env.Ctx, "foo.go", `package main`)
+		env.Await(
+			CompletedWork(lsp.DiagnosticWorkTitle(lsp.FromDidOpen), 1),
+		)
+		env.CloseBuffer("foo.go")
+		env.Await(
+			OnceMet(
+				CompletedWork(lsp.DiagnosticWorkTitle(lsp.FromDidClose), 1),
+				NoLogMatching(protocol.Info, "packages=0"),
+			),
+		)
+	})
+}

internal/lsp/source/view.go

@@ -285,6 +285,9 @@ type Cache interface {
 	// FileSet returns the shared fileset used by all files in the system.
 	FileSet() *token.FileSet
 
+	// GetFile returns a file handle for the given URI.
+	GetFile(ctx context.Context, uri span.URI) (FileHandle, error)
+
 	// ParseGoHandle returns a ParseGoHandle for the given file handle.
 	ParseGoHandle(ctx context.Context, fh FileHandle, mode ParseMode) ParseGoHandle
 }

internal/lsp/text_synchronization.go

@@ -237,7 +237,10 @@ func (s *Server) didClose(ctx context.Context, params *protocol.DidCloseTextDocu
 	if snapshot == nil {
 		return errors.Errorf("no snapshot for %s", uri)
 	}
-	fh, err := snapshot.GetFile(ctx, uri)
+	// Check if the file exists on disk after it has been closed. Calling
+	// snapshot.GetFile will add it back to the snapshot even if it doesn't
+	// exist, which will cause problems.
+	fh, err := snapshot.View().Session().Cache().GetFile(ctx, uri)
 	if err != nil {
 		return err
 	}