From e6ce0ddf03215642dccfd6f6193d16f0408bd310 Mon Sep 17 00:00:00 2001
From: Rebecca Stambler <rstambler@golang.org>
Date: Fri, 7 Jun 2019 11:34:41 -0400
Subject: [PATCH] internal/lsp: add an implementation for textDocument/didSave

This change marks the overlay for a saved file as "on disk".
This will reduce the number of overlays we provide to go/packages, which
can be expensive.

Updates golang/go#31796, golang/go#32457

Change-Id: I8e69503ab80bba29caf4e42491d87e643bf17f1a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/181123
Reviewed-by: Ian Cottrell <iancottrell@google.com>
Reviewed-by: Peter Weinberger <pjw@google.com>
---
 internal/lsp/cache/session.go        | 13 +++++++++++++
 internal/lsp/text_synchronization.go |  5 ++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/internal/lsp/cache/session.go b/internal/lsp/cache/session.go
index 4dd169fc..2c3b2422 100644
--- a/internal/lsp/cache/session.go
+++ b/internal/lsp/cache/session.go
@@ -42,6 +42,10 @@ type overlay struct {
 	uri     span.URI
 	data    []byte
 	hash    string
+
+	// onDisk is true if a file has been saved on disk,
+	// and therefore does not need to be part of the overlay sent to go/packages.
+	onDisk bool
 }
 
 func (s *session) Shutdown(ctx context.Context) {
@@ -181,6 +185,12 @@ func (s *session) DidOpen(uri span.URI) {
 }
 
 func (s *session) DidSave(uri span.URI) {
+	s.overlayMu.Lock()
+	defer s.overlayMu.Unlock()
+
+	if overlay, ok := s.overlays[uri]; ok {
+		overlay.onDisk = true
+	}
 }
 
 func (s *session) DidClose(uri span.URI) {
@@ -236,6 +246,9 @@ func (s *session) buildOverlay() map[string][]byte {
 
 	overlays := make(map[string][]byte)
 	for uri, overlay := range s.overlays {
+		if overlay.onDisk {
+			continue
+		}
 		if filename, err := uri.Filename(); err == nil {
 			overlays[filename] = overlay.data
 		}
diff --git a/internal/lsp/text_synchronization.go b/internal/lsp/text_synchronization.go
index edf7dfa7..55176198 100644
--- a/internal/lsp/text_synchronization.go
+++ b/internal/lsp/text_synchronization.go
@@ -100,9 +100,8 @@ func (s *Server) applyChanges(ctx context.Context, params *protocol.DidChangeTex
 }
 
 func (s *Server) didSave(ctx context.Context, params *protocol.DidSaveTextDocumentParams) error {
-	uri := span.NewURI(params.TextDocument.URI)
-	s.session.DidSave(uri)
-	return nil // ignore
+	s.session.DidSave(span.NewURI(params.TextDocument.URI))
+	return nil
 }
 
 func (s *Server) didClose(ctx context.Context, params *protocol.DidCloseTextDocumentParams) error {