From e8e5b37084ab41357340419ff15cba5fb08af935 Mon Sep 17 00:00:00 2001
From: Rob Findley <rfindley@google.com>
Date: Thu, 30 Jun 2022 14:01:50 -0400
Subject: [PATCH] internal/lsp/cache: don't construct a new metadata graph if
 no changes

Change-Id: I3f074d1fd29cf7ad0323cec76154f9b2e31f7356
Reviewed-on: https://go-review.googlesource.com/c/tools/+/415494
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
---
 internal/lsp/cache/graph.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/internal/lsp/cache/graph.go b/internal/lsp/cache/graph.go
index dc7d4faef7..ad39aa8d86 100644
--- a/internal/lsp/cache/graph.go
+++ b/internal/lsp/cache/graph.go
@@ -32,6 +32,10 @@ type metadataGraph struct {
 // Clone creates a new metadataGraph, applying the given updates to the
 // receiver.
 func (g *metadataGraph) Clone(updates map[PackageID]*KnownMetadata) *metadataGraph {
+	if len(updates) == 0 {
+		// Optimization: since the graph is immutable, we can return the receiver.
+		return g
+	}
 	result := &metadataGraph{metadata: make(map[PackageID]*KnownMetadata, len(g.metadata))}
 	// Copy metadata.
 	for id, m := range g.metadata {