From dd28f1271b494dda70be299bd30f5cb42e573661 Mon Sep 17 00:00:00 2001
From: Andrew Casey <andrew.casey@microsoft.com>
Date: Thu, 5 May 2022 10:59:04 -0700
Subject: [PATCH] Harden combineProjectOutputForReferences against empty
 results

Getting an empty result doesn't seem expected, but a deeper fix doesn't make sense until #48619 is merged.

Fixes #48963
---
 src/server/session.ts                                        | 2 +-
 .../referencesToNonPropertyNameStringLiteral.baseline.jsonc  | 1 +
 .../server/referencesToNonPropertyNameStringLiteral.ts       | 5 +++++
 3 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/referencesToNonPropertyNameStringLiteral.baseline.jsonc
 create mode 100644 tests/cases/fourslash/server/referencesToNonPropertyNameStringLiteral.ts

diff --git a/src/server/session.ts b/src/server/session.ts
index 8c92d71db1bdd..ecd5b76ac46f0 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -356,7 +356,7 @@ namespace ts.server {
                 logger.info(`Finding references to ${location.fileName} position ${location.pos} in project ${project.getProjectName()}`);
                 const projectOutputs = project.getLanguageService().findReferences(location.fileName, location.pos);
                 if (projectOutputs) {
-                    const clearIsDefinition = projectOutputs[0].references[0].isDefinition === undefined;
+                    const clearIsDefinition = projectOutputs[0]?.references[0]?.isDefinition === undefined;
                     for (const referencedSymbol of projectOutputs) {
                         const mappedDefinitionFile = getMappedLocation(project, documentSpanLocation(referencedSymbol.definition));
                         const definition: ReferencedSymbolDefinitionInfo = mappedDefinitionFile === undefined ?
diff --git a/tests/baselines/reference/referencesToNonPropertyNameStringLiteral.baseline.jsonc b/tests/baselines/reference/referencesToNonPropertyNameStringLiteral.baseline.jsonc
new file mode 100644
index 0000000000000..0637a088a01e8
--- /dev/null
+++ b/tests/baselines/reference/referencesToNonPropertyNameStringLiteral.baseline.jsonc
@@ -0,0 +1 @@
+[]
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/referencesToNonPropertyNameStringLiteral.ts b/tests/cases/fourslash/server/referencesToNonPropertyNameStringLiteral.ts
new file mode 100644
index 0000000000000..cf21c74c2d56e
--- /dev/null
+++ b/tests/cases/fourslash/server/referencesToNonPropertyNameStringLiteral.ts
@@ -0,0 +1,5 @@
+/// <reference path="../fourslash.ts"/>
+
+////const str: string = "hello/*1*/";
+
+verify.baselineFindAllReferences('1')