From 16b25b4312bb85cee06946579291dff123892df8 Mon Sep 17 00:00:00 2001
From: cushon <cushon@google.com>
Date: Wed, 27 May 2020 16:33:52 -0700
Subject: [PATCH] Fix an NPE in InvalidLink

Discovered while validating 2.4.0 release (#1639)

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=313487177
---
 .../errorprone/bugpatterns/javadoc/InvalidLink.java  |  3 +++
 .../bugpatterns/javadoc/InvalidLinkTest.java         | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/javadoc/InvalidLink.java b/core/src/main/java/com/google/errorprone/bugpatterns/javadoc/InvalidLink.java
index ce13da5bf67..1d6183582b3 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/javadoc/InvalidLink.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/javadoc/InvalidLink.java
@@ -141,6 +141,9 @@ public Void visitErroneous(ErroneousTree erroneousTree, Void unused) {
 
     @Override
     public Void visitLink(LinkTree linkTree, Void unused) {
+      if (linkTree.getReference() == null) {
+        return super.visitLink(linkTree, null);
+      }
       String reference = linkTree.getReference().getSignature();
       Element element = null;
       try {
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/javadoc/InvalidLinkTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/javadoc/InvalidLinkTest.java
index 70b1e5a1383..5441f8f2a05 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/javadoc/InvalidLinkTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/javadoc/InvalidLinkTest.java
@@ -157,4 +157,16 @@ public void multiField() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void emptyLinkTest() {
+    helper
+        .addSourceLines(
+            "Test.java", //
+            "interface Test {",
+            "  /** {@link} */",
+            "  void foo();",
+            "}")
+        .doTest();
+  }
 }