InvalidSnippet: don't flag external snippets that use the class attribute

core/src/main/java/com/google/errorprone/bugpatterns/javadoc/InvalidSnippet.java

@@ -96,9 +96,14 @@ public Void visitErroneous(ErroneousTree erroneousTree, Void unused) {
     @Override
     public Void visitSnippet(SnippetTree snippetTree, Void unused) {
       if (snippetTree.getBody() == null) {
+        // External snippets reference their content via a `file` or `class` attribute, in which
+        // case the colon, newline and body may be omitted.
         if (snippetTree.getAttributes().stream()
             .anyMatch(
-                a -> a instanceof AttributeTree attr && attr.getName().contentEquals("file"))) {
+                a ->
+                    a instanceof AttributeTree attr
+                        && (attr.getName().contentEquals("file")
+                            || attr.getName().contentEquals("class")))) {
           return super.visitSnippet(snippetTree, null);
         }
         String message =

core/src/test/java/com/google/errorprone/bugpatterns/javadoc/InvalidSnippetTest.java

@@ -90,4 +90,44 @@ interface Test {}
             """)
         .doTest();
   }
+
+  @Test
+public void snippetWithoutBody_butWithClass() {
+  helper
+      .addSourceLines(
+          "Test.java",
+          """
+          /** {@snippet class=com.example.Snippets region=builder lang=java} */
+          interface Test {}
+          """)
+      .doTest();
+}
+
+@Test
+public void snippetWithoutBody_butWithClassAndTrailingSpace() {
+  helper
+      .addSourceLines(
+          "Test.java",
+          """
+          /** {@snippet class=HelloWorld } */
+          interface Test {}
+          """)
+      .doTest();
+}
+
+@Test
+public void snippetWithoutBody_andWithoutFileOrClass() {
+  helper
+      .addSourceLines(
+          "Test.java",
+          """
+          /**
+           * // BUG: Diagnostic contains: This @snippet has no body
+           * {@snippet region=builder lang=java}
+           */
+          interface Test {}
+          """)
+      .doTest();
+}
+
 }