Fix hasFlowShorthandAnnotationComment check (#5497)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

src/language-js/utils.js

@@ -54,7 +54,7 @@ function hasFlowShorthandAnnotationComment(node) {
   return (
     node.extra &&
     node.extra.parenthesized &&
-    node.trailingComments &&
+    isNonEmptyArray(node.trailingComments) &&
     isBlockComment(node.trailingComments[0]) &&
     FLOW_SHORTHAND_ANNOTATION.test(node.trailingComments[0].value)
   );

tests_integration/__tests__/parser-api.js

@@ -29,6 +29,23 @@ test("allows usage of prettier's supported parsers", () => {
   expect(output).toEqual("bar();\n");
 });
 
+test("allows add empty `trailingComments` array", () => {
+  const output = prettier.format("(foo /* comment */)( )", {
+    parser(text, parsers) {
+      const ast = parsers.babel(text);
+
+      // This may happens in this use case https://github.com/prettier/prettier/pull/5497#issuecomment-439841965
+      // Simply simulate it
+      const callExpression = ast.program.body[0].expression;
+      callExpression.extra = { parenthesized: true };
+      callExpression.trailingComments = [];
+
+      return ast;
+    },
+  });
+  expect(output).toEqual("foo(/* comment */);\n");
+});
+
 describe("allows passing a string to resolve a parser", () => {
   runPrettier("./custom-parsers/", [
     "--end-of-line",