Tweak and add tests to babel-helper-annotate-as-pure (#7245)

packages/babel-helper-annotate-as-pure/src/index.js

@@ -2,13 +2,9 @@ import * as t from "@babel/types";
 
 const PURE_ANNOTATION = "#__PURE__";
 
-const isPureAnnotated = node => {
-  const { leadingComments } = node;
-  if (leadingComments === undefined) {
-    return false;
-  }
-  return leadingComments.some(comment => /[@#]__PURE__/.test(comment.value));
-};
+const isPureAnnotated = ({ leadingComments }) =>
+  leadingComments &&
+  leadingComments.some(comment => /[@#]__PURE__/.test(comment.value));
 
 export default function annotateAsPure(pathOrNode) {
   const node = pathOrNode.node || pathOrNode;

packages/babel-helper-annotate-as-pure/test/index.js

@@ -0,0 +1,36 @@
+import annotateAsPure from "../";
+import assert from "assert";
+
+describe("@babel/helper-annotate-as-pure", () => {
+  it("will add leading comment", () => {
+    const node = {};
+    annotateAsPure(node);
+
+    assert.deepEqual(node.leadingComments, [
+      {
+        type: "CommentBlock",
+        value: "#__PURE__",
+      },
+    ]);
+  });
+
+  it("will not add an extra leading comment", () => {
+    const node = {
+      leadingComments: [
+        {
+          type: "CommentBlock",
+          value: "#__PURE__",
+        },
+      ],
+    };
+
+    annotateAsPure(node);
+
+    assert.deepEqual(node.leadingComments, [
+      {
+        type: "CommentBlock",
+        value: "#__PURE__",
+      },
+    ]);
+  });
+});