fix(source-node): replace right on empty nodes

lib/source-node.js

@@ -280,7 +280,7 @@ class SourceNode {
    */
   replaceRight(aPattern, aReplacement) {
     const lastChild = this.children[this.children.length - 1];
-    if (lastChild[isSourceNode]) {
+    if (lastChild && lastChild[isSourceNode]) {
       lastChild.replaceRight(aPattern, aReplacement);
     } else if (typeof lastChild === "string") {
       this.children[this.children.length - 1] = lastChild.replace(

test/test-source-node-empty.js

@@ -0,0 +1,101 @@
+/* -*- Mode: js; js-indent-level: 2; -*- */
+/*
+ * Copyright 2011 Mozilla Foundation and contributors
+ * Licensed under the New BSD license. See LICENSE or:
+ * http://opensource.org/licenses/BSD-3-Clause
+ */
+
+const SourceNode = require("../lib/source-node").SourceNode;
+
+exports["test .replaceRight on an empty node"] = function (assert) {
+  const node = new SourceNode();
+  assert.equal(node.replaceRight(/$/, "suffix"), node);
+  assert.equal(node.toString(), "suffix");
+};
+
+exports["test .replaceRight after ignored empty chunks"] = function (assert) {
+  const node = new SourceNode(null, null, null, ["", [""]]);
+  assert.equal(node.children.length, 0);
+  assert.equal(node.replaceRight(/missing/, "replacement"), node);
+  assert.equal(node.toString(), "");
+};
+
+exports["test .replaceRight on a nested empty node"] = function (assert) {
+  const child = new SourceNode();
+  const node = new SourceNode(null, null, null, ["prefix", child]);
+  assert.equal(node.replaceRight(/$/, "suffix"), node);
+  assert.equal(node.toString(), "prefixsuffix");
+  assert.equal(node.children[1], child);
+  assert.equal(child.toString(), "suffix");
+};
+
+exports["test .replaceRight empty string pattern"] = function (assert) {
+  const node = new SourceNode();
+  assert.equal(node.replaceRight("", "inserted"), node);
+  assert.equal(node.toString(), "inserted");
+};
+
+exports["test .replaceRight callback on an empty node"] = function (assert) {
+  const node = new SourceNode();
+  let calls = 0;
+  assert.equal(
+    node.replaceRight(/$/, function (match, offset, input) {
+      calls++;
+      assert.equal(match, "");
+      assert.equal(offset, 0);
+      assert.equal(input, "");
+      return "generated";
+    }),
+    node
+  );
+  assert.equal(calls, 1);
+  assert.equal(node.toString(), "generated");
+};
+
+exports["test .replaceRight mapped callback preserves original location"] = function (assert) {
+  const node = new SourceNode(4, 2, "input.js", "hello world", "original");
+  let calls = 0;
+  assert.equal(
+    node.replaceRight(/world/, function (match, offset, input) {
+      calls++;
+      assert.equal(match, "world");
+      assert.equal(offset, 6);
+      assert.equal(input, "hello world");
+      return "universe";
+    }),
+    node
+  );
+  assert.equal(calls, 1);
+  assert.equal(node.toString(), "hello universe");
+  let snippets = 0;
+  node.walk(function (text, location) {
+    snippets++;
+    assert.equal(text, "hello universe");
+    assert.equal(location.source, "input.js");
+    assert.equal(location.line, 4);
+    assert.equal(location.column, 2);
+    assert.equal(location.name, "original");
+  });
+  assert.equal(snippets, 1);
+};
+
+exports["test .replaceRight changes only the rightmost unmapped snippet"] = function (assert) {
+  const node = new SourceNode(null, null, null, ["left world ", "right world"]);
+  assert.equal(node.replaceRight(/world/, "end"), node);
+  assert.equal(node.toString(), "left world right end");
+  assert.equal(node.children[0], "left world ");
+};
+
+exports["test .replaceRight nonmatching pattern preserves text"] = function (assert) {
+  const node = new SourceNode(null, null, null, "unchanged");
+  let calls = 0;
+  assert.equal(
+    node.replaceRight(/absent/, function () {
+      calls++;
+      return "replacement";
+    }),
+    node
+  );
+  assert.equal(calls, 0);
+  assert.equal(node.toString(), "unchanged");
+};