From 7952c6fd4155ce88ec726eac69cadd3bc5b3f3a5 Mon Sep 17 00:00:00 2001
From: "Nicholas C. Zakas" <nicholas@nczconsulting.com>
Date: Fri, 10 Sep 2021 04:20:34 -0700
Subject: [PATCH] Breaking: Disallow reserved words in ES3 (#513)

* Breaking: Disallow reserved words in ES3

* Switch allowReserved to false for ES > 3
---
 lib/espree.js             |  1 +
 lib/options.js            |  9 ++++++++-
 tests/lib/ecma-version.js | 20 ++++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/lib/espree.js b/lib/espree.js
index aec180d7..e0be3b5a 100644
--- a/lib/espree.js
+++ b/lib/espree.js
@@ -71,6 +71,7 @@ export default () => Parser => {
                 sourceType: options.sourceType,
                 ranges: options.ranges,
                 locations: options.locations,
+                allowReserved: options.allowReserved,
 
                 // Truthy value is true for backward compatibility.
                 allowReturnOutsideFunction: Boolean(ecmaFeatures.globalReturn),
diff --git a/lib/options.js b/lib/options.js
index ae441ac3..acc1e3a2 100644
--- a/lib/options.js
+++ b/lib/options.js
@@ -87,9 +87,16 @@ export function normalizeOptions(options) {
     const sourceType = normalizeSourceType(options.sourceType);
     const ranges = options.range === true;
     const locations = options.loc === true;
+    const allowReserved = ecmaVersion === 3 ? "never" : false;
 
     if (sourceType === "module" && ecmaVersion < 6) {
         throw new Error("sourceType 'module' is not supported when ecmaVersion < 2015. Consider adding `{ ecmaVersion: 2015 }` to the parser options.");
     }
-    return Object.assign({}, options, { ecmaVersion, sourceType, ranges, locations });
+    return Object.assign({}, options, {
+        ecmaVersion,
+        sourceType,
+        ranges,
+        locations,
+        allowReserved
+    });
 }
diff --git a/tests/lib/ecma-version.js b/tests/lib/ecma-version.js
index 179afa49..05d76e0f 100644
--- a/tests/lib/ecma-version.js
+++ b/tests/lib/ecma-version.js
@@ -176,6 +176,26 @@ describe("ecmaVersion", () => {
             }, /ecmaVersion must be a number or "latest". Received value of type string instead/u);
         });
 
+        it("Should throw error when using ES3 and reserved words", () => {
+            assert.throws(() => {
+                espree.parse(
+                    "var char = 'c'", {
+                        ecmaVersion: 3
+                    }
+                );
+            }, /'char' is reserved/u);
+        });
+
+        it("Should throw error when using ES3 and reserved words in object literals", () => {
+            assert.throws(() => {
+                espree.parse(
+                    "var x = { char: 'c' }", {
+                        ecmaVersion: 3
+                    }
+                );
+            }, /'char' is reserved/u);
+        });
+
         it("Should throw error when using module in pre-ES6", () => {
             assert.throws(() => {
                 espree.parse(