feat(replace): prevent accidental replacement within assignment

packages/replace/README.md

@@ -65,6 +65,13 @@ Default: `['\b', '\b']`
 
 Specifies the boundaries around which strings will be replaced. By default, delimiters are [word boundaries](https://www.regular-expressions.info/wordboundaries.html). See [Word Boundaries](#word-boundaries) below for more information.
 
+### `preventAssignment`
+
+Type: `Boolean`<br>
+Default: `false`
+
+Prevents replacing strings where they are followed by a single equals sign (e.g. `process.env.DEBUG = false`).
+
 ### `exclude`
 
 Type: `String` | `Array[...String]`<br>

packages/replace/src/index.js

@@ -37,14 +37,22 @@ function mapToFunctions(object) {
 
 export default function replace(options = {}) {
   const filter = createFilter(options.include, options.exclude);
-  const { delimiters } = options;
+  const { delimiters, preventAssignment } = options;
   const functionValues = mapToFunctions(getReplacements(options));
-  const keys = Object.keys(functionValues)
-    .sort(longest)
-    .map(escape);
+  const keys = Object.keys(functionValues).sort(longest).map(escape);
+  if (![true, false].includes(preventAssignment)) {
+    // eslint-disable-next-line no-console
+    console.warn(
+      "replace: 'preventAssignment' currently defaults to false. It is recommended to configure this option explicitly, as it may default to true in a future major version."
+    );
+  }
+  const lookahead = preventAssignment ? '(?!\\s*=[^=])' : '';
   const pattern = delimiters
-    ? new RegExp(`${escape(delimiters[0])}(${keys.join('|')})${escape(delimiters[1])}`, 'g')
-    : new RegExp(`\\b(${keys.join('|')})\\b`, 'g');
+    ? new RegExp(
+        `${escape(delimiters[0])}(${keys.join('|')})${escape(delimiters[1])}${lookahead}`,
+        'g'
+      )
+    : new RegExp(`\\b(${keys.join('|')})\\b${lookahead}`, 'g');
 
   return {
     name: 'replace',

packages/replace/test/fixtures/form/assignment/_config.js

@@ -0,0 +1,7 @@
+module.exports = {
+  description: "doesn't replace lvalue in assignment",
+  options: {
+    'process.env.DEBUG': 'replaced',
+    preventAssignment: true
+  }
+};

packages/replace/test/fixtures/form/assignment/input.js

@@ -0,0 +1 @@
+process.env.DEBUG = 'test';

packages/replace/test/fixtures/form/assignment/output.js

@@ -0,0 +1 @@
+process.env.DEBUG = 'test';

packages/replace/test/snapshots/form.js.md

@@ -58,3 +58,9 @@ Generated by [AVA](https://ava.li).
     `const one = 1; // eslint-disable-line␊
     ␊
     console.log(one);`
+
+## assignment: doesn't replace lvalue in assignment
+
+> Snapshot 1
+
+    'process.env.DEBUG = \'test\';'