fix(replace): update delimiters to respect valid js identifier chars (#1938)

* fix(replace): update delimiters to respect valid js identifier chars

* test: update snapshots

Author: danielroe

packages/replace/README.md

@@ -61,14 +61,14 @@ In addition to the properties and values specified for replacement, users may al
 ### `delimiters`
 
 Type: `Array[String, String]`<br>
-Default: `['\\b', '\\b(?!\\.)']`
+Default: `['(?<![_$a-zA-Z0-9\\xA0-\\uFFFF])', '(?![_$a-zA-Z0-9\\xA0-\\uFFFF])(?!\\.)']`
 
-Specifies the boundaries around which strings will be replaced. By default, delimiters are [word boundaries](https://www.regular-expressions.info/wordboundaries.html) and also prevent replacements of instances with nested access. See [Word Boundaries](#word-boundaries) below for more information.
+Specifies the boundaries around which strings will be replaced. By default, delimiters match JavaScript identifier boundaries and also prevent replacements of instances with nested access. See [Word Boundaries](#word-boundaries) below for more information.
 For example, if you pass `typeof window` in `values` to-be-replaced, then you could expect the following scenarios:
 
 - `typeof window` **will** be replaced
-- `typeof window.document` **will not** be replaced due to `(?!\.)` boundary
-- `typeof windowSmth` **will not** be replaced due to a `\b` boundary
+- `typeof window.document` **will not** be replaced due to the `(?!\.)` boundary
+- `typeof windowSmth` **will not** be replaced due to identifier boundaries
 
 Delimiters will be used to build a `Regexp`. To match special characters (any of `.*+?^${}()|[]\`), be sure to [escape](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#escaping) them.
 
@@ -194,7 +194,7 @@ replace({
 
 ## Word Boundaries
 
-By default, values will only match if they are surrounded by _word boundaries_.
+By default, values will only match if they are surrounded by _word boundaries_ that respect JavaScript's rules for valid identifiers (including `$` and `_` as valid identifier characters).
 
 Consider the following options and build file:
 

packages/replace/src/index.js

@@ -54,7 +54,11 @@ function expandTypeofReplacements(replacements) {
 
 export default function replace(options = {}) {
   const filter = createFilter(options.include, options.exclude);
-  const { delimiters = ['\\b', '\\b(?!\\.)'], preventAssignment, objectGuards } = options;
+  const {
+    delimiters = ['(?<![_$a-zA-Z0-9\\xA0-\\uFFFF])', '(?![_$a-zA-Z0-9\\xA0-\\uFFFF])(?!\\.)'],
+    preventAssignment,
+    objectGuards
+  } = options;
   const replacements = getReplacements(options);
   if (objectGuards) expandTypeofReplacements(replacements);
   const functionValues = mapToFunctions(replacements);

packages/replace/test/fixtures/form/dollar-sign-boundary/_config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  description: 'should not replace when followed by valid identifier characters',
+  options: {
+    values: {
+      'typeof window': '"undefined"'
+    },
+    preventAssignment: true
+  }
+};

packages/replace/test/fixtures/form/dollar-sign-boundary/input.js

@@ -0,0 +1,20 @@
+/* eslint-disable no-undef */
+// Should NOT be replaced - window$1 is a different identifier
+if (typeof window$1 === 'undefined') {
+  console.log('no window$1');
+}
+
+// Should be replaced - standalone typeof window
+if (typeof window === 'undefined') {
+  console.log('no window');
+}
+
+// Should NOT be replaced - window_ is a different identifier  
+if (typeof window_ !== 'undefined') {
+  console.log('has window_');
+}
+
+// Should be replaced - typeof window followed by dot
+if (typeof window.document !== 'undefined') {
+  console.log('has document');
+}

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

@@ -20,6 +20,31 @@ Generated by [AVA](https://avajs.dev).
       <%original %>␊
     \`);`
 
+## dollar-sign-boundary: should not replace when followed by valid identifier characters
+
+> Snapshot 1
+
+    `/* eslint-disable no-undef */␊
+    // Should NOT be replaced - window$1 is a different identifier␊
+    if (typeof window$1 === 'undefined') {␊
+      console.log('no window$1');␊
+    }␊
+    ␊
+    // Should be replaced - standalone "undefined"␊
+    if ("undefined" === 'undefined') {␊
+      console.log('no window');␊
+    }␊
+    ␊
+    // Should NOT be replaced - window_ is a different identifier  ␊
+    if (typeof window_ !== 'undefined') {␊
+      console.log('has window_');␊
+    }␊
+    ␊
+    // Should be replaced - "undefined" followed by dot␊
+    if (typeof window.document !== 'undefined') {␊
+      console.log('has document');␊
+    }`
+
 ## match-variables: matches most specific variables
 
 > Snapshot 1