always enable modifiers parsing (#98)

Author: JLHwung

README.md

@@ -140,13 +140,7 @@ These options can be set to `false` or `'transform'`. When using `'transform'`,
   // → '(?:(?![f-h])[\s\S])' (to be used without /u)
   ```
 
-#### Experimental regular expression features
-
-These options can be set to `false`, `'parse'` and `'transform'`. When using `'transform'`, the corresponding features are compiled to older syntax that can run in older browsers. When using `'parse'`, they are parsed and left as-is in the output pattern. When using `false` (the default), they result in a syntax error if used.
-
-Once these features become stable (when the proposals are accepted as part of ECMAScript), they will be parsed by default and thus `'parse'` will behave like `false`.
-
-- `modifiers` - [Inline `m`/`s`/`i` modifiers](https://github.com/tc39/proposal-regexp-modifiers)
+- `modifiers` - [Inline `i`/`m`/`s` modifiers](https://github.com/tc39/proposal-regexp-modifiers)
 
   ```js
   rewritePattern('(?i:[a-z])[a-z]', '', {
@@ -155,6 +149,12 @@ Once these features become stable (when the proposals are accepted as part of EC
   // → '(?:[a-zA-Z])([a-z])'
   ```
 
+#### Experimental regular expression features
+
+These options can be set to `false`, `'parse'` and `'transform'`. When using `'transform'`, the corresponding features are compiled to older syntax that can run in older browsers. When using `'parse'`, they are parsed and left as-is in the output pattern. When using `false` (the default), they result in a syntax error if used.
+
+Once these features become stable (when the proposals are accepted as part of ECMAScript), they will be parsed by default and thus `'parse'` will behave like `false`.
+
 #### Miscellaneous options
 
 - `onNamedGroup`

rewrite-pattern.js

@@ -822,6 +822,7 @@ const validateOptions = (options) => {
 					throw new Error(`.${key} must be false (default) or 'transform'.`);
 				}
 				break;
+			// todo: remove modifiers: 'parse' in regexpu-core v7
 			case 'modifiers':
 				if (value != null && value !== false && value !== 'parse' && value !== 'transform') {
 					throw new Error(`.${key} must be false (default), 'parse' or 'transform'.`);
@@ -867,9 +868,8 @@ const rewritePattern = (pattern, flags, options) => {
 	config.modifiersData.m = undefined;
 
 	const regjsparserFeatures = {
-		'modifiers': Boolean(options && options.modifiers),
-
 		// Enable every stable RegExp feature by default
+		'modifiers': true,
 		'unicodePropertyEscape': true,
 		'unicodeSet': true,
 		'namedGroups': true,

tests/fixtures/modifiers.js

@@ -60,7 +60,7 @@ const modifiersFixtures = [
 	{
 		'pattern': '(?i:[\\q{ab|cd|abc}--\\q{abc}--\\q{cd}])',
 		'flags': 'v',
-		'options':  { unicodeSetsFlag: 'transform', modifiers: 'parse' },
+		'options':  { unicodeSetsFlag: 'transform', modifiers: false },
 		'expected': '(?i:(?:ab))',
 		'expectedFlags': 'u',
 	},	{
@@ -200,7 +200,7 @@ const modifiersFixtures = [
 	{
 		'pattern': '(?-i:[\\q{ab|cd|abc}--\\q{abc}--\\q{cd}])',
 		'flags': 'iv',
-		'options':  { unicodeSetsFlag: 'transform', modifiers: 'parse' },
+		'options':  { unicodeSetsFlag: 'transform', modifiers: false },
 		'expected': '(?-i:(?:ab))',
 		'expectedFlags': 'iu',
 	},	{
@@ -314,6 +314,13 @@ const modifiersFixtures = [
 		'expected': '(?:(?:^|(?<=[\\n\\r\\u2028\\u2029]))[A-Za-z])',
 		'expectedFlags': '',
 	},
+	{
+		'pattern': '(?ims:^[a-z])',
+		'flags': '',
+		'expected': '(?ims:^[a-z])',
+		'expectedFlags': '',
+		'options': { 'modifiers': false }
+	},
 	// -ims
 	{
 		'pattern': '(?-ims:^[a-z].)(^[a-z].)',
@@ -326,6 +333,12 @@ const modifiersFixtures = [
 		'expected': '(?:^[a-z].)(^[a-z].)',
 		'expectedFlags': '',
 	},
+	{
+		'pattern': '(?-ims:^[a-z].)(^[a-z].)',
+		'expected': '(?-ims:^[a-z].)(^[a-z].)',
+		'expectedFlags': '',
+		'options': { 'modifiers': false }
+	},
 ].filter(Boolean);
 
 exports.modifiersFixtures = modifiersFixtures;

tests/tests.js

@@ -401,11 +401,5 @@ describe('modifiers', () => {
 			}
 		});
 	}
-
-	it('No `modifiers:"transform"`', () => {
-		assert.throws(() => {
-			rewritePattern('(?i:a)', '');
-		});
-	})
 });