Support and defer to native /d flag in ES2021 environments

Author: slevithan

src/addons/matchrecursive.js

@@ -125,7 +125,7 @@ export default (XRegExp) => {
                     // `right` when they were passed through the XRegExp constructor above.
                     XRegExp.union([left, right], '', {conjunction: 'or'}).source
                 })[^${escapeChar}])+)+`,
-                // Flags `gy` not needed here
+                // Flags `dgy` not needed here
                 flags.replace(XRegExp._hasNativeFlag('s') ? /[^imsu]/g : /[^imu]/g, '')
             );
         }

src/xregexp.js

@@ -72,6 +72,8 @@ function hasNativeFlag(flag) {
     }
     return isSupported;
 }
+// Check for ES2021 `d` flag support
+const hasNativeD = hasNativeFlag('d');
 // Check for ES2018 `s` flag support
 const hasNativeS = hasNativeFlag('s');
 // Check for ES6 `u` flag support
@@ -80,6 +82,7 @@ const hasNativeU = hasNativeFlag('u');
 const hasNativeY = hasNativeFlag('y');
 // Tracker for known flags, including addon flags
 const registeredFlags = {
+    d: hasNativeD,
     g: true,
     i: true,
     m: true,
@@ -88,7 +91,7 @@ const registeredFlags = {
     y: hasNativeY
 };
 // Flags to remove when passing to native `RegExp` constructor
-const nonnativeFlags = hasNativeS ? /[^gimsuy]+/g : /[^gimuy]+/g;
+const nonnativeFlags = hasNativeS ? /[^dgimsuy]+/g : /[^dgimuy]+/g;
 
 /**
  * Attaches extended data and `XRegExp.prototype` properties to a regex object.
@@ -379,10 +382,10 @@ function prepareFlags(pattern, flags) {
         throw new SyntaxError(`Invalid duplicate regex flag ${flags}`);
     }
 
-    // Strip and apply a leading mode modifier with any combination of flags except g or y
+    // Strip and apply a leading mode modifier with any combination of flags except `dgy`
     pattern = pattern.replace(/^\(\?([\w$]+)\)/, ($0, $1) => {
-        if (/[gy]/.test($1)) {
-            throw new SyntaxError(`Cannot use flag g or y in mode modifier ${$0}`);
+        if (/[dgy]/.test($1)) {
+            throw new SyntaxError(`Cannot use flags dgy in mode modifier ${$0}`);
         }
         // Allow duplicate flags within the mode modifier
         flags = clipDuplicates(flags + $1);
@@ -519,6 +522,7 @@ function setNamespacing(on) {
  * @param {String|RegExp} pattern Regex pattern string, or an existing regex object to copy.
  * @param {String} [flags] Any combination of flags.
  *   Native flags:
+ *     - `d` - indices for groups (ES2021)
  *     - `g` - global
  *     - `i` - ignore case
  *     - `m` - multiline anchors

tests/.eslintrc.js

@@ -6,6 +6,7 @@ module.exports = {
         "XRegExp": true,
         "resetFeatures": true,
         "REGEX_DATA": true,
+        "hasNativeD": true,
         "hasNativeS": true,
         "hasNativeU": true,
         "hasNativeY": true,

tests/helpers/h.js

@@ -13,6 +13,8 @@ global.resetFeatures = function() {
 // Property name used for extended regex instance data
 global.REGEX_DATA = 'xregexp';
 
+// Check for ES2021 `d` flag support
+global.hasNativeD = XRegExp._hasNativeFlag('d');
 // Check for ES2018 `s` flag support
 global.hasNativeS = XRegExp._hasNativeFlag('s');
 // Check for ES6 `u` flag support

tests/spec/s-xregexp.js

@@ -101,6 +101,12 @@ describe('XRegExp()', function() {
         expect(XRegExp('', 'i').ignoreCase).toBe(true);
         expect(XRegExp('', 'm').multiline).toBe(true);
 
+        if (hasNativeD) {
+            expect(XRegExp('', 'd').hasIndices).toBe(true);
+        } else {
+            expect(function() {XRegExp('', 'd');}).toThrowError(SyntaxError);
+        }
+
         if (hasNativeU) {
             expect(XRegExp('', 'u').unicode).toBe(true);
         } else {
@@ -134,7 +140,8 @@ describe('XRegExp()', function() {
         expect(XRegExp('').global).toBe(false);
         expect(XRegExp('').ignoreCase).toBe(false);
         expect(XRegExp('').multiline).toBe(false);
-        // Should be `false` or `undefined`, depending of whether flags `uy` are supported natively
+        // Should be `false` or `undefined`, depending of whether flags `duy` are supported natively
+        expect(XRegExp('').hasIndices).toBeFalsy();
         expect(XRegExp('').unicode).toBeFalsy();
         expect(XRegExp('').sticky).toBeFalsy();
     });
@@ -302,7 +309,8 @@ describe('XRegExp()', function() {
                 //expect(XRegExp('(?A)').astral).toBeFalsy();
             });
 
-            it('should throw an exception if flag g or y is included', function() {
+            it('should throw an exception if any of flags dgy are included', function() {
+                expect(function() {XRegExp('(?d)');}).toThrowError(SyntaxError);
                 expect(function() {XRegExp('(?g)');}).toThrowError(SyntaxError);
                 expect(function() {XRegExp('(?y)');}).toThrowError(SyntaxError);
                 expect(function() {XRegExp('(?gi)');}).toThrowError(SyntaxError);

types/index.d.ts

@@ -16,6 +16,7 @@ export = XRegExp;
  * @param flags - Any combination of flags.
  *
  *   Native flags:
+ *     - `d` - indices for groups (ES2021)
  *     - `g` - global
  *     - `i` - ignore case
  *     - `m` - multiline anchors