Defer to native /s flag in ES2018 environments

Author: slevithan

src/xregexp.js

@@ -72,6 +72,8 @@ function hasNativeFlag(flag) {
     }
     return isSupported;
 }
+// Check for ES2018 `s` flag support
+const hasNativeS = hasNativeFlag('s');
 // Check for ES6 `u` flag support
 const hasNativeU = hasNativeFlag('u');
 // Check for ES6 `y` flag support
@@ -81,9 +83,12 @@ const registeredFlags = {
     g: true,
     i: true,
     m: true,
+    s: hasNativeS,
     u: hasNativeU,
     y: hasNativeY
 };
+// Flags to remove when passing to native `RegExp` constructor
+const nonnativeFlags = hasNativeS ? /[^gimsuy]+/g : /[^gimuy]+/g;
 
 /**
  * Attaches extended data and `XRegExp.prototype` properties to a regex object.
@@ -521,7 +526,7 @@ function setNamespacing(on) {
  *     - `y` - sticky (Firefox 3+, ES6)
  *   Additional XRegExp flags:
  *     - `n` - explicit capture
- *     - `s` - dot matches all (aka singleline)
+ *     - `s` - dot matches all (aka singleline) - works even when not natively supported
  *     - `x` - free-spacing and line comments (aka extended)
  *     - `A` - astral (requires the Unicode Base addon)
  *   Flags cannot be provided when constructing one `RegExp` from another.
@@ -611,7 +616,7 @@ function XRegExp(pattern, flags) {
             // separated. However, more than one empty group in a row is never needed.
             pattern: output.replace(/(?:\(\?:\))+/g, '(?:)'),
             // Strip all but native flags
-            flags: appliedFlags.replace(/[^gimuy]+/g, ''),
+            flags: appliedFlags.replace(nonnativeFlags, ''),
             // `context.captureNames` has an item for each capturing group, even if unnamed
             captures: context.hasNamedCapture ? context.captureNames : null
         };
@@ -1772,16 +1777,18 @@ XRegExp.addToken(
 );
 
 /*
- * Dot, in dotall mode (aka singleline mode, flag s) only.
+ * Dot, in dotAll mode (aka singleline mode, flag s) only.
  */
-XRegExp.addToken(
-    /\./,
-    () => '[\\s\\S]',
-    {
-        flag: 's',
-        leadChar: '.'
-    }
-);
+if (!hasNativeS) {
+    XRegExp.addToken(
+        /\./,
+        () => '[\\s\\S]',
+        {
+            flag: 's',
+            leadChar: '.'
+        }
+    );
+}
 
 /*
  * Named backreference: `\k<name>`. Backreference names can use RegExpIdentifierName characters

tests/.eslintrc.js

@@ -6,6 +6,7 @@ module.exports = {
         "XRegExp": true,
         "resetFeatures": true,
         "REGEX_DATA": true,
+        "hasNativeS": true,
         "hasNativeU": true,
         "hasNativeY": true,
         "hasStrictMode": 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 ES2018 `s` flag support
+global.hasNativeS = XRegExp._hasNativeFlag('s');
 // Check for ES6 `u` flag support
 global.hasNativeU = XRegExp._hasNativeFlag('u');
 // Check for ES6 `y` flag support

tests/spec/s-xregexp.js

@@ -121,10 +121,10 @@ describe('XRegExp()', function() {
 
     // These properties are `undefined`, but future ES may define them with value `false`
     it('should not set properties for nonnative flags', function() {
+        if (!hasNativeS) {
+            expect(XRegExp('', 's').dotAll).toBeFalsy();
+        }
         expect(XRegExp('', 'n').explicitCapture).toBeFalsy();
-        expect(XRegExp('', 's').singleline).toBeFalsy();
-        expect(XRegExp('', 's').dotall).toBeFalsy();
-        expect(XRegExp('', 's').dotAll).toBeFalsy();
         expect(XRegExp('', 'x').extended).toBeFalsy();
         // Flag A is added by Unicode Base
         //expect(XRegExp('', 'A').astral).toBeFalsy();
@@ -293,10 +293,10 @@ describe('XRegExp()', function() {
 
             // These properties are `undefined`, but future ES may define them with value `false`
             it('should not set properties for nonnative flags', function() {
+                if (!hasNativeS) {
+                    expect(XRegExp('(?s)').dotAll).toBeFalsy();
+                }
                 expect(XRegExp('(?n)').explicitCapture).toBeFalsy();
-                expect(XRegExp('(?s)').singleline).toBeFalsy();
-                expect(XRegExp('(?s)').dotall).toBeFalsy();
-                expect(XRegExp('(?s)').dotAll).toBeFalsy();
                 expect(XRegExp('(?x)').extended).toBeFalsy();
                 // Flag A is added by Unicode Base
                 //expect(XRegExp('(?A)').astral).toBeFalsy();
@@ -332,8 +332,11 @@ describe('XRegExp()', function() {
                 expect(regex.ignoreCase).toBe(true);
                 expect(regex.global).toBe(true);
                 expect(regex.multiline).toBe(true);
-                // Test nonnative flag s
-                expect(regex.test('\n')).toBe(true);
+                if (hasNativeS) {
+                    expect(regex.dotAll).toBe(true);
+                } else {
+                    expect(regex.test('\n')).toBe(true);
+                }
             });
 
             it('should throw an exception if unknown flags are used', function() {

types/index.d.ts

@@ -24,7 +24,7 @@ export = XRegExp;
  *
  *   Additional XRegExp flags:
  *     - `n` - explicit capture
- *     - `s` - dot matches all (aka singleline)
+ *     - `s` - dot matches all (aka singleline) - works even when not natively supported
  *     - `x` - free-spacing and line comments (aka extended)
  *     - `A` - astral (requires the Unicode Base addon)
  *