Include the generated source in invalid regex err msgs in all envs (#25)

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## Unreleased changes
 
+### 🚀 Features
+
+- When an invalid regex throws, include the generated source in the error message (some browsers automatically include the source, but Firefox and Safari don't).
+
 ### 🐞 Fixes
 
 - Convert numbers interpolated in enclosed `\u{…}` to hexadecimal. In other words, although `` regex`\u{${'160'}}` `` (string interpolated) returns `/\u{160}/`, `` regex`\u{${160}}` `` (number interpolated) now returns `/\u{A0}/`. (#24, @graphemecluster)

spec/index.html

@@ -26,6 +26,7 @@
   <script src="./regex-tag.spec.js"></script>
   <script src="./rewrite.spec.js"></script>
   <script src="./pattern.spec.js"></script>
+  <script src="./interpolate-number.spec.js"></script>
   <script src="./interpolate-pattern.spec.js"></script>
   <script src="./interpolate-regexp.spec.js"></script>
   <script src="./interpolate-string.spec.js"></script>

spec/regex-tag.spec.js

@@ -60,6 +60,17 @@ describe('regex', () => {
     expect(() => regex({}, {raw: ['']})).toThrow();
   });
 
+  it('should include the generated regex in the error if the RegExp constructor throws', () => {
+    const values = [
+      ['\\u', '\\u'],
+      ['(?<a>.)\\g<a>|*', '(?<a>.)(?:.)|*'],
+    ];
+    values.forEach(([input, output]) => {
+      expect(() => regex({raw: [input]})).toThrowMatching(err => err.message.includes(`/${output}/`));
+      expect(() => regex({subclass: true})({raw: [input]})).toThrowMatching(err => err.message.includes(`/${output}/`));
+    });
+  });
+
   describe('options', () => {
     it('should allow setting flags via an option', () => {
       expect(regex({flags: ''})``.global).toBeFalse();

src/regex.js

@@ -102,11 +102,21 @@ const regexFromTemplate = (options, template, ...substitutions) => {
   });
 
   expression = handlePlugins(expression, opts);
+  let captureMap;
   if (opts.subclass) {
-    const unmarked = unmarkEmulationGroups(expression);
-    return new WrappedRegExp(unmarked.expression, opts.flags, {captureMap: unmarked.captureMap});
+    ({expression, captureMap} = unmarkEmulationGroups(expression));
+  }
+  try {
+    return opts.subclass ?
+      new WrappedRegExp(expression, opts.flags, {captureMap}) :
+      new RegExp(expression, opts.flags);
+  } catch (err) {
+    // Improve DX by always including the generated source in the error message. Some browsers
+    // include it automatically, but not Firefox or Safari
+    const stripped = err.message.replace(/ \/.+\/[a-z]*:/, '');
+    err.message = `${stripped}: /${expression}/${opts.flags}`;
+    throw err;
   }
-  return new RegExp(expression, opts.flags);
 }
 
 /**