Correct regex for function source cleaning

- Treat tabs etc. as spaces.
- Match function name for removal.
- Match only non-`)` inside the function parameter list for removal instead of `.`; prevents matching through later in the first line e.g. `function(){ if ([condition]) { ...`.
- Match 0 or more spaces before } on the end for removal rather than 1 or more.
- Make the closing } optional for arrow functions with a single-statement body just like the opening {.
- Add tests for these cases.

lib/utils.js

@@ -264,8 +264,8 @@ exports.slug = function(str) {
 exports.clean = function(str) {
   str = str
     .replace(/\r\n?|[\n\u2028\u2029]/g, '\n').replace(/^\uFEFF/, '')
-    .replace(/^function *\(.*\)\s*\{|\(.*\) *=> *\{?/, '')
-    .replace(/\s+\}$/, '');
+    // (traditional)->  space/name     parameters    body     (lambda)-> parameters       body   multi-statement/single          keep body content
+    .replace(/^function(?:\s*|\s+[^(]*)\([^)]*\)\s*\{((?:.|\n)*?)\s*\}$|^\([^)]*\)\s*=>\s*(?:\{((?:.|\n)*?)\s*\}|((?:.|\n)*))$/, '$1$2$3');
 
   var spaces = str.match(/^\n?( *)/)[1].length;
   var tabs = str.match(/^\n?(\t*)/)[1].length;

test/utils.js

@@ -19,6 +19,30 @@ describe('utils', function() {
     it('should remove tab character indentation from the function body', function() {
       clean('\t//line1\n\t\t//line2').should.equal('//line1\n\t//line2');
     });
+
+    it('should handle functions with tabs in their declarations', function() {
+      clean('function\t(\t)\t{\n//code\n}').should.equal('//code');
+    });
+
+    it('should handle named functions without space after name', function() {
+      clean('function withName() {\n//code\n}').should.equal('//code');
+    });
+
+    it('should handle named functions with space after name', function() {
+      clean('function withName () {\n//code\n}').should.equal('//code');
+    });
+
+    it('should handle functions with no space between the end and the closing brace', function() {
+      clean('function() {/*code*/}').should.equal('/*code*/');
+    });
+
+    it('should handle functions with parentheses in the same line', function() {
+      clean('function() { if (true) { /* code */ } }').should.equal('if (true) { /* code */ }');
+    });
+
+    it('should handle empty functions', function() {
+      clean('function() {}').should.equal('');
+    });
   });
 
   describe('.isBuffer()', function() {