Fix issue where the strict mode was not detected when a comment was before "strict mode";

Fixes jhnns#54

Author: jhnns

lib/detectStrictMode.js

@@ -1,3 +1,7 @@
+var multiLineComment = /^\s*\/\*.*?\*\//;
+var singleLineComment = /^\s*\/\/.*?[\r\n]/;
+var strictMode = /^\s*(?:"use strict"|'use strict')[ \t]*(?:[\r\n]|;)/;
+
 /**
  * Returns true if the source code is intended to run in strict mode. Does not detect
  * "use strict" if it occurs in a nested function.
@@ -6,7 +10,19 @@
  * @return {Boolean}
  */
 function detectStrictMode(src) {
-    return (/^\s*(?:"use strict"|'use strict')[ \t]*(?:[\r\n]|;)/g).test(src);
+    var singleLine;
+    var multiLine;
+
+    while ((singleLine = singleLineComment.test(src)) || (multiLine = multiLineComment.test(src))) {
+        if (singleLine) {
+            src = src.replace(singleLineComment, "");
+        }
+        if (multiLine) {
+            src = src.replace(multiLineComment, "");
+        }
+    }
+
+    return strictMode.test(src);
 }
 
-module.exports = detectStrictMode;
+module.exports = detectStrictMode;

test/detectStrictMode.test.js

@@ -2,6 +2,7 @@ var expect = require("expect.js"),
     detectStrictMode = require("../lib/detectStrictMode.js");
 
 describe("detectStrictMode", function () {
+
     it("should detect all valid uses of \"use strict\";", function () {
         expect(detectStrictMode('"use strict";')).to.be(true);
         expect(detectStrictMode("'use strict';")).to.be(true);
@@ -11,13 +12,22 @@ describe("detectStrictMode", function () {
         expect(detectStrictMode('"use strict"\r\n')).to.be(true);
         expect(detectStrictMode('"use strict" ; test();')).to.be(true);
     });
+
+    it("should be allowed to place comments before \"use strict\";", function () {
+        expect(detectStrictMode('// some comment\n"use strict";')).to.be(true);
+        expect(detectStrictMode('/* yo! */"use strict"; /* another comment */')).to.be(true);
+        expect(detectStrictMode('   // yes yo\r\n\r\n\r\n   /*oh yoh*/\r\n//oh snap!\r /* yoh! */"use strict";')).to.be(true);
+    });
+
     it("should not detect invalid uses of \"use strict\";", function () {
         expect(detectStrictMode('" use strict ";')).to.be(false);
         expect(detectStrictMode('"use strict".replace("use", "fail");')).to.be(false);
         expect(detectStrictMode('"use strict" .replace("use", "fail");')).to.be(false);
         expect(detectStrictMode(';"use strict";')).to.be(false);
     });
+
     it("should not detect \"use strict\"; if it occurs in some nested function", function () {
         expect(detectStrictMode('function () {"use strict";}')).to.be(false);
     });
-});
+
+});