Fix: Preserve first dot of relative path (fixes #5)

Author: sttk

index.js

@@ -12,7 +12,22 @@ function replaceExt(npath, ext) {
   }
 
   var nFileName = path.basename(npath, path.extname(npath)) + ext;
-  return path.join(path.dirname(npath), nFileName);
+  var nFilepath = path.join(path.dirname(npath), nFileName);
+
+  // Because `path.join` removes the head './' from the given path.
+  // This removal can cause a problem when passing the result to `require` or
+  // `import`.
+  if (startsWithSingleDot(npath)) {
+    return '.' + path.sep + nFilepath;
+  }
+
+  return nFilepath;
+}
+
+function startsWithSingleDot(fpath) {
+  var first2chars = fpath.slice(0, 2);
+  return (first2chars === '.' + path.sep) ||
+         (first2chars === './');
 }
 
 module.exports = replaceExt;

test/main.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var path = require('path');
+var os = require('os');
 
 var expect = require('expect');
 
@@ -61,4 +62,27 @@ describe('replace-ext', function() {
     done();
   });
 
+  it('Should preserve the first dot of relative dir name.', function(done) {
+    if (os.platform() === 'win32') {
+      expect(replaceExt('a/b/c.js', '.ts')).toEqual('a\\b\\c.ts');
+      expect(replaceExt('./a/b/c.js', '.ts')).toEqual('.\\a\\b\\c.ts');
+      expect(replaceExt('../a/b/c.js', '.ts')).toEqual('..\\a\\b\\c.ts');
+      expect(replaceExt('/a/b/c.js', '.ts')).toEqual('\\a\\b\\c.ts');
+
+      expect(replaceExt('C:/a/b/c.js', '.ts')).toEqual('C:\\a\\b\\c.ts');
+
+      expect(replaceExt('a\\b\\c.js', '.ts')).toEqual('a\\b\\c.ts');
+      expect(replaceExt('.\\a\\b\\c.js', '.ts')).toEqual('.\\a\\b\\c.ts');
+      expect(replaceExt('..\\a\\b\\c.js', '.ts')).toEqual('..\\a\\b\\c.ts');
+      expect(replaceExt('\\a\\b\\c.js', '.ts')).toEqual('\\a\\b\\c.ts');
+
+      expect(replaceExt('C:\\a\\b\\c.js', '.ts')).toEqual('C:\\a\\b\\c.ts');
+    } else {
+      expect(replaceExt('a/b/c.js', '.ts')).toEqual('a/b/c.ts');
+      expect(replaceExt('./a/b/c.js', '.ts')).toEqual('./a/b/c.ts');
+      expect(replaceExt('../a/b/c.js', '.ts')).toEqual('../a/b/c.ts');
+      expect(replaceExt('/a/b/c.js', '.ts')).toEqual('/a/b/c.ts');
+    }
+    done();
+  });
 });