Preserve frontmatter format after leading whitespace

frontmatter/__init__.py

@@ -188,7 +188,7 @@ def loads(
         ...     post = frontmatter.loads(f.read())
 
     """
-    text = u(text, encoding)
+    text = u(text, encoding).strip()
     handler = handler or detect_format(text, handlers)
     metadata, content = parse(text, encoding, handler, **defaults)
     return Post(content, handler, **metadata)

tests/unit_test.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
+import io
 import os
 import shutil
 import tempfile
@@ -186,6 +187,26 @@ def test_sanity_all(self):
         for filename, Handler in self.TEST_FILES.items():
             self.sanity_check(filename, Handler)
 
+    def test_leading_whitespace_preserves_handler(self):
+        "Preserve the detected format when parsing strips leading whitespace"
+        for filename, Handler in self.TEST_FILES.items():
+            with open(filename, encoding="utf-8") as f:
+                text = f.read()
+            expected = frontmatter.loads(text)
+            for prefix in ("\n", " \t\r\n"):
+                for loader in (
+                    frontmatter.loads,
+                    lambda text: frontmatter.load(io.StringIO(text)),
+                ):
+                    with self.subTest(filename=filename, prefix=prefix, loader=loader):
+                        post = loader(prefix + text)
+                        self.assertEqual(post.metadata, expected.metadata)
+                        self.assertEqual(post.content, expected.content)
+                        self.assertIsInstance(post.handler, Handler)
+                        self.assertEqual(
+                            frontmatter.dumps(post), frontmatter.dumps(expected)
+                        )
+
     def test_no_handler(self):
         "default to YAMLHandler when no handler is attached"
         post = frontmatter.load("tests/yaml/hello-world.txt")