Merge pull request #263 from asottile/first-line-ending

use first line ending rather than most common

reorder_python_imports.py

@@ -371,15 +371,14 @@ def apply_import_sorting(
     return pre_import_code + new_imports + rest
 
 
-def _most_common_line_ending(s: str) -> str:
-    # initialize in case there's no line endings at all
-    counts = collections.Counter({'\n': 0})
-    for line in s.splitlines(True):
-        for ending in ('\r\n', '\r', '\n'):
-            if line.endswith(ending):
-                counts[ending] += 1
-                break
-    return counts.most_common(1)[0][0]
+def _first_line_ending(s: str) -> str:
+    sio = io.StringIO(s, newline='')
+    line = sio.readline()
+    for nl in ('\r\n', '\r'):
+        if line.endswith(nl):
+            return nl
+    else:
+        return '\n'
 
 
 def fix_file_contents(
@@ -391,7 +390,7 @@ def fix_file_contents(
         settings: Settings = Settings(),
 ) -> str:
     # internally use `'\n` as the newline and normalize at the very end
-    nl = _most_common_line_ending(contents)
+    nl = _first_line_ending(contents)
     contents = contents.replace('\r\n', '\n').replace('\r', '\n').rstrip()
     if contents:
         contents += '\n'

tests/reorder_python_imports_test.py

@@ -829,6 +829,27 @@ def test_fix_cr():
     assert ret == s
 
 
+def test_fix_mixed_uses_first_newline():
+    s = (
+        '"""foo"""\n'
+        'import os\r\n'
+        'import sys\r\n'
+        'x = 1\r\n'
+    )
+    ret = fix_file_contents(
+        s,
+        to_add=(),
+        to_remove=set(),
+        to_replace=Replacements.make([]),
+    )
+    assert ret == (
+        '"""foo"""\n'
+        'import os\n'
+        'import sys\n'
+        'x = 1\n'
+    )
+
+
 @pytest.mark.parametrize(
     ('opt', 'expected'),
     (