Fix #1575: Leading space is removed from wrong line

isort/core.py

@@ -275,7 +275,7 @@ def write(self, *a, **kw):
                     ):
                         cimport_statement = True
 
-                    if cimport_statement != cimports or (new_indent != indent and import_section):
+                    if cimport_statement != cimports and import_section:
                         if import_section:
                             next_cimports = cimport_statement
                             next_import_section = import_statement
@@ -284,8 +284,12 @@ def write(self, *a, **kw):
                             line = ""
                         else:
                             cimports = cimport_statement
-
-                    indent = new_indent
+                    else:
+                        if new_indent != indent:
+                            if import_section:
+                                import_statement = import_statement.lstrip()
+                            else:
+                                indent = new_indent
                     import_section += import_statement
                 else:
                     not_imports = True

tests/unit/test_ticketed_features.py

@@ -876,3 +876,18 @@ def test_api_to_allow_custom_diff_and_output_stream_1583(capsys, tmpdir):
 
     isort_output.seek(0)
     assert isort_output.read().splitlines() == ["import a", "import b"]
+
+
+def test_autofix_mixed_indent_imports_1575():
+    """isort should automatically fix import statements that are sent in
+    with incorrect mixed indentation.
+    See: https://github.com/PyCQA/isort/issues/1575
+    """
+    assert isort.code("""
+import os
+  import os
+  """) == """
+import os
+"""
+
+