Fix new_indent behavior

isort/core.py

@@ -246,6 +246,7 @@ def write(self, *a, **kw):
                 ):
                     import_section += line
                 elif stripped_line.startswith(IMPORT_START_IDENTIFIERS):
+                    did_contain_imports = contains_imports
                     contains_imports = True
 
                     new_indent = line[: -len(line.lstrip())]
@@ -286,7 +287,7 @@ def write(self, *a, **kw):
                             cimports = cimport_statement
                     else:
                         if new_indent != indent:
-                            if import_section:
+                            if import_section and did_contain_imports:
                                 import_statement = import_statement.lstrip()
                             else:
                                 indent = new_indent

tests/unit/test_ticketed_features.py

@@ -876,18 +876,21 @@ 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("""
+    assert (
+        isort.code(
+            """
 import os
   import os
-  """) == """
+  """
+        )
+        == """
 import os
 """
-
-
+    )