Fixed #1398: isort: off comment doesn't work, if it's the top comment…

… in the file.

isort/core.py

@@ -137,6 +137,9 @@ def process(
                 if file_skip_comment in line:
                     raise FileSkipComment("Passed in content")
 
+            if not in_quote and stripped_line == "# isort: off":
+                isort_off = True
+
             if (
                 (index == 0 or (index in (1, 2) and not contains_imports))
                 and stripped_line.startswith("#")
@@ -175,13 +178,9 @@ def process(
 
             not_imports = bool(in_quote) or in_top_comment or isort_off
             if not (in_quote or in_top_comment):
-                stripped_line = line.strip()
                 if isort_off:
                     if stripped_line == "# isort: on":
                         isort_off = False
-                elif stripped_line == "# isort: off":
-                    not_imports = True
-                    isort_off = True
                 elif stripped_line.endswith("# isort: split"):
                     not_imports = True
                 elif stripped_line in CODE_SORT_COMMENTS:

tests/test_action_comments.py

@@ -0,0 +1,47 @@
+"""Tests for isort action comments, such as isort: skip"""
+import isort
+
+
+def test_isort_off_and_on():
+    """Test so ensure isort: off action comment and associated on action comment work together"""
+
+    # as top of file comment
+    assert (
+        isort.code(
+            """# isort: off
+import a
+import a
+
+# isort: on
+import a
+import a
+"""
+        )
+        == """# isort: off
+import a
+import a
+
+# isort: on
+import a
+"""
+    )
+    # as middle comment
+    assert (
+        isort.code(
+            """
+import a
+import a
+
+# isort: off
+import a
+import a
+"""
+        )
+        == """
+import a
+
+# isort: off
+import a
+import a
+"""
+    )