ParserSyntaxError when a module have a "from django.utils import timezone" import

Describe the bug

I’m migrating a medium-sized codebase, and I found this strange behavior: if the code has a “from django.utils import timezone” import, a ParserSyntaxError is raised

$ pre-commit run -a
djcodemod................................................................Failed
- hook id: djcodemod
- exit code: 1

Running codemods: AssignmentTagTransformer, CookieDateTransformer, FixedOffsetTransformer, FloatRangeFormFieldTransformer, FloatRangeModelFieldTransformer, InlineHasAddPermissionsTransformer, ModelsPermalinkTransformer, OnDeleteTransformer, QuerySetPaginatorTransformer, SignalDisconnectWeakTransformer, URLResolversTransformer
Executing codemod...
Finished codemodding 62 files!
 - Transformed 62 files successfully.
 - Skipped 0 files.
 - Failed to codemod 0 files.
 - 0 warnings were generated.
Running codemods: AssignmentTagTransformer, CookieDateTransformer, FixedOffsetTransformer, FloatRangeFormFieldTransformer, FloatRangeModelFieldTransformer, InlineHasAddPermissionsTransformer, ModelsPermalinkTransformer, OnDeleteTransformer, QuerySetPaginatorTransformer, SignalDisconnectWeakTransformer, URLResolversTransformer
Executing codemod...
Codemodding /home/luzfcb/projects/big_project/foobar/tests/test_managers.py
Traceback (most recent call last):
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_parser/base_parser.py", line 152, in _add_token
    plan = stack[-1].dfa.transitions[transition]
KeyError: ReservedString(import)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/_cli.py", line 295, in _execute_transform
    output_tree = transformer.transform_module(input_tree)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/_command.py", line 88, in transform_module
    tree = self._instantiate_and_run(transform, tree)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/_command.py", line 58, in _instantiate_and_run
    return inst.transform_module(tree)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/_codemod.py", line 108, in transform_module
    return self.transform_module_impl(tree_with_metadata)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/_visitor.py", line 32, in transform_module_impl
    return tree.visit(self)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_nodes/module.py", line 91, in visit
    result = super(Module, self).visit(visitor)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_nodes/base.py", line 235, in visit
    leave_result = visitor.on_leave(self, with_updated_children)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/matchers/_visitors.py", line 512, in on_leave
    retval = CSTTransformer.on_leave(self, original_node, updated_node)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_visitors.py", line 72, in on_leave
    updated_node = leave_func(original_node, updated_node)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/visitors/_add_imports.py", line 393, in leave_Module
    *[
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/codemod/visitors/_add_imports.py", line 394, in <listcomp>
    parse_statement(
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_parser/entrypoints.py", line 100, in parse_statement
    result = _parse(
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_parser/entrypoints.py", line 51, in _parse
    result = parser.parse()
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_parser/base_parser.py", line 111, in parse
    self._add_token(token)
  File "/home/luzfcb/.cache/pre-commit/repof_bg4wfe/py_env-python3/lib/python3.9/site-packages/libcst/_parser/base_parser.py", line 187, in _add_token
    raise ParserSyntaxError(
libcst._exceptions.ParserSyntaxError: Syntax Error @ 1:7.
Incomplete input. Encountered 'import', but expected '.', '...', or 'NAME'.

from  import datetime
      ^

Failed to codemod /home/luzfcb/projects/big_project/foobar/tests/test_managers.py

To Reproduce

pipx install "django-codemod==1.5.5"

echo "from django.utils import timezone" > foobar.py

djcodemod run --deprecated-in 1.9 --deprecated-in 1.10 --deprecated-in 1.11 --deprecated-in 2.0 --deprecated-in 2.1 --deprecated-in 2.2 foobar.py

Additional context

[browniebroke]

The problem should no longer happen in 1.5.6, I’ve disabled the problematic feature for now. I’ll try to fix it properly later, not really have time at the moment…

[browniebroke]

Yes I think I’ve nailed down the problem to this section, it’s just wrong (it replaces the import for the parent module, even if the thing being codemodded isn’t used in the file):

https://github.com/browniebroke/django-codemod/blob/7942036744d3b1ef28123bda9e4a8e7fbc88ddb4/django_codemod/visitors/base.py#L167-L175

I’ll probably disable this feature and push a new release (hopefully tomorrow) until I can make a fix, this is probably breaking a lot of other things.