typer <path_or_module> utils raises AttributeError: 'NoneType' object has no attribute '__dict__' from dataclasses when using from __future__ import annotations

[Deltik]

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• I searched the Typer documentation, with the integrated search.
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• I already read and followed all the tutorials in the docs and didn't find an answer.
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Example Code

from __future__ import annotations

from typer import Typer
from dataclasses import dataclass

@dataclass
class DoesNotMatter:
    id: int

app = Typer()

@app.command()
def main() -> None:
    pass

if __name__ == "__main__":
    app()

Description

The typer command crashes with AttributeError: 'NoneType' object has no attribute '__dict__' under these two conditions:

• The Typer module/script source uses the @dataclasses.dataclass decorator.
• The script specifies from __future__ import annotations.

Instant copy-and-paste reproducer for Linux shells:

#!/bin/bash
rm -rf /tmp/repro
python3 -m venv /tmp/repro/.venv
. /tmp/repro/.venv/bin/activate
pip install typer
cat > /tmp/repro/demo.py <<EOF
from __future__ import annotations

from typer import Typer
from dataclasses import dataclass

@dataclass
class DoesNotMatter:
    id: int

app = Typer()

@app.command()
def main() -> None:
    pass

if __name__ == "__main__":
    app()
EOF
typer /tmp/repro/demo.py utils docs

Stack trace:

$ typer demo.py utils docs
╭──────────────────────────────────── Traceback (most recent call last) ─────────────────────────────────────╮
│ /tmp/repro/.venv/bin/typer:8 in <module>                                                                   │
│                                                                                                            │
│   5 from typer.cli import main                                                                             │
│   6 if __name__ == '__main__':                                                                             │
│   7 │   sys.argv[0] = re.sub(r'(-script\.pyw|\.exe)?$', '', sys.argv[0])                                   │
│ ❱ 8 │   sys.exit(main())                                                                                   │
│   9                                                                                                        │
│                                                                                                            │
│ ╭──────────────────────────── locals ────────────────────────────╮                                         │
│ │ main = <function main at 0x71ab92739e40>                       │                                         │
│ │   re = <module 're' from '/usr/lib/python3.12/re/__init__.py'> │                                         │
│ │  sys = <module 'sys' (built-in)>                               │                                         │
│ ╰────────────────────────────────────────────────────────────────╯                                         │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/cli.py:299 in main                                     │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/main.py:338 in __call__                                │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/main.py:321 in __call__                                │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/click/core.py:1157 in __call__                               │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/core.py:728 in main                                    │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/core.py:197 in _main                                   │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/cli.py:64 in invoke                                    │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/cli.py:69 in maybe_add_run                             │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/cli.py:142 in maybe_add_run_to_cli                     │
│                                                                                                            │
│ /tmp/repro/.venv/lib/python3.12/site-packages/typer/cli.py:134 in get_typer_from_state                     │
│ in exec_module:995                                                                                         │
│ ╭─────────────────────────────────────── locals ───────────────────────────────────────╮                   │
│ │   code = <code object <module> at 0x71ab932e8f50, file "/tmp/repro/demo.py", line 1> │                   │
│ │ module = <module 'demo.py' from '/tmp/repro/demo.py'>                                │                   │
│ │   self = <_frozen_importlib_external.SourceFileLoader object at 0x71ab927354f0>      │                   │
│ ╰──────────────────────────────────────────────────────────────────────────────────────╯                   │
│ in _call_with_frames_removed:488                                                                           │
│ ╭──────────────────────────────────────────────── locals ────────────────────────────────────────────────╮ │
│ │ args = (                                                                                               │ │
│ │        │   <code object <module> at 0x71ab932e8f50, file "/tmp/repro/demo.py", line 1>,                │ │
│ │        │   {                                                                                           │ │
│ │        │   │   '__name__': 'demo.py',                                                                  │ │
│ │        │   │   '__doc__': None,                                                                        │ │
│ │        │   │   '__package__': 'demo',                                                                  │ │
│ │        │   │   '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x71ab927354f0>,   │ │
│ │        │   │   '__spec__': ModuleSpec(name='demo.py',                                                  │ │
│ │        loader=<_frozen_importlib_external.SourceFileLoader object at 0x71ab927354f0>,                  │ │
│ │        origin='/tmp/repro/demo.py'),                                                                   │ │
│ │        │   │   '__file__': '/tmp/repro/demo.py',                                                       │ │
│ │        │   │   '__cached__': '/tmp/repro/__pycache__/demo.cpython-312.pyc',                            │ │
│ │        │   │   '__builtins__': {                                                                       │ │
│ │        │   │   │   '__name__': 'builtins',                                                             │ │
│ │        │   │   │   '__doc__': 'Built-in functions, types, exceptions, and other objects.\n\nThis       │ │
│ │        module provides '+346,                                                                          │ │
│ │        │   │   │   '__package__': '',                                                                  │ │
│ │        │   │   │   '__loader__': <class '_frozen_importlib.BuiltinImporter'>,                          │ │
│ │        │   │   │   '__spec__': ModuleSpec(name='builtins', loader=<class                               │ │
│ │        '_frozen_importlib.BuiltinImporter'>, origin='built-in'),                                       │ │
│ │        │   │   │   '__build_class__': <built-in function __build_class__>,                             │ │
│ │        │   │   │   '__import__': <built-in function __import__>,                                       │ │
│ │        │   │   │   'abs': <built-in function abs>,                                                     │ │
│ │        │   │   │   'all': <built-in function all>,                                                     │ │
│ │        │   │   │   'any': <built-in function any>,                                                     │ │
│ │        │   │   │   ... +147                                                                            │ │
│ │        │   │   },                                                                                      │ │
│ │        │   │   'annotations': _Feature((3, 7, 0, 'beta', 1), None, 16777216),                          │ │
│ │        │   │   'Typer': <class 'typer.main.Typer'>,                                                    │ │
│ │        │   │   ... +1                                                                                  │ │
│ │        │   }                                                                                           │ │
│ │        )                                                                                               │ │
│ │    f = <built-in function exec>                                                                        │ │
│ │ kwds = {}                                                                                              │ │
│ ╰────────────────────────────────────────────────────────────────────────────────────────────────────────╯ │
│                                                                                                            │
│ /tmp/repro/demo.py:6 in <module>                                                                           │
│                                                                                                            │
│    3 from typer import Typer                                                                               │
│    4 from dataclasses import dataclass                                                                     │
│    5                                                                                                       │
│ ❱  6 @dataclass                                                                                            │
│    7 class DoesNotMatter:                                                                                  │
│    8 │   id: int                                                                                           │
│    9                                                                                                       │
│                                                                                                            │
│ ╭─────────────────────────── locals ───────────────────────────╮                                           │
│ │ annotations = _Feature((3, 7, 0, 'beta', 1), None, 16777216) │                                           │
│ │   dataclass = <function dataclass at 0x71ab92bf04a0>         │                                           │
│ │       Typer = <class 'typer.main.Typer'>                     │                                           │
│ ╰──────────────────────────────────────────────────────────────╯                                           │
│                                                                                                            │
│ /usr/lib/python3.12/dataclasses.py:1268 in dataclass                                                       │
│                                                                                                            │
│   1265 │   │   return wrap                                                                                 │
│   1266 │                                                                                                   │
│   1267 │   # We're called as @dataclass without parens.                                                    │
│ ❱ 1268 │   return wrap(cls)                                                                                │
│   1269                                                                                                     │
│   1270                                                                                                     │
│   1271 def fields(class_or_instance):                                                                      │
│                                                                                                            │
│ ╭────────────────────────────── locals ───────────────────────────────╮                                    │
│ │          cls = <class 'demo.py.DoesNotMatter'>                      │                                    │
│ │           eq = True                                                 │                                    │
│ │       frozen = False                                                │                                    │
│ │         init = True                                                 │                                    │
│ │      kw_only = False                                                │                                    │
│ │   match_args = True                                                 │                                    │
│ │        order = False                                                │                                    │
│ │         repr = True                                                 │                                    │
│ │        slots = False                                                │                                    │
│ │  unsafe_hash = False                                                │                                    │
│ │ weakref_slot = False                                                │                                    │
│ │         wrap = <function dataclass.<locals>.wrap at 0x71ab9273a2a0> │                                    │
│ ╰─────────────────────────────────────────────────────────────────────╯                                    │
│                                                                                                            │
│ /usr/lib/python3.12/dataclasses.py:1258 in wrap                                                            │
│                                                                                                            │
│   1255 │   """                                                                                             │
│   1256 │                                                                                                   │
│   1257 │   def wrap(cls):                                                                                  │
│ ❱ 1258 │   │   return _process_class(cls, init, repr, eq, order, unsafe_hash,                              │
│   1259 │   │   │   │   │   │   │     frozen, match_args, kw_only, slots,                                   │
│   1260 │   │   │   │   │   │   │     weakref_slot)                                                         │
│   1261                                                                                                     │
│                                                                                                            │
│ ╭──────────────────── locals ────────────────────╮                                                         │
│ │          cls = <class 'demo.py.DoesNotMatter'> │                                                         │
│ │           eq = True                            │                                                         │
│ │       frozen = False                           │                                                         │
│ │         init = True                            │                                                         │
│ │      kw_only = False                           │                                                         │
│ │   match_args = True                            │                                                         │
│ │        order = False                           │                                                         │
│ │         repr = True                            │                                                         │
│ │        slots = False                           │                                                         │
│ │  unsafe_hash = False                           │                                                         │
│ │ weakref_slot = False                           │                                                         │
│ ╰────────────────────────────────────────────────╯                                                         │
│                                                                                                            │
│ /usr/lib/python3.12/dataclasses.py:983 in _process_class                                                   │
│                                                                                                            │
│    980 │   │   # See if this is a marker to change the value of kw_only.                                   │
│    981 │   │   if (_is_kw_only(type, dataclasses)                                                          │
│    982 │   │   │   or (isinstance(type, str)                                                               │
│ ❱  983 │   │   │   │   and _is_type(type, cls, dataclasses, dataclasses.KW_ONLY,                           │
│    984 │   │   │   │   │   │   │    _is_kw_only))):                                                        │
│    985 │   │   │   # Switch the default to kw_only=True, and ignore this                                   │
│    986 │   │   │   # annotation: it's not a real field.                                                    │
│                                                                                                            │
│ ╭──────────────────────────────────────── locals ────────────────────────────────────────╮                 │
│ │     any_frozen_base = False                                                            │                 │
│ │                   b = <class 'object'>                                                 │                 │
│ │         base_fields = None                                                             │                 │
│ │                 cls = <class 'demo.py.DoesNotMatter'>                                  │                 │
│ │     cls_annotations = {'id': 'int'}                                                    │                 │
│ │          cls_fields = []                                                               │                 │
│ │         dataclasses = <module 'dataclasses' from '/usr/lib/python3.12/dataclasses.py'> │                 │
│ │                  eq = True                                                             │                 │
│ │              fields = {}                                                               │                 │
│ │              frozen = False                                                            │                 │
│ │             globals = {}                                                               │                 │
│ │ has_dataclass_bases = False                                                            │                 │
│ │                init = True                                                             │                 │
│ │             kw_only = False                                                            │                 │
│ │        KW_ONLY_seen = False                                                            │                 │
│ │          match_args = True                                                             │                 │
│ │                name = 'id'                                                             │                 │
│ │               order = False                                                            │                 │
│ │                repr = True                                                             │                 │
│ │               slots = False                                                            │                 │
│ │                type = 'int'                                                            │                 │
│ │         unsafe_hash = False                                                            │                 │
│ │        weakref_slot = False                                                            │                 │
│ ╰────────────────────────────────────────────────────────────────────────────────────────╯                 │
│                                                                                                            │
│ /usr/lib/python3.12/dataclasses.py:749 in _is_type                                                         │
│                                                                                                            │
│    746 │   │   if not module_name:                                                                         │
│    747 │   │   │   # No module name, assume the class's module did                                         │
│    748 │   │   │   # "from dataclasses import InitVar".                                                    │
│ ❱  749 │   │   │   ns = sys.modules.get(cls.__module__).__dict__                                           │
│    750 │   │   else:                                                                                       │
│    751 │   │   │   # Look up module_name in the class's module.                                            │
│    752 │   │   │   module = sys.modules.get(cls.__module__)                                                │
│                                                                                                            │
│ ╭─────────────────────────────────────── locals ───────────────────────────────────────╮                   │
│ │          a_module = <module 'dataclasses' from '/usr/lib/python3.12/dataclasses.py'> │                   │
│ │            a_type = <dataclasses._KW_ONLY_TYPE object at 0x71ab92bdd610>             │                   │
│ │        annotation = 'int'                                                            │                   │
│ │               cls = <class 'demo.py.DoesNotMatter'>                                  │                   │
│ │ is_type_predicate = <function _is_kw_only at 0x71ab92bafc40>                         │                   │
│ │             match = <re.Match object; span=(0, 3), match='int'>                      │                   │
│ │       module_name = None                                                             │                   │
│ │                ns = None                                                             │                   │
│ ╰──────────────────────────────────────────────────────────────────────────────────────╯                   │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
AttributeError: 'NoneType' object has no attribute '__dict__'

Operating System

Linux

Operating System Details

Ubuntu 24.04.1

Typer Version

0.12.5

Python Version

3.12.3

Additional Context

Other issues involving from __future__ import annotations that are not duplicates of this issue:

• from __future__ import annotations breaks typer in lower python version #977
• Bug in python 3.8 when you use Annotated and annotations from __future__ #708
• Path validations not working when using `from __future__ import annotations` #698
• `Annotated` in Typer v0.9.0 is broken with `from __future__ import annotations` #598

[YuriiMotov]

The issue only appears when run as typer demo.py ....

Works well with python demo.py --help

[Deltik]

Yes, but this doesn't solve the use case of running typer … utils docs.

[YuriiMotov]

Sure, I just added this in case it can give some hint on why it happens

[Deltik]

Ah, I see. I dug more into the issue and think I have a solution to the error. All it should take is this patch to Typer:

diff --git a/typer/cli.py b/typer/cli.py
index c962cec..3cec462 100644
--- a/typer/cli.py
+++ b/typer/cli.py
@@ -129,17 +129,18 @@ def get_typer_from_module(module: Any) -> Optional[typer.Typer]:
 def get_typer_from_state() -> Optional[typer.Typer]:
     spec = None
     if state.file:
         module_name = state.file.name
         spec = importlib.util.spec_from_file_location(module_name, str(state.file))
     elif state.module:
         spec = importlib.util.find_spec(state.module)
     if spec is None:
         if state.file:
             typer.echo(f"Could not import as Python file: {state.file}", err=True)
         else:
             typer.echo(f"Could not import as Python module: {state.module}", err=True)
         sys.exit(1)
     module = importlib.util.module_from_spec(spec)
+    sys.modules[module.__name__] = module
     spec.loader.exec_module(module)  # type: ignore
     obj = get_typer_from_module(module)
     return obj

Correct me if I'm wrong, but what I see is that Typer doesn't register the dynamically loaded module in sys.modules before executing it. When the @dataclass decorator runs, it tries to resolve type annotations by looking up the module in sys.modules but fails because the module isn't registered there.