🐛 Fix evaluating stringified annotations in Python 3.10 (also `from _…

…_future__ import annotations`) (#721)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_annotated.py

@@ -2,6 +2,8 @@
 from typer.testing import CliRunner
 from typing_extensions import Annotated
 
+from .utils import needs_py310
+
 runner = CliRunner()
 
 
@@ -21,6 +23,23 @@ def cmd(val: Annotated[int, typer.Argument()] = 0):
     assert "hello 42" in result.output
 
 
+@needs_py310
+def test_annotated_argument_in_string_type_with_default():
+    app = typer.Typer()
+
+    @app.command()
+    def cmd(val: "Annotated[int, typer.Argument()]" = 0):
+        print(f"hello {val}")
+
+    result = runner.invoke(app)
+    assert result.exit_code == 0, result.output
+    assert "hello 0" in result.output
+
+    result = runner.invoke(app, ["42"])
+    assert result.exit_code == 0, result.output
+    assert "hello 42" in result.output
+
+
 def test_annotated_argument_with_default_factory():
     app = typer.Typer()
 

tests/utils.py

@@ -0,0 +1,7 @@
+import sys
+
+import pytest
+
+needs_py310 = pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="requires python3.10+"
+)

typer/utils.py

@@ -1,4 +1,5 @@
 import inspect
+import sys
 from copy import copy
 from typing import Any, Callable, Dict, List, Tuple, Type, cast, get_type_hints
 
@@ -106,7 +107,11 @@ def _split_annotation_from_typer_annotations(
 
 
 def get_params_from_function(func: Callable[..., Any]) -> Dict[str, ParamMeta]:
-    signature = inspect.signature(func)
+    if sys.version_info >= (3, 10):
+        signature = inspect.signature(func, eval_str=True)
+    else:
+        signature = inspect.signature(func)
+
     type_hints = get_type_hints(func)
     params = {}
     for param in signature.parameters.values():