fix: Don't leak future annotations in user code

Issue-47: #47

src/markdown_exec/formatters/_exec_python.py

@@ -0,0 +1,8 @@
+"""Special module without future annotations for executing Python code."""
+
+from typing import Any, Dict, Optional
+
+
+def exec_python(code: str, filename: str, exec_globals: Optional[Dict[str, Any]] = None) -> None:
+    compiled = compile(code, filename=filename, mode="exec")
+    exec(compiled, exec_globals)  # noqa: S102

src/markdown_exec/formatters/python.py

@@ -11,6 +11,7 @@
 from types import ModuleType
 from typing import Any
 
+from markdown_exec.formatters._exec_python import exec_python
 from markdown_exec.formatters.base import ExecutionError, base_format
 from markdown_exec.rendering import code_block
 
@@ -67,8 +68,7 @@ def _run_python(
     exec_globals["print"] = partial(_buffer_print, buffer)
 
     try:
-        compiled = compile(code, filename=code_block_id, mode="exec")
-        exec(compiled, exec_globals)  # noqa: S102
+        exec_python(code, code_block_id, exec_globals)
     except Exception as error:  # noqa: BLE001
         trace = traceback.TracebackException.from_exception(error)
         for frame in trace.stack:

tests/test_python.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import re
 from textwrap import dedent
 from typing import TYPE_CHECKING
 
@@ -203,3 +204,28 @@ def func():
         ),
     )
     assert "_code_block_n" in html
+
+
+def test_future_annotations_do_not_leak_into_user_code(md: Markdown) -> None:
+    """Assert future annotations do not leak into user code.
+
+    Parameters:
+        md: A Markdown instance (fixture).
+    """
+    html = md.convert(
+        dedent(
+            """
+            ```python exec="1"
+            class Int:
+                ...
+
+            def f(x: Int) -> None:
+                return x + 1.0
+
+            print(f"`{f.__annotations__['x']}`")
+            ```
+            """,
+        ),
+    )
+    assert "<code>Int</code>" not in html
+    assert re.search(r"class '_code_block_n\d+_\.Int'", html)