fix: change the way we reexec mergify to enable PYTHONUTF8 (#777)

poetry/setuptools creates a windows binary on windows.

The current reexec code does not work with this binary as we expect the
sys.argv[0] to be python script.

This changes the way we enable UTF8 mode to reexec the exact binary that
launch the initial process.

This should works on all platforms whatever the console script file is a
python file or a binary.

Author: sileht

mergify_cli/cli.py

@@ -16,7 +16,6 @@
 from __future__ import annotations
 
 import os
-import subprocess
 import sys
 
 import click
@@ -51,11 +50,8 @@ def enforce_utf8_mode() -> None:
     if sys.flags.utf8_mode:
         return
 
-    argv = [sys.executable, "-X", "utf8"]
-    argv.extend(subprocess._args_from_interpreter_flags())  # type: ignore[attr-defined]  # noqa: SLF001
-    argv.extend(sys.argv)
-
-    os.execv(argv[0], argv)  # noqa: S606
+    os.environ["PYTHONUTF8"] = "1"
+    os.execvpe(sys.argv[0], sys.argv, os.environ)  # noqa: S606
 
 
 def main() -> None:
@@ -65,4 +61,10 @@ def main() -> None:
     #   Let's try our best by forcing utf-8 and if it's impossible, just returns escaped character
     if os.name == "nt":
         enforce_utf8_mode()
+
+    # We do that to test the console script generated by poetry
+    if os.getenv("MERGIFY_CLI_TESTING_UTF8_MODE"):
+        print(f"utf8_mode={int(sys.flags.utf8_mode)}")  # noqa: T201
+        print("✅")  # noqa: T201
+
     cli()

mergify_cli/tests/test_cli.py

@@ -1,51 +1,28 @@
 import os
-import pathlib
 import subprocess
-import sys
-import textwrap
 
 
-def test_reexec_enables_utf8_and_prints_emoji(
-    tmp_path: pathlib.Path,
-) -> None:
+def test_reexec_enables_utf8_and_prints_emoji() -> None:
     """
     Run in a child process so os.execv can safely replace it.
     We patch mymodule.cli inside the child (no mocks), then call main().
     We assert:
       - sys.flags.utf8_mode == 1 at print time
       - the emoji is present in stdout
     """
-    script = tmp_path / "runner.py"
-    script.write_text(
-        textwrap.dedent(
-            """
-            import sys
-            import os
-
-            from mergify_cli import cli
-
-            # Make cli() print a probe + the emoji
-            def _cli():
-                print(f"utf8_mode={int(sys.flags.utf8_mode)}")
-                print("✅")
-
-            cli.cli = _cli
-            cli.main()
-            """,
-        ),
-        encoding="utf-8",
-    )
-
     # Force utf8_mode OFF initially so enforce_utf8_mode triggers on Windows.
     env = os.environ.copy()
     env["PYTHONUTF8"] = "0"  # ensure not already in UTF-8 mode
+    env["MERGIFY_CLI_TESTING_UTF8_MODE"] = "1"
 
-    proc = subprocess.run(
-        [sys.executable, str(script)],
+    # We need to use shell to get binary PATH lookup working on windows
+    proc = subprocess.run(  # noqa: S602
+        "mergify --help",
         check=False,
         env=env,
         capture_output=True,
         text=True,
+        shell=True,
     )
 
     assert proc.returncode == 0, proc.stderr