gh-140287: Handle `PYTHONSTARTUP` script exceptions in the asyncio REPL #140288

johnslavik · 2025-10-18T10:09:59Z

This is generally a work in progress; tests are needed.
The asyncio patch is simple and ready.

Issue: The asyncio REPL interactive daemon thread doesn't handle PYTHONSTARTUP exceptions #140287

…epl-handle-python-startup

johnslavik · 2025-10-23T14:57:12Z

Please merge #140298 first.

This reverts commit 9355da7.

johnslavik · 2025-10-27T01:13:33Z

Lib/test/test_repl.py

+    # Isolated mode implies -E, -P and -s, purifies sys.path and ignores PYTHON*
+    # variables.
+    if isolated:
+        cmd_line.append('-I')


To reuse this routine and spawn_asyncio_repl below, we need to have a knob to not pass -I since that ignores PYTHONSTARTUP completely.

The asyncio REPL currently doesn't comply to that, which is a separate issue I'll report having learnt this.

Tracking the -I edge case in #140648.

johnslavik · 2025-10-27T01:15:03Z

Lib/test/test_repl.py

-    def test_asyncio_repl_reaches_python_startup_script(self):
-        with os_helper.temp_dir() as tmpdir:
-            script = os.path.join(tmpdir, "pythonstartup.py")
-            with open(script, "w") as f:
-                f.write("print('pythonstartup done!')" + os.linesep)
-                f.write("exit(0)" + os.linesep)
-
-            env = os.environ.copy()
-            env["PYTHON_HISTORY"] = os.path.join(tmpdir, ".asyncio_history")
-            env["PYTHONSTARTUP"] = script
-            subprocess.check_call(
-                [sys.executable, "-m", "asyncio"],
-                stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE,
-                env=env,
-                timeout=SHORT_TIMEOUT,
-            )


Covered by TestPythonStartup now, so not needed here.

johnslavik · 2025-11-08T01:13:33Z

It seems that the asyncio REPL on Windows leaks the event loop:

❯ PYTHONSTARTUP='' python -m asyncio
Running Debug|x64 interpreter...
asyncio REPL 3.15.0a1+ (heads/asyncio-repl-handle-python-startup-dirty:ce03ccef689, Nov  8 2025, 02:06:1) [MSC v.1944 64 bit (AMD64)] on win32
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> exit
exiting asyncio REPL...
C:\Users\zenon\Python\cpython\Lib\asyncio\base_events.py:758: ResourceWarning: unclosed event loop <ProactorEventLoop running=False closed=False debug=False>

Definitely a bug, we'll track it elsewhere soon.

EDIT: Tracking in #141262

johnslavik · 2025-12-05T12:31:19Z

This is ready, but Windows doesn't pass because of GH-141262.

johnslavik · 2025-12-16T03:00:11Z

It seems that these unclosed loop warnings regressed (stopped appearing) in the recent releases -- this is bad, but we can fix them separately and we can also fix the asyncio REPL in this regard by actually closing the loop (in a separate PR).

In the meantime, updating this branch should make the CI green.

johnslavik · 2025-12-16T03:21:55Z

Looks like I was confused about the regression -- that's good news!

This will have to wait until the loop is properly closed in the asyncio REPL.

johnslavik · 2025-12-16T03:54:51Z

Cherry-picked 92f629b (875fd2a) from GH-142785 to see if it fixes the problem.

johnslavik · 2025-12-16T04:35:36Z

to see if it fixes the problem.

It does! Cool!

This reverts commit 875fd2a.

johnslavik · 2025-12-20T17:35:57Z

Lib/asyncio/__main__.py

+                    except SystemExit:
+                        raise


This resembles the original behavior of the REPLs -- see GH-143023.
I don't think this is correct though. We can remove this as part of GH-143023.

Suggested change

except SystemExit:

raise

# TODO: Revisit in GH-143023

except SystemExit:

raise

This is also why I didn't add a test for this.

Handle PYTHONSTARTUP script exceptions

faa22f4

bedevere-app bot mentioned this pull request Oct 18, 2025

The asyncio REPL interactive daemon thread doesn't handle PYTHONSTARTUP exceptions #140287

Open

johnslavik added 6 commits October 18, 2025 12:13

Add blurb

5b3ad2c

Use console.showtraceback() instead of sys.excepthook()

00edac4

Properly run asyncio REPL in REPL tests

e396622

Move comment to a better place

4079074

Add tests

0440d0e

Merge branch 'properly-run-asyncio-repl-in-repl-tests' into asyncio-r…

af6f657

…epl-handle-python-startup

johnslavik marked this pull request as ready for review October 23, 2025 14:57

johnslavik requested review from 1st1, asvetlov, kumaraditya303 and willingc as code owners October 23, 2025 14:57

bedevere-app bot added the awaiting review label Oct 23, 2025

johnslavik marked this pull request as draft October 23, 2025 15:00

bedevere-app bot removed the awaiting review label Oct 23, 2025

johnslavik added 4 commits October 24, 2025 23:31

Merge branch 'main' into asyncio-repl-handle-python-startup

848638d

Improve test structure

d158dbf

Use SHORT_TIMEOUT

9355da7

Revert "Use SHORT_TIMEOUT"

3dc4cac

This reverts commit 9355da7.

johnslavik commented Oct 27, 2025

View reviewed changes

johnslavik marked this pull request as ready for review October 27, 2025 01:15

bedevere-app bot added the awaiting review label Oct 27, 2025

johnslavik mentioned this pull request Oct 27, 2025

The asyncio REPL reaches for PYTHONSTARTUP in isolated mode #140648

Open

johnslavik added 5 commits October 27, 2025 02:26

Force no colorization

c786584

Linecache doesn't matter and shouldn't break tests

b76db67

Don't rely on line numbering on Windows...

cad1748

Different names

d114ed5

Idiomatize and simplify

e6e10ad

johnslavik added 2 commits November 8, 2025 13:35

Use default histfile

9e92510

Fix newline

0a50a50

johnslavik force-pushed the asyncio-repl-handle-python-startup branch from b85a31b to 0a50a50 Compare November 8, 2025 12:35

johnslavik added 2 commits November 8, 2025 13:41

Use TestCase.enterContext

f8b8d53

Remove lines with ps1

5701fef

johnslavik closed this Dec 2, 2025

johnslavik deleted the asyncio-repl-handle-python-startup branch December 2, 2025 00:44

johnslavik restored the asyncio-repl-handle-python-startup branch December 5, 2025 12:28

johnslavik reopened this Dec 5, 2025

johnslavik marked this pull request as ready for review December 5, 2025 12:31

bedevere-app bot added the awaiting review label Dec 5, 2025

Merge branch 'main' into asyncio-repl-handle-python-startup

393aaad

johnslavik mentioned this pull request Dec 16, 2025

The asyncio REPL does not manage the event loop properly #142784

Closed

johnslavik marked this pull request as draft December 16, 2025 03:51

bedevere-app bot removed the awaiting review label Dec 16, 2025

Employ asyncio.Runner in the asyncio REPL

875fd2a

Revert "Employ asyncio.Runner in the asyncio REPL"

4377d82

This reverts commit 875fd2a.

johnslavik mentioned this pull request Dec 16, 2025

gh-142784: Make the asyncio REPL call .close() on the loop #142785

Merged

Merge branch 'main' into asyncio-repl-handle-python-startup

c4e488e

johnslavik mentioned this pull request Dec 20, 2025

SystemExit raised by PYTHONSTARTUP can prevent the REPL from starting #143023

Open

johnslavik commented Dec 20, 2025

View reviewed changes

Add a todo for future

b9ffea7

johnslavik marked this pull request as ready for review December 20, 2025 17:36

bedevere-app bot added the awaiting review label Dec 20, 2025

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gh-140287: Handle `PYTHONSTARTUP` script exceptions in the asyncio REPL #140288

gh-140287: Handle `PYTHONSTARTUP` script exceptions in the asyncio REPL #140288

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