gh-135645: Added supports_isolated_interpreters to sys.implementation

[sobolevn]

• Issue: 3.14: missing sys.implementation.supports_isolated_interpreters? #135645

---

📚 Documentation preview 📚: https://cpython-previews--135667.org.readthedocs.build/

[vstinner]

LGTM

[sobolevn]

Thank you, @vstinner! I would like to get a review from:

• @ericsnowcurrently as a code-owner
• and from @hugovk as the RM, because this is techincally a feature, and now it is a feature freeze

[vstinner]

and from @hugovk as the RM, because this is techincally a feature, and now it is a feature freeze

PEP 734 got an exception to be added to Python 3.14 after the feature freeze, no?

[bedevere-app]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @sobolevn for commit 028b498 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F135667%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[ericsnowcurrently]

LGTM

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @sobolevn for commit 5fe139c 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F135667%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[sobolevn]

This test fails on iOS: https://buildbot.python.org/#/builders/1382/builds/539

cpython/Lib/test/test_build_details.py

Lines 76 to 84 in 9731dd2

	def test_implementation(self):
	for key, value in self.key('implementation').items():
	with self.subTest(part=key):
	if key == 'version':
	self.assertEqual(len(value), len(sys.implementation.version))
	for part_name, part_value in value.items():
	self.assertEqual(getattr(sys.implementation.version, part_name), part_value)
	else:
	self.assertEqual(getattr(sys.implementation, key), value)

======================================================================
FAIL: test_implementation (test.test_build_details.CPythonBuildDetailsTests.test_implementation) (part='supports_isolated_interpreters')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/buildbot/Library/Developer/XCTestDevices/19518409-EE82-48CA-B217-EBE32ABD5E73/data/Containers/Bundle/Application/DBA97A4E-0ECF-4103-AA68-4BEF211EB6BE/iOSTestbed.app/python/lib/python3.15/test/test_build_details.py", line 84, in test_implementation
    self.assertEqual(getattr(sys.implementation, key), value)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: False != True

@freakboy3742 can you please help me with understanding why? I don't know enough details about our iOS build process :(

[sobolevn]

Looks like that we generate build-details.json via generate-build-details.py on the emulator first (regular linux), then use this file on ios 🤔

[freakboy3742]

@sobolevn It looks like this is a cross-compile issue. The build-details.json file is being seeded with the build python (macOS), but with _PYTHON_SYSCONFIGDATA_PATH defined to point at the host Python configuration (iOS) so that iOS-specific details are surfaced. That won't help with the contents of sys.implementation though, as none of those values are modified.

So - the fix will be some sort of override to pass cross-platform details for sys can be passed into the build. I'm not sure what @FFY00 had in mind for this - it's not obvious (to me, anyway) what the intended use of generate-build-details.py would be for setting properties that aren't overwritten by sysconfigdata - and in particular, the contents of sys.implementation. The handling of MULTIARCH is the only comparable value I can see - maybe analogous handling is needed for supports_isolated_interpreters?

That said - in this specific instance, I'm not clear why supports_isolated_interpreters is being set to False for iOS. iOS provides the _interpreters module, and runs (and passes) the test_interpreters and test_concurrent_futures.test_interpreter_pool tests... is there some other limitation I'm missing?

[freakboy3742]

So - the fix will be some sort of override to pass cross-platform details for sys can be passed into the build. I'm not sure what @FFY00 had in mind for this - it's not obvious (to me, anyway) what the intended use of generate-build-details.py would be for setting properties that aren't overwritten by sysconfigdata - and in particular, the contents of sys.implementation. The handling of MULTIARCH is the only comparable value I can see - maybe analogous handling is needed for supports_isolated_interpreters?

@sobolevn Also - flagging that although this isn't an issue for iOS, it will be an issue for Emscripten and WASI. There's no buildbot for Emscripten yet (hopefully that will land early next week), but the WASI buildbot appears to be flagging the same problem, for exactly the same reason.

[sobolevn]

!buildbot wasi

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @sobolevn for commit 9e3fa38 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F135667%2Fmerge

The command will test the builders whose names match following regular expression: wasi

The builders matched are:

• wasm32-wasi Non-Debug PR
• wasm32-wasi PR
• wasm32 WASI 8Core PR

[sobolevn]

but the WASI buildbot appears to be flagging the same problem, for exactly the same reason.

🤔
@freakboy3742 looks like test_sys passes on all WASI buildbots.
test_capi failures are unrelated: #135721

[freakboy3742]

but the WASI buildbot appears to be flagging the same problem, for exactly the same reason.

🤔 @freakboy3742 looks like test_sys passes on all WASI buildbots. test_capi failures are unrelated: #135721

Ah - the entire build-details.json test suite is excluded (and it looks like build-details.json isn't generate for Emscripten at least.) I guess that's more of an indication that those builds haven't got PEP 739 support yet.