Fix FutureWarning: split() requires a non-empty pattern match #485

jessp01 · 2025-09-02T20:59:43Z

These warnings are emitted with Python 3.6.8 (and probably other versions as well).

Fixes FutureWarning: split() requires a non-empty pattern match

This can be easily reproduced with the below:

import sys
from specfile import Specfile

specfile = Specfile(sys.argv[1])
with specfile as spec:
    print (spec.expanded_release)

Sample stacktrace:

Traceback (most recent call last):
  File "/tmp/3.py", line 11, in <module>
    print (spec.expanded_release)
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/specfile.py", line 770, in expanded_release
    return self.expand(self.release, extra_macros=[("dist", "")])
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/specfile.py", line 761, in release
    return self._split_raw_release(self.raw_release)[0]
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/specfile.py", line 667, in getter
    with self.tags() as tags:
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/context_management.py", line 134, in __call__
    self.values[key] = next(self.generators[key])
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/specfile.py", line 393, in tags
    tags = Tags.parse(section, context=self)
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/tags.py", line 514, in parse
    line, prefix, suffix = split_conditional_macro_expansion(line)
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/utils.py", line 315, in split_conditional_macro_expansion
    nodes = ValueParser.parse(value)
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/value_parser.py", line 278, in parse
    ConditionalMacroExpansion(condition, cls.parse(body))
  File "/home/jesse/.local/lib/python3.6/site-packages/specfile/value_parser.py", line 132, in __init__
    tokens = re.split(r"^([?!]*)", condition, maxsplit=1)
  File "/usr/lib64/python3.6/re.py", line 212, in split
    return _compile(pattern, flags).split(string, maxsplit)

gemini-code-assist

Summary of Changes

Hello @jessp01, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a FutureWarning that arises in Python 3.6.8 and later versions when using re.split with a pattern that can match an empty string. The changes ensure that the regular expressions used for parsing macro substitutions and conditional macro expansions always require at least one character to match, thus eliminating the warning and improving compatibility with newer Python versions.

Highlights

Resolve FutureWarning for re.split: Updated regular expression patterns in specfile/value_parser.py from ([?!]*) to ([?!]+) to prevent FutureWarning: split() requires a non-empty pattern match when using Python 3.6.8 and newer versions.

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gemini-code-assist

Code Review

This pull request addresses a FutureWarning from re.split by changing the regex pattern r"^([?!]*)" to r"^([?!]+)" in four places. This is a good fix for the warning. However, one of the changes, in ValueParser.parse, introduces a subtle bug because the logic in the following line was not updated to account for the new behavior of re.split. I've left a detailed comment on that. The other three changes are correct.

specfile/value_parser.py

softwarefactory-project-zuul · 2025-09-02T21:02:16Z

Build succeeded.
https://softwarefactory-project.io/zuul/t/packit-service/buildset/af2128dd16b44c449bc3a8d921f5504f

✔️ pre-commit SUCCESS in 1m 56s
✔️ specfile-tests-rpm-deps SUCCESS in 1m 43s
✔️ specfile-tests-pip-deps SUCCESS in 1m 43s

softwarefactory-project-zuul · 2025-09-02T21:11:57Z

Build succeeded.
https://softwarefactory-project.io/zuul/t/packit-service/buildset/ef01873e5d0b40bf9f509ee852cfa16e

✔️ pre-commit SUCCESS in 2m 01s
✔️ specfile-tests-rpm-deps SUCCESS in 1m 47s
✔️ specfile-tests-pip-deps SUCCESS in 1m 44s

nforro

These warnings are emitted with Python 3.6.8 (and probably other versions as well).

The warnings are emitted only with Python 3.6, newer versions not only don't complain, but also always split the string into 3 tokens, so there is no need for the length-checking condition. But yes, for Python 3.6 (hopefully we can drop the support soon) empty matches shouldn't be there and good catch Gemini with the bug fix (which is correct even though half of the justification is nonsense).

These warnings are emitted with Python 3.6.8.

re.split will return a list with a single element: the condition string itself. Consequently, len(tokens) will be 1, and prefix on line 275 will be assigned the entire condition string.

softwarefactory-project-zuul · 2025-09-09T06:59:17Z

Build succeeded.
https://softwarefactory-project.io/zuul/t/packit-service/buildset/addad6e32cce4614abac18f20b9969cd

✔️ pre-commit SUCCESS in 2m 02s
✔️ specfile-tests-rpm-deps SUCCESS in 1m 51s
✔️ specfile-tests-pip-deps SUCCESS in 1m 47s

nforro · 2025-09-09T07:43:44Z

/packit-stg build

softwarefactory-project-zuul · 2025-09-09T14:52:48Z

Build succeeded (gate pipeline).
https://softwarefactory-project.io/zuul/t/packit-service/buildset/6f5a72c1160140b9a6d990d5893bf792

✔️ pre-commit SUCCESS in 1m 58s

usercont-release-bot added this to Packit Kanban Board Sep 2, 2025

github-project-automation bot moved this to new in Packit Kanban Board Sep 2, 2025

gemini-code-assist bot reviewed Sep 2, 2025

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specfile/value_parser.py Show resolved Hide resolved

TomasTomecek requested a review from nforro September 4, 2025 07:48

nforro self-assigned this Sep 8, 2025

nforro approved these changes Sep 9, 2025

View reviewed changes

jessp01 added 2 commits September 9, 2025 08:56

Fix FutureWarning: split() requires a non-empty pattern match

5dbd1ca

These warnings are emitted with Python 3.6.8.

With the new regex r"^([?!]+)", if condition does not start with ? or !,

755e08f

re.split will return a list with a single element: the condition string itself. Consequently, len(tokens) will be 1, and prefix on line 275 will be assigned the entire condition string.

nforro force-pushed the fix-split-requires-a-non-empty-pattern-match branch from bf7ba1f to 755e08f Compare September 9, 2025 06:56

nforro added the mergeit Merge via Zuul label Sep 9, 2025

softwarefactory-project-zuul bot merged commit 1eb3c14 into packit:main Sep 9, 2025
45 of 49 checks passed

github-project-automation bot moved this from new to done in Packit Kanban Board Sep 9, 2025

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Fix FutureWarning: split() requires a non-empty pattern match #485

Fix FutureWarning: split() requires a non-empty pattern match #485

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jessp01 commented Sep 2, 2025 •

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Fix FutureWarning: split() requires a non-empty pattern match #485

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