fix: resolve falsy config values in string interpolation by dimbleby · Pull Request #10808 · python-poetry/poetry · GitHub

config.process() treated falsy values (0, False, empty string) as missing, returning the literal template string instead of the resolved value. Changed the check from 'if config_value:' to 'if config_value is not None:' and added str() conversion for re.sub compatibility. Fixed return type annotation on the inner callback to match its actual return type.

Pull Request Check List

Resolves: #issue-number-here

Added tests for changed code.
Updated documentation for changed code.

Summary by Sourcery

Ensure config string interpolation correctly handles falsy values and update its typing.

Bug Fixes:

Treat falsy configuration values (such as 0 and False) as valid during string interpolation instead of considering them missing.

Tests:

Add a regression test confirming that falsy configuration values are interpolated into strings as expected.

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adjusts config value interpolation to treat falsy values (like 0 and False) as valid, ensures interpolated values are always strings for re.sub, and adds a regression test for the new behavior.

Class diagram for updated config interpolation in Config.process

classDiagram
    class Config {
        +process(value Any) Any
        +get(key str) Any
    }

    class process_inner_resolve_from_config {
        +__call__(match re_Match_str) str
    }

    Config ..> process_inner_resolve_from_config : defines

    class re_Match_str {
        +group(index int) str
    }

File-Level Changes

Change	Details	Files
Update config interpolation logic to treat falsy config values as present and always return strings from the regex callback.	Change the interpolation callback return type annotation from Any to str to reflect actual usage with re.sub. Replace a truthiness check on config values with an explicit None check so falsy values (0, False, "") are not treated as missing. Wrap returned config values in str() to guarantee compatibility with re.sub string replacement semantics.	src/poetry/config/config.py
Add a regression test to verify falsy config values are interpolated instead of being treated as missing.	Introduce a new unit test that asserts a numeric falsy config value (0) is correctly interpolated into a template string. Document via the test docstring that falsy values such as False and 0 must not be treated as missing during interpolation.	tests/config/test_config.py

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Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="src/poetry/config/config.py" line_range="369-370" />
<code_context>
             config_value = self.get(key)
-            if config_value:
-                return config_value
+            if config_value is not None:
+                return str(config_value)

             # The key doesn't exist in the config but might be resolved later,
</code_context>
<issue_to_address>
**suggestion (bug_risk):** Blindly stringifying `config_value` may hide type issues and produce surprising representations for complex types.

This keeps `re.sub` happy, but it also silently coerces any type (lists, dicts, custom objects) via `str()`, which may hide misconfigurations and produce unexpected strings. Consider restricting `config_value` to specific types (e.g. `str`, numbers, bool) and raising for others, or normalizing known types to well-defined string formats.
</issue_to_address>

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Documentation Updates

1 document(s) were updated by changes in this PR:

CHANGELOG

View Changes

@@ -11,6 +11,7 @@
 - Fix an issue where HTTP Basic Authentication credentials could be corrupted during request preparation, causing authentication failures with long tokens ([#10748](https://github.com/python-poetry/poetry/pull/10748)).
 - Fix an issue where `poetry publish --no-interaction --build` requested user interaction ([#10769](https://github.com/python-poetry/poetry/pull/10769)).
 - Fix an issue where `poetry init` and `poetry new` created a deprecated `project.license` format ([#10787](https://github.com/python-poetry/poetry/pull/10787)).
+- Fix an issue where falsy config values (`0`, `False`, empty string `""`) were incorrectly treated as missing during string interpolation in `config.process()`, returning the literal template string instead of the resolved value ([#10808](https://github.com/python-poetry/poetry/pull/10808)).
 
 ### Docs

How did I do? Any feedback?

config.process() treated falsy values (0, False, empty string) as missing, returning the literal template string instead of the resolved value. Changed the check from 'if config_value:' to 'if config_value is not None:' and added str() conversion for re.sub compatibility. Fixed return type annotation on the inner callback to match its actual return type. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.

sourcery-ai Bot reviewed Mar 30, 2026

View reviewed changes

Comment thread src/poetry/config/config.py

radoering approved these changes Mar 31, 2026

View reviewed changes

radoering enabled auto-merge (squash) March 31, 2026 16:33

radoering force-pushed the fix/config-falsy-values branch from a3175c1 to 4ee275c Compare March 31, 2026 16:37

radoering merged commit e6f1ded into python-poetry:main Mar 31, 2026
54 checks passed

dimbleby deleted the fix/config-falsy-values branch March 31, 2026 16:48

github-actions Bot locked as resolved and limited conversation to collaborators May 1, 2026

fix: resolve falsy config values in string interpolation by dimbleby · Pull Request #10808 · python-poetry/poetry · GitHub

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fix: resolve falsy config values in string interpolation - #10808

fix: resolve falsy config values in string interpolation#10808
radoering merged 1 commit into
python-poetry:mainfrom
dimbleby:fix/config-falsy-values

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fix: resolve falsy config values in string interpolation by dimbleby · Pull Request #10808 · python-poetry/poetry · GitHub

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fix: resolve falsy config values in string interpolation - #10808

fix: resolve falsy config values in string interpolation#10808radoering merged 1 commit intopython-poetry:mainpython-poetry/poetry:mainfrom dimbleby:fix/config-falsy-valuesdimbleby/poetry:fix/config-falsy-valuesCopy head branch name to clipboard

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Reviewer's Guide

Class diagram for updated config interpolation in Config.process

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fix: resolve falsy config values in string interpolation#10808
radoering merged 1 commit into
python-poetry:mainfrom
dimbleby:fix/config-falsy-values

dimbleby commented Mar 30, 2026 •
edited by sourcery-ai Bot
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