feat: replace python-dateutil with stdlib datetime.fromisoformat#1429
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splch wants to merge 4 commits into
Open
feat: replace python-dateutil with stdlib datetime.fromisoformat#1429splch wants to merge 4 commits into
splch wants to merge 4 commits into
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Drop the python-dateutil dependency from both the generator and all
generated client code. Date/datetime parsing now uses the stdlib:
- datetime fields: datetime.datetime.fromisoformat(v.replace("Z", "+00:00"))
- date fields: datetime.date.fromisoformat(v)
The .replace("Z", "+00:00") call is needed because Python 3.10's
fromisoformat() does not accept the Z timezone suffix (added in 3.11).
It is a no-op on strings that do not contain Z.
Default values in OpenAPI specs are normalized at generation time
(Z replaced with +00:00), so the generated default expressions are
clean datetime.datetime.fromisoformat("...") calls without the
replace.
This removes one runtime dependency from every generated client
package, reducing install size and eliminating a dependency that is
in maintenance-only mode upstream.
dbanty
reviewed
May 25, 2026
| if value is None or isinstance(value, Value): | ||
| return value | ||
| if isinstance(value, str): | ||
| normalized = value.replace("Z", "+00:00") |
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We should either put this behind a version check or leave a comment to remove it when we drop 3.10 support (so when I search for 3.10-specific things in a few months I'll find it)
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sounds good :) i added a comment with a TODO to make it easy to find
| @@ -1,5 +1,5 @@ | |||
| {% macro construct_function(property, source) %} | |||
| isoparse({{ source }}) | |||
| datetime.datetime.fromisoformat({{ source }}.replace("Z", "+00:00")) | |||
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Leave a comment on this one too.
| [[package]] | ||
| name = "coverage" | ||
| version = "7.11.0" | ||
| version = "7.13.5" |
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Looks like this file was not updated with -S direct_minimal_versions. The goal of it is to make sure everything works with lower bounds.
Same with other minimal lock file
Make the .replace("Z", "+00:00") workaround discoverable by both
`rg TODO` and `rg "3.10|py3.10"` so it can be cleanly removed
when the project drops Python 3.10 support.
Brings in 8 commits since the PR opened, notably:
- typer constraint bump to <0.27
- uv_build 0.11 template update
- mypy v2 cast cleanup in generated output
Conflict resolution:
- pdm.lock, integration-tests/pdm.lock: regenerated via 'pdm lock'
against the merged pyproject.toml.
- Golden records: regenerated via 'pdm run regen' to absorb the
mypy-cast cleanup; the dateutil -> fromisoformat change from this
branch is preserved.
Verified locally with ruff check, ruff format --check, mypy, and the
unit-test suite (283 passed, 4 skipped).
The minimal lockfiles were previously regenerated without
'-S direct_minimal_versions', so direct dependencies were locked
to highest-compatible versions instead of lowest. That defeats the
point of the test_min_deps CI job, which exists to verify the
declared lower bounds in pyproject.toml still work.
Re-locked both pdm.minimal.lock files using:
pdm lock -S direct_minimal_versions -L pdm.minimal.lock
Strategy marker confirmed as
["direct_minimal_versions", "inherit_metadata"] in the metadata
of both files. python-dateutil is absent (this branch's main change).
This was referenced May 27, 2026
Closed
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Summary
Drop the
python-dateutildependency from both the generator and all generated client packages. Date/datetime parsing now uses Python's built-indatetime.fromisoformat()instead ofdateutil.parser.isoparse().This removes one runtime dependency from every generated client, reducing install size and eliminating a dependency that is unmaintained upstream and being deprecated by Fedora 45 (no releases since March 2024).
Changes
Generator source (
openapi_python_client/parser/properties/):datetime.py: Validate defaults withdatetime.datetime.fromisoformat()instead ofisoparse(). NormalizeZto+00:00at generation time so the emitted Python code is clean.date.py: Validate defaults withdatetime.date.fromisoformat()instead ofisoparse().date()."from dateutil.parser import isoparse"from the import set returned byget_imports().Jinja templates (
openapi_python_client/templates/property_templates/):datetime_property.py.jinja:isoparse(x)->datetime.datetime.fromisoformat(x.replace("Z", "+00:00"))date_property.py.jinja:isoparse(x).date()->datetime.date.fromisoformat(x)Dependency removal (all 4 metadata formats):
pyproject_uv.toml.jinja,pyproject_poetry.toml.jinja,pyproject_pdm.toml.jinja,setup.py.jinja: Removepython-dateutilfrom generated dependencies.pyproject.toml(generator): Removepython-dateutilfrom runtime deps andtypes-python-dateutilfrom dev deps.integration-tests/pyproject.toml: Remove both as well.Tests & golden records: All regenerated. Unit tests pass (283 passed, 4 skipped).
Python 3.10 compatibility
datetime.fromisoformat()gained full ISO 8601 support (including theZsuffix) in Python 3.11. On Python 3.10, theZsuffix raises aValueError:The generated datetime parsing code uses
.replace("Z", "+00:00")to normalizeZto an explicit UTC offset before callingfromisoformat(), which works on both 3.10 and 3.11+. This is a no-op on strings withoutZ. Date parsing does not need this since date strings have no timezone component.Default values in OpenAPI specs are normalized at generation time (Z -> +00:00), so the emitted default expressions are clean
datetime.datetime.fromisoformat("...")calls.