[codeofwxz]

Related #250.

With the default ENV lookup strategy, a field named CC_2TEST only checks CC_2_TEST and cc_2_test. A same-named environment variable or dotenv entry is therefore ignored, and the field keeps its default or raises MissingVars.

This change adds the original spelling as a final fallback only for ASCII uppercase environment identifiers whose normalization consists exclusively of inserting underscores between digits and uppercase letters. For example, the lookup order becomes CC_2_TEST, cc_2_test, then CC_2TEST. Existing normalized keys still win when multiple spellings are present, including when their value is an empty string.

The shared snake-case conversion is unchanged. FIELD_FIRST, STRICT, explicit alias precedence, and prefix handling retain their existing behavior. Mixed-case names, punctuation, and names whose normalization also collapses repeated underscores do not gain this fallback. The ENV strategy docstring describes the new lookup behavior. This is a proposed limited compatibility fix, not a previously confirmed maintainer policy.

Validation:

• The 20 new regression cases go from 9 failures / 11 passes on the original implementation to all passing. They cover environment and explicit synthetic dotenv input, inheritance, digit positions, candidate order, prefixes, aliases, missing fields/defaults, and other strategies.
• The environment suite passes all 77 tests on Python 3.12.14 and 3.14.4.
• Full unit tests on both versions: 903 passed, 1 failed, 2 skipped, 6 xfailed, 4 xpassed. The unchanged baseline has 883 passed and the same remaining statuses. The one failure is the existing v0 dotenv date assertion (2021-12-18 versus 2021-12-17). These are not full-suite passes; Python 3.14 coverage is 89% under the existing coverage configuration.
• The configured pre-commit hooks pass, as do sdist/wheel builds and twine check.
• The documented Flake8/Pylint commands were attempted. Flake8 has the same 1,782 diagnostics as the baseline after accounting for shifted line numbers. Pylint diagnostics on the two changed production files are unchanged; the new test file passes Pylint independently. Repository-wide lint is not clean on the baseline.

Tests ran on Windows using a task-local synthetic process environment. The full supported Python/PyPy and Linux CI matrix has not been run locally.

The README's EnvWizard feature list now documents the numeric-name fallback and the priority of existing normalized keys, including empty values.

[Copilot]

🔵 Needs a closer look

Add coverage confirming normalized keys with empty-string values retain precedence.

Pull request overview

Adds a narrowly scoped fallback for uppercase environment names containing digit-to-letter boundaries while preserving existing lookup precedence.

Changes:

• Implements the fallback candidate logic.
• Documents updated ENV lookup behavior.
• Adds regression coverage for numeric names, precedence, aliases, prefixes, and strategies.

File summaries

File	Description
tests/unit/environ/test_numeric_names.py	Regression tests for numeric environment names
dataclass_wizard/utils/_string_conv.py	Implements the fallback candidate logic
dataclass_wizard/enums.py	Documents the new lookup behavior

Review details

Suppressed comments (1)

tests/unit/environ/test_numeric_names.py:26

• The PR description explicitly guarantees that a normalized key still wins when its value is an empty string, but this precedence parameterization only exercises non-empty values. Add an empty-string case so a future truthiness check cannot regress this behavior without being caught.

@pytest.mark.parametrize('values, expected', [
    ({'CC_2TEST': 'original'}, 'original'),
    ({'CC_2TEST': 'original', 'cc_2_test': 'snake'}, 'snake'),
    ({'CC_2TEST': 'original', 'cc_2_test': 'snake', 'CC_2_TEST': 'upper'},
     'upper'),
])

• Files reviewed: 3/3 changed files
• Comments generated: 0
• Review effort level: Lite

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[codeofwxz]

Added three precedence cases covering empty normalized values while the original spelling remains non-empty. Both normalized candidates retain priority, including when both are empty. All 80 environment tests pass on Python 3.12 and 3.14; this update changes tests only.

The full-suite and platform-validation limitations recorded in the PR description remain unchanged; this update does not claim a full-suite or CI pass.