fix(i18n): resolve language codes case-insensitively (#927)

BCP 47 language tags are case-insensitive (RFC 5646 §2.1.1) but the locale files mix conventions (pt-br.json vs zh-CN.json). On case-sensitive filesystems, '--lang PT-BR' or '--lang zh-cn' silently missed the file, _load_entity_section returned {}, and entity detection ran in English with no warning. The cache key in get_entity_patterns was built from raw input, so ('PT-BR',) and ('pt-br',) produced two distinct entries, both wrong. Add _canonical_lang(lang) that resolves any casing to the on-disk filename stem via lowercase comparison, and route load_lang, _load_entity_section, and the cache key through it. Closes #927
2026-04-15 23:33:42 +02:00
parent 122ce38811
commit 0174b93d0f
2 changed files with 117 additions and 8 deletions
@@ -0,0 +1,86 @@
+"""Regression tests for issue #927 — language code lookup must be case-insensitive.
+
+The locale files use mixed case for the region subtag (``pt-br.json`` vs
+``zh-CN.json``). BCP 47 tags are case-insensitive (RFC 5646 §2.1.1), so
+``--lang PT-BR``, ``--lang zh-cn``, and ``--lang ZH-TW`` must all resolve
+to the canonical file rather than silently falling back to English.
+"""
+
+import pytest
+
+from mempalace import i18n
+from mempalace.i18n import (
+    _canonical_lang,
+    _load_entity_section,
+    available_languages,
+    get_entity_patterns,
+    load_lang,
+)
+
+
+@pytest.fixture(autouse=True)
+def _reset_state():
+    """Reset the module-level entity cache between tests."""
+    i18n._entity_cache.clear()
+    yield
+    i18n._entity_cache.clear()
+
+
+def test_canonical_lang_lowercase_passthrough():
+    assert _canonical_lang("en") == "en"
+    assert _canonical_lang("pt-br") == "pt-br"
+
+
+def test_canonical_lang_uppercase_resolves():
+    assert _canonical_lang("PT-BR") == "pt-br"
+    assert _canonical_lang("ZH-CN") == "zh-CN"
+    assert _canonical_lang("zh-cn") == "zh-CN"
+    assert _canonical_lang("Pt-Br") == "pt-br"
+
+
+def test_canonical_lang_unknown_returns_none():
+    assert _canonical_lang("xx") is None
+    assert _canonical_lang("") is None
+
+
+def test_load_lang_case_insensitive():
+    """`load_lang('PT-BR')` must load the pt-br dictionary, not English."""
+    en = load_lang("en")
+    pt_lower = load_lang("pt-br")
+    pt_upper = load_lang("PT-BR")
+    assert pt_lower == pt_upper, "case should not change the loaded dict"
+    # If load_lang silently fell back to English, both would equal `en`.
+    if "pt-br" in available_languages() and pt_lower != en:
+        assert i18n.current_lang() == "pt-br"
+
+
+def test_entity_section_loads_for_uppercase_input():
+    """`_load_entity_section('PT-BR')` must read pt-br.json, not return {}."""
+    pt_lower = _load_entity_section("pt-br")
+    pt_upper = _load_entity_section("PT-BR")
+    assert pt_lower == pt_upper
+
+
+def test_get_entity_patterns_case_insensitive():
+    """Entity patterns must be identical regardless of input case."""
+    lower = get_entity_patterns(("pt-br",))
+    upper = get_entity_patterns(("PT-BR",))
+    assert lower == upper
+
+
+def test_get_entity_patterns_shares_cache_across_cases():
+    """Different casing must hit the same cache entry — not duplicate work."""
+    get_entity_patterns(("zh-CN",))
+    cache_keys = list(i18n._entity_cache.keys())
+    get_entity_patterns(("ZH-CN",))
+    get_entity_patterns(("zh-cn",))
+    assert len(i18n._entity_cache) == len(
+        cache_keys
+    ), "different casings of the same language must not create new cache entries"
+
+
+def test_unknown_language_still_falls_back_to_english():
+    """A code with no matching file must fall through to English (existing contract)."""
+    patterns = get_entity_patterns(("xx-yy",))
+    en = get_entity_patterns(("en",))
+    assert patterns["candidate_patterns"] == en["candidate_patterns"]