Improve handling of no-inheritance-marker in timezone data

Fixes #1192 (but uncovers another bug)

Author: akx

babel/dates.py

@@ -649,7 +649,9 @@ def get_timezone_name(
     info = locale.time_zones.get(zone, {})
     # Try explicitly translated zone names first
     if width in info and zone_variant in info[width]:
-        return info[width][zone_variant]
+        value = info[width][zone_variant]
+        if value != NO_INHERITANCE_MARKER:
+            return value
 
     metazone = get_global('meta_zones').get(zone)
     if metazone:
@@ -660,7 +662,7 @@ def get_timezone_name(
                 # If the short form is marked no-inheritance,
                 # try to fall back to the long name instead.
                 name = metazone_info.get('long', {}).get(zone_variant)
-            if name:
+            if name and name != NO_INHERITANCE_MARKER:
                 return name
 
     # If we have a concrete datetime, we assume that the result can't be

tests/test_dates.py

@@ -1187,3 +1187,33 @@ def test_issue_1089():
 def test_issue_1162(locale, format, negative, expected):
     delta = timedelta(seconds=10800) * (-1 if negative else +1)
     assert dates.format_timedelta(delta, add_direction=True, format=format, locale=locale) == expected
+
+
+def test_issue_1192():
+    # The actual returned value here is not actually strictly specified ("get_timezone_name"
+    # is not an operation specified as such). Issue #1192 concerned this invocation returning
+    # the invalid "no inheritance marker" value; _that_ should never be returned here.
+    # IOW, if the below "Hawaii-Aleutian Time" changes with e.g. CLDR updates, that's fine.
+    assert dates.get_timezone_name('Pacific/Honolulu', 'short', locale='en_GB') == "Hawaii-Aleutian Time"
+
+
+@pytest.mark.xfail
+def test_issue_1192_fmt(timezone_getter):
+    """
+    There is an issue in how we format the fallback for z/zz in the absence of data
+    (esp. with the no inheritance marker present).
+    This test is marked xfail until that's fixed.
+    """
+    # env TEST_TIMEZONES=Pacific/Honolulu TEST_LOCALES=en_US,en_GB TEST_TIME_FORMAT="YYYY-MM-dd H:mm z" bin/icu4c_date_format
+    # Defaulting TEST_TIME to 2025-03-04T13:53:00Z
+    # Pacific/Honolulu        en_US   2025-03-04 3:53 HST
+    # Pacific/Honolulu        en_GB   2025-03-04 3:53 GMT-10
+    # env TEST_TIMEZONES=Pacific/Honolulu TEST_LOCALES=en_US,en_GB TEST_TIME_FORMAT="YYYY-MM-dd H:mm zz" bin/icu4c_date_format
+    # Pacific/Honolulu        en_US   2025-03-04 3:53 HST
+    # Pacific/Honolulu        en_GB   2025-03-04 3:53 GMT-10
+    tz = timezone_getter("Pacific/Honolulu")
+    dt = _localize(tz, datetime(2025, 3, 4, 13, 53, tzinfo=UTC))
+    assert dates.format_datetime(dt, "YYYY-MM-dd H:mm z", locale="en_US") == "2025-03-04 3:53 HST"
+    assert dates.format_datetime(dt, "YYYY-MM-dd H:mm z", locale="en_GB") == "2025-03-04 3:53 GMT-10"
+    assert dates.format_datetime(dt, "YYYY-MM-dd H:mm zz", locale="en_US") == "2025-03-04 3:53 HST"
+    assert dates.format_datetime(dt, "YYYY-MM-dd H:mm zz", locale="en_GB") == "2025-03-04 3:53 GMT-10"