Fix broken data for time-zones with no transitions

While an invalid time-zone shall have no transitions, so may various
constant zones, like UTC.  The TZ data may include only the POSIX rule
for such a zone, in which case we should use it, even if there are no
transitions.

Broke out a piece of repeated code as a common method, in the process,
since I was complicating it further.

Added test for the case that revealed this; and made sure we see a
warning if any of the checkOffset() tests gets skipped because its
zone is unsupported.

Fixes: QTBUG-74614
Change-Id: Ic8e039a2a9b3f4e0f567585682a94f4b494b558d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp b/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp
index a25fd39693..eff9835776 100644
--- a/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp
+++ b/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp
@@ -539,6 +539,8 @@ void tst_QTimeZone::checkOffset_data()
         int year, month, day, hour, min, sec;
         int std, dst;
     } table[] = {
+        // Zone with no transitions (QTBUG-74614, when TZ backend uses minimalist data)
+        { "Etc/UTC", "epoch", 1970, 1, 1, 0, 0, 0, 0, 0 },
         // Kiev: regression test for QTBUG-64122 (on MS):
         { "Europe/Kiev", "summer", 2017, 10, 27, 12, 0, 0, 2 * 3600, 3600 },
         { "Europe/Kiev", "winter", 2017, 10, 29, 12, 0, 0, 2 * 3600, 0 }
@@ -551,6 +553,8 @@ void tst_QTimeZone::checkOffset_data()
                 << QDateTime(QDate(entry.year, entry.month, entry.day),
                              QTime(entry.hour, entry.min, entry.sec), zone)
                 << entry.dst + entry.std << entry.std << entry.dst;
+        } else {
+            qWarning("Skipping %s@%s test as zone is invalid", entry.zone, entry.nick);
         }
     }
 }