Fix datetime %Z parsing

Author: fangerer

graalpython/com.oracle.graal.python.test/src/tests/test_datetime.py

@@ -38,6 +38,11 @@
 # SOFTWARE.
 
 import datetime
+import os
+import subprocess
+import sys
+import textwrap
+import time
 import unittest
 
 class DateTest(unittest.TestCase):
@@ -542,12 +547,29 @@ def test_strptime(self):
         actual = datetime.datetime.strptime("+00:00 GMT", "%z %Z")
         self.assertEqual(actual.tzinfo.tzname(None), "GMT")
 
-        import time
         timezone_name = time.localtime().tm_zone
         self.assertIsNotNone(timezone_name)
         actual = datetime.datetime.strptime(f"+00:00 {timezone_name}", "%z %Z")
         self.assertEqual(actual.tzinfo.tzname(None), timezone_name)
 
+        if hasattr(time, "tzset") and sys.executable:
+            proc = subprocess.run(
+                [sys.executable, "-c", textwrap.dedent("""\
+                    import datetime
+                    import time
+
+                    time.tzset()
+                    timezone_name = time.localtime().tm_zone
+                    actual = datetime.datetime.strptime(f"+00:00 {timezone_name}", "%z %Z")
+                    assert actual.tzinfo.tzname(None) == timezone_name
+                """)],
+                env={**os.environ, "TZ": "Etc/GMT-1"},
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                text=True,
+            )
+            self.assertEqual(proc.returncode, 0, proc.stderr)
+
         # time zone name without utc offset is ignored
         actual = datetime.datetime.strptime("UTC", "%Z")
         self.assertIsNone(actual.tzinfo)

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/datetime/DateTimeBuiltins.java

@@ -2310,22 +2310,14 @@ private static Object parse(String string, String format, PythonContext context,
                                 TimeZone timeZone = TimeModuleBuiltins.getGlobalTimeZone(context);
                                 String zoneName = timeZone.getDisplayName(false, TimeZone.SHORT);
                                 String zoneNameDaylightSaving = timeZone.getDisplayName(true, TimeZone.SHORT);
+                                String matchedZoneName = matchTimeZoneName(string, i, zoneName, zoneNameDaylightSaving, "UTC", "GMT");
 
-                                if (string.startsWith("UTC", i)) {
-                                    builder.setTimeZoneName("UTC");
-                                    i += 3;
-                                } else if (string.startsWith("GMT", i)) {
-                                    builder.setTimeZoneName("GMT");
-                                    i += 3;
-                                } else if (string.startsWith(zoneName, i)) {
-                                    builder.setTimeZoneName(zoneName);
-                                    i += zoneName.length();
-                                } else if (string.startsWith(zoneNameDaylightSaving, i)) {
-                                    builder.setTimeZoneName(zoneNameDaylightSaving);
-                                    i += zoneNameDaylightSaving.length();
-                                } else {
+                                if (matchedZoneName == null) {
                                     throw PRaiseNode.raiseStatic(inliningTarget, ValueError, ErrorMessages.TIME_DATA_S_DOES_NOT_MATCH_FORMAT_S, string, format);
                                 }
+
+                                builder.setTimeZoneName(matchedZoneName);
+                                i += matchedZoneName.length();
                             }
                             case 'j' -> {
                                 var pos = new ParsePosition(i);
@@ -2487,6 +2479,16 @@ private static Integer parseDigits(String source, int from, int digitsCount) {
             return result;
         }
 
+        private static String matchTimeZoneName(String string, int from, String... candidates) {
+            String matched = null;
+            for (String candidate : candidates) {
+                if (candidate != null && string.startsWith(candidate, from) && (matched == null || candidate.length() > matched.length())) {
+                    matched = candidate;
+                }
+            }
+            return matched;
+        }
+
         @TruffleBoundary
         private static Integer parseDigitsUpTo(String source, ParsePosition from, int maxDigitsCount) {
             int result = 0;