Add "GMT+?" field to data struct, fall back to it (#5694)

This will be added to CLDR in the future.

components/datetime/src/provider/time_zones.rs

@@ -62,6 +62,9 @@ pub struct TimeZoneEssentialsV1<'data> {
     /// The localized zero-offset format.
     #[cfg_attr(feature = "serde", serde(borrow))]
     pub offset_zero: Cow<'data, str>,
+    /// The localized unknown-offset format.
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    pub offset_unknown: Cow<'data, str>,
 }
 
 /// An ICU4X mapping to the CLDR timeZoneNames exemplar cities.
@@ -82,9 +85,6 @@ pub struct LocationsV1<'data> {
     /// Per-zone location display name
     #[cfg_attr(feature = "serde", serde(borrow))]
     pub locations: ZeroMap<'data, TimeZoneBcp47Id, str>,
-    /// The display name for an unknown time zone. This is not combined with a pattern.
-    #[cfg_attr(feature = "serde", serde(borrow))]
-    pub unknown: Cow<'data, str>,
     /// The format string for a region's generic time.
     #[cfg_attr(
         feature = "serde",

components/datetime/src/time_zone.rs

@@ -74,12 +74,18 @@ impl ResolvedNeoTimeZoneSkeleton {
                     self.to_field().length,
                 )),
                 Some(TimeZoneFormatterUnit::GenericLocation),
-                None,
+                Some(TimeZoneFormatterUnit::LocalizedOffset(
+                    self.to_field().length,
+                )),
             ],
             // 'VVVV'
-            ResolvedNeoTimeZoneSkeleton::Location => {
-                [Some(TimeZoneFormatterUnit::GenericLocation), None, None]
-            }
+            ResolvedNeoTimeZoneSkeleton::Location => [
+                Some(TimeZoneFormatterUnit::GenericLocation),
+                Some(TimeZoneFormatterUnit::LocalizedOffset(
+                    self.to_field().length,
+                )),
+                None,
+            ],
             // `O`, `OOOO`, `ZZZZ`
             ResolvedNeoTimeZoneSkeleton::OffsetShort | ResolvedNeoTimeZoneSkeleton::OffsetLong => [
                 Some(TimeZoneFormatterUnit::LocalizedOffset(
@@ -459,15 +465,16 @@ impl FormatTimeZone for LocalizedOffsetFormat {
         data_payloads: TimeZoneDataPayloadsBorrowed,
         fdf: Option<&FixedDecimalFormatter>,
     ) -> Result<Result<(), FormatTimeZoneError>, fmt::Error> {
-        let Some(offset) = input.offset else {
-            return Ok(Err(FormatTimeZoneError::MissingInputField("zone_offset")));
-        };
         let Some(essentials) = data_payloads.essentials else {
             return Ok(Err(FormatTimeZoneError::MissingZoneSymbols));
         };
         let Some(fdf) = fdf else {
             return Ok(Err(FormatTimeZoneError::MissingFixedDecimalFormatter));
         };
+        let Some(offset) = input.offset else {
+            sink.write_str(&essentials.offset_unknown)?;
+            return Ok(Ok(()));
+        };
         Ok(if offset.is_zero() {
             sink.write_str(&essentials.offset_zero)?;
             Ok(())
@@ -554,14 +561,14 @@ impl FormatTimeZone for GenericLocationFormat {
             return Ok(Err(FormatTimeZoneError::MissingZoneSymbols));
         };
 
-        if let Some(location) = locations.locations.get(&time_zone_id) {
-            locations
-                .pattern_generic
-                .interpolate([location])
-                .write_to(sink)?;
-        } else {
-            sink.write_str(&locations.unknown)?;
-        }
+        let Some(location) = locations.locations.get(&time_zone_id) else {
+            return Ok(Err(FormatTimeZoneError::Fallback));
+        };
+
+        locations
+            .pattern_generic
+            .interpolate([location])
+            .write_to(sink)?;
 
         Ok(Ok(()))
     }
@@ -591,19 +598,19 @@ impl FormatTimeZone for SpecificLocationFormat {
             return Ok(Err(FormatTimeZoneError::MissingZoneSymbols));
         };
 
-        if let Some(location) = locations.locations.get(&time_zone_id) {
-            if zone_variant == ZoneVariant::daylight() {
-                &locations.pattern_daylight
-            } else if zone_variant == ZoneVariant::standard() {
-                &locations.pattern_standard
-            } else {
-                &locations.pattern_generic
-            }
-            .interpolate([location])
-            .write_to(sink)?;
+        let Some(location) = locations.locations.get(&time_zone_id) else {
+            return Ok(Err(FormatTimeZoneError::Fallback));
+        };
+
+        if zone_variant == ZoneVariant::daylight() {
+            &locations.pattern_daylight
+        } else if zone_variant == ZoneVariant::standard() {
+            &locations.pattern_standard
         } else {
-            sink.write_str(&locations.unknown)?;
+            &locations.pattern_generic
         }
+        .interpolate([location])
+        .write_to(sink)?;
 
         Ok(Ok(()))
     }
@@ -691,7 +698,8 @@ impl FormatTimeZone for Iso8601Format {
         _fdf: Option<&FixedDecimalFormatter>,
     ) -> Result<Result<(), FormatTimeZoneError>, fmt::Error> {
         let Some(offset) = input.offset else {
-            return Ok(Err(FormatTimeZoneError::MissingInputField("zone_offset")));
+            sink.write_str("+?")?;
+            return Ok(Ok(()));
         };
         self.format_infallible(sink, offset).map(|()| Ok(()))
     }

components/datetime/tests/datetime.rs

@@ -487,9 +487,7 @@ fn test_time_zone_format_offset_seconds() {
 
 #[test]
 fn test_time_zone_format_offset_not_set_debug_assert_panic() {
-    use icu_datetime::{
-        neo_marker::NeoTimeZoneOffsetMarker, neo_skeleton::NeoSkeletonLength, DateTimeWriteError,
-    };
+    use icu_datetime::{neo_marker::NeoTimeZoneOffsetMarker, neo_skeleton::NeoSkeletonLength};
 
     let time_zone = TimeZoneInfo {
         time_zone_id: TimeZoneIdMapper::new()
@@ -502,11 +500,7 @@ fn test_time_zone_format_offset_not_set_debug_assert_panic() {
         NeoTimeZoneOffsetMarker::with_length(NeoSkeletonLength::Medium),
     )
     .unwrap();
-    assert_try_writeable_eq!(
-        tzf.format(&time_zone),
-        "{O}",
-        Err(DateTimeWriteError::MissingInputField("zone_offset"))
-    );
+    assert_try_writeable_eq!(tzf.format(&time_zone), "GMT+?",);
 }
 
 #[test]

components/datetime/tests/fixtures/tests/components_with_zones.json

@@ -23,7 +23,7 @@
         },
         "output": {
             "values": {
-                "en": "Tuesday, January 21, 2020, 08:25:07 Unknown City Time"
+                "en": "Tuesday, January 21, 2020, 08:25:07 GMT+5"
             }
         }
     },
@@ -51,7 +51,7 @@
         },
         "output": {
             "values": {
-                "en": "Tuesday, January 21, 2020, 08:25:07 Unknown City Time"
+                "en": "Tuesday, January 21, 2020, 08:25:07 GMT+5"
             }
         }
     },

components/datetime/tests/patterns/tests/time_zones.json

@@ -987,13 +987,16 @@
           "z",
           "zz",
           "zzz",
+          "v",
           "O"
         ],
         "configs": [],
         "expected": ["GMT-7"]
       },
       {
         "patterns": [
+          "vvvv",
+          "VVVV",
           "OOOO",
           "zzzz",
           "ZZZZ"
@@ -1016,15 +1019,6 @@
         ],
         "configs": [],
         "expected": ["-07:00"]
-      },
-      {
-        "patterns": [
-          "v",
-          "vvvv",
-          "VVVV"
-        ],
-        "configs": [],
-        "expected": ["Unknown City Time"]
       }
     ]
   },
@@ -1037,6 +1031,7 @@
           "z",
           "zz",
           "zzz",
+          "v",
           "O"
         ],
         "configs": [],
@@ -1045,6 +1040,8 @@
       {
         "patterns": [
           "ZZZZ",
+          "vvvv",
+          "VVVV",
           "zzzz",
           "OOOO"
         ],
@@ -1066,15 +1063,6 @@
         ],
         "configs": [],
         "expected": ["-07:00"]
-      },
-      {
-        "patterns": [
-          "v",
-          "vvvv",
-          "VVVV"
-        ],
-        "configs": [],
-        "expected": ["Unknown City Time"]
       }
     ]
   },
@@ -1097,28 +1085,22 @@
           "Z",
           "ZZ",
           "ZZZ",
-          "ZZZZ",
           "ZZZZZ"
         ],
         "configs": [],
-        "expected": ["{Z}"]
+        "expected": ["+?"]
       },
       {
         "patterns": [
           "O",
-          "OOOO"
-        ],
-        "configs": [],
-        "expected": ["{O}"]
-      },
-      {
-        "patterns": [
+          "ZZZZ",
+          "OOOO",
           "v",
           "vvvv",
           "VVVV"
         ],
         "configs": [],
-        "expected": ["Unknown City Time"]
+        "expected": ["GMT+?"]
       }
     ]
   }