fix: support utc formatting for ordinal data

examples/compiled/time_parse_utc.vg.json

@@ -71,7 +71,7 @@
       "format": {
         "signal": "timeUnitSpecifier([\"hours\"], {\"year-month\":\"%b %Y \",\"year-month-date\":\"%b %d, %Y \"})"
       },
-      "formatType": "time",
+      "formatType": "utc",
       "labelOverlap": true,
       "zindex": 0
     }

site/_includes/docs_toc.md

@@ -287,7 +287,6 @@
         - [Nominal]({{site.baseurl}}/docs/type.html#nominal)
         - [GeoJSON]({{site.baseurl}}/docs/type.html#geojson)
     - [Value]({{site.baseurl}}/docs/value.html)
-        - [Examples]({{site.baseurl}}/docs/value.html#examples)
 - [Projection]({{site.baseurl}}/docs/projection.html)
     - [Documentation Overview]({{site.baseurl}}/docs/projection.html#documentation-overview)
     - [Projection Properties]({{site.baseurl}}/docs/projection.html#projection-properties)
@@ -330,7 +329,6 @@
     - [Using Parameters]({{site.baseurl}}/docs/parameter.html#using-parameters)
     - [Selection Configuration]({{site.baseurl}}/docs/parameter.html#config)
     - [Value]({{site.baseurl}}/docs/value.html)
-        - [Examples]({{site.baseurl}}/docs/value.html#examples)
     - [Expr]({{site.baseurl}}/docs/parameter.html)
         - [Documentation Overview]({{site.baseurl}}/docs/parameter.html#documentation-overview)
         - [Defining a Parameter]({{site.baseurl}}/docs/parameter.html#defining-a-parameter)

src/compile/format.ts

@@ -160,7 +160,7 @@ export function guideFormatType(
     return formatType;
   }
   if (isFieldOrDatumDefForTimeFormat(fieldOrDatumDef) && scaleType !== 'time' && scaleType !== 'utc') {
-    return 'time';
+    return isFieldDef(fieldOrDatumDef) && normalizeTimeUnit(fieldOrDatumDef?.timeUnit)?.utc ? 'utc' : 'time';
   }
   return undefined;
 }

test/compile/format.test.ts

@@ -1,5 +1,5 @@
 import {vgField} from '../../src/channeldef';
-import {formatSignalRef, numberFormat, timeFormatExpression} from '../../src/compile/format';
+import {formatSignalRef, guideFormatType, numberFormat, timeFormatExpression} from '../../src/compile/format';
 import {defaultConfig} from '../../src/config';
 import {NOMINAL, ORDINAL, QUANTITATIVE, TEMPORAL} from '../../src/type';
 
@@ -130,4 +130,17 @@ describe('Format', () => {
       });
     });
   });
+
+  describe('guideFormatType()', () => {
+    it('should return existing format type', () => {
+      expect(guideFormatType('number', {field: ' foo', type: 'quantitative'}, 'ordinal')).toBe('number');
+      expect(guideFormatType('time', {field: ' foo', type: 'quantitative'}, 'ordinal')).toBe('time');
+    });
+
+    it('should return utc for utc time units', () => {
+      expect(
+        guideFormatType('', {field: ' foo', type: 'ordinal', timeUnit: {utc: true, unit: 'year'}}, 'ordinal')
+      ).toBe('utc');
+    });
+  });
 });