Transformations: Ignore value displayName for columns for matrix grouping (#106647)

* Ignore value displayName for columns for matrix grouping

* Fix spelling

packages/grafana-data/src/transformations/transformers/groupingToMatrix.test.ts

@@ -226,6 +226,52 @@ describe('Grouping to Matrix', () => {
     });
   });
 
+  it('properly handles the value display name (by ignoring it)', async () => {
+    const cfg: DataTransformerConfig<GroupingToMatrixTransformerOptions> = {
+      id: DataTransformerID.groupingToMatrix,
+      options: {
+        columnField: 'Column',
+        rowField: 'Row',
+        valueField: 'CustomName',
+      },
+    };
+
+    const seriesA = toDataFrame({
+      name: 'A',
+      fields: [
+        { name: 'Column', type: FieldType.string, values: ['C1', 'C1', 'C2'] },
+        { name: 'Row', type: FieldType.string, values: ['R1', 'R2', 'R1'] },
+        { name: 'Temp', type: FieldType.number, values: [1, 4, 5], config: { displayName: 'CustomName' } },
+      ],
+    });
+
+    await expect(transformDataFrame([cfg], [seriesA])).toEmitValuesWith((received) => {
+      const processed = received[0];
+      const expected: Field[] = [
+        {
+          name: 'Row\\Column',
+          type: FieldType.string,
+          values: ['R1', 'R2'],
+          config: {},
+        },
+        {
+          name: 'C1',
+          type: FieldType.number,
+          values: [1, 4],
+          config: {},
+        },
+        {
+          name: 'C2',
+          type: FieldType.number,
+          values: [5, ''],
+          config: {},
+        },
+      ];
+
+      expect(processed[0].fields).toEqual(expected);
+    });
+  });
+
   it('generates Matrix with multiple fields and value type', async () => {
     const cfg: DataTransformerConfig<GroupingToMatrixTransformerOptions> = {
       id: DataTransformerID.groupingToMatrix,

packages/grafana-data/src/transformations/transformers/groupingToMatrix.ts

@@ -60,7 +60,7 @@ export const groupingToMatrixTransformer: DataTransformerInfo<GroupingToMatrixTr
       numFields += frame.fields.length;
     }
 
-    return `Grouping to matrix requiers at least 3 fields to work. Currently there are ${numFields} fields.`;
+    return `Grouping to matrix requires at least 3 fields to work. Currently there are ${numFields} fields.`;
   },
   operator: (options: GroupingToMatrixTransformerOptions, ctx: DataTransformContext) => (source) =>
     source.pipe(
@@ -126,6 +126,9 @@ export const groupingToMatrixTransformer: DataTransformerInfo<GroupingToMatrixTr
             valueField.config = { ...valueField.config, displayNameFromDS: undefined };
           }
 
+          // the names of these columns need to be the selected column values, and not be overridden with the display name
+          delete valueField.config.displayName;
+
           fields.push({
             name: columnName?.toString() ?? null,
             values: values,