Transformations: Keep original field.labels.name when joining frames (#88873)

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

@@ -477,6 +477,38 @@ describe('align frames', () => {
     `);
   });
 
+  it('add frame.name as field.labels.name only when field.labels.name does not exist', () => {
+    const series1 = toDataFrame({
+      name: 'Frame A',
+      fields: [
+        { name: 'Time', type: FieldType.time, values: [1000, 2000] },
+        { name: 'Metric 1', type: FieldType.number, values: [1, 100], labels: { name: 'bar' } },
+      ],
+    });
+
+    const series2 = toDataFrame({
+      name: 'Frame B',
+      fields: [
+        { name: 'Time', type: FieldType.time, values: [1000] },
+        { name: 'Metric 2', type: FieldType.number, values: [150] },
+      ],
+    });
+
+    const series3 = toDataFrame({
+      name: 'Frame C',
+      fields: [
+        { name: 'Time', type: FieldType.time, values: [1000] },
+        { name: 'Value', type: FieldType.number, values: [150] }, // weird that in this "Value" case it doesnt get moved into field.labels.name
+      ],
+    });
+
+    const out = joinDataFrames({ frames: [series1, series2, series3] })!;
+
+    expect(out.fields[1].labels).toEqual({ name: 'bar' });
+    expect(out.fields[2].labels).toEqual({ name: 'Frame B' });
+    expect(out.fields[3].labels).toEqual({});
+  });
+
   it('supports duplicate times', () => {
     //----------
     // NOTE!!!

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

@@ -203,7 +203,8 @@ export function joinDataFrames(options: JoinOptions): DataFrame | undefined {
         if (frame.name) {
           if (field.name === TIME_SERIES_VALUE_FIELD_NAME) {
             name = frame.name;
-          } else {
+          } else if (labels.name == null) {
+            // add the name label from frame
             labels = { ...labels, name: frame.name };
           }
         }
@@ -211,7 +212,7 @@ export function joinDataFrames(options: JoinOptions): DataFrame | undefined {
         fields.push({
           ...field,
           name,
-          labels, // add the name label from frame
+          labels,
         });
       }