Logs: Fix displaying the wrong field as body (#73025)

* fix displaying the wrong field as body

* fix test

* fix `getFirstFieldOfType` with non-present type

packages/grafana-data/src/dataframe/FieldCache.test.ts

@@ -100,4 +100,22 @@ describe('FieldCache', () => {
       expect(field!.index).toEqual(2);
     });
   });
+
+  describe('getFirstFieldOfType', () => {
+    let fieldCache: FieldCache;
+    beforeEach(() => {
+      const frame = toDataFrame({
+        fields: [
+          { name: 'time', type: FieldType.time, values: [100, 200, 300] },
+          { name: 'value', type: FieldType.number, values: [1, 2, 3] },
+        ],
+      });
+      fieldCache = new FieldCache(frame);
+    });
+
+    it('should return undefined if type is not present', () => {
+      const field = fieldCache.getFirstFieldOfType(FieldType.string);
+      expect(field).toBeUndefined();
+    });
+  });
 });

packages/grafana-data/src/dataframe/FieldCache.ts

@@ -59,7 +59,7 @@ export class FieldCache {
 
   getFirstFieldOfType(type: FieldType, includeHidden = false): FieldWithIndex | undefined {
     const fields = this.fieldByType[type];
-    const firstField = fields.find((field) => includeHidden || !field.config.custom?.hidden);
+    const firstField = fields?.find((field) => includeHidden || !field.config.custom?.hidden);
     return firstField;
   }
 

public/app/features/explore/Logs/LogsMetaRow.test.tsx

@@ -3,7 +3,7 @@ import userEvent from '@testing-library/user-event';
 import saveAs from 'file-saver';
 import React, { ComponentProps } from 'react';
 
-import { LogLevel, LogsDedupStrategy, MutableDataFrame } from '@grafana/data';
+import { FieldType, LogLevel, LogsDedupStrategy, toDataFrame } from '@grafana/data';
 
 import { MAX_CHARACTERS } from '../../logs/components/LogRowMessage';
 import { logRowsToReadableJson } from '../../logs/utils';
@@ -150,7 +150,24 @@ describe('LogsMetaRow', () => {
       {
         rowIndex: 1,
         entryFieldIndex: 0,
-        dataFrame: new MutableDataFrame(),
+        dataFrame: toDataFrame({
+          name: 'logs',
+          fields: [
+            {
+              name: 'time',
+              type: FieldType.time,
+              values: ['1970-01-01T00:00:00Z'],
+            },
+            {
+              name: 'message',
+              type: FieldType.string,
+              values: ['INFO 1'],
+              labels: {
+                foo: 'bar',
+              },
+            },
+          ],
+        }),
         entry: 'test entry',
         hasAnsi: false,
         hasUnescapedContent: false,

public/app/features/logs/legacyLogsFrame.ts

@@ -34,8 +34,8 @@ function makeLabelsGetter(
 
 export function parseLegacyLogsFrame(frame: DataFrame): LogsFrame | null {
   const cache = new FieldCache(frame);
-  const timeField = cache.getFields(FieldType.time)[0];
+  const timeField = cache.getFirstFieldOfType(FieldType.time);
-  const bodyField = cache.getFields(FieldType.string)[0];
+  const bodyField = cache.getFirstFieldOfType(FieldType.string);
 
   // these two are mandatory
   if (timeField === undefined || bodyField === undefined) {

public/app/features/logs/logsFrame.test.ts

@@ -186,6 +186,31 @@ describe('parseLogsFrame should parse different logs-dataframe formats', () => {
     expect(result!.getAttributes()).toBeNull();
     expect(result?.extraFields).toStrictEqual([]);
   });
+
+  it('should parse an old-style frame with a hidden string field', () => {
+    const time = makeTime('Time', [1687185711795, 1687185711995]);
+    const hidden = makeString('Hidden', ['hidden1', 'hidden2']);
+    const line = makeString('Line', ['line1', 'line2']);
+
+    hidden.config.custom = {
+      hidden: true,
+    };
+
+    const result = parseLogsFrame({
+      fields: [time, hidden, line],
+      length: 2,
+    });
+
+    expect(result).not.toBeNull();
+
+    expect(result!.timeField.values[0]).toBe(time.values[0]);
+    expect(result!.bodyField.values[0]).toBe(line.values[0]);
+    expect(result!.severityField).toBeNull();
+    expect(result!.idField).toBeNull();
+    expect(result!.timeNanosecondField).toBeNull();
+    expect(result!.getAttributesAsLabels()).toBeNull();
+    expect(result!.getAttributes()).toBeNull();
+  });
 });
 
 describe('attributesToLabels', () => {