Loki: Adds line format operation (#47015)

public/app/plugins/datasource/loki/querybuilder/LokiQueryModeller.test.ts

@@ -112,6 +112,15 @@ describe('LokiQueryModeller', () => {
     ).toBe('{app="grafana"} | unwrap count');
   });
 
+  it('Can render with line_format operation', () => {
+    expect(
+      modeller.renderQuery({
+        labels: [{ label: 'app', op: '=', value: 'grafana' }],
+        operations: [{ id: LokiOperationId.LineFormat, params: ['{{.status_code}}'] }],
+      })
+    ).toBe('{app="grafana"} | line_format "{{.status_code}}"');
+  });
+
   it('Can render simply binary operation with scalar', () => {
     expect(
       modeller.renderQuery({

public/app/plugins/datasource/loki/querybuilder/operations.ts

@@ -57,6 +57,34 @@ export function getOperationDefintions(): QueryBuilderOperationDef[] {
       explainHandler: () =>
         `This will extract all keys and values from a [logfmt](https://grafana.com/docs/loki/latest/logql/log_queries/#logfmt) formatted log line as labels. The extracted lables can be used in label filter expressions and used as values for a range aggregation via the unwrap operation. `,
     },
+    {
+      id: LokiOperationId.LineFormat,
+      name: 'Line format',
+      params: [
+        {
+          name: 'String',
+          type: 'string',
+          hideName: true,
+          placeholder: '{{.status_code}}',
+          description: 'A line template that can refer to stream labels and extracted labels.',
+          minWidth: 20,
+        },
+      ],
+      defaultParams: [''],
+      alternativesKey: 'format',
+      category: LokiVisualQueryOperationCategory.Formats,
+      orderRank: LokiOperationOrder.LineFormats,
+      renderer: (model, def, innerExpr) => `${innerExpr} | line_format "${model.params[0]}"`,
+      addOperationHandler: addLokiOperation,
+      explainHandler: () =>
+        `This will replace log line using a specified template. The template can refer to stream labels and extracted labels. 
+
+        Example: \`{{.status_code}} - {{.message}}\`
+
+        [Read the docs](https://grafana.com/docs/loki/latest/logql/log_queries/#line-format-expression) for more.
+        `,
+    },
+
     {
       id: LokiOperationId.LineContains,
       name: 'Line contains',

public/app/plugins/datasource/loki/querybuilder/types.ts

@@ -30,6 +30,7 @@ export enum LokiVisualQueryOperationCategory {
 export enum LokiOperationId {
   Json = 'json',
   Logfmt = 'logfmt',
+  LineFormat = 'line_format',
   Rate = 'rate',
   CountOverTime = 'count_over_time',
   SumOverTime = 'sum_over_time',