Tracing: Prevent createSpanLink from returning an invalid Loki query (#46864)

public/app/features/explore/TraceView/createSpanLink.test.ts

@@ -195,6 +195,25 @@ describe('createSpanLinkFactory', () => {
         )}`
       );
     });
+
+    it('handles empty queries', () => {
+      const createLink = setupSpanLinkFactory({
+        tags: [],
+      });
+      expect(createLink).toBeDefined();
+      const linkDef = createLink!(
+        createTraceSpan({
+          process: {
+            serviceName: 'service',
+            tags: [
+              { key: 'service.name', value: 'serviceName' },
+              { key: 'k8s.pod.name', value: 'podName' },
+            ],
+          },
+        })
+      );
+      expect(linkDef).toBeUndefined();
+    });
   });
 });
 

public/app/features/explore/TraceView/createSpanLink.tsx

@@ -75,12 +75,17 @@ function legacyCreateSpanLinkFactory(splitOpenFn: SplitOpen, traceToLogsOptions?
     return undefined;
   }
 
-  return function SpanLink(span: TraceSpan): SpanLinkDef {
+  return function SpanLink(span: TraceSpan): SpanLinkDef | undefined {
     // This is reusing existing code from derived fields which may not be ideal match so some data is a bit faked at
     // the moment. Issue is that the trace itself isn't clearly mapped to dataFrame (right now it's just a json blob
     // inside a single field) so the dataLinks as config of that dataFrame abstraction breaks down a bit and we do
     // it manually here instead of leaving it for the data source to supply the config.
 
+    const expr = getLokiQueryFromSpan(span, traceToLogsOptions);
+    if (!expr) {
+      return undefined;
+    }
+
     const dataLink: DataLink<LokiQuery> = {
       title: dataSourceSettings.name,
       url: '',
@@ -88,7 +93,7 @@ function legacyCreateSpanLinkFactory(splitOpenFn: SplitOpen, traceToLogsOptions?
         datasourceUid: dataSourceSettings.uid,
         datasourceName: dataSourceSettings.name,
         query: {
-          expr: getLokiQueryFromSpan(span, traceToLogsOptions),
+          expr,
           refId: '',
         },
       },
@@ -122,7 +127,7 @@ function legacyCreateSpanLinkFactory(splitOpenFn: SplitOpen, traceToLogsOptions?
  */
 const defaultKeys = ['cluster', 'hostname', 'namespace', 'pod'];
 
-function getLokiQueryFromSpan(span: TraceSpan, options: TraceToLogsOptions): string {
+function getLokiQueryFromSpan(span: TraceSpan, options: TraceToLogsOptions): string | undefined {
   const { tags: keys, filterByTraceID, filterBySpanID, mapTagNamesEnabled, mappedTags } = options;
 
   // In order, try to use mapped tags -> tags -> default tags
@@ -143,6 +148,11 @@ function getLokiQueryFromSpan(span: TraceSpan, options: TraceToLogsOptions): str
     return acc;
   }, [] as string[]);
 
+  // If no tags found, return undefined to prevent an invalid Loki query
+  if (!tags.length) {
+    return undefined;
+  }
+
   let query = `{${tags.join(', ')}}`;
 
   if (filterByTraceID && span.traceID) {