chore: add info about entity if tech docs building fails

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

.changeset/hip-mugs-camp.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs-backend': patch
+---
+
+Add info about the entity when tech docs fail to build

plugins/techdocs-backend/src/service/DocsSynchronizer.test.ts

@@ -258,7 +258,7 @@ describe('DocsSynchronizer', () => {
       expect(mockResponseHandler.log).toHaveBeenCalledTimes(1);
       expect(mockResponseHandler.log).toHaveBeenCalledWith(
         expect.stringMatching(
-          /error.*: Failed to build the docs page: Some random error/,
+          /error.*: Failed to build the docs page for entity component:default\/test: Some random error/,
         ),
       );
       expect(mockResponseHandler.finish).toHaveBeenCalledTimes(0);

plugins/techdocs-backend/src/service/DocsSynchronizer.ts

@@ -15,7 +15,11 @@
  */
 
 import { PluginEndpointDiscovery } from '@backstage/backend-common';
-import { Entity, DEFAULT_NAMESPACE } from '@backstage/catalog-model';
+import {
+  DEFAULT_NAMESPACE,
+  Entity,
+  stringifyEntityRef,
+} from '@backstage/catalog-model';
 import { Config } from '@backstage/config';
 import { assertError, NotFoundError } from '@backstage/errors';
 import { ScmIntegrationRegistry } from '@backstage/integration';
@@ -142,7 +146,9 @@ export class DocsSynchronizer {
       }
     } catch (e) {
       assertError(e);
-      const msg = `Failed to build the docs page: ${e.message}`;
+      const msg = `Failed to build the docs page for entity ${stringifyEntityRef(
+        entity,
+      )}: ${e.message}`;
       taskLogger.error(msg);
       this.logger.error(msg, e);
       error(e);