MINOR: Fix error message on Datasource connection failure. (#2124)

* MINOR: Fix error message on Datasource connection failure.

Caught error might be just a string from a rejected promise.

Signed-off-by: Andres Mandado <andres.mandado-almajano@here.com>

* MINOR: Address review comments.

@here/harp-mapview/lib/MapView.ts

@@ -2148,7 +2148,10 @@ export class MapView extends EventDispatcher {
 
             this.update();
         } catch (error) {
-            logger.error(`Failed to connect to datasource ${dataSource.name}: ${error.message}`);
+            // error is a string if a promise was rejected.
+            logger.error(
+                `Failed to connect to datasource ${dataSource.name}: ${error.message ?? error}`
+            );
 
             this.m_failedDataSources.add(dataSource.name);
             this.dispatchEvent({

@here/harp-vectortile-datasource/lib/VectorTileDataSource.ts

@@ -331,7 +331,9 @@ export class VectorTileDataSource extends TileDataSource {
         try {
             await super.connect();
         } catch (error) {
+            // error is a string if the promise was rejected.
             if (
+                error.message &&
                 WorkerServiceProtocol.isUnknownServiceError(error) &&
                 !missingOmvDecoderServiceInfoEmitted
             ) {
@@ -341,7 +343,7 @@ export class VectorTileDataSource extends TileDataSource {
                 );
                 missingOmvDecoderServiceInfoEmitted = true;
             }
-            throw error;
+            throw typeof error === "string" ? new Error(error) : error;
         }
         this.configureDecoder(undefined, this.m_decoderOptions);
     }

@here/harp-vectortile-datasource/test/OmvDataSourceTest.ts

@@ -13,7 +13,12 @@ import { TileKey } from "@here/harp-geoutils";
 import { DataProvider } from "@here/harp-mapview-decoder";
 import { GeoJsonTiler } from "@here/harp-mapview-decoder/index-worker";
 import { silenceLoggingAroundFunction } from "@here/harp-test-utils";
-import { assert } from "chai";
+import * as chai from "chai";
+const { expect, assert } = chai;
+// Install chai-as-promised plugin to support promise assertions like:
+// expect(promise).to.eventually.be.rejectedWith()
+import * as chai_as_promised from "chai-as-promised";
+chai.use(chai_as_promised);
 import * as sinon from "sinon";
 
 import {
@@ -211,4 +216,18 @@ describe("DataProviders", function () {
 
         assert.isFalse(markTilesDirty.called);
     });
+
+    it("connect returns promise rejection as error", function () {
+        const rejectMsg = "connection failed";
+        const mockDataProvider = new MockDataProvider();
+
+        sinon.stub(mockDataProvider, "connect").callsFake(() => {
+            return Promise.reject(rejectMsg);
+        });
+        const omvDataSource = new VectorTileDataSource({
+            decoder: new VectorTileDecoder(),
+            dataProvider: mockDataProvider
+        });
+        expect(omvDataSource.connect()).to.eventually.throw("Error", rejectMsg);
+    });
 });