Emit warning when a remote context lookup is being done

Author: rubensworks

lib/rdf/PrefetchedDocumentLoader.ts

@@ -35,13 +35,21 @@ export class PrefetchedDocumentLoader extends FetchDocumentLoader {
   }
 
   public async load(url: string): Promise<IJsonLdContext> {
+    // Warn on deprecated context usage
     if (this.logger &&
       url === 'https://linkedsoftwaredependencies.org/bundles/npm/componentsjs/^3.0.0/components/context.jsonld') {
       this.logger.warn(`Detected deprecated context URL '${url}'${this.path ? ` in ${this.path}` : ''}. Prefer using version '^4.0.0' instead.`);
     }
+
+    // Load prefetched contexts
     if (url in this.contexts) {
       return this.contexts[url];
     }
+
+    // Warn before doing a remote context lookup
+    if (this.logger) {
+      this.logger.warn(`Detected remote context lookup for '${url}'${this.path ? ` in ${this.path}` : ''}. This may indicate a missing or invalid dependency, or an invalid context URL.`);
+    }
     return super.load(url);
   }
 }

test/unit/rdf/PrefetchedDocumentLoader-test.ts

@@ -66,5 +66,32 @@ describe('PrefetchedDocumentLoader', () => {
       expect(await loader.load('http://remote.org/context'))
         .toEqual({ x: 'y' });
     });
+
+    it('for a non-prefetched context with a logger', async() => {
+      const logger: any = {
+        warn: jest.fn(),
+      };
+      loader = new PrefetchedDocumentLoader({
+        contexts: {},
+        logger,
+        path: 'PATH',
+      });
+      expect(await loader.load('http://remote.org/context'))
+        .toEqual({ x: 'y' });
+      expect(logger.warn).toHaveBeenCalledWith(`Detected remote context lookup for 'http://remote.org/context' in PATH. This may indicate a missing or invalid dependency, or an invalid context URL.`);
+    });
+
+    it('for a non-prefetched context with a logger without path', async() => {
+      const logger: any = {
+        warn: jest.fn(),
+      };
+      loader = new PrefetchedDocumentLoader({
+        contexts: {},
+        logger,
+      });
+      expect(await loader.load('http://remote.org/context'))
+        .toEqual({ x: 'y' });
+      expect(logger.warn).toHaveBeenCalledWith(`Detected remote context lookup for 'http://remote.org/context'. This may indicate a missing or invalid dependency, or an invalid context URL.`);
+    });
   });
 });