recipe-client-addon: Use URL object to manipulate URLs.

recipe-client-addon/lib/NormandyApi.jsm

@@ -62,12 +62,12 @@ this.NormandyApi = {
   },
 
   async getApiUrl(name) {
-    let apiBase = prefs.getCharPref("api_url");
-    if (!apiBase.endsWith('/')) {
-      apiBase += '/';
+    let apiBase = new URL(prefs.getCharPref("api_url"));
+    if (!apiBase.pathname.endsWith('/')) {
+      apiBase.pathname += '/';
     }
     if (!indexPromise) {
-      indexPromise = this.get(apiBase).then(res => res.json());
+      indexPromise = this.get(apiBase.toString()).then(res => res.json());
     }
     const index = await indexPromise;
     if (!(name in index)) {

recipe-client-addon/test/unit/test_NormandyApi.js

@@ -105,7 +105,7 @@ add_task(withMockApiServer(async function test_getApiUrlSlashes(serverUrl, prefe
     equal(endpoint, `${serverUrl}/test/`);
     ok(mockGet.calledWithExactly(`${serverUrl}/api/v1/`), "trailing slash was added");
     mockGet.reset();
-  };
+  }
 
   // with slash
   {
@@ -117,6 +117,7 @@ add_task(withMockApiServer(async function test_getApiUrlSlashes(serverUrl, prefe
     mockGet.reset();
   }
 
+  NormandyApi.clearIndexCache();
   mockGet.restore();
 }));