fix(http): honor RequestArgs.search and RequestArgs.params map type

Currently `new Request({search: ...})` is not honored, and
`new Request({params: {'x': 'y'}) doesn't work either, as this object would have
toString() called. This change allows both of these cases to work, as proved by
the 2 new tests.

Fixes angular#15761

packages/http/src/static_request.ts

@@ -76,8 +76,14 @@ export class Request extends Body {
     // TODO: assert that url is present
     const url = requestOptions.url;
     this.url = requestOptions.url !;
-    if (requestOptions.params) {
-      const params = requestOptions.params.toString();
+    const paramsArg = requestOptions.params || requestOptions.search;
+    if (paramsArg) {
+      let params: string;
+      if (typeof paramsArg === 'object' && !(paramsArg instanceof URLSearchParams)) {
+        params = urlEncodeParams(paramsArg).toString();
+      } else {
+        params = paramsArg.toString();
+      }
       if (params.length > 0) {
         let prefix = '?';
         if (this.url.indexOf('?') != -1) {
@@ -163,6 +169,19 @@ export class Request extends Body {
   }
 }
 
+function urlEncodeParams(params: {[key: string]: any}): URLSearchParams {
+  const searchParams = new URLSearchParams();
+  Object.keys(params).forEach(key => {
+    const value = params[key];
+    if (value && Array.isArray(value)) {
+      value.forEach(element => searchParams.append(key, element.toString()));
+    } else {
+      searchParams.append(key, value.toString());
+    }
+  });
+  return searchParams;
+}
+
 const noop = function() {};
 const w = typeof window == 'object' ? window : noop;
 const FormData = (w as any /** TODO #9100 */)['FormData'] || noop;

packages/http/test/static_request_spec.ts

@@ -109,5 +109,15 @@ export function main() {
 
       expect(req.text()).toEqual('');
     });
+
+    it('should use object params', () => {
+      const req = new Request({url: 'http://test.com', params: {'a': 3, 'b': ['x', 'y']}});
+      expect(req.url).toBe('http://test.com?a=3&b=x&b=y');
+    });
+
+    it('should use search if present', () => {
+      const req = new Request({url: 'http://test.com', search: 'a=1&b=2'});
+      expect(req.url).toBe('http://test.com?a=1&b=2');
+    })
   });
 }