fix(router): handle urls with only secondary top-level segments

modules/@angular/router/src/recognize.ts

@@ -41,8 +41,9 @@ class InheritedFromParent {
 export function recognize(rootComponentType: Type, config: Routes, urlTree: UrlTree, url: string):
     Observable<RouterStateSnapshot> {
   try {
+    const rootSegment = split(urlTree.root, [], [], config).segment;
     const children =
-        processSegment(config, urlTree.root, InheritedFromParent.empty(null), PRIMARY_OUTLET);
+        processSegment(config, rootSegment, InheritedFromParent.empty(null), PRIMARY_OUTLET);
     const root = new ActivatedRouteSnapshot(
         [], Object.freeze({}), {}, PRIMARY_OUTLET, rootComponentType, null, urlTree.root, -1,
         InheritedResolve.empty);
@@ -127,6 +128,8 @@ function processPathsWithParamsAgainstRoute(
   const childConfig = getChildConfig(route);
 
   const {segment, slicedPath} = split(rawSegment, consumedPaths, rawSlicedPath, childConfig);
+  // console.log("raw", rawSegment)
+  // console.log(segment.toString(), childConfig)
 
   const snapshot = new ActivatedRouteSnapshot(
       consumedPaths, Object.freeze(merge(inherited.allParams, parameters)),

modules/@angular/router/src/url_tree.ts

@@ -195,8 +195,10 @@ export function serializePaths(segment: UrlSegment): string {
 }
 
 function serializeSegment(segment: UrlSegment, root: boolean): string {
-  if (segment.children[PRIMARY_OUTLET] && root) {
+  if (segment.hasChildren() && root) {
-    const primary = serializeSegment(segment.children[PRIMARY_OUTLET], false);
+    const primary = segment.children[PRIMARY_OUTLET] ?
+        serializeSegment(segment.children[PRIMARY_OUTLET], false) :
+        '';
     const children: string[] = [];
     forEach(segment.children, (v: UrlSegment, k: string) => {
       if (k !== PRIMARY_OUTLET) {
@@ -307,7 +309,10 @@ class UrlParser {
       this.capture('/');
     }
 
-    const paths = [this.parsePathWithParams()];
+    let paths: any[] = [];
+    if (!this.peekStartsWith('(')) {
+      paths.push(this.parsePathWithParams());
+    }
 
     while (this.peekStartsWith('/') && !this.peekStartsWith('//') && !this.peekStartsWith('/(')) {
       this.capture('/');
@@ -325,7 +330,10 @@ class UrlParser {
       res = this.parseParens(false);
     }
 
-    res[PRIMARY_OUTLET] = new UrlSegment(paths, children);
+    if (paths.length > 0 || Object.keys(children).length > 0) {
+      res[PRIMARY_OUTLET] = new UrlSegment(paths, children);
+    }
+
     return res;
   }
 
@@ -413,7 +421,6 @@ class UrlParser {
   parseParens(allowPrimary: boolean): {[key: string]: UrlSegment} {
     const segments: {[key: string]: UrlSegment} = {};
     this.capture('(');
-
     while (!this.peekStartsWith(')') && this.remaining.length > 0) {
       let path = matchPathWithParams(this.remaining);
       let outletName: string;
@@ -434,7 +441,6 @@ class UrlParser {
       }
     }
     this.capture(')');
-
     return segments;
   }
 }

modules/@angular/router/test/recognize.spec.ts

@@ -494,6 +494,22 @@ describe('recognize', () => {
               checkActivatedRoute(c[1], 'c', {}, ComponentC, 'aux');
             });
       });
+
+      it('should work when split is at the root level', () => {
+        checkRecognize(
+            [
+              {path: '', component: ComponentA}, {path: 'b', component: ComponentB},
+              {path: 'c', component: ComponentC, outlet: 'aux'}
+            ],
+            '(aux:c)', (s: RouterStateSnapshot) => {
+              checkActivatedRoute(s.root, '', {}, RootComponent);
+
+              const children = s.children(s.root);
+              expect(children.length).toEqual(2);
+              checkActivatedRoute(children[0], '', {}, ComponentA);
+              checkActivatedRoute(children[1], 'c', {}, ComponentC, 'aux');
+            });
+      });
     });
 
     describe('split at the end (right child)', () => {

modules/@angular/router/test/url_serializer.spec.ts

@@ -6,7 +6,6 @@ describe('url serializer', () => {
 
   it('should parse the root url', () => {
     const tree = url.parse('/');
-
     expectSegment(tree.root, '');
     expect(url.serialize(tree)).toEqual('/');
   });
@@ -27,6 +26,26 @@ describe('url serializer', () => {
     expect(url.serialize(tree)).toEqual('/one/two(left:three//right:four)');
   });
 
+  it('should parse top-level nodes with only secondary segment', () => {
+    const tree = url.parse('/(left:one)');
+
+    expect(tree.root.numberOfChildren).toEqual(1);
+    expectSegment(tree.root.children['left'], 'one');
+
+    expect(url.serialize(tree)).toEqual('/(left:one)');
+  });
+
+  it('should parse nodes with only secondary segment', () => {
+    const tree = url.parse('/one/(left:two)');
+
+    const one = tree.root.children[PRIMARY_OUTLET];
+    expectSegment(one, 'one', true);
+    expect(one.numberOfChildren).toEqual(1);
+    expectSegment(one.children['left'], 'two');
+
+    expect(url.serialize(tree)).toEqual('/one/(left:two)');
+  });
+
   it('should not parse empty path segments with params', () => {
     expect(() => url.parse('/one/two/(;a=1//right:;b=2)'))
         .toThrowError(/Empty path url segment cannot have parameters/);
@@ -167,6 +186,9 @@ describe('url serializer', () => {
 });
 
 function expectSegment(segment: UrlSegment, expected: string, hasChildren: boolean = false): void {
+  if (segment.pathsWithParams.filter(s => s.path === '').length > 0) {
+    throw new Error(`UrlPathWithParams cannot be empty ${segment.pathsWithParams}`);
+  }
   const p = segment.pathsWithParams.map(p => serializePath(p)).join('/');
   expect(p).toEqual(expected);
   expect(Object.keys(segment.children).length > 0).toEqual(hasChildren);