Add public Router#resolve method as per #831. (#918)

Necessary docs, tests, typings. Fixes per code review.

Author: hogart

docs/en/api/router-instance.md

@@ -39,3 +39,7 @@
 - **router.getMatchedComponents()**
 
   Returns an Array of the components (definition/constructor, not instances) matched by the current route. This is mostly used during server-side rendering to perform data prefetching.
+  
+- **router.resolve(location, current?, append?)**
+
+  Reverse URL resolving. Given location in form same as used in `<router-link/>`, returns object with string property `href`.

src/components/link.js

@@ -1,8 +1,6 @@
 /* @flow */
 
-import { cleanPath } from '../util/path'
 import { createRoute, isSameRoute, isIncludedRoute } from '../util/route'
-import { normalizeLocation } from '../util/location'
 import { _Vue } from '../install'
 
 // work around weird flow bug
@@ -27,14 +25,10 @@ export default {
   render (h: Function) {
     const router = this.$router
     const current = this.$route
-    const to = normalizeLocation(this.to, current, this.append)
-    const resolved = router.match(to, current)
-    const fullPath = resolved.redirectedFrom || resolved.fullPath
-    const base = router.history.base
-    const href = createHref(base, fullPath, router.mode)
+    const { normalizedTo, resolved, href } = router.resolve(this.to, current, this.append)
     const classes = {}
     const activeClass = this.activeClass || router.options.linkActiveClass || 'router-link-active'
-    const compareTarget = to.path ? createRoute(null, to) : resolved
+    const compareTarget = normalizedTo.path ? createRoute(null, normalizedTo) : resolved
     classes[activeClass] = this.exact
       ? isSameRoute(current, compareTarget)
       : isIncludedRoute(current, compareTarget)
@@ -57,9 +51,9 @@ export default {
 
         e.preventDefault()
         if (this.replace) {
-          router.replace(to)
+          router.replace(normalizedTo)
         } else {
-          router.push(to)
+          router.push(normalizedTo)
         }
       }
     }
@@ -106,8 +100,3 @@ function findAnchor (children) {
     }
   }
 }
-
-function createHref (base, fullPath, mode) {
-  var path = mode === 'hash' ? '/#' + fullPath : fullPath
-  return base ? cleanPath(base + path) : path
-}

src/index.js

@@ -7,6 +7,8 @@ import { HTML5History, getLocation } from './history/html5'
 import { AbstractHistory } from './history/abstract'
 import { inBrowser, supportsHistory } from './util/dom'
 import { assert } from './util/warn'
+import { cleanPath } from './util/path'
+import { normalizeLocation } from './util/location'
 
 export default class VueRouter {
   static install: () => void;
@@ -120,6 +122,24 @@ export default class VueRouter {
       })
     }))
   }
+
+  resolve (to: RawLocation, current?: Route, append?: boolean): {href: string} {
+    const normalizedTo = normalizeLocation(to, current || this.history.current, append)
+    const resolved = this.match(normalizedTo, current)
+    const fullPath = resolved.redirectedFrom || resolved.fullPath
+    const base = this.history.base
+    const href = createHref(base, fullPath, this.mode)
+    return {
+      normalizedTo,
+      resolved,
+      href
+    }
+  }
+}
+
+function createHref (base: string, fullPath: string, mode) {
+  var path = mode === 'hash' ? '/#' + fullPath : fullPath
+  return base ? cleanPath(base + path) : path
 }
 
 VueRouter.install = install

types/router.d.ts

@@ -28,6 +28,7 @@ declare class VueRouter {
   back (): void;
   forward (): void;
   getMatchedComponentes (): Component;
+  resolve (to: RawLocation, current?: Route, append?: boolean): {href: string};
 
   static install: PluginFunction<never>;
 }