scheduler ACLs: improve ACL-related error handling in UI and API.

scheduler/appengine/ui/job.go

 // Copyright 2015 The LUCI Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 19 matching lines @@
 
 func jobPage(ctx *router.Context) {
         c, w, r, p := ctx.Context, ctx.Writer, ctx.Request, ctx.Params
 
         projectID := p.ByName("ProjectID")
         jobName := p.ByName("JobName")
         cursor := r.URL.Query().Get("c")
 
         // Grab the job from the datastore.
         job, err := config(c).Engine.GetVisibleJob(c, projectID+"/"+jobName)
-        if err != nil {
-                panic(err)
-        }
-        if job == nil {
+        switch {
+        case err == engine.ErrNoSuchJob:
                 http.Error(w, "No such job or no access to it", http.StatusNotFound)
                 return
+        case err != nil:
+                panic(err)
         }
 
         // Grab latest invocations from the datastore.
         invs, nextCursor, err := config(c).Engine.ListVisibleInvocations(c, job.JobID, 50, cursor)
         if err != nil {
                 panic(err)
         }
 
         // memcacheKey hashes cursor to reduce its length, since full cursor doesn't
         // fit into memcache key length limits. Use 'v2' scheme for this ('v1' was
@@ skipping 122 matching lines @@
         jobName := c.Params.ByName("JobName")
         switch err := cb(projectID + "/" + jobName); {
         case err == engine.ErrNoOwnerPermission:
                 http.Error(c.Writer, "Forbidden", 403)
         case err != nil:
                 panic(err)
         default:
                 http.Redirect(c.Writer, c.Request, fmt.Sprintf("/jobs/%s/%s", projectID, jobName), http.StatusFound)
         }
 }