Milo: Fix ?limit= param

milo/frontend/middleware.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package frontend
 
 import (
         "bytes"
         "fmt"
         "html/template"
@@ skipping 207 matching lines @@
 
 // shortHash abbriviates a git hash into 6 characters.
 func shortHash(s string) string {
         if len(s) > 6 {
                 return s[0:6]
         }
         return s
 }
 
 // GetLimit extracts the "limit", "numbuilds", or "num_builds" http param from
-// the request, or returns "-1" implying no limit was specified.
-func GetLimit(r *http.Request) (int, error) {
+// the request, or returns def implying no limit was specified.
+func GetLimit(r *http.Request, def int) int {
         sLimit := r.FormValue("limit")
         if sLimit == "" {
                 sLimit = r.FormValue("numbuilds")
                 if sLimit == "" {
                         sLimit = r.FormValue("num_builds")
                         if sLimit == "" {
-                                return -1, nil
+                                return def
                         }
                 }
         }
         limit, err := strconv.Atoi(sLimit)
-        if err != nil {
-                return -1, fmt.Errorf("limit parameter value %q is not a number: %s", sLimit, err)
+        if err != nil || limit < 0 {
+                return def
         }
-        if limit < 0 {
-                return -1, fmt.Errorf("limit parameter value %q is less than 0", sLimit)
-        }
-        return limit, nil
+        return limit
 }
 
 // pagedURL returns a self URL with the given cursor and limit paging options.
 // if limit is set to 0, then inherit whatever limit is set in request.  If
 // both are unspecified, then limit is omitted.
 func pagedURL(r *http.Request, limit int, cursor string) string {
         if limit == 0 {
-                var err error
-                limit, err = GetLimit(r)
-                if err != nil {
-                        // This should not happen because the handler should've already validated the
-                        // limit earlier in the process.
-                        panic(err)
-                }
+                limit = GetLimit(r, -1)
                 if limit < 0 {
                         limit = 0
                 }
         }
         values := r.URL.Query()
         switch cursor {
         case "EMPTY":
                 values.Del("cursor")
         case "":
                 // Do nothing, just leave the cursor in.
@@ skipping 100 matching lines @@
         c.Context = withRequest(c.Context, c.Request)
         next(c)
 }
 
 func getRequest(c context.Context) *http.Request {
         if req, ok := c.Value(&requestKey).(*http.Request); ok {
                 return req
         }
         panic("No http.request found in context")
 }