Make HTTP middleware easier to use

server/settings/admin/settings.go

Index: server/settings/admin/settings.go
diff --git a/server/settings/admin/settings.go b/server/settings/admin/settings.go
index c6aed6509a277ab929d795bd1b8a086f810bc0ae..f02c093fab17b46d4b80780512a65b0f2d3f8cb4 100644
--- a/server/settings/admin/settings.go
+++ b/server/settings/admin/settings.go
@@ -12,6 +12,7 @@ import (
 
 	"github.com/luci/luci-go/server/auth"
 	"github.com/luci/luci-go/server/auth/xsrf"
+	"github.com/luci/luci-go/server/router"
 	"github.com/luci/luci-go/server/settings"
 	"github.com/luci/luci-go/server/templates"
 )
@@ -44,21 +45,21 @@ func withPage(c context.Context, rw http.ResponseWriter, p httprouter.Params, cb
 	}
 }
 
-func settingsPageGET(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-	withPage(c, rw, p, func(id string, page settings.UIPage) error {
-		title, err := page.Title(c)
+func settingsPageGET(c *router.Context) {
+	withPage(c.Context, c.Writer, c.Params, func(id string, page settings.UIPage) error {
+		title, err := page.Title(c.Context)
 		if err != nil {
 			return err
 		}
-		overview, err := page.Overview(c)
+		overview, err := page.Overview(c.Context)
 		if err != nil {
 			return err
 		}
-		fields, err := page.Fields(c)
+		fields, err := page.Fields(c.Context)
 		if err != nil {
 			return err
 		}
-		values, err := page.ReadSettings(c)
+		values, err := page.ReadSettings(c.Context)
 		if err != nil {
 			return err
 		}
@@ -71,24 +72,24 @@ func settingsPageGET(c context.Context, rw http.ResponseWriter, r *http.Request,
 			}
 		}
 
-		templates.MustRender(c, rw, "pages/settings.html", templates.Args{
+		templates.MustRender(c.Context, c.Writer, "pages/settings.html", templates.Args{
 			"ID":             id,
 			"Title":          title,
 			"Overview":       overview,
 			"Fields":         withValues,
-			"XsrfTokenField": xsrf.TokenField(c),
+			"XsrfTokenField": xsrf.TokenField(c.Context),
 		})
 		return nil
 	})
 }
 
-func settingsPagePOST(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-	withPage(c, rw, p, func(id string, page settings.UIPage) error {
-		title, err := page.Title(c)
+func settingsPagePOST(c *router.Context) {
+	withPage(c.Context, c.Writer, c.Params, func(id string, page settings.UIPage) error {
+		title, err := page.Title(c.Context)
 		if err != nil {
 			return err
 		}
-		fields, err := page.Fields(c)
+		fields, err := page.Fields(c.Context)
 		if err != nil {
 			return err
 		}
@@ -100,7 +101,7 @@ func settingsPagePOST(c context.Context, rw http.ResponseWriter, r *http.Request
 			if !f.Type.IsEditable() {
 				continue
 			}
-			val := r.PostFormValue(f.ID)
+			val := c.Request.PostFormValue(f.ID)
 			values[f.ID] = val
 			if f.Validator != nil {
 				if err := f.Validator(val); err != nil {
@@ -113,8 +114,8 @@ func settingsPagePOST(c context.Context, rw http.ResponseWriter, r *http.Request
 			}
 		}
 		if len(validationErrors) != 0 {
-			rw.WriteHeader(http.StatusBadRequest)
-			templates.MustRender(c, rw, "pages/validation_error.html", templates.Args{
+			c.Writer.WriteHeader(http.StatusBadRequest)
+			templates.MustRender(c.Context, c.Writer, "pages/validation_error.html", templates.Args{
 				"ID":     id,
 				"Title":  title,
 				"Errors": validationErrors,
@@ -123,11 +124,11 @@ func settingsPagePOST(c context.Context, rw http.ResponseWriter, r *http.Request
 		}
 
 		// Store.
-		err = page.WriteSettings(c, values, auth.CurrentUser(c).Email, "modified via web UI")
+		err = page.WriteSettings(c.Context, values, auth.CurrentUser(c.Context).Email, "modified via web UI")
 		if err != nil {
 			return err
 		}
-		templates.MustRender(c, rw, "pages/done.html", templates.Args{
+		templates.MustRender(c.Context, c.Writer, "pages/done.html", templates.Args{
 			"ID":    id,
 			"Title": title,
 		})