go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/cipd/appengine/ui/errors.go (about)

     1  // Copyright 2018 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package ui
    16  
    17  import (
    18  	"unicode"
    19  	"unicode/utf8"
    20  
    21  	"google.golang.org/grpc/status"
    22  
    23  	"go.chromium.org/luci/grpc/grpcutil"
    24  	"go.chromium.org/luci/server/router"
    25  	"go.chromium.org/luci/server/templates"
    26  )
    27  
    28  // renderErr is a handler wrapper converts gRPC errors into HTML pages.
    29  func renderErr(h func(*router.Context) error) router.Handler {
    30  	return func(ctx *router.Context) {
    31  		err := h(ctx)
    32  		if err == nil {
    33  			return
    34  		}
    35  
    36  		s, _ := status.FromError(err)
    37  		message := s.Message()
    38  		if message != "" {
    39  			// Convert the first rune to upper case.
    40  			r, n := utf8.DecodeRuneInString(message)
    41  			message = string(unicode.ToUpper(r)) + message[n:]
    42  		} else {
    43  			message = "Unspecified error" // this should not really happen
    44  		}
    45  
    46  		ctx.Writer.Header().Set("Content-Type", "text/html; charset=utf-8")
    47  		ctx.Writer.WriteHeader(grpcutil.CodeStatus(s.Code()))
    48  		templates.MustRender(ctx.Request.Context(), ctx.Writer, "pages/error.html", map[string]any{
    49  			"Message": message,
    50  		})
    51  	}
    52  }