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e7ac9a4b90
This change is to make JSONHandler error handling intuitive, as before there would be two sources of HTTP status code when HTTPErrors were generated: one as the first return value of the handler function, and one nested inside the HTTPError. Previously, it took the first return value as the status code, and ignored the code inside the HTTPError. Now, it should expect the first return value to be 0 if there is an error, and it takes the status code of the HTTPError to set as the response code. Signed-off-by: Daniel Chung <daniel@tailscale.com>
92 lines
2.5 KiB
Go
92 lines
2.5 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tsweb
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import (
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"encoding/json"
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"fmt"
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"net/http"
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)
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type response struct {
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Status string `json:"status"`
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Error string `json:"error,omitempty"`
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Data interface{} `json:"data,omitempty"`
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}
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// JSONHandlerFunc is an HTTP ReturnHandler that writes JSON responses to the client.
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//
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// Return a HTTPError to show an error message, otherwise JSONHandlerFunc will
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// only report "internal server error" to the user with status code 500.
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type JSONHandlerFunc func(r *http.Request) (status int, data interface{}, err error)
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// ServeHTTPReturn implements the ReturnHandler interface.
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//
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// Use the following code to unmarshal the request body
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//
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// body := new(DataType)
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// if err := json.NewDecoder(r.Body).Decode(body); err != nil {
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// return http.StatusBadRequest, nil, err
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// }
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//
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// See jsonhandler_test.go for examples.
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func (fn JSONHandlerFunc) ServeHTTPReturn(w http.ResponseWriter, r *http.Request) error {
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w.Header().Set("Content-Type", "application/json")
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var resp *response
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status, data, err := fn(r)
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if err != nil {
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if werr, ok := err.(HTTPError); ok {
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resp = &response{
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Status: "error",
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Error: werr.Msg,
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Data: data,
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}
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// Unwrap the HTTPError here because we are communicating with
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// the client in this handler. We don't want the wrapping
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// ReturnHandler to do it too.
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err = werr.Err
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if werr.Msg != "" {
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err = fmt.Errorf("%s: %w", werr.Msg, err)
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}
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// take status from the HTTPError to encourage error handling in one location
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if status != 0 && status != werr.Code {
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err = fmt.Errorf("[unexpected] non-zero status that does not match HTTPError status, status: %d, HTTPError.code: %d: %w", status, werr.Code, err)
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}
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status = werr.Code
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} else {
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status = http.StatusInternalServerError
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resp = &response{
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Status: "error",
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Error: "internal server error",
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}
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}
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} else if status == 0 {
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status = http.StatusInternalServerError
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resp = &response{
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Status: "error",
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Error: "internal server error",
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}
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} else if err == nil {
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resp = &response{
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Status: "success",
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Data: data,
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}
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}
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b, jerr := json.Marshal(resp)
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if jerr != nil {
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w.WriteHeader(http.StatusInternalServerError)
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w.Write([]byte(`{"status":"error","error":"json marshal error"}`))
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if err != nil {
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return fmt.Errorf("%w, and then we could not respond: %v", err, jerr)
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}
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return jerr
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}
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w.WriteHeader(status)
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w.Write(b)
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return err
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}
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