Add error & subroute handlers; weakString; other minor handler changes

modules/caddyhttp/staticerror.go

@@ -0,0 +1,95 @@
+// Copyright 2015 Matthew Holt and The Caddy 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,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyhttp
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+
+	"github.com/caddyserver/caddy/v2"
+)
+
+func init() {
+	caddy.RegisterModule(caddy.Module{
+		Name: "http.handlers.error",
+		New:  func() interface{} { return new(StaticError) },
+	})
+}
+
+// StaticError implements a simple handler that returns an error.
+type StaticError struct {
+	Error      string     `json:"error,omitempty"`
+	StatusCode weakString `json:"status_code,omitempty"`
+}
+
+func (e StaticError) ServeHTTP(w http.ResponseWriter, r *http.Request, _ Handler) error {
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+
+	statusCode := http.StatusInternalServerError
+	if codeStr := e.StatusCode.String(); codeStr != "" {
+		intVal, err := strconv.Atoi(repl.ReplaceAll(codeStr, ""))
+		if err != nil {
+			return Error(http.StatusInternalServerError, err)
+		}
+		statusCode = intVal
+	}
+
+	return Error(statusCode, fmt.Errorf("%s", e.Error))
+}
+
+// Interface guard
+var _ MiddlewareHandler = (*StaticError)(nil)
+
+// weakString is a type that unmarshals any JSON value
+// as a string literal, and provides methods for
+// getting the value as different primitive types.
+// However, using this type removes any type safety
+// as far as deserializing JSON is concerned.
+type weakString string
+
+// UnmarshalJSON satisfies json.Unmarshaler. It
+// unmarshals b by always interpreting it as a
+// string literal.
+func (ws *weakString) UnmarshalJSON(b []byte) error {
+	*ws = weakString(strings.Trim(string(b), `"`))
+	return nil
+}
+
+// Int returns ws as an integer. If ws is not an
+// integer, 0 is returned.
+func (ws weakString) Int() int {
+	num, _ := strconv.Atoi(string(ws))
+	return num
+}
+
+// Float64 returns ws as a float64. If ws is not a
+// float value, the zero value is returned.
+func (ws weakString) Float64() float64 {
+	num, _ := strconv.ParseFloat(string(ws), 64)
+	return num
+}
+
+// Bool returns ws as a boolean. If ws is not a
+// boolean, false is returned.
+func (ws weakString) Bool() bool {
+	return string(ws) == "true"
+}
+
+// String returns ws as a string.
+func (ws weakString) String() string {
+	return string(ws)
+}