feat: have the handler implement ErrorRequestHandler

so that it can also handle any caught exception and intercept calls to `next(err)`

fixes #7

Author: tpluscode

src/HttpProblemResponse.ts

@@ -1,40 +1,27 @@
-import express, { Send } from 'express'
+import express from 'express'
 import { NextFunction } from 'connect'
-import { Handler } from 'express-serve-static-core'
-import { StatusCodeErrorMapper, IMappingStrategy, ErrorStatusCodes } from 'http-problem-details-mapper'
+import { ErrorRequestHandler } from 'express-serve-static-core'
+import { IMappingStrategy } from 'http-problem-details-mapper'
 
 class HttpProblemResponseOptions {
   public strategy: IMappingStrategy;
 }
 
-function HttpProblemResponse (options: HttpProblemResponseOptions): Handler {
-  return function HttpProblemDetailsMiddleware (request: express.Request,
-    response: express.Response, next: NextFunction): void {
-    const temp = response.send
-    const strategy = options.strategy
-
-    response.send = function (body): void {
-      let problem = null
-      let isErrorInstance = body instanceof Error
-
-      if (body && isErrorInstance) {
-        problem = strategy.map(body)
-        response.statusCode = problem.status
-      }
-
-      if (!body && ErrorStatusCodes.includes(response.statusCode)) {
-        problem = StatusCodeErrorMapper.mapStatusCode(response.statusCode)
-      }
-
-      if (problem) {
-        response.setHeader('Content-Type', 'application/problem+json')
-        temp.apply(this, [JSON.stringify(problem)])
-      } else {
-        temp.apply(this, [body])
-      }
-    } as Send
-
-    return next()
+function HttpProblemResponse (options: HttpProblemResponseOptions): ErrorRequestHandler {
+  const { strategy } = options
+
+  return function HttpProblemDetailsMiddleware (error: Error,
+    request: express.Request,
+    response: express.Response,
+    next: NextFunction): void { // eslint-disable-line @typescript-eslint/no-unused-vars
+    let problem = strategy.map(error)
+    if (!problem.detail && error.message) {
+      problem.detail = error.message
+    }
+
+    response.statusCode = problem.status
+    response.setHeader('Content-Type', 'application/problem+json')
+    response.send(JSON.stringify(problem))
   }
 }