implement RFC7807

index.d.ts

@@ -12,6 +12,45 @@ declare namespace createError {
     code: string;
     name: string;
     statusCode?: number;
+
+    toRFC7807: (instance?: RFC7807Error['instance'], details?: RFC7807Error['details']) => RFC7807Error;
+  }
+
+  interface RFC7807Error {
+    /**
+     * A URI reference [RFC3986] that identifies the
+     * problem type.  This specification encourages that, when
+     * dereferenced, it provide human-readable documentation for the
+     * problem type (e.g., using HTML [W3C.REC-html5-20141028]).
+     * When this member is not present, its value is assumed to be
+     * "about:blank".
+     */
+    type: string;
+    /**
+     * A short, human-readable summary of the problem
+     * type.  It SHOULD NOT change from occurrence to occurrence of the
+     * problem, except for purposes of localization (e.g., using
+     * proactive content negotiation; see [RFC7231], Section 3.4).
+     */
+    title: string;
+    /**
+     * The HTTP status code ([RFC7231], Section 6)
+     * generated by the origin server for this occurrence of the problem.
+     */
+    status: number;
+    /**
+     * A human-readable explanation specific to this
+     * occurrence of the problem.
+     */
+    detail: string;
+    /**
+     * A URI reference that identifies the specific
+     * occurrence of the problem. It may or may not yield further
+     * information if dereferenced.
+     */
+    instance: string;
+    code: string;
+    details: { [key: string]: any };
   }
 
   interface FastifyErrorConstructor {

index.js

@@ -2,7 +2,7 @@
 
 const { inherits, format } = require('util')
 
-function createError (code, message, statusCode = 500, Base = Error) {
+function createError (code, message, statusCode = 500, Base = Error, uriReference) {
   if (!code) throw new Error('Fastify error code must not be empty')
   if (!message) throw new Error('Fastify error message must not be empty')
 
@@ -28,13 +28,26 @@ function createError (code, message, statusCode = 500, Base = Error) {
     }
 
     this.statusCode = statusCode || undefined
+    this.uriReference = uriReference || undefined
   }
   FastifyError.prototype[Symbol.toStringTag] = 'Error'
 
   FastifyError.prototype.toString = function () {
     return `${this.name} [${this.code}]: ${this.message}`
   }
 
+  FastifyError.prototype.toRFC7807 = function (instance, details) {
+    return {
+      type: this.uriReference || 'about:blank',
+      title: this.name,
+      status: this.statusCode,
+      detail: this.message,
+      instance: instance || '',
+      code: this.code,
+      details: details || {}
+    }
+  }
+
   inherits(FastifyError, Base)
 
   return FastifyError

index.test-d.ts

@@ -1,4 +1,4 @@
-import createError, { FastifyError, FastifyErrorConstructor } from './'
+import createError, { FastifyError, FastifyErrorConstructor, RFC7807Error } from './'
 import { expectType } from 'tsd'
 
 const CustomError = createError('ERROR_CODE', 'message')
@@ -7,4 +7,8 @@ const err = new CustomError()
 expectType<FastifyError>(err)
 expectType<string>(err.code)
 expectType<string>(err.message)
-expectType<number>(err.statusCode!)
+expectType<number>(err.statusCode!)
+
+expectType<RFC7807Error>(err.toRFC7807());
+expectType<RFC7807Error>(err.toRFC7807('/dev/null'));
+expectType<RFC7807Error>(err.toRFC7807(undefined, { description: 'missing value for key'}));

test.js

@@ -104,3 +104,33 @@ test('Create the error without the new keyword', t => {
   t.is(err.statusCode, 500)
   t.truthy(err.stack)
 })
+
+test('FastifyError.toRFC7807 returns RFC7807 conform Object', t => {
+  const NewError = createError('CODE', 'foo')
+  const err = new NewError()
+  t.is(typeof err.toRFC7807(), 'object')
+  t.is(err.toRFC7807().code, 'CODE')
+  t.is(err.toRFC7807().detail, 'foo')
+  t.is(err.toRFC7807().title, 'FastifyError')
+  t.is(err.toRFC7807().type, 'about:blank')
+  t.deepEqual(err.toRFC7807().details, {})
+  t.is(err.toRFC7807().instance, '')
+})
+
+test('FastifyError.toRFC7807 accepts instance', t => {
+  const NewError = createError('CODE', 'foo')
+  const err = new NewError()
+  t.is(err.toRFC7807('/dev/null').instance, '/dev/null')
+})
+
+test('FastifyError.toRFC7807 accepts details', t => {
+  const NewError = createError('CODE', 'foo')
+  const err = new NewError()
+  t.deepEqual(err.toRFC7807(undefined, { max: 'not a valid maximum value for key' }).details, { max: 'not a valid maximum value for key' })
+})
+
+test('FastifyError accepts an uriReference which is later used for toRFC7807 type attribute', t => {
+  const NewError = createError('CODE', 'foo', undefined, undefined, 'https://www.fastify.io/docs/latest/Reference/Errors/#fst_err_bad_url')
+  const err = new NewError()
+  t.is(err.toRFC7807().type, 'https://www.fastify.io/docs/latest/Reference/Errors/#fst_err_bad_url')
+})