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1# ajv-errors
2Custom error messages in JSON-Schema for Ajv validator
3
4[![Build Status](https://travis-ci.org/epoberezkin/ajv-errors.svg?branch=master)](https://travis-ci.org/epoberezkin/ajv-errors)
5[![npm version](https://badge.fury.io/js/ajv-errors.svg)](http://badge.fury.io/js/ajv-errors)
6[![Coverage Status](https://coveralls.io/repos/github/epoberezkin/ajv-errors/badge.svg?branch=master)](https://coveralls.io/github/epoberezkin/ajv-errors?branch=master)
7[![Gitter](https://img.shields.io/gitter/room/ajv-validator/ajv.svg)](https://gitter.im/ajv-validator/ajv)
8
9
10## Contents
11
12- [Install](#install)
13- [Usage](#usage)
14 - [Single message](#single-message)
15 - [Messages for keywords](#messages-for-keywords)
16 - [Messages for properties and items](#messages-for-properties-and-items)
17 - [Default message](#default-message)
18- [Templates](#templates)
19- [Options](#options)
20- [License](#license)
21
22
23## Install
24
25```
26npm install ajv-errors
27```
28
29
30## Usage
31
32Add the keyword `errorMessages` to Ajv instance:
33
34```javascript
35var Ajv = require('ajv');
36var ajv = new Ajv({allErrors: true, jsonPointers: true});
37// Ajv options allErrors and jsonPointers are required
38require('ajv-errors')(ajv /*, {singleError: true} */);
39```
40
41See [Options](#options) below.
42
43
44### Single message
45
46Replace all errors in the current schema and subschemas with a single message:
47
48```javascript
49var schema = {
50 type: 'object',
51 required: ['foo'],
52 properties: {
53 foo: { type: 'integer' }
54 },
55 additionalProperties: false,
56 errorMessage: 'should be an object with an integer property foo only'
57};
58
59var validate = ajv.compile(schema);
60console.log(validate({foo: 'a', bar: 2})); // false
61console.log(validate.errors); // processed errors
62```
63
64Processed errors:
65
66```javascript
67[
68 {
69 keyword: 'errorMessage',
70 message: 'should be an object with an integer property foo only',
71 // ...
72 params: {
73 errors: [
74 { keyword: 'additionalProperties', dataPath: '' /* , ... */ },
75 { keyword: 'type', dataPath: '.foo' /* , ... */ }
76 ]
77 }
78 }
79]
80```
81
82
83### Messages for keywords
84
85Replace errors for certain keywords in the current schema only:
86
87```javascript
88var schema = {
89 type: 'object',
90 required: ['foo'],
91 properties: {
92 foo: { type: 'integer' }
93 },
94 additionalProperties: false,
95 errorMessage: {
96 type: 'should be an object', // will not replace internal "type" error for the property "foo"
97 required: 'should have property foo',
98 additionalProperties: 'should not have properties other than foo'
99 }
100};
101
102var validate = ajv.compile(schema);
103console.log(validate({foo: 'a', bar: 2})); // false
104console.log(validate.errors); // processed errors
105```
106
107Processed errors:
108
109```javascript
110[
111 {
112 // original error
113 keyword: type,
114 dataPath: '/foo',
115 // ...
116 message: 'should be integer'
117 },
118 {
119 // generated error
120 keyword: 'errorMessage',
121 message: 'should not have properties other than foo',
122 // ...
123 params: {
124 errors: [
125 { keyword: 'additionalProperties' /* , ... */ }
126 ]
127 },
128 }
129]
130```
131
132For keywords "required" and "dependencies" it is possible to specify different messages for different properties:
133
134```javascript
135var schema = {
136 type: 'object',
137 required: ['foo', 'bar'],
138 properties: {
139 foo: { type: 'integer' },
140 bar: { type: 'string' }
141 },
142 errorMessage: {
143 type: 'should be an object', // will not replace internal "type" error for the property "foo"
144 required: {
145 foo: 'should have an integer property "foo"',
146 bar: 'should have a string property "bar"'
147 }
148 }
149};
150```
151
152
153### Messages for properties and items
154
155Replace errors for properties / items (and deeper), regardless where in schema they were created:
156
157```javascript
158var schema = {
159 type: 'object',
160 required: ['foo', 'bar'],
161 allOf: [{
162 properties: {
163 foo: { type: 'integer', minimum: 2 },
164 bar: { type: 'string', minLength: 2 }
165 },
166 additionalProperties: false
167 }],
168 errorMessage: {
169 properties: {
170 foo: 'data.foo should be integer >= 2',
171 bar: 'data.bar should be string with length >= 2'
172 }
173 }
174};
175
176var validate = ajv.compile(schema);
177console.log(validate({foo: 1, bar: 'a'})); // false
178console.log(validate.errors); // processed errors
179```
180
181Processed errors:
182
183```javascript
184[
185 {
186 keyword: 'errorMessage',
187 message: 'data.foo should be integer >= 2',
188 dataPath: '/foo',
189 // ...
190 params: {
191 errors: [
192 { keyword: 'minimum' /* , ... */ }
193 ]
194 },
195 },
196 {
197 keyword: 'errorMessage',
198 message: 'data.bar should be string with length >= 2',
199 dataPath: '/bar',
200 // ...
201 params: {
202 errors: [
203 { keyword: 'minLength' /* , ... */ }
204 ]
205 },
206 }
207]
208```
209
210
211### Default message
212
213When the value of keyword `errorMessage` is an object you can specify a message that will be used if any error appears that is not specified by keywords/properties/items:
214
215```javascript
216var schema = {
217 type: 'object',
218 required: ['foo', 'bar'],
219 allOf: [{
220 properties: {
221 foo: { type: 'integer', minimum: 2 },
222 bar: { type: 'string', minLength: 2 }
223 },
224 additionalProperties: false
225 }],
226 errorMessage: {
227 type: 'data should be an object',
228 properties: {
229 foo: 'data.foo should be integer >= 2',
230 bar: 'data.bar should be string with length >= 2'
231 },
232 _: 'data should have properties "foo" and "bar" only'
233 }
234};
235
236var validate = ajv.compile(schema);
237console.log(validate({})); // false
238console.log(validate.errors); // processed errors
239```
240
241Processed errors:
242
243```javascript
244[
245 {
246 keyword: 'errorMessage',
247 message: 'data should be an object with properties "foo" and "bar" only',
248 dataPath: '',
249 // ...
250 params: {
251 errors: [
252 { keyword: 'required' /* , ... */ },
253 { keyword: 'required' /* , ... */ }
254 ]
255 },
256 }
257]
258```
259
260The message in property `_` of `errorMessage` replaces the same errors that would have been replaced if `errorMessage` were a string.
261
262
263## Templates
264
265Custom error messages used in `errorMessage` keyword can be templates using [JSON-pointers](https://tools.ietf.org/html/rfc6901) or [relative JSON-pointers](http://tools.ietf.org/html/draft-luff-relative-json-pointer-00) to data being validated, in which case the value will be interpolated. Also see [examples](https://gist.github.com/geraintluff/5911303) of relative JSON-pointers.
266
267The syntax to interpolate a value is `${<pointer>}`.
268
269The values used in messages will be JSON-stringified:
270- to differentiate between `false` and `"false"`, etc.
271- to support structured values.
272
273Example:
274
275```json
276{
277 "type": "object",
278 "properties": {
279 "size": {
280 "type": "number",
281 "minimum": 4
282 }
283 },
284 "errorMessage": {
285 "properties": {
286 "size": "size should be a number bigger or equal to 4, current value is ${/size}"
287 }
288 }
289}
290```
291
292
293## Options
294
295Defaults:
296
297```javascript
298{
299 keepErrors: false,
300 singleError: false
301}
302```
303
304- _keepErrors_: keep original errors. Default is to remove matched errors (they will still be available in `params.errors` property of generated error). If an error was matched and included in the error generated by `errorMessage` keyword it will have property `emUsed: true`.
305- _singleError_: create one error for all keywords used in `errorMessage` keyword (error messages defined for properties and items are not merged because they have different dataPaths). Multiple error messages are concatenated. Option values:
306 - `false` (default): create multiple errors, one for each message
307 - `true`: create single error, messages are concatenated using `"; "`
308 - non-empty string: this string is used as a separator to concatenate messages
309
310
311## Supporters
312
313[<img src="https://media.licdn.com/mpr/mpr/shrinknp_400_400/AAEAAQAAAAAAAAwEAAAAJDg1YzBlYzFjLTA3YWYtNGEzOS1iMTdjLTQ0MTU1NWZjOGM0ZQ.jpg" width="48" height="48">](https://www.linkedin.com/in/rogerkepler/) [Roger Kepler](https://www.linkedin.com/in/rogerkepler/)
314
315
316## License
317
318[MIT](https://github.com/epoberezkin/ajv-errors/blob/master/LICENSE)
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