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feat: implement instanceof (#149)
* feat: implement instanceof * improve test * add test * why not? * rework test * log * normalize Path for macos and win * try to fix windows run * simplify * log more * use lastIndexOf instead of indexOf to avoid issues in GH Runner with Windows * hope this fixes it * log more * log more * another try to fix the crossplatform issues * another try * ignore the first character of testDirectoryPrefix in hope it fixes the issue * another try * modify Readme * Apply suggestions from code review Co-authored-by: Frazer Smith <frazer.dev@icloud.com> Signed-off-by: Aras Abbasi <aras.abbasi@googlemail.com> --------- Signed-off-by: Aras Abbasi <aras.abbasi@googlemail.com> Co-authored-by: Frazer Smith <frazer.dev@icloud.com>
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‎README.md

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@@ -15,7 +15,7 @@ npm i @fastify/error
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The module exports a function that you can use for consistent error objects, it takes 4 parameters:
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```
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```js
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createError(code, message [, statusCode [, Base [, captureStackTrace]]])
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```
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@@ -58,6 +58,83 @@ new CustomError('world')
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new CustomError(1)
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```
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### instanceof
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All errors created with `createError` will be instances of the base error constructor you provided, or `Error` if none was provided.
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```js
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const createError = require('@fastify/error')
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const CustomError = createError('ERROR_CODE', 'Hello %s', 500, TypeError)
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const customError = new CustomError('world')
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console.log(customError instanceof CustomError) // true
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console.log(customError instanceof TypeError) // true
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console.log(customError instanceof Error) // true
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```
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All instantiated errors are instances of the `FastifyError` class, which can be required directly from the module.
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```js
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const { createError, FastifyError } = require('@fastify/error')
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const CustomError = createError('ERROR_CODE', 'Hello %s', 500, TypeError)
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const customError = new CustomError('world')
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console.log(customError instanceof FastifyError) // true
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```
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A `FastifyError` created by `createError` can extend another `FastifyError` while maintaining correct `instanceof` behavior.
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```js
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const { createError, FastifyError } = require('@fastify/error')
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const CustomError = createError('ERROR_CODE', 'Hello %s', 500, TypeError)
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const ChildCustomError = createError('CHILD_ERROR_CODE', 'Hello %s', 500, CustomError)
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const customError = new ChildCustomError('world')
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console.log(customError instanceof ChildCustomError) // true
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console.log(customError instanceof CustomError) // true
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console.log(customError instanceof FastifyError) // true
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console.log(customError instanceof TypeError) // true
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console.log(customError instanceof Error) // true
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```
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If `fastify-error` is installed multiple times directly or as a transitive dependency, `instanceof` checks for errors created by `createError` will still work correctly across these installations, as long as their error codes (e.g., `FST_ERR_CUSTOM_ERROR`) are identical.
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```js
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const { createError, FastifyError } = require('@fastify/error')
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// CustomError from `@fastify/some-plugin` is created with `createError` and
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// has its own `@fastify/error` installation as dependency. CustomError has
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// FST_ERR_CUSTOM_ERROR as code.
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const { CustomError: CustomErrorFromPlugin } = require('@fastify/some-plugin')
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const CustomError = createError('FST_ERR_CUSTOM_ERROR', 'Hello %s', 500)
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const customError = new CustomError('world')
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const customErrorFromPlugin = new CustomErrorFromPlugin('world')
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console.log(customError instanceof CustomError) // true
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console.log(customError instanceof CustomErrorFromPlugin) // true
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console.log(customErrorFromPlugin instanceof CustomError) // true
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console.log(customErrorFromPlugin instanceof CustomErrorFromPlugin) // true
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```
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Changing the code of an instantiated Error will not change the result of the `instanceof` operator.
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```js
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const { createError, FastifyError } = require('@fastify/error')
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const CustomError = createError('ERROR_CODE', 'Hello %s', 500, TypeError)
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const AnotherCustomError = createError('ANOTHER_ERROR_CODE', 'Hello %s', 500, CustomError)
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const customError = new CustomError('world')
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customError.code = 'ANOTHER_ERROR_CODE'
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console.log(customError instanceof CustomError) // true
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console.log(customError instanceof AnotherCustomError) // false
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```
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## License
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Licensed under [MIT](./LICENSE).

‎index.js

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@@ -6,13 +6,23 @@ function toString () {
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return `${this.name} [${this.code}]: ${this.message}`
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}
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const FastifyGenericErrorSymbol = Symbol.for('fastify-error-generic')
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function createError (code, message, statusCode = 500, Base = Error, captureStackTrace = createError.captureStackTrace) {
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const shouldCreateFastifyGenericError = code === FastifyGenericErrorSymbol
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if (shouldCreateFastifyGenericError) {
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code = 'FST_ERR'
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}
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if (!code) throw new Error('Fastify error code must not be empty')
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if (!message) throw new Error('Fastify error message must not be empty')
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code = code.toUpperCase()
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!statusCode && (statusCode = undefined)
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const FastifySpecificErrorSymbol = Symbol.for(`fastify-error ${code}`)
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function FastifyError (...args) {
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if (!new.target) {
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return new FastifyError(...args)
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enumerable: false,
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writable: true,
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configurable: true
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},
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[FastifyGenericErrorSymbol]: {
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value: true,
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enumerable: false,
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writable: false,
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configurable: false
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},
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[FastifySpecificErrorSymbol]: {
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value: true,
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enumerable: false,
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writable: false,
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configurable: false
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}
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})
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if (shouldCreateFastifyGenericError) {
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Object.defineProperty(FastifyError, Symbol.hasInstance, {
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value (instance) {
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return instance && instance[FastifyGenericErrorSymbol]
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},
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configurable: false,
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writable: false,
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enumerable: false
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})
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} else {
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Object.defineProperty(FastifyError, Symbol.hasInstance, {
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value (instance) {
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return instance && instance[FastifySpecificErrorSymbol]
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},
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configurable: false,
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writable: false,
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enumerable: false
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})
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}
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FastifyError.prototype[Symbol.toStringTag] = 'Error'
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FastifyError.prototype.toString = toString
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createError.captureStackTrace = true
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const FastifyErrorConstructor = createError(FastifyGenericErrorSymbol, 'Fastify Error', 500, Error)
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module.exports = createError
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module.exports.FastifyError = FastifyErrorConstructor
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module.exports.default = createError
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module.exports.createError = createError

‎test/index.test.js

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'use strict'
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const test = require('node:test')
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const createError = require('..')
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const { createError, FastifyError } = require('..')
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test('Create error with zero parameter', (t) => {
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t.plan(6)
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t.assert.ok(err instanceof Error)
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t.assert.ifError(err.cause)
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})
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test('check if FastifyError is instantiable', (t) => {
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t.plan(2)
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const err = new FastifyError()
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t.assert.ok(err instanceof FastifyError)
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t.assert.ok(err instanceof Error)
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})

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