Added support for custom validation

Author: coreybutler

README.md

@@ -143,7 +143,8 @@ Args.configure({
     type: string_or_primitive, // example: 'boolean' or Boolean
     alias: string,
     allowMultipleValues: true/false,
-    options: [...]
+    options: [...],
+    validate: function(){}/RegExp
   }, {
     ...
   }
@@ -159,6 +160,7 @@ _Purpose:_
 - `aliases` - Support for multiple aliases.
 - `allowMultipleValues` - If a flag is specified more than once, capture all values (instead of only the last one specified).
 - `options` - An array of valid values for the flag.
+- `validate` - This is a function or regular expression that determines whether the value of the flag is valid or not. A function receives the value as the only argument and is expected to return `true` or `false` (where `true` means the value is valid). If a RegExp is provided, the [RegExp.test()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/test) method is executed against the flag value. The validate feature is used **in addition** to other validation mechanisms (options, typing, etc).
 
 ### Using Individual Methods
 

flag.js

@@ -12,6 +12,7 @@ export default class Flag {
   #value = null
   #violations = new Set()
   #recognized = false
+  #validator = null
 
   constructor (cfg = {}) {
     if (typeof cfg === 'string') {
@@ -60,6 +61,14 @@ export default class Flag {
     if (cfg.hasOwnProperty('options')) {
       this.options = cfg.options
     }
+
+    if (cfg.hasOwnProperty('validate')) {
+      if (!(cfg.validate instanceof RegExp || typeof cfg.validate === 'function')) {
+        throw new Error(`The "validate" configuration attribute for ${this.#rawName} is invalid. Only RegExp and functions are supported (received ${typeof cfg.validate})`)
+      }
+
+      this.#validator = cfg.validate
+    }
   }
 
   get inputName () {
@@ -124,6 +133,25 @@ export default class Flag {
         }
       }
     }
+
+    if (this.#validator !== null) {
+      if (typeof this.#validator === 'function') {
+        if (!this.#validator(value)) {
+          this.#violations.add(`"${value}" is invalid (failed custom validation).`)
+          return false
+        }
+      } else {
+        if (typeof value !== 'string' && this.#validator instanceof RegExp) {
+          this.#violations.add(`"${value}" is invalid (failed custom validation).`)
+          return false
+        }
+
+        if (!this.#validator.test(value)) {
+          this.#violations.add(`"${value}" is invalid (failed custom validation).`)
+          return false
+        }
+      }
+    }
 
     return true
   }

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@author.io/arg",
-  "version": "1.2.6",
+  "version": "1.3.0",
   "description": "An argument parser for CLI applications.",
   "main": "index.js",
   "scripts": {

package.json

@@ -21,5 +21,46 @@ test('Escaped parameters', t => {
     , 'Parsed complex input'
   )
 
+  console.log(new Parser('cfw run -r -hdr "CF-IPCountry=US" -kv "test=something" -kv "a=test" demo.js', {
+    kv: {
+      allowMultipleValues: true
+    },
+    header: {
+      alias: 'hdr',
+      allowMultipleValues: true
+    }
+  }).data)
+
+  t.end()
+})
+
+test('Support custom validation methods', t => {
+  const input = 'test -v ok -b notok'
+  const cfg = {
+    value: {
+      alias: 'v',
+      validate: value => value === 'ok'
+    }
+  }
+
+  let Args = new Parser(input, cfg)
+  t.ok(Args.violations.length === 0, `Expected no violations, recognized ${Args.violations.length}.`)
+
+  cfg.bad = {
+    alias: 'b',
+    validate: value => value === 'ok'
+  }
+
+  Args = new Parser(input, cfg)
+  t.ok(Args.violations.length === 1, `Expected 1 violation, recognized ${Args.violations.length}.`)
+
+  Args = new Parser('test --pass abbbbc', {
+    pass: {
+      validate: /^a.*c$/gi
+    }
+  })
+
+  t.ok(Args.violations.length === 0, `Expected no violations, recognized ${Args.violations.length}.`)
+
   t.end()
 })