feat: function argument validation (#773)

BREAKING CHANGE: there's a good chance this will throw exceptions for a few folks who are using the API in an unexpected way.

lib/argsert.js

@@ -0,0 +1,66 @@
+const command = require('./command')()
+
+const positionName = ['first', 'second', 'third', 'fourth', 'fifth', 'sixth']
+
+module.exports = function (expected, callerArguments, length) {
+  // preface the argument description with "cmd", so
+  // that we can run it through yargs' command parser.
+  var position = 0
+  var parsed = {demanded: [], optional: []}
+  if (typeof expected === 'object') {
+    length = callerArguments
+    callerArguments = expected
+  } else {
+    parsed = command.parseCommand('cmd ' + expected)
+  }
+  const args = [].slice.call(callerArguments)
+
+  while (args.length && args[args.length - 1] === undefined) args.pop()
+  length = length || args.length
+
+  if (length < parsed.demanded.length) {
+    throw Error('Not enough arguments provided. Expected ' + parsed.demanded.length +
+      ' but received ' + args.length + '.')
+  }
+
+  const totalCommands = parsed.demanded.length + parsed.optional.length
+  if (length > totalCommands) {
+    throw Error('Too many arguments provided. Expected max ' + totalCommands +
+      ' but received ' + length + '.')
+  }
+
+  parsed.demanded.forEach(function (demanded) {
+    const arg = args.shift()
+    const observedType = guessType(arg)
+    const matchingTypes = demanded.cmd.filter(function (type) {
+      return type === observedType || type === '*'
+    })
+    if (matchingTypes.length === 0) argumentTypeError(observedType, demanded.cmd, position, false)
+    position += 1
+  })
+
+  parsed.optional.forEach(function (optional) {
+    if (args.length === 0) return
+    const arg = args.shift()
+    const observedType = guessType(arg)
+    const matchingTypes = optional.cmd.filter(function (type) {
+      return type === observedType || type === '*'
+    })
+    if (matchingTypes.length === 0) argumentTypeError(observedType, optional.cmd, position, true)
+    position += 1
+  })
+}
+
+function guessType (arg) {
+  if (Array.isArray(arg)) {
+    return 'array'
+  } else if (arg === null) {
+    return 'null'
+  }
+  return typeof arg
+}
+
+function argumentTypeError (observedType, allowedTypes, position, optional) {
+  throw Error('Invalid ' + (positionName[position] || 'manyith') + ' argument.' +
+    ' Expected ' + allowedTypes.join(' or ') + ' but received ' + observedType + '.')
+}

lib/command.js

@@ -28,9 +28,9 @@ module.exports = function (yargs, usage, validation) {
       return
     }
 
-    var parsedCommand = parseCommand(cmd)
+    var parsedCommand = self.parseCommand(cmd)
     aliases = aliases.map(function (alias) {
-      alias = parseCommand(alias).cmd // remove positional args
+      alias = self.parseCommand(alias).cmd // remove positional args
       aliasMap[alias] = parsedCommand.cmd
       return alias
     })
@@ -94,7 +94,7 @@ module.exports = function (yargs, usage, validation) {
     return false
   }
 
-  function parseCommand (cmd) {
+  self.parseCommand = function (cmd) {
     var extraSpacesStrippedCommand = cmd.replace(/\s{2,}/g, ' ')
     var splitCommand = extraSpacesStrippedCommand.split(/\s+(?![^[]*]|[^<]*>)/)
     var bregex = /\.*[\][<>]/g

lib/usage.js

@@ -235,7 +235,7 @@ module.exports = function (yargs, y18n) {
 
         var extra = [
           type,
-          demandedOptions[key] ? '[' + __('required') + ']' : null,
+          (key in demandedOptions) ? '[' + __('required') + ']' : null,
           options.choices && options.choices[key] ? '[' + __('choices:') + ' ' +
             self.stringifiedValues(options.choices[key]) + ']' : null,
           defaultString(options.default[key], options.defaultDescription[key])
@@ -330,7 +330,7 @@ module.exports = function (yargs, y18n) {
         // copy descriptions.
         if (descriptions[alias]) self.describe(key, descriptions[alias])
         // copy demanded.
-        if (demandedOptions[alias]) yargs.demandOption(key, demandedOptions[alias].msg)
+        if (alias in demandedOptions) yargs.demandOption(key, demandedOptions[alias])
         // type messages.
         if (~options.boolean.indexOf(alias)) yargs.boolean(key)
         if (~options.count.indexOf(alias)) yargs.count(key)

lib/validation.js

@@ -98,7 +98,7 @@ module.exports = function (yargs, usage, y18n) {
     if (missing) {
       const customMsgs = []
       Object.keys(missing).forEach(function (key) {
-        const msg = missing[key].msg
+        const msg = missing[key]
         if (msg && customMsgs.indexOf(msg) < 0) {
           customMsgs.push(msg)
         }

test/argsert.js

@@ -0,0 +1,98 @@
+/* global describe, it */
+
+const argsert = require('../lib/argsert')
+const expect = require('chai').expect
+
+require('chai').should()
+
+describe('Argsert', function () {
+  it('does not throw exception if optional argument is not provided', function () {
+    argsert('[object]', [].slice.call(arguments))
+  })
+
+  it('throws exception if wrong type is provided for optional argument', function () {
+    function foo (opts) {
+      argsert('[object|number]', [].slice.call(arguments))
+    }
+    expect(function () {
+      foo('hello')
+    }).to.throw(/Invalid first argument. Expected object or number but received string./)
+  })
+
+  it('does not throw exception if optional argument is valid', function () {
+    function foo (opts) {
+      argsert('[object]', [].slice.call(arguments))
+    }
+    foo({foo: 'bar'})
+  })
+
+  it('throws exception if required argument is not provided', function () {
+    expect(function () {
+      argsert('<object>', [].slice.call(arguments))
+    }).to.throw(/Not enough arguments provided. Expected 1 but received 0./)
+  })
+
+  it('throws exception if required argument is of wrong type', function () {
+    function foo (opts) {
+      argsert('<object>', [].slice.call(arguments))
+    }
+    expect(function () {
+      foo('bar')
+    }).to.throw(/Invalid first argument. Expected object but received string./)
+  })
+
+  it('supports a combination of required and optional arguments', function () {
+    function foo (opts) {
+      argsert('<array> <string|object> [string|object]', [].slice.call(arguments))
+    }
+    foo([], 'foo', {})
+  })
+
+  it('throws an exception if too many arguments are provided', function () {
+    function foo (expected) {
+      argsert('<array> [batman]', [].slice.call(arguments))
+    }
+    expect(function () {
+      foo([], 33, 99)
+    }).to.throw(/Too many arguments provided. Expected max 2 but received 3./)
+  })
+
+  it('configures function to accept 0 parameters, if only arguments object is provided', function () {
+    function foo (expected) {
+      argsert([].slice.call(arguments))
+    }
+    expect(function () {
+      foo(99)
+    }).to.throw(/Too many arguments provided. Expected max 0 but received 1./)
+  })
+
+  it('allows for any type if * is provided', function () {
+    function foo (opts) {
+      argsert('<*>', [].slice.call(arguments))
+    }
+    foo('bar')
+  })
+
+  it('should ignore trailing undefined values', function () {
+    function foo (opts) {
+      argsert('<*>', [].slice.call(arguments))
+    }
+    foo('bar', undefined, undefined)
+  })
+
+  it('should not ignore undefined values that are not trailing', function () {
+    function foo (opts) {
+      argsert('<*>', [].slice.call(arguments))
+    }
+    expect(function () {
+      foo('bar', undefined, undefined, 33)
+    }).to.throw(/Too many arguments provided. Expected max 1 but received 4./)
+  })
+
+  it('supports null as special type', function () {
+    function foo (arg) {
+      argsert('<null>', [].slice.call(arguments))
+    }
+    foo(null)
+  })
+})