Add support for allowNegative ("--no-foo")

README.md

@@ -16,7 +16,7 @@ changes:
                  using `tokens` in input `config` and returned properties.
 -->
 
-> Stability: 1 - Experimental
+> Stability: 2 - Stable
 
 * `config` {Object} Used to provide arguments for parsing and to configure
   the parser. `config` supports the following properties:
@@ -40,6 +40,9 @@ changes:
   * `allowPositionals` {boolean} Whether this command accepts positional
     arguments.
     **Default:** `false` if `strict` is `true`, otherwise `true`.
+  * `allowNegative` {boolean} If `true`, allows explicitly setting boolean
+    options to `false` by prefixing the option name with `--no-`.
+    **Default:** `false`.
   * `tokens` {boolean} Return the parsed tokens. This is useful for extending
     the built-in behavior, from adding additional checks through to reprocessing
     the tokens in different ways.
@@ -125,9 +128,9 @@ that appear more than once in args produce a token for each use. Short option
 groups like `-xy` expand to a token for each option. So `-xxx` produces
 three tokens.
 
-For example to use the returned tokens to add support for a negated option
-like `--no-color`, the tokens can be reprocessed to change the value stored
-for the negated option.
+For example, to add support for a negated option like `--no-color` (which
+`allowNegative` supports when the option is of `boolean` type), the returned
+tokens can be reprocessed to change the value stored for the negated option.
 
 ```mjs
 import { parseArgs } from 'node:util';

index.js

@@ -1,5 +1,7 @@
 'use strict';
 
+/* eslint max-len: ["error", {"code": 120}], */
+
 const {
   ArrayPrototypeForEach,
   ArrayPrototypeIncludes,
@@ -95,14 +97,24 @@ To specify an option argument starting with a dash use ${example}.`;
  * @param {object} token - from tokens as available from parseArgs
  */
 function checkOptionUsage(config, token) {
-  if (!ObjectHasOwn(config.options, token.name)) {
-    throw new ERR_PARSE_ARGS_UNKNOWN_OPTION(
-      token.rawName, config.allowPositionals);
+  let tokenName = token.name;
+  if (!ObjectHasOwn(config.options, tokenName)) {
+    // Check for negated boolean option.
+    if (config.allowNegative && StringPrototypeStartsWith(tokenName, 'no-')) {
+      tokenName = StringPrototypeSlice(tokenName, 3);
+      if (!ObjectHasOwn(config.options, tokenName) || optionsGetOwn(config.options, tokenName, 'type') !== 'boolean') {
+        throw new ERR_PARSE_ARGS_UNKNOWN_OPTION(
+          token.rawName, config.allowPositionals);
+      }
+    } else {
+      throw new ERR_PARSE_ARGS_UNKNOWN_OPTION(
+        token.rawName, config.allowPositionals);
+    }
   }
 
-  const short = optionsGetOwn(config.options, token.name, 'short');
-  const shortAndLong = `${short ? `-${short}, ` : ''}--${token.name}`;
-  const type = optionsGetOwn(config.options, token.name, 'type');
+  const short = optionsGetOwn(config.options, tokenName, 'short');
+  const shortAndLong = `${short ? `-${short}, ` : ''}--${tokenName}`;
+  const type = optionsGetOwn(config.options, tokenName, 'type');
   if (type === 'string' && typeof token.value !== 'string') {
     throw new ERR_PARSE_ARGS_INVALID_OPTION_VALUE(`Option '${shortAndLong} <value>' argument missing`);
   }
@@ -115,17 +127,25 @@ function checkOptionUsage(config, token) {
 
 /**
  * Store the option value in `values`.
- *
- * @param {string} longOption - long option name e.g. 'foo'
- * @param {string|undefined} optionValue - value from user args
+ * @param {object} token - from tokens as available from parseArgs
  * @param {object} options - option configs, from parseArgs({ options })
  * @param {object} values - option values returned in `values` by parseArgs
+ * @param {boolean} allowNegative - allow negative optinons if true
  */
-function storeOption(longOption, optionValue, options, values) {
+function storeOption(token, options, values, allowNegative) {
+  let longOption = token.name;
+  let optionValue = token.value;
   if (longOption === '__proto__') {
     return; // No. Just no.
   }
 
+  if (allowNegative && StringPrototypeStartsWith(longOption, 'no-') && optionValue === undefined) {
+    // Boolean option negation: --no-foo
+    longOption = StringPrototypeSlice(longOption, 3);
+    token.name = longOption;
+    optionValue = false;
+  }
+
   // We store based on the option value rather than option type,
   // preserving the users intent for author to deal with.
   const newValue = optionValue ?? true;
@@ -295,15 +315,17 @@ const parseArgs = (config = kEmptyObject) => {
   const strict = objectGetOwn(config, 'strict') ?? true;
   const allowPositionals = objectGetOwn(config, 'allowPositionals') ?? !strict;
   const returnTokens = objectGetOwn(config, 'tokens') ?? false;
+  const allowNegative = objectGetOwn(config, 'allowNegative') ?? false;
   const options = objectGetOwn(config, 'options') ?? { __proto__: null };
   // Bundle these up for passing to strict-mode checks.
-  const parseConfig = { args, strict, options, allowPositionals };
+  const parseConfig = { args, strict, options, allowPositionals, allowNegative };
 
   // Validate input configuration.
   validateArray(args, 'args');
   validateBoolean(strict, 'strict');
   validateBoolean(allowPositionals, 'allowPositionals');
   validateBoolean(returnTokens, 'tokens');
+  validateBoolean(allowNegative, 'allowNegative');
   validateObject(options, 'options');
   ArrayPrototypeForEach(
     ObjectEntries(options),
@@ -365,7 +387,7 @@ const parseArgs = (config = kEmptyObject) => {
         checkOptionUsage(parseConfig, token);
         checkOptionLikeValue(token);
       }
-      storeOption(token.name, token.value, options, result.values);
+      storeOption(token, options, result.values, parseConfig.allowNegative);
     } else if (token.kind === 'positional') {
       if (!allowPositionals) {
         throw new ERR_PARSE_ARGS_UNEXPECTED_POSITIONAL(token.value);

test/allow-negative.js

@@ -0,0 +1,75 @@
+/* global assert */
+/* eslint max-len: 0 */
+'use strict';
+
+const { test } = require('./utils');
+const { parseArgs } = require('../index');
+
+test('disable negative options and args are started with "--no-" prefix', () => {
+  const args = ['--no-alpha'];
+  const options = { alpha: { type: 'boolean' } };
+  assert.throws(() => {
+    parseArgs({ args, options });
+  }, {
+    code: 'ERR_PARSE_ARGS_UNKNOWN_OPTION'
+  });
+});
+
+test('args are passed `type: "string"` and allow negative options', () => {
+  const args = ['--no-alpha', 'value'];
+  const options = { alpha: { type: 'string' } };
+  assert.throws(() => {
+    parseArgs({ args, options, allowNegative: true });
+  }, {
+    code: 'ERR_PARSE_ARGS_UNKNOWN_OPTION'
+  });
+});
+
+test('args are passed `type: "boolean"` and allow negative options', () => {
+  const args = ['--no-alpha'];
+  const options = { alpha: { type: 'boolean' } };
+  const expected = { values: { __proto__: null, alpha: false }, positionals: [] };
+  assert.deepStrictEqual(parseArgs({ args, options, allowNegative: true }), expected);
+});
+
+test('args are passed `default: "true"` and allow negative options', () => {
+  const args = ['--no-alpha'];
+  const options = { alpha: { type: 'boolean', default: true } };
+  const expected = { values: { __proto__: null, alpha: false }, positionals: [] };
+  assert.deepStrictEqual(parseArgs({ args, options, allowNegative: true }), expected);
+});
+
+test('args are passed `default: "false" and allow negative options', () => {
+  const args = ['--no-alpha'];
+  const options = { alpha: { type: 'boolean', default: false } };
+  const expected = { values: { __proto__: null, alpha: false }, positionals: [] };
+  assert.deepStrictEqual(parseArgs({ args, options, allowNegative: true }), expected);
+});
+
+test('allow negative options and multiple as true', () => {
+  const args = ['--no-alpha', '--alpha', '--no-alpha'];
+  const options = { alpha: { type: 'boolean', multiple: true } };
+  const expected = { values: { __proto__: null, alpha: [false, true, false] }, positionals: [] };
+  assert.deepStrictEqual(parseArgs({ args, options, allowNegative: true }), expected);
+});
+
+test('allow negative options and passed multiple arguments', () => {
+  const args = ['--no-alpha', '--alpha'];
+  const options = { alpha: { type: 'boolean' } };
+  const expected = { values: { __proto__: null, alpha: true }, positionals: [] };
+  assert.deepStrictEqual(parseArgs({ args, options, allowNegative: true }), expected);
+});
+
+test('auto-detect --no-foo as negated when strict:false and allowNegative', () => {
+  const holdArgv = process.argv;
+  process.argv = [process.argv0, 'script.js', '--no-foo'];
+  const holdExecArgv = process.execArgv;
+  process.execArgv = [];
+  const result = parseArgs({ strict: false, allowNegative: true });
+
+  const expected = { values: { __proto__: null, foo: false },
+                     positionals: [] };
+  assert.deepStrictEqual(result, expected);
+  process.argv = holdArgv;
+  process.execArgv = holdExecArgv;
+});