fix: detect the correct flag syntax in all cases

src/command.ts

@@ -11,6 +11,7 @@ import {
   NEGATE_FULL_PREFIX,
   OPT_SHORT_PREFIX,
   NEGATE_SHORT_PREFIX,
+  Prefixes,
 } from './option'
 import { DeepRequired, setOrPush, deepMerge } from './utils'
 import { MassargExample, ExampleConfig } from './example'
@@ -97,6 +98,15 @@ export class MassargCommand<Args extends ArgsObject = ArgsObject> {
     this.parent = parent
   }
 
+  get optionPrefixes(): Prefixes {
+    return {
+      optionPrefix: this.optionPrefix,
+      aliasPrefix: this.optionAliasPrefix,
+      negateFlagPrefix: this.negateFlagPrefix,
+      negateAliasPrefix: this.negateAliasPrefix,
+    }
+  }
+
   get helpConfig(): DeepRequired<HelpConfig> {
     if (this.parent) {
       return deepMerge(this.parent.helpConfig, this._helpConfig)
@@ -310,10 +320,10 @@ export class MassargCommand<Args extends ArgsObject = ArgsObject> {
   }
 
   private parseOption(arg: string, argv: string[]) {
-    const option = this.options.find((o) => o._match(arg))
+    const option = this.options.find((o) => o._match(arg, this.optionPrefixes))
     if (!option) {
       throw new ValidationError({
-        path: [MassargOption.getName(arg)],
+        path: [MassargOption.findNameInArg(arg, this.optionPrefixes)],
         code: 'unknown_option',
         message: 'Unknown option',
       })
@@ -367,7 +377,7 @@ export class MassargCommand<Args extends ArgsObject = ArgsObject> {
     while (_argv.length) {
       const arg = _argv.shift()!
       // make sure option exists
-      const found = this.options.some((o) => o._isOption(arg))
+      const found = this.options.some((o) => o._isOption(arg, this.optionPrefixes))
       if (found) {
         _argv = this.parseOption(arg, _argv)
         _args = { ..._args, ...this.args }

src/help.ts

@@ -254,7 +254,7 @@ export class HelpGenerator {
           usageText
             ? strConcat(
               format('Usage:', this.config.usageStyle.prefix),
-              format(usageText, this.config.usageStyle.command),
+              format(usageText, this.config.usageStyle.main),
             )
             : [
               format(`Usage:`, this.config.usageStyle.prefix),

src/option.ts

@@ -50,6 +50,14 @@ export type OptionConfig<T = unknown, Args extends ArgsObject = ArgsObject> = z.
   ReturnType<typeof OptionConfig<T, Args>>
 >
 
+export const FlagConfig = OptionConfig<boolean>(z.any()).merge(
+  z.object({
+    /** Whether the flag can be negated, e.g. `--no-verbose` */
+    negatable: z.boolean().optional(),
+  }),
+)
+export type FlagConfig = z.infer<typeof FlagConfig>
+
 export type Parser<Args extends ArgsObject = ArgsObject, OptionType extends any = any> = (
   x: string,
   y: Args,
@@ -94,6 +102,13 @@ export const OPT_SHORT_PREFIX = '-'
 export const NEGATE_FULL_PREFIX = 'no-'
 export const NEGATE_SHORT_PREFIX = '^'
 
+export type Prefixes = {
+  optionPrefix: string
+  aliasPrefix: string
+  negateFlagPrefix: string
+  negateAliasPrefix: string
+}
+
 /** @internal */
 export type ArgvValue<T> = { argv: string[]; value: T; key: string }
 
@@ -191,29 +206,11 @@ export class MassargOption<OptionType extends any = unknown, Args extends ArgsOb
     return `--${this.name}${aliases} ${this.description}`
   }
 
-  _match(arg: string): boolean {
-    if (!arg) return false
-    // full prefix
-    if (arg.startsWith(OPT_FULL_PREFIX)) {
-      // negate full prefix
-      if (arg.startsWith(`--${NEGATE_FULL_PREFIX}`)) {
-        return this.name === arg.slice(`--${NEGATE_FULL_PREFIX}`.length)
-      }
-      return this.name === arg.slice(OPT_FULL_PREFIX.length)
-    }
-    // short prefix
-    if (arg.startsWith(OPT_SHORT_PREFIX) || arg.startsWith(NEGATE_SHORT_PREFIX)) {
-      return this.aliases.includes(arg.slice(OPT_SHORT_PREFIX.length))
-    }
-    // negate short prefix
-    if (arg.startsWith(NEGATE_SHORT_PREFIX)) {
-      return this.aliases.includes(arg.slice(NEGATE_SHORT_PREFIX.length))
-    }
-    // no prefix
-    return false
+  _match(arg: string, prefixes: Prefixes): boolean {
+    return MassargOption.findNameInArg(arg, prefixes) !== '<blank>'
   }
 
-  _isOption(arg: string): boolean {
+  _isOption(arg: string, prefixes: Prefixes): boolean {
     return (
       arg.startsWith(OPT_FULL_PREFIX) ||
       arg.startsWith(OPT_SHORT_PREFIX) ||
@@ -221,21 +218,25 @@ export class MassargOption<OptionType extends any = unknown, Args extends ArgsOb
     )
   }
 
-  static getName(arg: string): string {
-    if (arg.startsWith(OPT_FULL_PREFIX)) {
+  static findNameInArg(
+    arg: string,
+    prefixes: Prefixes,
+  ): string {
+    const { optionPrefix, aliasPrefix, negateFlagPrefix, negateAliasPrefix } = prefixes
+    if (arg.startsWith(optionPrefix)) {
       // negate full prefix
-      if (arg.startsWith(`--${NEGATE_FULL_PREFIX}`)) {
-        return arg.slice(`--${NEGATE_FULL_PREFIX}`.length)
+      if (arg.startsWith(`--${negateFlagPrefix}`)) {
+        return arg.slice(`--${negateFlagPrefix}`.length)
       }
-      return arg.slice(OPT_FULL_PREFIX.length)
+      return arg.slice(optionPrefix.length)
     }
     // short prefix
-    if (arg.startsWith(OPT_SHORT_PREFIX) || arg.startsWith(NEGATE_SHORT_PREFIX)) {
-      return arg.slice(OPT_SHORT_PREFIX.length)
+    if (arg.startsWith(aliasPrefix) || arg.startsWith(negateAliasPrefix)) {
+      return arg.slice(aliasPrefix.length)
     }
     // negate short prefix
-    if (arg.startsWith(NEGATE_SHORT_PREFIX)) {
-      return arg.slice(NEGATE_SHORT_PREFIX.length)
+    if (arg.startsWith(negateAliasPrefix)) {
+      return arg.slice(negateAliasPrefix.length)
     }
     return '<blank>'
   }
@@ -300,7 +301,7 @@ export class MassargNumber extends MassargOption<number> {
  *
  * A flag can be negated by prefixing it with `no-`. For example, `--no-verbose`,
  * or by prefixing the alias with `^` instead of `-`. This is configurable via the command's
- * configuration.
+ * configuration. To turn this behavior on, set `negatable: true` in the flag's configuration.
  *
  * @example
  * ```ts
@@ -313,11 +314,14 @@ export class MassargNumber extends MassargOption<number> {
  * ```
  */
 export class MassargFlag extends MassargOption<boolean> {
-  constructor(options: Omit<OptionConfig<boolean>, 'parse'>) {
+  negatable: boolean
+
+  constructor(options: FlagConfig) {
     super({
       ...options,
       parse: () => true as any,
     })
+    this.negatable = options.negatable ?? false
   }
 
   _parseDetails(argv: string[]): ArgvValue<boolean> {