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F_SYSTEM_DUPLICATE_HANDLER

Duplicate handler registration

Two command definitions claim a handler role or token that must be unique within the same application scope.

Updated 2 weeks ago

Current versions keep this code for compatibility but emit F_SYSTEM_MULTIPLE_MAJOR_COMMANDS, F_SYSTEM_MULTIPLE_MISSING_COMMANDS, F_SYSTEM_DUPLICATE_COMMAND_TOKEN, F_SYSTEM_DUPLICATE_OPTION_TOKEN, or F_SYSTEM_MULTIPLE_DEFAULT_HANDLERS for the corresponding invariant.

Reproduction

Registering more than one major command is one way to trigger this error:

src/app.module.ts 
import { CommandMajor, FuncModule, Handler, run } from 'func'

@CommandMajor()
class FirstMajor {
  @Handler()
  run() {}
}

@CommandMajor()
class SecondMajor {
  @Handler()
  run() {}
}

@FuncModule({ commands: [FirstMajor, SecondMajor] })
class AppModule {}

run(AppModule)

What this error means

func found more than one owner for something that must be unique. The same code is also used when:

  • multiple missing-command handlers are registered;
  • command names or aliases collide;
  • field options, sub-options, or handler flags reuse an option token;
  • a command declares more than one default @Handler() method.

The error details normally includes the conflicting handlers, methods, or token.

How to fix it

Keep one major and one missing-command handler at most. Give every command and option a unique name and alias, and keep only one handler without a flag or path in each command. If the error includes a token, search for that exact token across field options, @SubOptions(), and method handlers.