Prevent aliases already in use and subcommands with such an alias or the name already in use from being added

[aweebit]

Pull Request

Problem

Adding aliases that are already in use and subcommands with such an alias or the name that is already in use is allowed.

Demo

program.command('sub').action(() => console.log('first'));
program.command('sub').action(() => console.log('second'));
program.parse(['sub'], { from: 'user' }); // output will always be first

program.command('sub').action(() => console.log('first'));
const explicit = new Command('explicit')
  .alias('sub')
  .action(() => console.log('second'));
program.addCommand(explicit);
program.parse(['sub'], { from: 'user' }); // output will always be first

program.command('sub');
const explicit = new Command('explicit');
program.addCommand(explicit);
explicit.alias('sub'); // does not throw

Original issue

• Commander unsafely allows commands with duplicate names to be registered #1903

ChangeLog

Changed

• Breaking: throw an error when trying to add a subcommand with a name or an alias that is already in use
• Breaking: throw an error when trying to add an alias that is already in use to a subcommand

Peer PRs

…solving similar problems

• Prevent options with flags already in use from being added #1923

[shadowspawn]

I had done some thinking when issue first added, and aliases are a complication. With current PR code aliases on the first command get checked when the second command is added. But I think not vice versa.

Some possibilities:

• don't worry, covered much more than before!
• do the whole conflict command check from start of parse rather than as command added (this is reasonable, just slightly annoying to mix logic). Still highly likely to be detected by author rather than found by end-user, plugins excepted.
• check at runtime and throw if ambiguous name used (bad, because depends on parameters used so may be missed by author. But mentioned it because I considered it!)

[aweebit]

I had done some thinking when issue first added, and aliases are a complication. With current PR code aliases on the first command get checked when the second command is added. But I think not vice versa.

Some possibilities:

• don't worry, covered much more than before!
• do the whole conflict command check from start of parse rather than as command added (this is reasonable, just slightly annoying to mix logic). Still highly likely to be detected by author rather than found by end-user, plugins excepted.
• check at runtime and throw if ambiguous name used (bad, because depends on parameters used so may be missed by author. But mentioned it because I considered it!)

I have come up with a better solution, check bd12c90 and the updated PR description.

[aweebit]

I have come up with a better solution, check bd12c90 and the updated PR description.

My suggestion from the first comment in #1917 enabling sharing and stand-alone use of subcommands won't work if this change is accepted, though. If we decide to implement the suggestion, the checks will have to be done at the beginning of parse calls as you suggested, which I honestly don't like because parse calls are only supposed to throw exceptions from user code (argParsers, hooks, actions), so might be a good idea to just dump that suggestion of mine.

Update: There will be no problem if all parent commands are stored, see #1938 for an implementation. When that PR is merged, the check in alias() will simply have to iterate over all of them.

[shadowspawn]

The way commands with alias get displayed in the help is like one|1, so a compact way to describe command name and an alias.

I tried a rework to use that form in error messages:

  _checkForConflictingCommandNames(name, aliases = []) {
    let newKey;
    let oldKey;
    const makeKey = (nameOrAlias, matchingCommand) => {
      if (nameOrAlias === matchingCommand.name()) return nameOrAlias;
      return `${matchingCommand.name()}|${nameOrAlias}`;
    };
    let matchingCommand = this._findCommand(name);
    if (matchingCommand) {
      newKey = name;
      oldKey = makeKey(name, matchingCommand);
    } else {
      const alias = aliases.find((alias) => {
        matchingCommand = this._findCommand(alias);
        return matchingCommand;
      });
      if (matchingCommand) {
        newKey = `${name}|${alias}`;
        oldKey = makeKey(alias, matchingCommand);
      }
    }
    if (matchingCommand) {
      throw new Error(`Cannot add command '${newKey}'${this._name && ` to '${this._name}'`} since command '${oldKey}' has already been added`);
    }
  }

Example error when use addCommand() and alias clashes with alias :

Error: Cannot add command 'three|1' since command 'one|1' has already been added

[shadowspawn]

Closing in favour of #2059 (added co-author on that PR).