Throw error when add option with clashing flags

[shadowspawn]

Pull Request

Problem

There are no warnings/errors for adding options with overlapping flags.

One of the "more usage errors" suggestion in a poll: #1978 (comment)

Solution

Throw an error from .option() or .addOption() if there are clashing flags.

This is building on #1923, and adds tests.

Example:

% node index.mjs
/Users/john/Documents/Sandpits/commander/my-fork/lib/command.js:552
      throw new Error(`Cannot add option '${option.flags}'${this._name && ` to command '${this._name}'`} due to conflicting flag '${matchingFlag}'
            ^

Error: Cannot add option '-e, --erase' to command 'main' due to conflicting flag '-e'
-  already used by option '-e, --example'
...

ChangeLog

• Breaking: throw an error if add an option with flags which are already in use

[abetomo]

LGTM

[yoyo837]

Is it possible to provide an option to allow adding flags with already in use options?

[shadowspawn]

There is not support for turning this off currently.

What is the use case @yoyo837 ? Why do you want to be able to add flags which are already in use?

[yoyo837]

When I combine different npm scripts,When I combine different npm scripts to call multiple nodejs files, they can be run separately or in combination:

it looks something like this:

{
  "scripts": {
    "s1": "npm run xxx --javaenv $javaenv",
    "s2": "npm run yyy --javaenv $javaenv",
    "s3": "npm run s1 && npm run s2 --javaenv $javaenv"
  }
}

[shadowspawn]

Sorry, I don't understand how the npm script example relates to your question.

This PR makes it an error if the author has overlapping option flags, like this where two options both use -a:

var program = new Command();
program
  .option('-a, --first')
  .option('-a, --second');

Is that what you want to turn off @yoyo837 ?