yargs.option("version") is admitted, but fails silently

[JJ]

Using something like:

yargs.option("version", {
                type: "string",
                default: "0.0.1",
                describe: "→ Version string for the package.json",
            });

Will not raise any kind of error or warning, but it will make parsing fail and print the version string instead.

[bcoe]

@jly36963 didn't you do some work in this area already, regarding warning when version was used in unexpected ways?

[RoBorg]

I just came across basically the same issue, but using a positional:

import yargs from 'yargs';

yargs(process.argv.slice(2))
    .command(
        'install [version]',
        'Install a thing',
        (yargs) => { yargs.positional('version', { default: 'hello' }) },
        (argv) => console.log(`Installing ${argv.version}`)
    ).parse();

The problem seems to be when you add a default - if this is omitted then the warning is correctly shown.

[shadowspawn]

A warning about a name collision with the default version option got added in #1986. Unfortunately, it turns out process.emitWarning() is not synchronous so the process.exit() called after showing the version terminates the program before the warning is displayed!

By default, whenever a warning is issued using process.emitWarning(), Node.js will print that warning to stderr on process.nextTick().

https://medium.com/@jasnell/introducing-process-warnings-in-node-v6-3096700537ee

[shadowspawn]

The warning (which should have been displayed) explains the issue and possible work-arounds:

(node:31602) Warning: "version" is a reserved word.
Please do one of the following:
- Disable version with `yargs.version(false)` if using "version" as an option
- Use the built-in `yargs.version` method instead (if applicable)
- Use a different option key

[shadowspawn]

(I will re-label this as a bug since the warning is not appearing in some circumstances.)

[shadowspawn]

@RoBorg correctly identified the additional factor which means the warning does not get displayed.

When the author supplied version option or positional has a default value, this triggers the built-in version handler which assumes the user has specified --version and so displays the version and exits.