Throw for likely option name problems

[shadowspawn]

Pull Request

One day we might change the default behaviour to make options safer! In the meantime, we can try harder to warn about possible problems.

Problem

While the default behaviour is to store options values as properties, people may hit issues with clashes with existing properties:

Collected issues: #933
Recent --name: #1226 #1282
Recent --no-emit: #1237

Solution

Throw an error if the user has not called storeOptionsAsProperties and the property matching the option is already defined.

Takes a reasonable amount of code to avoid incorrect warnings, but hopefully helps programmer resolve the problem.

ChangeLog

• throw an error with advice on how to resolve if there might be a clash between option name and a Command property

Example

program
  .option('-E,--no-emit')

...
      throw new Error(`option '${option.flags}' clashes with existing property '${option.attributeName()}' on Command
      ^

Error: option '--no-emit' clashes with existing property 'emit' on Command
- call storeOptionsAsProperties(false) to store option values safely,
- or call storeOptionsAsProperties(true) to suppress this check,
- or change option name
...

[shadowspawn]

Adding as draft for a few days in case I think of more cases to cover.

[shadowspawn]

Moved out of draft, ready for review.

[abetomo]

Thank you for all the great work you do.

[shadowspawn]

Thanks @abetomo