Escapable commas in CLI options?

The commander argument parser for the --ignore option:
https://github.com/reactjs/react-docgen/blob/f5d644a3041c227c4889059e787fcbaab57ec70e/packages/react-docgen-cli/src/commands/parse/command.ts#L26-L39
https://github.com/reactjs/react-docgen/blob/f5d644a3041c227c4889059e787fcbaab57ec70e/packages/react-docgen-cli/src/commands/parse/command.ts#L62-L67

... splits on a comma, which makes it impossible to use glob brace expansion for this option or commas in general for any option that also uses this argument parser.

Would supporting escapable commas be possible?

To avoid breaking changes you may need to make it opt-in (behind a new option --comma-escaping or similar.)

The problem seems common enough and has been solved different ways in different languages. Here is a rough first pass after a little (very little) research:

/**
 * Split on commas (","), unless they are escaped with a backslash("\,").
 *
 * Escaped commas are replaced with individual commas.
 */
export function splitOnComma(str: string): string[] {
  if (typeof str !== 'string') {
    const errorMessage = 'input must be a string'
    throw new TypeError(errorMessage)
  }
  const DELIMETER = ','
  const ESCAPE_CHAR = '\\'
  const ESCAPED_DELIMETER = ESCAPE_CHAR + DELIMETER
  const hasEscapedDelimeter = str.includes(ESCAPED_DELIMETER)

  // Negative Lookbehind: https://www.regular-expressions.info/lookaround.html
  const result = str.split(/,(?<!\\,)/)

  if (hasEscapedDelimeter) {
    return result.map((subStr) => subStr.replace(/\\,/gi, DELIMETER))
  }
  return result
}

I don't have experience with negative lookbehinds. I wrote the example to favor being excessively self-documenting. Refinements could include:

• improved error message
• reducing the number of lines needed
• adding unit tests
• if the build tools are configured for ES2021+, String.prototype.replaceAll could be used instead.
  • subStr.replaceAll(ESCAPED_DELIMETER, DELIMETER))
• perform the replacement in fewer operations / general performance improvement

Start with the --ignore definitions and parsing flow in packages/react-docgen-cli/src/commands/parse/command.ts, then compare them with Commander’s argument-parser typings at the linked typings/index.d.ts lines. Determine how escaped commas should be enabled without changing existing comma splitting, and verify that --ignore accepts comma-containing values while ordinary values retain their current behavior.