Checkjs implies allowjs

[sandersn]

If it's not explicitly provided.

Note that it's still an error to explicitly provide checkJs: true, allowJs: false.

This change makes the compiler options easier to use and to describe.

[sandersn]

@DanielRosenwasser @RyanCavanaugh @orta Do you think the new behaviour is reasonable?

@sheetalkamat @weswigham Is createProgram the right place to put this?

[weswigham]

For other defaulted flags dependent on other flags, we have something like a getStrictCompilerOptionValue helper that we use everywhere rather than checking the compiler options directly (no, I don't think createProgram handles all inputs - transpileModule is notable for probably being unaffected). You should probably add a getAllowJSCompilerOption helper that we use everywhere rather than checking the flags directly.

[sandersn]

I thought that might be the case. I switched to an accessor function getAllowJSCompilerOption instead.

[sheetalkamat]

This seems incorrect condition. You want to check if options.allowJs === false here instead

[sandersn]

Duh, thanks for the catch.

[sandersn]

No, wait, that undoes the loosening from this PR. THe current code only errors when checkJs: true but allowJs: false explicitly.

[ExE-Boss]

Suggested change

	if (options.checkJs && !getAllowJSCompilerOption(options)) {
	if (options.checkJs && options.allowJs === false) {

will also work and won’t require a function call.

[DanielRosenwasser]

I'm not so sure how I feel about this. But I can't think of any reason why it's bad.

[sandersn]

Chatted with @RyanCavanaugh, he couldn't either.

He also pointed out that maybe allowJs should default to true now. I'll investigate that next.