Remove error on redundant isolatedModules/verbatimModuleSyntax combination

[andrewbranch]

This was intended to drive clarity, but doesn’t seem worth it since it’s caused a few problems.

Fixes #53601

[andrewbranch]

@typescript-bot cherry-pick to release-5.0

[typescript-bot]

Heya @andrewbranch, I've started to run the task to cherry-pick this into release-5.0 on this PR at f0bc7bd. You can monitor the build here.

[typescript-bot]

Hey @andrewbranch, I've opened #53612 for you.

[jakebailey]

Was there any code in transformModule that can now go away re: unsetting bad combos?

[fatcerberus]

Just for posterity, does this error also break the case I mentioned here? (base config with isolatedModules, extending config sets verbatimModuleSyntax) Because if so, there would probably be no workaround in the absence of this PR.

[andrewbranch]

Was there any code in transformModule that can now go away re: unsetting bad combos?

Very little, because the combo with importsNotUsedAsValues and preserveValueImports is still bad and has to be unset. I could have removed the unsetting of isolatedModules but it doesn’t really change anything.

Just for posterity, does this error also break the case I mentioned #53240 (comment)? (base config with isolatedModules, extending config sets verbatimModuleSyntax) Because if so, there would probably be no workaround in the absence of this PR.

That was never an error, IIUC. I was careful to make it an error to specify the old options on top of the new options but not vice versa. You could extend a config with isolatedModules and apply verbatimModuleSyntax because the latter does more than the former.

[fatcerberus]

That was never an error, IIUC.

thanks, I wouldn’t have suspected there was asymmetry in the implementation between the “base” options and “extended” options - I figured the two configs were just merged to get the effective config, since that seems the most obvious implementation.