Fix noFallthroughCasesInSwitch/jsx object is not extensible

[ryota-murakami]

Relative Issues #9868 #9429

I fixed broken yarn start that cause react-scripts can't handle correctly noFallthroughCasesInSwitch and jsx compileOptions.

Thank you for your decent review 😀

[mrmckeb]

@iansu @ianschmitz I've had this reported to me privately too, this seems like a change to the behaviour of ts.readConfigFile where the object is no longer extensible.

[mrmckeb]

Re-running CI.

[benneq]

@ryota-murakami Have you check the inner properties of compilerOptions? Those should be frozen, too. Though a simple appTsConfig.compilerOptions = { ...appTsConfig.compilerOptions }; might not work.

[ryota-murakami]

@benneq @KonstantinSimeonov I'm sorry for slow response.

Have you check the inner properties of compilerOptions? Those should be frozen, too. Though a simple appTsConfig.compilerOptions = { ...appTsConfig.compilerOptions }; might not work.

I've checked inner properties of compilerOptions are frozen.
Bellow screenshot showing Object.isFrozen(appTsConfig.compilerOptions.module) return true after destructured property of appTsConfig.compilerOptions on new Object.

And I'll share video clip that recorded running bellow code without Error.

  if (appTsConfig.compilerOptions == null) {
    appTsConfig.compilerOptions = {};
    firstTimeSetup = true;
  } else {
    appTsConfig.compilerOptions = { ...appTsConfig.compilerOptions };
    for(const option in appTsConfig.compilerOptions) {
      if (!Object.isFrozen(option)) new Error('appTsConfig.compilerOptions option should be frozen')
    }
  }

https://www.dropbox.com/s/912pp3xudr9rn9s/Screen%20Recording%202020-10-30%20at%2021.40.54.mov?dl=0

[KonstantinSimeonov]

@ryota-murakami

    for(const option in appTsConfig.compilerOptions) {
      if (!Object.isFrozen(option)) new Error('appTsConfig.compilerOptions option should be frozen')
    }

This is iterating over the keys of the object, which are strings and are always frozen and is not checking whether the properties are frozen or not 😛 . I think @benneq 's idea was to make sure that no crashes would occur if any of appTsConfig.compilerOptions's properties is frozen. Although I think that this is unlikely, you can safeguard against it by deep cloning the whole object.

[ryota-murakami]

@KonstantinSimeonov Thanks, that iterator is garbage 😅
And merge your suggested solution. I confirm that working.

But I don't understand why guys care about property frozen status?
This problem root is Object isn't extensible, co script couldn't add suggested config.
I think it doesn't matter frozen status 🤔

[ianschmitz]

Thanks folks!

[ryota-murakami]

@benneq @KonstantinSimeonov I got it why should we handle isFroze() result of each compileOptions.
If isFroze(someOption) === true and original config from reading files value is different from CRA suggested,
the script couldn't apply change to suggested value.

Thank you for your support about this PR!

[vegawong]

@ianschmitz should it make a new release version?

[cseas]

Can we please have a release with this fix? The problem is occurring for a lot of people in #9868