Typescript: Better error message for missing member in tslib

[DanielRosenwasser]

@amcasey brought this up while upgrading Yammer to 3.6/3.7.

This syntax requires an imported helper named '__spreadArrays', but module 'tslib' has no exported member '__spreadArrays'.

The error message tells us something that is technically correct, but which is not clearly actionable. The user has no idea why __spreadArrays gets imported during an upgrade.

We should indicate that the user should try upgrading tslib.

This syntax requires an imported helper named '__spreadArrays' which does not exist in 'tslib'. Consider upgrading your version of 'tslib'.

[m-henderson]

@DanielRosenwasser did upgrading tslib fix the error?

[amcasey]

@m-henderson yep.

[m-henderson]

@amcasey @DanielRosenwasser it looks like there are a lot of places that the message is referenced:

Are we going to want to recommend a tslib upgraded on every instance of the message or only when tslib as no exported member of _spreadArrays ?

[DanielRosenwasser]

It should just be a matter of updating the message in diagnosticMessages.json, running gulp generate-diagnostics, updating the place where the error is issued in src, and accepting new error message baselines. Please check out our CONTRIBUTING.md at the root of the repo.

[m-henderson]

@DanielRosenwasser I opened a PR. Just let me know if any changes need to be made to it and I will take care of it.

https://github.com/microsoft/TypeScript/pull/33625

[DanielRosenwasser]

Thanks @m-henderson!

[m-henderson]

@DanielRosenwasser no problem! thank you for helping me out with the detailed comment :

It should just be a matter of updating the message in diagnosticMessages.json, running gulp generate-diagnostics, updating the place where the error is issued in src, and accepting new error message baselines. Please check out our CONTRIBUTING.md at the root of the repo.

[markterrill]

Thanks!
Upgraded to 1.10.0 and all ok.

My error had been for ionic / cordova and the android logcat error was:

"Uncaught TypeError: tslib.__spreadArrays is not a function"