Project compiles OK but hangs when --watch is added

TypeScript Version: 3.0.0-dev.20180616 and 2.9.2

Search Terms: typescript watch --watch hangs stalls slow

Hi I have minimized one of my projects to an example source (which I have attached [1]) that:

1. Compile fine when not using watch mode (takes about 5 seconds to compile on my machine)
2. Hangs the compiler when using watch mode (doesn’t complete it’s compile).

To compile the example:

1. download the zip and unzip it and enter that directory
2. run yarn install to add the project’s deps. 3a. run yarn tsc-ok for the example where it does compile 3b. run yarn tsc-bad for the example where it doesn’t

BTW: Is there some way for me to tell the compiler to dump out the source files it is processing as it processes them? It would be extremely helpful for tracking this down to the specific issue.

1: Source Code: tsc-watch-hangs.zip

[Bnaya]

Hey @benjaminjackman @pelotom I’m struggling with similar issues

Something that really helped with spinning up watch is to mask MST models behind interfaces, especially for composited models. (is a similar manner to your examples )

i didn’t check how its effect decelerations emits, just tsc -w startup times (from forever to 10 secs) and im still playing with it.

A quick and minimal example:

export type ForDirectExtend<T> = T;

const MyAModelInferred = types.model("MyAModel", {
  items: types.array(types.string)
});

interface MyAModelType extends ForDirectExtend<typeof MyAModelInferred> {}

// now MyAModel is fast!
const MyAModel: MyAModelType = MyAModelInferred;


// Now even MyBModelInferred is not very slow, becouse its referencing the "fast" MyAModel and not the inferred thing
const MyBModelInferred = types.model("MyBModel", {
  somethingsomething: types.map(MyAModel)
});

interface MyBModelType extends ForDirectExtend<typeof MyBModelInferred> {}

const MyBModel: MyBModelType = MyBModelInferred;

And if we could hint typescript to create intermediate type names instead all of it, that would be great!

[benjaminjackman]

I made a gist that describes how to use chokidar to call tsc --noEmit whenever a file changes in case anyone stumbles into this ticket: