Minor code changes causing massive differences in compilation time/memory use

[aloker]

I'm running into very inconsistent memory use and compilation time when changing certain things in my code. A minor change in code can change my project from being compilable to causing out of memory issues and excessive build times.

TypeScript Version:
Tested with 1.7.5 and 1.8.9
rxjs 5.0.0-beta.2

Code

Variant 1:

import {Observable, ReplaySubject} from "rxjs/Rx";

export class Test {

  constructor() {
    // no types
    const changes$ = new ReplaySubject<number>(1);
    const editState$ = Observable.merge(Observable.of(true));

    Observable.combineLatest(
      editState$, changes$, // passed in as single arguments
      (edit:boolean, id:number) => {
        return {}
      });
  }
}

This compiles reasonably well, even though 1.7.5 is considerably faster:
Compiled with 1.7.5:

Files:              70
Lines:           25698
Nodes:          112017
Identifiers:     39588
Symbols:         53549
Types:           15397
I/O read:        0.17s
I/O write:       0.00s
Parse time:      0.57s
Bind time:       0.19s
Check time:      0.84s
Emit time:       0.02s
Total time:      1.62s

Compiled with 1.8.9

Files:              70
Lines:           25802
Nodes:          118578
Identifiers:     45679
Symbols:       1771501
Types:           13536
Memory used:    84667K
I/O read:        0.25s
I/O write:       0.02s
Parse time:      0.85s
Bind time:       0.55s
Check time:      1.67s
Emit time:       0.05s
Total time:      3.12s 

Variant 2

Instead of passing the observables to Observable.combineLatest as single arguments, I chose to pass them in as an array:

import {Observable, ReplaySubject} from "rxjs/Rx";

export class Test {

  constructor() {
    // no types
    const changes$ = new ReplaySubject<number>(1);
    const editState$ = Observable.merge(Observable.of(true));

    Observable.combineLatest(
      [editState$, changes$], // passed in as array
      (edit:boolean, id:number) => {
        return {}
      });
  }
}

Now compilation is MUCH slower using way more memory:

Compiled with 1.7.5:

Files:              70
Lines:           25698
Nodes:          112018
Identifiers:     39588
Symbols:        649435
Types:          366854
I/O read:        0.19s
I/O write:       0.00s
Parse time:      0.62s
Bind time:       0.21s
Check time:     11.12s
Emit time:       0.03s
Total time:     11.98s <--

Compiled with 1.8.9

Files:              70
Lines:           25802
Nodes:          118579
Identifiers:     45679
Symbols:       2367311
Types:          364975
Memory used:   531080K <-- 531M vs 84M
I/O read:        0.03s
I/O write:       0.02s
Parse time:      0.66s
Bind time:       0.55s
Check time:     15.70s
Emit time:       0.08s
Total time:     16.98s <--

Variant 3

If I give the two constants explicit types, things change again:

import {Observable, ReplaySubject} from "rxjs/Rx";

export class Test {

  constructor() {
    // with types
    const changes$:Observable<number> = new ReplaySubject<number>(1);
    const editState$:Observable<boolean> = Observable.merge(Observable.of(true));

    Observable.combineLatest(
      [editState$, changes$], // passed in as array
      (edit:boolean, id:number) => {
        return {}
      });
  }
}

It's still not as efficient as variant 1, but at least comparable
Compiled with 1.7.5:

Files:              70
Lines:           25698
Nodes:          112024
Identifiers:     39590
Symbols:         95917
Types:           41030
I/O read:        0.16s
I/O write:       0.00s
Parse time:      0.56s
Bind time:       0.18s
Check time:      1.13s
Emit time:       0.03s
Total time:      1.90s

Compiled with 1.8.9

Files:              70
Lines:           25802
Nodes:          118585
Identifiers:     45681
Symbols:       1813809
Types:           39154
Memory used:   112982K
I/O read:        0.08s
I/O write:       0.01s
Parse time:      0.64s
Bind time:       0.53s
Check time:      2.44s
Emit time:       0.06s
Total time:      3.67s

tsconfig.json used in all cases:

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "sourceMap": false
  },
  "exclude": [
    "node_modules",
    "typings/main.d.ts",
    "typings/main"
  ]
}

Typings

{
  "dependencies": {
    "es6-promise": "github:typed-typings/npm-es6-promise#fb04188767acfec1defd054fc8024fafa5cd4de7"
  },
  "ambientDependencies": {
    "es6-shim": "github:DefinitelyTyped/DefinitelyTyped/es6-shim/es6-shim.d.ts#4de74cb527395c13ba20b438c3a7a419ad931f1c"
  }
}

Is this expected behavior? Is there a way to get more consistent results?

P.S.: checked with 1.9.0-dev.20160321 with similar results.

[vladima]

Please see this comment.

[aloker]

Thanks. I must have missed the other issues. I'll close the issue for now.