fix(@ngtools/webpack): fix compilation not working properly with webpack-dev-server

[ryanclark]

When using @ngtools/webpack with webpack-dev-server, the AoT compiler would use a program created from the last build, causing files not to compile unless the process was restarted or another build was triggered.

Creating a new program just before compilation from the old program to grab the latest source code fixes this.

Fixes #3084

[ryanclark]

Also fixes #2576

[hansl]

@filipesilva please check this. We need to be aware of performance impacting PRs such as this one. We already rebuild the program and re-rebuild it a second time might be a problem.

[filipesilva]

@hansl benchmark over master:

Angular-CLI Benchmark
Extra flags per benchmark: --aot
Iterations per benchmark: 5

=========================================
Base command: ng serve --no-progress
Comment: third rebuild time

Full command: ng serve --no-progress
Average time: 1396
Results: 1401,1385,1397,1392,1405

Full command: ng serve --no-progress --aot
Average time: 2895.6
Results: 2873,2935,2857,2963,2850

Benchmark execution time: 182722.018ms

Benchmark with these changes:

Angular-CLI Benchmark
Extra flags per benchmark: --aot
Iterations per benchmark: 5

=========================================
Base command: ng serve --no-progress
Comment: third rebuild time

Full command: ng serve --no-progress
Average time: 1456
Results: 1434,1579,1401,1417,1449

Full command: ng serve --no-progress --aot
Average time: 3484
Results: 3485,3451,3471,3469,3544

Benchmark execution time: 193738.856ms

So:

• 4% increase on non-aot rebuilds
• 20% increase on aot rebuilds

I think the change on non-aot is just variance since the code change doesn't even run outside of aot.

As far as the the PR is concerned, I don't think speed should be a major concern for --aot rebuilds really.

[filipesilva]

@rynclark is this still a problem? @ngtools/webpack changed a lot in the last month so I wonder if this was fixed as well.

[randombk]

I can confirm that this issue still occurs in 1.2.11. Applying this patch fixes the issue.

[randombk]

In hopes of getting this merged asap, I updated this patch to the new codebase and added some observations from my own investigation into this issue at #5164.

[filipesilva]

Heya @rynclark @randombk, the original issue you were trying to solved seemed to be broken webpack configuration (#3084 (comment)).

I'm looking at this PR in relation to #5137 though, which seems to be exactly what you describe.

The changes in this PR break CI however, showing the following error:

ERROR in /tmp/angular-cli-e2e-11723-3750-1s602l2.d8uh0py14i/assets/webpack/test-app/app/main.aot.ts (3,34): Cannot find module './ngfactory/app/app.module.ngfactory'.)

This makes me think there's something missing in your solution.

[ryanclark]

Not sure why it's breaking CI, it was working when created - haven't had the chance to update it to reflect any recent changes however.

This is why I created @ultimate/aot-loader - might be worth poking around there and seeing what we do differently from each other to get a solid solution.

[randombk]

@filipesilva The comment you linked does not help with this issue - I already had @ngtools/webpack in my config.

The issue continues to occur in 1.3.0, with webpack 2.4.1. Webpack no longer picks up changes in TypeScript code or angular templates. Multiple edits+saves are required before changes are registered.

My original PR (e2d8276) continues to work with the latest version, but after using it for a while, I noticed that only changes in TypeScript code are handled, while the issue persists with templates. This suggests that the real issue(s) is somewhere deeper in the codebase.

[clydin]

This should no longer be needed with the new Angular 5 compiler pipeline.

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