ngc watch is not incremental, runs full build

I'm submitting a...


[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

To compile my project it takes 11 seconds for tsc (typescript@2.6), however ngc takes 25 seconds.
The watch mode is similar 3 seconds versus 10+ for a single file (component) change.
Is there a way to debug the problem or is this the desired behavior.

Expected behavior

The durations should be close

Environment


Angular version: 5.2.0-rc0
TypeScript version (both global and project): 2.6



For Tooling issues:
- Node version: 8.9.3 and 9.3.0
- Platform: Both Windows and the Linux subsystem (Ubuntu)

tsconfig:
{
  "compilerOptions": {
    "target": "ES2017",
    "module": "ES2015",
    "moduleResolution": "node",
    "sourceMap": false,
    "importHelpers": true,
    "emitDecoratorMetadata": false,
    "experimentalDecorators": true,
    "lib": [
      "es2015",
      "dom",
      "es2017.object"
    ],
    "noImplicitAny": false,
    "isolatedModules": true,
    "suppressImplicitAnyIndexErrors": true,
    "allowSyntheticDefaultImports": true,
    "allowJs": true,
    "skipLibCheck": true,
    "outDir": "../../compiled",
    "typeRoots": [
      "../../node_modules/@types/"
    ]
  },

  "files": [
    "./app.module.ts"
  ],

  "include": [
    "../../../../types/models/*.d.ts"
  ],

  "exclude": [
    "../../generated/**",
    "../../compiled/**",
    "../../node_modules/**"
  ]
}

"./node_modules/.bin/tsc" -p app/ts/tsconfig.watch.json -w
Synchronizing program
Files:          1186
Lines:        100855
Nodes:        411168
Identifiers:  125264
Symbols:      119669
Types:         21711
Memory used: 218908K
I/O read:      0.22s
I/O write:     0.69s
Parse time:    3.59s
Bind time:     1.04s
Check time:    3.58s
Emit time:     1.83s
Total time:   10.04s
10:21:07 - Compilation complete. Watching for file changes.


10:21:12 - File change detected. Starting incremental compilation...


Synchronizing program
Files:          1186
Lines:        100855
Nodes:        411168
Identifiers:  125264
Symbols:       83458
Types:            57
Memory used: 175269K
I/O read:      0.00s
I/O write:     0.00s
Parse time:    2.27s
Bind time:     0.00s
Check time:    0.00s
Emit time:     0.00s
Total time:    2.27s
10:21:14 - Compilation complete. Watching for file changes.

The same file & options:

"./node_modules/.bin/ngc" -p app/ts/tsconfig.watch.json -w
: Time for diagnostics: 10960ms.
: Emitted in 16648ms
- 1270 user ts files
- 249 generated ts files
- 860 generated json files

: Total time: 28s

: Compilation complete. Watching for file changes.

: File change detected. Starting incremental compilation.

: Time for diagnostics: 8575ms.
: Emitted in 11602ms
- 1270 user ts files
- 249 generated ts files
- 860 generated json files

: Total time: 20s

: Compilation complete. Watching for file changes.

There is one bug at least, the watch mode is broken in the last releases:

angular/packages/compiler-cli/src/perform_watch.ts

Lines 195 to 205 in 83d207d

    
           const oldProgram = cachedProgram; 
        
           // We clear out the `cachedProgram` here as a 
        
           // program can only be used as `oldProgram` 1x 
        
           cachedProgram = undefined; 
        
           const compileResult = performCompilation({ 
        
             rootNames: cachedOptions.rootNames, 
        
             options: cachedOptions.options, 
        
             host: cachedCompilerHost, 
        
             oldProgram: cachedProgram, 
        
             emitCallback: host.createEmitCallback(cachedOptions.options) 
        
           });

The oldProgram option is always undefined.

After the fix, it's definitely better.
...still fishy, 200 files changed by changing only 1 angular component:

node ./node_modules/@angular/compiler-cli/src/main.js -p app/ts/tsconfig.watch.json -w
: Time for diagnostics: 10057ms.
: Emitted in 10920ms
- 1270 user ts files
- 249 generated ts files
- 860 generated json files

: Total time: 21s

: Compilation complete. Watching for file changes.

: File change detected. Starting incremental compilation.

: Time for diagnostics: 7021ms.
: Emitted in 7045ms
- 1343 user ts files
- 99 generated ts files
- 99 generated json files

: Total time: 14s

: Compilation complete. Watching for file changes.

3rd and 4th runs are better, but still slow:

$ node ./node_modules/\@angular/compiler-cli/src/main.js -p app/tsconfig.watch.json -w
: Time for diagnostics: 10827ms.
: Emitted in 10415ms
- 1270 user ts files
- 249 generated ts files
- 860 generated json files

: Total time: 21s

: Compilation complete. Watching for file changes.

: File change detected. Starting incremental compilation.

: Time for diagnostics: 7426ms.
: Emitted in 7579ms
- 1343 user ts files
- 99 generated ts files
- 99 generated json files

: Total time: 15s

: Compilation complete. Watching for file changes.

: File change detected. Starting incremental compilation.

: Time for diagnostics: 7040ms.
: Emitted in 3325ms
- 1 user ts files
- 0 generated ts files
- 0 generated json files

: Total time: 10s

: Compilation complete. Watching for file changes.

: File change detected. Starting incremental compilation.

: Time for diagnostics: 6198ms.
: Emitted in 4309ms
- 1 user ts files
- 0 generated ts files
- 0 generated json files

: Total time: 11s

: Compilation complete. Watching for file changes.

@IgorMinar

The last change results in smaller generated code, which is unexpected for me. @IgorMinar or @tbosch who is familiar with this piece of code?

fix(compiler-cli): return oldTsProgram while compiling

@IgorMinar

@IgorMinar any updates? One of the two PRs is a single word typo, helps to make the watch a magnitude faster.

This is not something what should happen in open source. Maintaining code quality and having strategic goals in development is one thing, the intentional total lack of communication is an other. Not just not being able to fix a clear typo affecting the only compiler feature mentioned in Angular 5's release blog post (in 6 months!), but ignoring a contributors very first PR. This is not welcoming or inclusive. Better I stick to MS+FB+other open source projects, but not Google's next time.

I really appreciate your hard work, the amount of expertise and work you share is wonderful and unique. You really help everybody. It's just not the open source project I expected it to be.

fix(compiler-cli): use the oldProgram option in watch mode

fix(compiler-cli): use the oldProgram option in watch mode (#21364)

angular-cli or @ngtools/webpack doesn't rely on this code, so I guess ngc --watch is kind of in a blind spot.

They have written off this compiler already as they write a new compiler (ivy) that can run file2file instead of managing the hole project. At least they have to if they want to leverage the power of bazel.

Lets hope ivy works just like typescript. Can compile file by file and run diagnostics in a separate thread. So compile time comes done to milliseconds instead of seconds.

@alippai

Closing as fixed. @alippai's fix was merged in c6e5b97.

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ngc watch is not incremental, runs full build #21361

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	const oldProgram = cachedProgram;
	// We clear out the `cachedProgram` here as a
	// program can only be used as `oldProgram` 1x
	cachedProgram = undefined;
	const compileResult = performCompilation({
	rootNames: cachedOptions.rootNames,
	options: cachedOptions.options,
	host: cachedCompilerHost,
	oldProgram: cachedProgram,
	emitCallback: host.createEmitCallback(cachedOptions.options)
	});

ngc watch is not incremental, runs full build #21361

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I'm submitting a...

Current behavior

Expected behavior

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alippai commented on Jan 7, 2018

alippai commented on Jan 7, 2018

alippai commented on Jan 7, 2018

alippai commented on Jan 7, 2018

alippai commented on Jan 8, 2018

11 remaining items

alippai commented on May 31, 2018

alippai commented on Jun 16, 2018

sod commented on Aug 20, 2018

alxhub commented on May 28, 2020

angular-automatic-lock-bot commented on Jun 29, 2020

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