Prod build removing code that's being used

[zeratulmdq]

Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Command (mark with an x)

- [ ] new
- [x] build
- [x] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Versions

npm --version
6.4.1

node --version
v8.12.0

ng --version
@angular-devkit/architect         0.10.3
@angular-devkit/build-angular     0.10.3
@angular-devkit/build-optimizer   0.10.3
@angular-devkit/build-webpack     0.10.3
@angular-devkit/core              7.0.3
@angular-devkit/schematics        7.0.5
@angular/cli                      7.0.5
@ngtools/webpack                  7.0.3
@schematics/angular               7.0.5
@schematics/update                0.10.5
rxjs                              6.3.3
typescript                        3.1.6
webpack                           4.19.1

Repro steps

I had a NG5 app which I migrated to NG7. Everything working perfectly except one minor detail. I'm consuming a third party library which has this bit of code:

# index.ts
.....
import "./robot-ladder";
import "./robot-plug";

export const ERROR_PAGE_DIRECTIVES: Type<any>[] = [
    CspErrorPageComponent,
];
......

Both robot-ladder and robot-plug are being imported just for their side effects (no export on those files):

# robot-x.ts
import { ClarityIcons } from '@clr/icons';

ClarityIcons.add({
    "robot-plug": `
    ......
})

but the code from both files is excluded from the final bundle (CspErrorPageComponent is a component I'm using BTW).

This happens when building or running dev mode with prod set to true:

ng build
ng serve --prod=true

which makes me think it's UglifyJS related. The thing is, I'm following the same pattern on my own app (importing a file for it's side effects, also calling the ClarityIcons.add function in it) and the code is not removed from the bundle.

Mention any other details that might be useful

I have access to the third party repo so I can definitely submit a patch to export a function from those files and import it and call it inside index.ts. I guess my question would be: is this intended behavior? should library authors be aware of this in order to avoid the pattern?

EDIT: it works fine with NG6

[clydin]

Does the third party library have a “sideEffects” field in its package.json?

[clydin]

Also of note is that side effects such as that should be avoided whenever possible as it limits the ability to fully optimize the code.

[zeratulmdq]

Thanks @clydin

sideEffects was set to false and changing it to true solved the issue but I will remove the side effect and export a function instead.

I'll close this.

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