fixing merge() function not accepting with BufferGeometry-typed argument

[salaros]

Example of the error I was getting before applying this fix:

TS2345: Argument of type 'Geometry | BufferGeometry' is not assignable to parameter of type 'Geometry'

How to reproduce:

import { ObjectLoader } from 'three';

let objectInJson = <get the JSON object>;
let loader = new THREE.ObjectLoader();
let object = loader.parse( objectInJson  );
let geometry = new Geometry();
object.traverse( function(child) {
    if(child instanceof Mesh) {
        geometry.merge( child.geometry );
    }
});

[dt-bot]

types/three/three-core.d.ts

to authors (@gyohk @florentpoujol @SereznoKot @omni360 @ivoisbelongtous @piranha771 @qszhusightp @nakakura @s093294 @Pro @efokschaner Kon (account can't be detected)). Could you review this PR?
👍 or 👎?

[RyanCavanaugh]

@salaros Please fix the failures indicated in the Travis CI log.

[salaros]

@RyanCavanaugh I don't know if you have already read the log, but the failures reported by Travis-CI has nothing to do with my fix! The errors reported by Travis are tests-related (ban-comma-operator).
Please see a small portion of log below.

Do you want me to create yet another PR with fixes for this errors? Because IMO ban-comma-operator error has to be fixed apart. It's not a good practice to mix fixes for the main code-base with test-related stuff (I mean when tests failing are not directly affected by the changes committed to the code), I hope you understand what I mean.

Please accept this PR and I will create another one which fixes tests.

Error in three

Command failed: node /home/travis/build/DefinitelyTyped/DefinitelyTyped/node_modules/dtslint/bin/index.js

Error: /home/travis/build/DefinitelyTyped/DefinitelyTyped/types/three/test/css3d/css3d_sprites.ts

ERROR: 32:17 ban-comma-operator Don't use the comma operator.

ERROR: 32:17 ban-comma-operator Don't use the comma operator.

ERROR: 141:57 ban-comma-operator Don't use the comma operator.

/home/travis/build/DefinitelyTyped/DefinitelyTyped/types/three/test/webgl/webgl_materials.ts

ERROR: 181:62 ban-comma-operator Don't use the comma operator.

at /home/travis/build/DefinitelyTyped/DefinitelyTyped/node_modules/dtslint/bin/index.js:76:19

at Generator.next (<anonymous>)

at fulfilled (/home/travis/build/DefinitelyTyped/DefinitelyTyped/node_modules/dtslint/bin/index.js:5:58)

at <anonymous>

Error: /home/travis/build/DefinitelyTyped/DefinitelyTyped/types/three/test/css3d/css3d_sprites.ts

ERROR: 32:17 ban-comma-operator Don't use the comma operator.

ERROR: 32:17 ban-comma-operator Don't use the comma operator.

ERROR: 141:57 ban-comma-operator Don't use the comma operator.

/home/travis/build/DefinitelyTyped/DefinitelyTyped/types/three/test/webgl/webgl_materials.ts

ERROR: 181:62 ban-comma-operator Don't use the comma operator.

at /home/travis/build/DefinitelyTyped/DefinitelyTyped/node_modules/dtslint/bin/index.js:76:19

at Generator.next (<anonymous>)

at fulfilled (/home/travis/build/DefinitelyTyped/DefinitelyTyped/node_modules/dtslint/bin/index.js:5:58)

at <anonymous>

[efokschaner]

These lint issues also show up in #21171 and #21192

Having a look now to see why it might have happened.

On the plus side, they should be solved if you wait for #21171 to be merged and then pull it in to your branch.

I'll follow up shortly with a review of your changes.

[efokschaner]

Hey @salaros , judging from the implementation, you cannot pass a BufferGeometry to merge, see https://github.com/mrdoob/three.js/blob/master/src/core/Geometry.js#L704 , BufferGeometry does not seem to have the isGeometry tag.

Does that seem right to you?

[salaros]

So might this definition be a problem?

I mean if BufferGeometry type doesn't have isGeometry could we really use it as an alternative to Geometry type on Mesh/Object3D.geometry property?

export class Mesh extends Object3D {
    constructor(geometry?: Geometry | BufferGeometry, material?: Material | Material []);

    geometry: Geometry|BufferGeometry;
 
   .......
}

I feel that in vanilla Three.js or @types/three there is some sort of type inconsistency across Geometry-related methods and properties.
For now I will use an extra type check in my code snippet to avoid compilation errors:

this.object.traverse( function(child) {
    if(child instanceof Mesh && child.geometry instanceof Geometry) {
         geometry.merge( child.geometry );
     }
});

However if you think my there is still something wrong with TS wrapper, just let me know - I really willing to help.

[efokschaner]

I don't think the Mesh definition is wrong, see: https://threejs.org/docs/#api/objects/Mesh.geometry

Instead of excluding BufferGeometry you could also consider handling them, something like this (untested):

this.object.traverse( function(child) {
    if(child instanceof Mesh) {
        if(child.geometry instanceof Geometry){
            geometry.merge( child.geometry );
        } else {
            let convertedGeometry = new Geometry();
            convertedGeometry.fromBufferGeometry(child.geometry);
            geometry.merge( convertedGeometry );
        }
     }
});

I will say that three.js is actually pretty unfriendly to static typing, it relies a lot on javascript's dynamic nature internally and on its interfaces, and so the type definitions here are far from perfect.

I appreciate you taking the time to help, and if you find anything else that could be improved I'd be pleased to hear from you again.

[salaros]

OK, thanks for the interesting solution, I will definitely give it a try