Fix ModelCollection missing Symbol.species, crashing on .push() after filter/map/slice

[jaysuk]

Summary

ModelCollection extends Array but never overrides the static Symbol.species getter. Per the ES2015 species-construction protocol, that means any Array method that derives a new array from a ModelCollection instance (filter, map, slice, concat, etc.) constructs the result via new ModelCollection(n), where n is the derived array's length — the same call shape as the plain Array(length) constructor.

ModelCollection's own constructor instead treats that first argument as itemConstructor:

constructor(itemConstructor: { new(): T }, itemFactory: ItemFactory<T> | null = null) {
    super();
    Object.setPrototypeOf(this, ModelCollection.prototype);
    Object.defineProperty(this, "$itemConstructor", { enumerable: false, value: itemConstructor });
    ...
}

So a derived array ends up with $itemConstructor set to a number (the length). Any later .push() on it then throws:

TypeError: Right-hand side of 'instanceof' is not an object

— since push() checks item instanceof that.$itemConstructor.

This reliably crashes any consumer — DWC core or a plugin — that does something as ordinary as:

objectModel.tools.filter(t => isOffsettable(t)).push(someCommand)

Nothing catches a TypeError thrown deep inside a shared model getter/setter, so it takes down the whole page.

How I found this

Investigating a crash report in a DWC plugin (duet-tool-align) that builds a G-code command list via objectModel.tools.filter(isOffsettable).map(g10For).filter(Boolean), then does cmds.push(saveCommand). Traced the minified production stack trace back to this exact class/method in a locally-built copy of v3.7-dev and reproduced it directly against ModelCollection with no plugin-specific logic involved — any chain of derived-array operations ending in .push() reproduces it.

Minimal repro (also covered by the added test):

const collection = new ModelCollection(SomeItemClass);
collection.push(/* ...items... */);
const filtered = collection.filter(() => true); // silently becomes a ModelCollection with $itemConstructor = collection.length
filtered.push(newItem); // throws: Right-hand side of 'instanceof' is not an object

Fix

Override Symbol.species to return the plain Array constructor, so filter/map/slice/etc. return ordinary arrays. This leaves the custom push()/update() behaviour only on genuine ModelCollection instances (constructed directly with an item type), which is the only place it's meaningful anyway.

Testing

• Added __tests__/collection.ts: constructs a ModelCollection, derives via filter/map, and asserts the result is a plain array and that .push() on it doesn't throw. Confirmed this test fails with the exact reported error on the unmodified class, and passes with the fix.
• npx tsc -p tsconfig.test.json --noEmit — clean.
• Full jest suite (npx jest --config jestconfig.json) — 36/36 passing, including the new test.

[chrishamm]

Thanks! I may clean up the comment above static override get [Symbol.species](): ArrayConstructor though.