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feat: bind this context to owner #132

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feat: bind this context to owner #132

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21 changes: 17 additions & 4 deletions addon/initializers/install-function-helper-manager.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,10 @@
// typed-ember doesn't have types for `@ember/helper` yet
// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-ignore
import { capabilities as helperCapabilities, setHelperManager } from '@ember/helper';
import {
capabilities as helperCapabilities,
setHelperManager,
} from '@ember/helper';

import type { Arguments } from '../-private/local-glimmer-interfaces-types';

Expand All @@ -18,6 +21,8 @@ export default {
initialize,
};

type Owner = unknown;

type FnArgs<Args extends Arguments = Arguments> =
| [...Args['positional'], Args['named']]
| [...Args['positional']];
Expand All @@ -36,6 +41,8 @@ export class FunctionHelperManager {
hasScheduledEffect: false,
});

owner?: Owner = undefined;

createHelper(fn: AnyFunction, args: Arguments): State {
return { fn, args };
}
Expand All @@ -44,10 +51,10 @@ export class FunctionHelperManager {
if (Object.keys(args.named).length > 0) {
let argsForFn: FnArgs<Arguments> = [...args.positional, args.named];

return fn(...argsForFn);
return fn.apply(this.owner, argsForFn);
}

return fn(...args.positional);
return fn.apply(this.owner, args.positional);
}

getDebugName(fn: AnyFunction): string {
Expand All @@ -61,4 +68,10 @@ export class FunctionHelperManager {

const FUNCTIONAL_HELPER_MANAGER = new FunctionHelperManager();

setHelperManager(() => FUNCTIONAL_HELPER_MANAGER, Function.prototype);
setHelperManager(
(owner: Owner) =>
Object.create(FUNCTIONAL_HELPER_MANAGER, {
owner: { value: owner, writable: false, configurable: false },
}),
Function.prototype
);
35 changes: 35 additions & 0 deletions tests/rendering/functions-test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,16 @@ import { hbs } from 'ember-cli-htmlbars';
import { module, test } from 'qunit';
import { setupRenderingTest } from 'ember-qunit';

interface Owner {
lookup(
key: string,
options?: {
singleton?: boolean | undefined;
instantiate?: boolean | undefined;
}
): unknown;
}

module('function helpers', function (hooks) {
setupRenderingTest(hooks);

Expand Down Expand Up @@ -100,4 +110,29 @@ module('function helpers', function (hooks) {
'x is 4, and opts.a is 6',
]);
});

test('the owner is bound as `this` context', async function (assert) {
function lookup(
this: Owner,
identifier: string,
options?: object
): unknown {
return this.lookup(identifier, options);
}

const testIdentifier = 'test-value:foo';
const testValue = 'foo';

this.owner.register(
testIdentifier,
{ string: testValue },
{ instantiate: false }
);

this.setProperties({ lookup, testIdentifier });

await render(hbs`{{get (this.lookup this.testIdentifier) "string"}}`);
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@NullVoxPopuli NullVoxPopuli Aug 10, 2022 •
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the intent is solid, but ultimately we need the VM to see property.path (when used in the invocation position), to do path.apply(property, args)

this way we get correctly bound functions on all objects.

like, XState interpreters, window globals, services, etc

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Yep! I've touched on that in my most recent comment in the RFC: emberjs/rfcs#756 (comment)

I also suggested not using the owner, but the invoking template context. I'd be very interested in your opinion on that.

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@NullVoxPopuli NullVoxPopuli Aug 10, 2022 •
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yeah, that would make sense to me.

the owner shouldn't get any special treatment with functions, but your functions should have whatever this you expect them to have.

so if your function needs the owner, you getOwner(this) in it.
but if your function is not defined in a place where this has an owner`, you won't get an owner.

function outerFunction() {
  getOwner(this); 
}

class extends Component {
  // can access owner
  myFunction = () => {
    let owner = getOwner(this);
  }
  
  outerFunction = outerFunction; // no owner
  boundOuterFunction = outerFunction.bind(this); // has owner
}


assert.dom().hasText(testValue);
});
});