Which @angular/* package(s) are the source of the bug?
compiler
Is this a regression?
No
Description
When using the null coalescing operator ?? in the track expression using the new @for control flow syntax, an error is thrown during template rendering (and the contents of the for-loop aren't rendered).
Example (see reproduction URL):
@for (item of myList; track item.field1 ?? item.field2) {
<p>{{ $index }}: {{ item.field1 }}, {{ item.field2 }}</p>
}Please provide a link to a minimal reproduction of the bug
https://stackblitz.com/edit/angular-for-template-bug?file=src%2Fmain.ts
Please provide the exception or error you saw
ERROR ReferenceError: tmp_7_0 is not defined
at _forTrack0 (main.ts:3:8)
at createOrAttach (chunk-ZNRRMEEJ.js?v=a3f8c8d7:17941:71)
at reconcile (chunk-ZNRRMEEJ.js?v=a3f8c8d7:17865:7)
at Module.ɵɵrepeater (chunk-ZNRRMEEJ.js?v=a3f8c8d7:18181:5)
at TodosComponent_Template (main.ts:11:5)
at executeTemplate (chunk-ZNRRMEEJ.js?v=a3f8c8d7:10767:5)
at refreshView (chunk-ZNRRMEEJ.js?v=a3f8c8d7:11789:7)
at detectChangesInView (chunk-ZNRRMEEJ.js?v=a3f8c8d7:11955:5)
at detectChangesInViewIfAttached (chunk-ZNRRMEEJ.js?v=a3f8c8d7:11938:3)
at detectChangesInComponent (chunk-ZNRRMEEJ.js?v=a3f8c8d7:11932:3)
Please provide the environment you discovered this bug in (run ng version)
Angular CLI: 18.0.2
Node: 18.20.3
Package Manager: npm 10.2.3
OS: linux x64
Angular: 18.0.1
... animations, common, compiler, compiler-cli, core, forms
... platform-browser, router
Package Version
---------------------------------------------------------
@angular-devkit/architect 0.1800.2
@angular-devkit/build-angular 18.0.2
@angular-devkit/core 18.0.2
@angular-devkit/schematics 18.0.2
@angular/cli 18.0.2
@schematics/angular 18.0.2
rxjs 7.8.1
typescript 5.4.5
zone.js 0.14.6
Anything else?
The error is similar to this previous issue, also concerning the use of the null coalescing operator in template expressions: #53295
The compiler turns the @for track expression into this statement, which throws an error because tmp_7_0 is never defined:
var _forTrack0 = ($index, $item) => (tmp_7_0 = $item.field1) !== null && tmp_7_0 !== void 0 ? tmp_7_0 : $item.field2;
Which @angular/* package(s) are the source of the bug?
compiler
Is this a regression?
No
Description
When using the null coalescing operator
??in thetrackexpression using the new@forcontrol flow syntax, an error is thrown during template rendering (and the contents of the for-loop aren't rendered).Example (see reproduction URL):
@for (item of myList; track item.field1 ?? item.field2) { <p>{{ $index }}: {{ item.field1 }}, {{ item.field2 }}</p> }Please provide a link to a minimal reproduction of the bug
https://stackblitz.com/edit/angular-for-template-bug?file=src%2Fmain.ts
Please provide the exception or error you saw
Please provide the environment you discovered this bug in (run
ng version)Anything else?
The error is similar to this previous issue, also concerning the use of the null coalescing operator in template expressions: #53295
The compiler turns the
@fortrackexpression into this statement, which throws an error becausetmp_7_0is never defined: