@for loop with string identifier throw exception after changing about angular

[pkozlowski-opensource]

why the ngFor behave different - its not much data and its tracked by the same property (overall its less than 1mb data)

NgFor didn't have any checks for the duplicated keys, this is a new and distinct feature of @for

[JoostK]

Please provide a minimal repro, either through StackBlitz or a Github repo, as without it this issue won't be actionable.

[alxhub]

A repro would be useful, but from the error and stack trace it looks like:

• your array/track fn are producing duplicate keys, which @for is trying to warn you about
• as part of that warning, it calls toString on the array value
• the toString implementation for the value itself is crashing, likely from trying to generate an exceptionally long string (hence the browser freeze)

[puschie286]

@alxhub thank you very much, that was exactly what happen. im still curious why the toString method crash and why the ngFor behave different - its not much data and its tracked by the same property (overall its less than 1mb data)

tried to create a stackblitz example but its behave differently there - no errors or warnings for the duplicated keys

[pkozlowski-opensource]

tried to create a stackblitz example but its behave differently there - no errors or warnings for the duplicated keys

The way you generate test data makes the key unique, hence no warning. I guess your real-life data are different and do have duplicate keys.

[puschie286]

The way you generate test data makes the key unique, hence no warning. I guess your real-life data are different and do have duplicate keys.

an duplicated key is explicit added at the bottom (for iterations lower 100)
edit: updated stackblitz to always generate the duplicated entry

[pkozlowski-opensource]

an duplicated key is explicit added at the bottom (for iterations lower 100)
edit: updated stackblitz to always generate the duplicated entry

Oh, the stackblitz runs Angular 17.3 while the new duplicate key check was only introduced in v18 (still RC). So the observed diff in warnings is likely due to the difference in Angular versions used.

[puschie286]

Oh, the stackblitz runs Angular 17.3 while the new duplicate key check was only introduced in v18 (still RC). So the observed diff in warnings is likely due to the difference in Angular versions used.

i posted "ng version" in the original issue text - its exactly the same version. maybe some angular.json configuration difference ? (we use nx, so im not sure if there is some hidden configuration applied)

[pkozlowski-opensource]

The check in question didn't land in v17.x: #55243

[puschie286]

the origin of the exception was a duplicated key that we could find and solve.

but even in this case, the generation of the exception message should not crash / freeze the browser - seems like there is still something wrong in generation of the message.

@pkozlowski-opensource hmm, than how can it be enabled in our 17.3.2 version ? even the html root component says it 17.3.2