Should we raise an error if non-default swizzle is used without feature enabled?

[beaufortfrancois]

Following up on #5217 (comment), I wonder if we should raise a GPU validation error if a non-default texture component swizzle is used without the feature enabled. We do something similar for unclippedDepth but I'd love the group to discuss and decide what's best in the context of the texture component swizzle proposal.

FWIW my understanding is that we should according to the following spec text:

Using a new dictionary member with a (correctly-typed) non-default value typically results in a validation error.

[kainino0x]

Yes, I think we definitely should raise a validation error in this case.

[kainino0x]

note: I'm not bothering to add this to the meeting agenda, this proposal matches other parts of the API, and our own design guidelines, so we should just incorporate it into the proposal and let it be reviewed when we do the final PR.

[beaufortfrancois]

@kainino0x It's not clear from the meeting notes whether this was approved eventually or not by the WebGPU group.

CW: e.g. if you don't enable it and pass the default swizzle of RGBA, is that an error?
KN: if an extension adds a dictionary member, it's generally OK to set it to the default value. Setting it to a non-default value is a validation error.
JB: gives content a bit more flexibility. Don't have to avoid providing the value at all.

[kainino0x]

@beaufortfrancois We basically just went over what guidelines we had written, and what that meant in various cases. For this I believe everyone was in agreement that we should raise an error if non-default swizzle is requested but we can't provide it because the feature is not enabled.

[beaufortfrancois]

Thank you @kainino0x! I'll close this issue once #5252 is merged then.

[Kangz]

GPU Web WG 2025-07-30 Atlantic-time

• CW: e.g. if you don't enable it and pass the default swizzle of RGBA, is that an error?
• KN: if an extension adds a dictionary member, it's generally OK to set it to the default value. Setting it to a non-default value is a validation error.
• JB: gives content a bit more flexibility. Don't have to avoid providing the value at all.