When shall we check if feature is enabled?

[beaufortfrancois]

Despite the features spec section, it is still not clear to me when content timeline or device timeline is bettter suited to check whether a GPUFeature is enabled on a device.

I've summarized below some instances in the current WebGPU spec where we check if a feature is enabled or not:

Content timeline:

• createQuerySet()
  • If descriptor.type is "timestamp", but "timestamp-query" is not enabled for this, throw a TypeError.
• Validate texture format required features of a format
  • If format requires a feature and device.[[features]] does not contain the feature, throw a TypeError.

Device timeline:

• Validate timestampWrites
  • "timestamp-query" must be enabled for device.
• Validate GPUPrimitiveState
  • If descriptor.unclippedDepth is true, "depth-clip-control" must be enabled for device.
• Validate GPUBlendComponent
  • If component.srcFactor or component.dstFactor requires a feature according to the GPUBlendFactor table and device.[[features]] does not contain the feature, throw a TypeError.
• createShaderModule()
  • For each enable extension in descriptor.code, the corresponding GPUFeatureName must be enabled

For info, I'm wondering about this because I'm working on the swizzle spec proposal and it's not obvious I should raise a validation error instead of TypeError when I call createView({swizzle}) if "texture-component-swizzle" feature is not enabled.

[kainino0x]

That section is really meant to give guidance to users. For API design there is https://github.com/gpuweb/gpuweb/blob/main/design/ErrorConventions.md

Though in this case I think it probably doesn't answer the question (I haven't reread it yet). I will consider this more closely tomorrow.

[beaufortfrancois]

Thanks for sharing https://github.com/gpuweb/gpuweb/blob/main/design/ErrorConventions.md

I wonder if this part is what I'm looking for.

If any object in A sets any key that is known to the browser, but part of a non-enabled feature, is set to any value other than its default: Must be an error and the error must not be synchronous.

In that case, I should raise a TypeError when I call createView({swizzle}) if "texture-component-swizzle" feature is not enabled.

[greggman]

If any object in A sets any key that is known to the browser, but part of a non-enabled feature, is set to any value other than its default: Must be an error and the error must not be synchronous.

In that case, I should raise a TypeError when I call createView({swizzle}) if "texture-component-swizzle" feature is not enabled.

Doesn't it say the opposite? the error must not be synchronous. So it a validation error, not a TypeError. Right?

[beaufortfrancois]

Morning! My bad, I totally misread that. I need to go grab a coffee.

I guess I can close this issue.