Small validator refactorings

[danieldk]

• Move validators to the validation module.
• Move validator tests to test_validation.
• Rename Validator to MetadataValidator, since we may want to support KernelValidators in the future as well.
• Let validators only take Metadata and the variant string. This makes it possible to change the dependency tree representation without breaking validators.

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[danieldk]

The nix fmt error is unrelated.

[drbh]

lgtm!

[drbh]

The nix fmt error is unrelated.

**nix formatting issue should be resolved by - #810

[github-actions]

Coverage report — kernels/

Measured on: Python 3.10 / Torch 2.13.0.
Other CI configurations are not included in this number.
Hardware-gated code paths (ROCm/XPU/NPU/Darwin/Windows) are excluded or unreachable on the Linux+CUDA runner.

Total coverage: 86.8% — threshold: 80% — ✅

Per-file breakdown

Name	Stmts	Miss	Cover	Missing
src/kernels/__init__.py	14	0	100%
src/kernels/_system.py	6	1	83%	10
src/kernels/_versions.py	78	9	88%	47, 53-54, 57-58, 97, 119, 130, 136
src/kernels/archs.py	56	1	98%	95
src/kernels/backends.py	212	62	71%	40, 44, 48-51, 68, 90, 108, 117, 121, 125-127, 148, 157, 161, 165-167, 188, 199, 201, 208-211, 224, 228, 232-252, 260, 283-303
src/kernels/compat.py	8	1	88%	5
src/kernels/deps.py	65	1	98%	58
src/kernels/hf_hub.py	62	2	97%	18, 20
src/kernels/importer.py	57	5	91%	112, 116, 119, 133-134
src/kernels/install.py	21	7	67%	77-101
src/kernels/layer/__init__.py	6	0	100%
src/kernels/layer/_interval_tree.py	103	4	96%	23, 52, 147, 150
src/kernels/layer/device.py	48	14	71%	42, 47-49, 91, 96-98, 101, 149, 152, 155-157
src/kernels/layer/func.py	87	6	93%	91, 124, 198, 320, 346, 376
src/kernels/layer/globals.py	5	0	100%
src/kernels/layer/kernelize.py	74	8	89%	255, 281, 289-290, 296, 300, 316-318
src/kernels/layer/layer.py	216	15	93%	183, 230, 256, 376, 456-457, 469, 478, 486, 497, 526, 530, 543, 596, 626
src/kernels/layer/mode.py	14	0	100%
src/kernels/layer/repos.py	144	42	71%	27, 33, 36-43, 63-64, 70, 73-76, 90, 94, 103-104, 110, 113-116, 123-124, 130, 133-136, 143-144, 150, 153-156, 163-164, 170, 173-176, 257
src/kernels/load.py	70	2	97%	329, 368
src/kernels/locking.py	89	64	28%	35-83, 91-98, 102-125, 137, 152-159, 165-175, 179-186
src/kernels/python_deps.py	58	6	90%	59-60, 64-65, 101, 104
src/kernels/resolver.py	141	2	99%	182, 188
src/kernels/status.py	49	2	96%	23, 81
src/kernels/validate.py	40	1	98%	58
src/kernels/variants.py	278	19	93%	64, 95, 116, 146, 255-256, 298-301, 303, 387-394, 400-406, 437-443, 455-461
src/kernels/verify.py	88	1	99%	32
TOTAL	2089	275	87%

Updated by the Test kernels workflow on commit f450e3846c241f96be2c68913999306a324f29ca.

[sayakpaul]

My main comment is if we should have separate validators like this. Right now the argument makes it clear that the validator is only for metadata validation. So, are we aiming for a design where we have arguments for different validators that differ in their areas? For example, for a kernel validator we would add a different argument?

[sayakpaul]

I think this should be a generic validator still because we might want to add a kernel validator in the future and we will have to add another argument for that, right?

[danieldk]

For kernel validators there would be a kernel_validator: KernelValidator argument. Otherwise we'd have MetadataValidator | KernelValidator, but you would not be able to pass both.

[danieldk]

Or, we'd need another Validator protocol, but it couldn't define any methods, since the arguments would be different between metadata and kernel validators.

[sayakpaul]

Fine to merge I think the nix related failures are unrelated. But I am still debating if it makes sense to have separate arguments for different validators or if they should clubbed. I don't have a clear picture of the pros and cons of both yet.