Add build tag to build without deprecated global name validation scheme

[aknuds1]

Add build tag localvalidationscheme, to support building without the deprecated global metric/label name validation scheme (model.NameValidationScheme). This is to support building projects such as Prometheus and Grafana Mimir with a configurable metric/label name validation scheme, without changing the API unless said build tag is used.

Since model.NameValidationScheme is deprecated, the new build tag should eventually become the default, but I figure we should move in stages.

I'm also updating the CircleCI job matrix to exercise building with the new tag.

I'm forced to update the client_golang dependency, since it's circular (ideally we'd get rid of this awkward dependency).

As agreed with @ywwg - I've documented the new, experimental, build tag in README.md.

See my client_golang draft PR for reference.

[Copilot]

Pull Request Overview

The PR introduces a localvalidationscheme build tag to switch between global and local name/metric/label validation schemes without changing the public API, and updates CI to test both modes.

• Replace uses of the global NameValidationScheme with parameterized validate methods and corresponding build-tag files.
• Add *_localvalidationscheme.go and *_globalvalidationscheme.go variants for silence, metric, labelset, labels, and alert.
• Update expfmt decoder to accept a validation scheme and adjust tests accordingly.
• Extend CircleCI matrix to run builds/tests with and without the localvalidationscheme tag.
• Bump client_golang and procfs dependencies.

Reviewed Changes

Copilot reviewed 36 out of 37 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
model/silence.go	Refactor Validate to validate(scheme) for local scheme.
model/silence_globalvalidationscheme.go	Global‐tagged Validate() implementations using global var.
model/silence_localvalidationscheme.go	Local‐tagged Validate(scheme) that forwards to internal method.
model/silence_test.go	Use validateMatcher / validateSilence helpers.
model/silence_globalvalidationscheme_test.go	Global build tests for silence validation.
model/silence_localvalidationscheme_test.go	Local build tests for silence validation.
model/metric.go	Rename IsValidMetricName to isValidMetricName(n, scheme).
model/metric_globalvalidationscheme.go	Global‐tagged IsValidMetricName(n) using global var.
model/metric_localvalidationscheme.go	Local‐tagged IsValidMetricName(n, scheme).
model/metric_test.go	Delegate to testIsValidMetricName.
model/metric_globalvalidationscheme_test.go	Global build metric tests.
model/metric_localvalidationscheme_test.go	Local build metric tests.
model/labelset.go	Rename Validate/UnmarshalJSON to internal validate(scheme).
model/labelset_globalvalidationscheme.go	Global‐tagged Validate()/UnmarshalJSON.
model/labelset_localvalidationscheme.go	Local‐tagged Validate(scheme)/UnmarshalJSON.
model/labels.go	Rename IsValid/Unmarshal* to isValid(scheme) and use json/yaml interfaces.
model/labels_globalvalidationscheme.go	Global‐tagged IsValid()/unmarshal methods.
model/labels_localvalidationscheme.go	Local‐tagged IsValid(scheme)/unmarshal methods.
model/alert.go	Rename Validate to validate(scheme) and pass scheme down.
model/alert_globalvalidationscheme.go	Global‐tagged Validate().
model/alert_localvalidationscheme.go	Local‐tagged Validate(scheme).
expfmt/decode.go	Remove unconditional NewDecoder; use scheme-aware decoder.
expfmt/decode_globalvalidationscheme.go	Global‐tagged NewDecoder(r, fmt) and protoDecoder logic.
expfmt/decode_localvalidationscheme.go	Local‐tagged NewDecoder(r, fmt, scheme) and protoDecoder.
expfmt/decode_test.go	Adapt tests to use newDecoder with scheme.
expfmt/decode_globalvalidationscheme_test.go	Global‐tagged decoder tests.
expfmt/decode_localvalidationscheme_test.go	Local‐tagged decoder tests.
.circleci/config.yml	Update CI matrix to include localvalidationscheme tag.
go.mod	Bump client_golang and procfs indirect dependencies.

Comments suppressed due to low confidence (1)

.circleci/config.yml:100

• The job name interpolation uses <<# matrix.build_tags >>, which is not valid CircleCI syntax. It should be << matrix.build_tags >>. To avoid an extra dash when the tag is empty, consider using separate job entries or conditional logic in the name field.

          name: go-<< matrix.go_version >><<# matrix.build_tags >>-<< matrix.build_tags >><</matrix.build_tags >>

[ywwg]

How long do you think we'll need the two build tags? It can be brittle to have two code paths like this, even if the divergence is small. I know other projects still need time to update their code for the new APIs but we'll want to try to set a deadline.

Usually a build tag is exposed somewhere in the Makefile, and that's a good place to mark it experimental. We'll also need README and other doc updates to explain what's going on.

[aknuds1]

I've discussed with @ywwg in Slack.

[ywwg]

trying to manage expectations for the future.

[ywwg]

Would it be possible to use a new function name for the API rather than rely on a build tag? Since the function signature has changed, all of the call sites in mimir will need to change already anyway, right?