refactor(pyroscope): Remove reflection workaround for NewOAuth2RoundTripper

[korniltsev-grafanista]

Summary

• Remove the reflect+unsafe workaround (reflect_oauth2.go) that was needed to call commonconfig.NewOAuth2RoundTripper with its previously unexported *httpClientOptions parameter
• Delete the associated layout-verification tests (reflect_oauth2_test.go) that ensured struct compatibility
• Call commonconfig.NewOAuth2RoundTripper directly using its new variadic ...HTTPClientOption signature
• Bump prometheus/common to include prometheus/common#898

Details

The upstream NewOAuth2RoundTripper accepted an unexported *httpClientOptions as its fourth parameter, making it uncallable from external packages without reflection. The promhttp2 package maintained a local mirror of the struct and used reflect.NewAt + unsafe.Pointer to pass it through — with extensive tests to assert struct layout, field order, and byte-for-byte default matching against the upstream type.

prometheus/common#898 changed the signature to accept variadic ...HTTPClientOption (an exported interface), matching the pattern already used by NewRoundTripperFromConfigWithContext. This makes the workaround unnecessary.

A new toUpstreamOpts() method on the local httpClientOptions converts fields to upstream option values so that any options passed by callers are correctly forwarded to the OAuth2 round tripper.

Net change: 194 lines deleted, 36 added.

Test plan

• go test ./internal/component/pyroscope/write/... passes
• All OAuth2-related tests (TestOAuth2, TestOAuth2WithFile, TestOAuth2WithJWTAuth, etc.) pass

[github-actions]

🔍 Dependency Review

github.com/prometheus/common v0.67.5 -> v0.67.6-0.20260415130754-a4fac5c9b6d9 — ❌ Changes Needed

Breaking/API changes were introduced in the config HTTP client utilities that affect existing call sites.

Key upstream change (in package github.com/prometheus/common/config):

• NewOAuth2RoundTripper API changed:
  • Before: returned (http.RoundTripper, error) and required an unexported *httpClientOptions.
  • After: returns http.RoundTripper and accepts variadic options ...HTTPClientOption (exported).
• Upstream now exports HTTPClientOption and WithXxx option builders (e.g., WithDialContextFunc, WithHTTP2Disabled, etc.), removing the need for local reflection hacks.

This PR already adapts local code to that breaking change. If there are any other remaining call sites, they must be updated similarly.

Recommended code updates (shown by this PR and required wherever applicable):

1. Replace reflection-based wrapper/newOAuth2RoundTripper calls with direct upstream calls and remove error handling:

- rt, err = newOAuth2RoundTripper(oauthCredential, cfg.OAuth2, rt, &opts)
- if err != nil {
-   return nil, fmt.Errorf("unable to create OAuth2RoundTripper: %w", err)
- }
+ rt = commonconfig.NewOAuth2RoundTripper(oauthCredential, cfg.OAuth2, rt, upstreamOpts...)

2. Update tests to reflect the new signature (no error return):

- rt, err := newOAuth2RoundTripper(secret, &expectedConfig, http.DefaultTransport, &defaultHTTPClientOptions)
- require.NoError(t, err)
+ rt := commonconfig.NewOAuth2RoundTripper(secret, &expectedConfig, http.DefaultTransport)

3. Replace local “reflection shim” with proper upstream options:

• Delete the reflection bridge files:
  • internal/component/pyroscope/write/promhttp2/reflect_oauth2.go
  • internal/component/pyroscope/write/promhttp2/reflect_oauth2_test.go

4. Introduce a local HTTPClientOption that:

• Applies local behavior (for existing internal option handling).
• Forwards the equivalent upstream commonconfig.HTTPClientOption to NewOAuth2RoundTripper:

- type HTTPClientOption interface {
-   applyToHTTPClientOptions(options *httpClientOptions)
- }
+ type HTTPClientOption struct {
+   applyLocal func(*httpClientOptions)
+   upstream   commonconfig.HTTPClientOption
+ }

5. Update local option constructors to carry upstream equivalents:

- func WithHTTP2Disabled() HTTPClientOption {
-   return httpClientOptionFunc(func(opts *httpClientOptions) {
-     opts.http2Enabled = false
-   })
- }
+ func WithHTTP2Disabled() HTTPClientOption {
+   return HTTPClientOption{
+     applyLocal: func(opts *httpClientOptions) { opts.http2Enabled = false },
+     upstream:   commonconfig.WithHTTP2Disabled(),
+   }
+ }

6. Accumulate and forward upstream options:

- for _, opt := range optFuncs {
-   opt.applyToHTTPClientOptions(&opts)
- }
+ upstreamOpts := make([]commonconfig.HTTPClientOption, 0, len(optFuncs))
+ for _, opt := range optFuncs {
+   opt.applyLocal(&opts)
+   if opt.upstream != nil {
+     upstreamOpts = append(upstreamOpts, opt.upstream)
+   }
+ }

Why this is required

• Upstream removed the unexported httpClientOptions parameter from NewOAuth2RoundTripper and switched to variadic options with exported HTTPClientOption. Code using the old signature or reflection will fail to compile.
• Upstream eliminated the error return; callers must remove error handling at call sites.

Evidence (upstream API change)

• New signature used in this PR:
  • commonconfig.NewOAuth2RoundTripper(secret, cfg, next, upstreamOpts...) http.RoundTripper
• Old local wrapper (now removed) and tests assumed:
  • (secret, cfg, next, *httpClientOptions) (http.RoundTripper, error)

References

• Upstream commit introducing exported HTTPClientOption and new NewOAuth2RoundTripper signature (for context): prometheus/common@a4fac5c9b6d9
• Package: github.com/prometheus/common/config

Notes

• The upgrade pins a pseudo-version (v0.67.6-0.20260415130754-a4fac5c9b6d9). Consider moving to the next tagged release when available for stability.
• No other dependency changes were included in this diff.

[marcsanmi]

LGTM