fix(gcp): normalize Cloud Storage catalog pricing units

[cristim]

A Cloud Storage catalog rate of $0.020/GiB-month produced a $175.20 annual total and $14.60 monthly charge. Normalize each selected capacity SKU using its usage unit so those values become $0.24 and $0.020. Preserve hourly rates and reject empty or unsupported units.

Select ordinary capacity names before validating units, so same-class operation SKUs cannot abort pricing. The selector matches the documented <class> Storage prefix and excludes (Early Delete). This bounded selection uses published SKU names rather than unverified category values: standard storage, nearline storage, and all four capacity classes in Doha. Selected capacity SKUs with unsupported units still error.

Tests exercise the public offering and recommendation paths through the Billing SDK with a confined local HTTP endpoint. They cover monthly, hourly, mixed units, one- and three-year terms, payment splits, unavailable pricing, and missing commitment SKUs. The regression failed before the fix on the 730x totals and missing unit errors, then passed. Full GCP race tests, build, vet, and golangci-lint 2.10.1 passed with Go 1.26.6.

The catalog fixtures contain synthetic commitment SKUs and an artificial STANDARD resource suffix. This verifies unit handling and propagation, not a live GCS commitment offering or purchase. The 730-hour divisor preserves the library's annual-average convention.

The original independent approval was superseded after automatic review found the same-class operations selection gap. The amendment reproduces that failure through the Billing SDK and both public consumers, then verifies operation records before and after valid prices. Matcher cases cover all four ordinary capacity classes, operations, retrieval and early-delete charges. Independent removal of the selector loses pricing; removal of unit validation wrongly accepts count-priced capacity. Both mutations fail for the intended assertions; restored tests and the full GCP checks pass. Normal installed precommit hooks also passed.

Final integrated exact-SHA independent review APPROVED f87771d9d2dfb32dae9a76eb88f817def7c1115a using gpt-6-astra, the user-authorized substitute for unavailable Opus. Main 6ce98fbeb892a2215033a2d6ac75f28b742665f5 was merged additively, preserving published history. The reviewer verified both parents, reread the complete two-file main-relative diff, asserted exact HEAD and a clean tree, and freshly ran SDK consumer, matcher and unsupported-purchase tests with -race -count=1 (PASS, 1.956 seconds). Both amendment and integration review passes were clean. Full GCP race tests passed on the integrated tree; normal merge hooks ran without bypass and skipped non-conflict files under precommit's merge behavior. The preceding fix commit passed every installed hook.

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Closes #77.

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📝 Walkthrough

Walkthrough

Cloud Storage pricing now converts monthly SKU rates to hourly rates, preserves hourly rates, and returns errors for unsupported units. Tests cover pricing calculations and recommendation outputs.

Changes

Cloud Storage pricing

Layer / File(s)	Summary
Convert SKU rates and propagate extraction errors providers/gcp/services/cloudstorage/client.go	SKU price extraction converts GiBy.mo rates to hourly rates and leaves GiBy.h rates unchanged. Unsupported units return errors that propagate through getStoragePricing. Missing pricing data still returns zero values without an extraction error.
Validate pricing and recommendation results providers/gcp/services/cloudstorage/client_test.go	Tests assert pricing values and cover monthly, hourly, and mixed SKU units for multiple terms and payment options. Invalid units and missing commitment pricing are also tested.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: 🟡 Moderate · up to a8b19

Cloud Storage offering lookup can fail when the catalog includes matching operation SKUs. Filter for storage-capacity SKUs before validating units and add the regression fixture before merging.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Issue #77 requires Cloud Storage pricing to use PricingExpression.UsageUnit, avoid the 730x monthly-to-annual error, preserve hourly units, and reject unsupported units. The client converts GiBy.mo pr…
Out of Scope Changes check	✅ Passed	The changes stay within issue #77. The new HTTP fixture helper and expanded tests verify catalog unit handling through public consumers. The client changes only modify Cloud Storage pricing extraction…
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: normalizing Cloud Storage catalog pricing units in GCP.

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Inline comments:
Review comments at @providers/gcp/services/cloudstorage/client.go:
- Around line 374-375: Update getStoragePricing to filter for storage-capacity
SKUs before calling extractStoragePriceFromSKU, so unrelated operation SKUs are
skipped while unsupported units on selected capacity SKUs still return errors.
Add a regression fixture with an operation SKU alongside valid capacity and
commitment SKUs.

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📒 Files selected for processing (2)

• providers/gcp/services/cloudstorage/client.go
• providers/gcp/services/cloudstorage/client_test.go

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