feat(aws/ladder): export the Savings Plan state set and region rule counted as existing commitment

[cristim]

Summary

The platform ladder reconciler (platform#852) copies the AWS ladder's unexported Savings Plan state set and EC2Instance region rule and pins them with a table. This exports both so it can call them directly and drop the copy.

• ExistingSPStates() []sptypes.SavingsPlanState: the states counted as existing commitment (active, payment-pending; rationale moved onto the doc). Returns a fresh copy; spListerStates stays the single source and DescribeSavingsPlans now takes its States from this function.
• CountsAsExistingSP(planType sptypes.SavingsPlanType, spRegion, ladderRegion string) bool: EC2Instance plans count only in their own region; Compute and every other type count everywhere. appendRegionScopedSPs now calls it, so there is one implementation. It takes no state because the state is the API filter and the region rule never reads it, which lets the platform apply it to its own DescribeSavingsPlans output. Its doc notes that an EC2Instance plan with an empty region returns false, so callers must validate the region (the adapter already rejects that case in mapActiveSP).

Behavior is unchanged: the predicate is the De Morgan inverse of the old exclusion, same fields, exact case-sensitive comparison against the SDK constant.

Closes #355

Tests

• TestExistingSPStates: contents, and mutating the returned slice does not affect the next call.
• TestCountsAsExistingSP: truth table over EC2Instance same/other/empty/case-differing region, Compute, SageMaker, and unknown or case-differing plan types.
• Mutation probes (scratch copies): return true fails TestCountsAsExistingSP and TestSPLister_OutOfRegionEC2InstanceExcluded; flipping the region compare fails 3 tests; flipping the plan-type compare fails 4+. All 265 ladder tests pass unmodified.

Verification

make build, make vet, (cd providers/aws && GOWORK=off go test -race -short ./...), pinned golangci-lint v2.10.1 (0 issues), gofmt, and the commit/pre-push hooks pass. Unit-level evidence only; no AWS call.

Local review: two adversarial passes by a non-author reviewer. Pass 1 had two optional nits (compare against the SDK constant directly, document the empty-region case), applied in the second commit; pass 2 found nothing actionable.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Savings Plans are now counted consistently across plan types. EC2 Instance plans count only when their region exactly matches the ladder region; other plan types count regardless of region.
  • Active and payment-pending Savings Plans are included when determining existing plans. Returned state lists no longer allow changes to affect later results.

[cristim]

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📥 Commits

Reviewing files that changed from the base of the PR and between d41a30d and 75fb3ff.

📒 Files selected for processing: 2

• providers/aws/ladder/adapters.go
• providers/aws/ladder/adapters_test.go

📝 Walkthrough

The ladder package now exposes the Savings Plan states used for listing and a predicate for region-scoped plan counting. The adapters use these functions, and tests cover the state slice and predicate behavior.

Changes: Savings Plan listing rules

Layer / File(s)	Summary
Expose and use Savings Plan states providers/aws/ladder/adapters.go, providers/aws/ladder/adapters_test.go	ExistingSPStates returns a fresh copy of the active and payment-pending states. ListActiveSPs uses the accessor. Tests check the returned states and slice independence.
Apply the existing-plan region rule providers/aws/ladder/adapters.go, providers/aws/ladder/adapters_test.go	CountsAsExistingSP counts every non-EC2Instance plan type and counts EC2Instance plans only when regions match exactly. The filter uses the predicate. Tests cover plan types and region comparisons.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Feature

Merge Risk: 🔵 Low · up to d41a3

The behavior is otherwise unchanged. The exported predicate's documentation slightly misstates its empty-region result, which could mislead a caller. Fix the documentation before or shortly after merge.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly summarizes the main changes: exporting Savings Plan state and region-counting rules for the AWS ladder.
Linked Issues check		Issue #355 requires the exact existing Savings Plan state set and region rule to be exported for reuse. ExistingSPStates() returns active and payment-pending states as a fresh copy. ListActiveSPs …
Out of Scope Changes check		The changes stay within issue #355. The production changes export the two requested rules, replace the local call sites, and document their behavior. The added tests verify the exported API and unchan…

Full details: Linked Issues check

Explanation

Issue #355 requires the exact existing Savings Plan state set and region rule to be exported for reuse. ExistingSPStates() returns active and payment-pending states as a fresh copy. ListActiveSPs uses this function for DescribeSavingsPlans. CountsAsExistingSP implements the EC2Instance exact-region rule and the global rule for other plan types. appendRegionScopedSPs uses the exported predicate. Tests cover the state contents, copy isolation, and region and plan-type cases.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue #355. The production changes export the two requested rules, replace the local call sites, and document their behavior. The added tests verify the exported API and unchanged filtering behavior. No unrelated production behavior or unrelated feature appears in the reviewed diff.

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[cristim]

Independent adversarial review: CLEAN at c0c4df1c355792f116139a6d1e1b070ab30c1cbd

Reviewer: an independent agent that did not write this change (Sonnet, high effort), cold brief, full diff. The PR body was treated as a claim.

Blocking findings: none.

Equivalence proof.

• The old exclusion skipped when entry.PlanType == spPlanTypeEC2Instance && entry.Region != region. spPlanTypeEC2Instance is string(sptypes.SavingsPlanTypeEc2Instance) (interfaces.go:28).
• The new predicate is planType != Ec2Instance || spRegion == ladderRegion (ladder/adapters.go:59-60). The call site (adapters.go:145) skips on !CountsAsExistingSP(...).
• By De Morgan, !(P != E || R == L) ≡ P == E && R != L. The plan type is a lossless string cast of the same field, and both sides use Go string ==/!=.
• So every input behaves identically: empty regions, case-differing regions or types, unknown plan types (SageMaker, Database, Other) and an empty ladder region.
• mapActiveSP (adapters.go:168) still rejects an empty EC2Instance region first.

State set.

• spListerStates is unchanged (active, payment-pending).
• DescribeSavingsPlans gets States: ExistingSPStates().
• ExistingSPStates returns append([]sptypes.SavingsPlanState(nil), spListerStates...), a fresh copy.
• Nothing else reads spListerStates, and no other mutable state is exported.

Tests and probes. The tests call the real functions, and the truth table has 10 rows.

Mutation probes (scratch copy, reverted):

• CountsAsExistingSP set to return true fails TestCountsAsExistingSP and TestSPLister_OutOfRegionEC2InstanceExcluded. I re-ran this locally.
• ExistingSPStates returning the shared slice fails TestExistingSPStates.

Non-blocking:

• The truth table has no empty-ladder-region or "Database" rows. The equivalence proof covers them.
• The ExistingSPStates doc comment layout is a little awkward.

Local verification (macOS, Go 1.27.2, exact SHA c0c4df1)

Unit-level evidence only; no AWS call:

• (cd providers/aws && GOWORK=off go test -race -short -count=1 ./...) exits 0 with 14 packages ok.
• make build and make vet pass.
• Mutation re-run: see the probes above.

Behaviour is unchanged by construction (the equivalence proof above), so there is no fail-before to show.

Labels mirror #355. CodeRabbit is quota-limited. If that holds at merge: CR waived: quota, adversarial review + local verification + green CI.

[cristim]

Rebased onto main (after #485 merged) using GitHub's server-side update-branch. New head d41a30d4542e703fda08b2d5fd9f52ba885da3d4.

git range-diff:

1:  25e2486 = 1:  fb456c4 feat(aws/ladder): export the Savings Plan state set and region rule ...
2:  c0c4df1 = 2:  d41a30d refactor(aws/ladder): compare the SP type against the SDK constant ...

Both commits are identical, so the CLEAN verdict for c0c4df1 carries over to d41a30d. CI is re-running. CR waived: quota, adversarial review + local verification + green CI.

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Actionable comments posted: 1

---

• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @providers/aws/ladder/adapters.go:
- Around line 55-57: Update CountsAsExistingSP to return false when spRegion is
empty, including when ladderRegion is also empty, so its behavior matches the
documented empty-region contract.

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📥 Commits

Reviewing files that changed from the base of the PR and between 56466ac and d41a30d.

📒 Files selected for processing: 2

• providers/aws/ladder/adapters.go
• providers/aws/ladder/adapters_test.go

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[cristim]

Updated onto main 7383c3a (after #484 and #487) using server-side update-branch. New head 9985a01fdaaf32771128e5a7963446fbd72d85e2. git range-diff shows both commits identical (fb456c4 = dbfaeba, d41a30d = 9985a01), so the CLEAN verdict carries over. CI is re-running. CR waived: quota, adversarial review + local verification + green CI.

[cristim]

Updated onto main 8aec9ef (after #489) using server-side update-branch. New head bb62d5e959a97f61f89e48979ad4dce293584589. git range-diff shows both commits identical (dbfaeba = 4149ba6, 9985a01 = bb62d5e), so the CLEAN verdict carries over. CI is re-running. CR waived: quota, adversarial review + local verification + green CI.

[cristim]

Delta review: CLEAN at 75fb3ff31d6c829dfc7b042869f8ccfee541fa77. Reviewer: claude-go-pr-merge-4 (merge driver, not the author).

• aa52406 resolves CodeRabbit's empty-region finding. The doc comment on CountsAsExistingSP now matches the code: two empty regions compare equal and count. Behaviour is unchanged by design. The new subtest TestCountsAsExistingSP/EC2Instance_both_regions_empty pins the case.
• It was then rebased server-side onto main c4c7158 (fix(azure/savingsplans): take the inventory resource type from the SKU, not the ARM name #494). git range-diff shows all three commits identical, ending aa52406 = 75fb3ff.
• The CR thread is answered and resolved.
• The implementer ran gofmt, go test -race ./ladder/... and go vet on the change: clean.

CodeRabbit reviewed d41a30d with 1 actionable finding, now fixed. CI is re-running on 75fb3ff31d6c829dfc7b042869f8ccfee541fa77.

[cristim]

Merged by squash at reviewed head 75fb3ff31d6c829dfc7b042869f8ccfee541fa77 as c479af14. The gates were met on that SHA:

• independent review CLEAN, posted above (carried across rebases by identical git range-diff)
• local verification posted above
• CI green on 75fb3ff3
• labels mirrored; no unresolved threads

CR waived: quota, adversarial review + local verification + green CI. A retrospective CodeRabbit review will run when quota returns. Closes #355. CodeRabbit reviewed d41a30d (1 actionable, fixed in aa52406, thread resolved).