fix(cmd): reject Savings Plan hourly commitments that round to 0.00

[IAmJSD]

Root cause

validateSavingsPlanPreconditions (cmd/savings_plan_purchase.go) only rejected HourlyCommitment <= 0. The library formats the commitment for CreateSavingsPlan with fmt.Sprintf("%.2f", ...) (cloud-commitments-go/providers/aws/services/savingsplans/client.go:235 at the pinned version), so a positive commitment below 0.005 (e.g. 0.004) passed validation, was reported as a success by the dry run, and was sent to AWS as "0.00".

Fix

Add a spCommitmentFormat = "%.2f" constant that mirrors the library's formatting and reject any commitment that formats as "0.00", with an error that says so and names the 0.005 minimum. validatePurchasePreconditions runs on both the main path and the --input-csv path, dry run and real run, so both now reject such rows before any API call.

Closes #2163

Verification

All evidence is unit-level (no AWS calls). Run with AWS_CONFIG_FILE=/dev/null AWS_SHARED_CREDENTIALS_FILE=/dev/null because this machine's default AWS profile is invalid, which otherwise breaks some unrelated tests.

New test TestValidatePurchasePreconditions_RejectsCommitmentThatRoundsToZero: 0.001, 0.004, 0.00499 must be rejected (error mentions 0.00); 0.005, 0.01, 1.5 must still be accepted.

• Fail before (test added, fix not yet applied):

  $ go test ./cmd -run TestValidatePurchasePreconditions -count=1
  --- FAIL: TestValidatePurchasePreconditions_RejectsCommitmentThatRoundsToZero
      Error: An error is expected but got nil.
      Messages: commitment 0.001 rounds to 0.00 and must be rejected
  

• Pass after:

  --- PASS: TestValidatePurchasePreconditions
  --- PASS: TestValidatePurchasePreconditions_RejectsCommitmentThatRoundsToZero
  

• go build -o cudly ./cmd: OK
• go test -short -race -count=1 ./...: ok github.com/LeanerCloud/cloud-commitments-cli/cmd
• go vet ./...: clean
• golangci-lint run (v2.10.1): 0 issues
• gocyclo -over 10 cmd/savings_plan_purchase.go: silent
• bash scripts/gosec-hook.sh cmd/savings_plan_purchase.go: 0 issues; gofmt -l cmd: clean; make tidy-check: clean

Mutation note: if the check is removed, or the format constant drifts to a finer precision (e.g. %.3f), the new test fails on 0.001.

Real-cloud gap: not exercised against a real CreateSavingsPlan call. The rejection depends only on the pinned library's %.2f formatting, which was checked in the module source. If the library's formatting changes, spCommitmentFormat must change with it.

Out of scope

• A non-finite commitment (NaN) still passes <= 0 and the new check, because it formats as "NaN". CSV parsing already validates numeric bounds (fix(cli): validate CSV headers, encoding and numeric bounds #2145), so this was left alone here.
• No library change. Sending more precision, or rejecting at the library boundary, would belong in cloud-commitments-go.

Maintainer: please mirror the issue's triage labels onto this PR: triaged, priority/p3, severity/low, urgency/eventually, impact/few, effort/xs, type/bug.

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📥 Commits

Reviewing files that changed from the base of the PR and between 817ab4b and 69a97e4.

📒 Files selected for processing: 2

• cmd/savings_plan_purchase.go
• cmd/savings_plan_purchase_test.go

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[cristim]

Merge-gate review verdict: CLEAN at 69a97e4

Independent adversarial review by a non-author agent (Sonnet high, cold brief, full diff 817ab4bc...69a97e45): no blocking findings.

Checked against the source of truth:

• Rounding parity. The provider sends fmt.Sprintf("%.2f", spDetails.HourlyCommitment) (cloud-commitments-go providers/aws/services/savingsplans/client.go:235, the version pinned in go.mod). The new check at cmd/savings_plan_purchase.go:151 uses the same verb on the same float64, so the two cannot disagree. 0.005 formats as 0.01 and is accepted.
• Placement and entry points. The check is in validateSavingsPlanPreconditions, which validatePurchasePreconditions runs before the single PurchaseCommitment call site (multi_service_helpers.go:302). Both callers, the flag/recommendation path (multi_service.go:636) and the CSV path (:1046), validate first (:613, :1039). Dry-run validates too. Nothing mutates HourlyCommitment after validation.
• Conflicts. The PR does not overlap the commits that landed on main since its base.

Non-blocking notes:

• NaN and ±Inf pass the existing <= 0 check and the new check. This behaviour pre-exists the PR and is outside fix(cmd): Savings Plan hourly commitment below 0.005 passes validation and is sent as 0.00 #2163; tracked as a follow-up in fix(cmd): reject NaN and Inf Savings Plan hourly commitments at validation #2213.
• The "at least 0.005" wording is nominal; the exact boundary depends on float representation. This is cosmetic.

Local verification on macOS at 69a97e4 (fixture-based unit tests, no AWS calls):

• go test ./... -count=1 (go1.26.9, AWS config and credentials set to /dev/null): ok cmd 81.4s.
• go build ./cmd OK; go vet ./... clean.
• Deletion probe: neutralising the new check fails TestValidatePurchasePreconditions_RejectsCommitmentThatRoundsToZero. This is equivalent to fail-before, since the base has no check.
• Mutation probe: changing %.2f to %.1f fails the same test. Both probes were reverted.
• Not run: the built binary against a 0.004 input, because the command needs AWS config. Real-account coverage gap noted.

Merge blockers (not code): the fork CI runs 38838595062 and 38838595305 need maintainer approval, and the PR is a draft for the author to mark ready. CodeRabbit will be run, or waived on quota, once the PR is ready.

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