fix(pegboard): reject empty actor kv values

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[NathanFlurry]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• test(engine): cover envoy Sleep crash policy wake and recovery paths #4816
• refactor(sqlite-storage): extract DBHead to vbare-versioned protocol crate #4815
• refactor(sqlite-storage): rename SqliteOrigin variants for clarity #4814
• fix(sqlite-storage): allow invalidate_v1_migration on non-migrating META #4813
• test(engine): stabilize runner and envoy suites #4809
• fix(pegboard): reject empty actor kv values #4808 👈 (View in Graphite)
• fix(pegboard): stabilize actor2 validation and lifecycle #4804 : 1 other dependent PR (#4805 )
• fix(pegboard): decode envoy actor eviction keys #4803
• fix(pegboard-envoy): subscribe before registering envoy #4802
• fix(envoy-client): clear processed_command_idx after ack send #4812
• fix(envoy-client): dedupe replayed commands by index #4811
• fix(envoy-client): complete command and request lifecycles #4801
• fix(envoy-protocol): advertise current protocol version #4800
• fix(guard): serialize gateway actor keys correctly #4655
• fix(rivetkit-native): expose full hibernation metadata to JS #4657
• chore(rivetkit): remove inline tests #4668
• fix(api): subscribe before namespace workflow dispatch #4654
• fix(rivetkit): restore hibernatable sockets and hydrate serverless starts #4658
• fix(pegboard): persist and replay hibernating requests #4656
• fix(rivetkit): keep internal error exposure behavior consistent #4661
• test(rivetkit): stabilize actor db driver tests #4664
• fix(test): stabilize lifecycle, sleep, queue, and run edge cases #4660 : 1 other dependent PR (#4665 )
• test(rivetkit): re-enable gateway URL and direct-registry coverage #4659
• fix(rivetkit): add lifecycle error retry and gateway HTTP routing #4666
• fix(rivetkit-core): remove legacy timeouts #4799
• docs: add replay guidance notes #4796
• fix(inspector): stream patched state updates #4795
• fix(rivetkit): refresh stale actor handles #4794
• test(rivetkit-napi): move private tests to crate root #4793
• test(rivetkit-core): move private tests to crate root #4792
• test(runner-configs): assert envoy protocol version #4791
• fix(serverless): split metadata protocol errors #4789 : 1 other dependent PR (#4790 )
• chore(sqlite): add open close lifecycle for envoy actors #4788
• fix(rivetkit): share lifecycle shutdown grace #4810
• fix(pegboard): move sqlite v1 migration into actor workflow #4787 : 1 other dependent PR (#4797 )
• test(rivetkit): cover c.db access from onWake/onSleep/onDestroy #4786
• fix(rivetkit-napi): run onMigrate before createState/onCreate/createVars #4785
• refactor(rivetkit-core): merge ready+started into lifecycle_started, drop redundant napi calls #4784
• fix(rivetkit): drain native sleep side tasks reliably #4782 : 1 other dependent PR (#4783 )
• fix(rivetkit): route raw request fetches to actors #4781
• fix(pegboard): refresh runner config after envoy connect #4778 : 2 other dependent PRs (#4779 , #4798 )
• chore(kitchen-sink): configurable endpoint #4766 : 2 other dependent PRs (#4754 , #4777 )
• refactor(rivetkit-core): rename StopReason to ShutdownKind and kill enum fallthroughs #4765
• chore(envoy-client): log command and event payloads #4751
• fix(rivetkit): minor sleep-cleanup follow-ups #4761
• docs(rivetkit): clean up stale setPreventSleep references in docs and JSDoc #4760
• docs(rivetkit): document keepAwake/waitUntil counter-arm race and surface bridge errors #4759
• test(engine): force overdue branch in alarm-during-sleep test with negative offset #4758
• fix(rivetkit-core): return stopping not starting when sleep/destroy called mid-shutdown #4757
• test(rivetkit): remove sleepWithPreventSleep fixture and tests #4756
• test(engine): add regression test for alarm-during-sleep-transition race #4755
• test(rivetkit-core): cover sleep/destroy guards and prevent_sleep no-op #4750
• docs: add keepAwake vs waitUntil table and internal sleep-sequence invariants #4749
• feat(rivetkit): expose c.keepAwake(promise) through native path #4748
• refactor(rivetkit): deprecate setPreventSleep to no-op in TypeScript #4747
• fix(rivetkit-core): enumerate non-drained counters in grace deadline warn log #4746
• fix(rivetkit-core): abort graceful cleanup task when grace deadline elapses #4745
• fix(rivetkit-core): error on sleep/destroy before startup or already-requested #4743
• fix(rivetkit-core): cap SerializeState shutdown timeout at 15s #4742
• refactor(rivetkit-core): remove prevent_sleep field and deprecate set_prevent_sleep to no-op #4741
• fix(api-public): remove orphan import_export actors module #4764
• main

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[claude]

PR Review: fix(pegboard): reject empty actor kv values

Overview: This is a minimal one-line fix that adds an ensure! guard rejecting empty byte slices ([]) in validate_entries, preventing them from being written to actor KV storage.

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Correctness

The fix is correct and closes a real gap. Without it:

1. (0..value.len()).step_by(VALUE_CHUNK_SIZE) in the put path produces an empty iterator for a zero-length value, so zero chunk keys are written to FDB.
2. The metadata key is still written (it's set unconditionally before the chunk loop).
3. On read, EntryBuilder::build() already guards against this with ensure!(!self.value.is_empty(), "empty value at key"), so the read-back would silently drop the entry or error. The new guard catches the problem earlier at write time with a cleaner error message surfaced to the caller.

The existing entry.rs check ("empty value at key") becomes a defence-in-depth fallback for the read path; the new check is the canonical rejection point on write.

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Minor suggestions

• Error message style. The surrounding ensure! messages use sentence-case ("A maximum of 128 key-value entries is allowed"). Consider "value cannot be empty" → "value cannot be empty (use kv.delete to remove a key)" or at minimum keep consistent with the project's sentence capitalisation. This is cosmetic only.

• Error code vs plain string. The KvStorageQuotaExceeded check above returns a typed errors::Actor::* error. If there is (or should be) a dedicated errors::Actor::KvEmptyValue variant, this would produce a machine-readable error code the client SDK can pattern-match on rather than a plain string. Not strictly required but worth considering for consistency.

• Tests. The PR description acknowledges missing tests. A unit test in utils.rs (or the tests/ directory per project conventions) covering:

  • validate_entries with one empty value → expect Err
  • validate_entries with one non-empty value → expect Ok
  • would make this regression-proof without relying only on the existing entry.rs read-path guard.

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Verdict

The change is correct and the logic is sound. The suggestions above are non-blocking. Good candidate to merge after the description checklist is filled in and, ideally, a small test is added.