fix: handle prototype-colliding external event names

[wangbill (YunchuWang)]

Summary

Fix external-event routing for valid names that collide with JavaScript object properties, including constructor and __proto__.

What changed?

• Initialize the received-event and pending-listener dictionaries without a prototype, while retaining their existing typed record contracts and queue operations.
• Add public in-memory client/worker regressions for listener-first and event-first delivery, mixed casing, FIFO ordering, falsy payloads, and unprocessed-event carryover through continue-as-new and replay.
• Add a core SDK changelog note.

Why is this change needed?

• Plain-object lookups could return inherited properties instead of event queues. Waiting for constructor failed before event delivery; an early constructor or __proto__ event failed the orchestration instead of being buffered.
• Non-empty event names remain accepted without a reserved-name blacklist. Case-insensitive matching, per-name ordering, payload serialization, and replay behavior are preserved.

Issues / work items

• Resolves: N/A; no linked issue.
• Related: N/A.

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Project checklist

• Release notes are not required for the next release
  • Otherwise: Notes added to CHANGELOG.md
• Backport is not required
  • Otherwise: Backport tracked by issue/PR (N/A)
• All required tests have been added/updated (unit tests, E2E tests)
• Breaking change?
  • If yes:
    • Impact: No public API or protocol change.
    • Migration guidance: None required for this fix.

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AI-assisted code disclosure (required)

Was an AI tool used? (select one)

• No
• Yes, AI helped write parts of this PR (e.g., GitHub Copilot)
• Yes, an AI agent generated most of this PR

If AI was used:

• Tool(s): GitHub Copilot.
• AI-assisted areas/files: Runtime event dictionary initialization, external-event-routing.spec.ts, CHANGELOG.md, and this description.
• What you changed after AI output: No human edits recorded; human review is pending.

AI verification (required if AI was used):

• I understand the code and can explain it
• I verified referenced APIs/types exist and are correct
• I reviewed edge cases/failure paths (timeouts, retries, cancellation, exceptions)
• I reviewed concurrency/async behavior
• I checked for unintended breaking or behavior changes

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Testing

Automated tests

• Result: Passed after the fix. Before the production change, 10 of the 19 new regressions failed with the expected public TypeError failure details; the other 9 new cases and 13 existing controls passed. The same focused selection then passed all 32 tests.
• npm run test:unit -w @microsoft/durabletask-js -- --silent - passed: 86 suites, 1,715 tests, including all 19 new regressions and existing empty-name/null-payload controls.
• npm run build:core - passed.
• .\node_modules\.bin\eslint.cmd packages\durabletask-js\src\worker\runtime-orchestration-context.ts packages\durabletask-js\test\external-event-routing.spec.ts - passed.
• git diff --check origin/main...HEAD - passed.
• Prettier: the complete new test and changelog content and the edited runtime hunk pass a check against the repository configuration after normalizing Windows checkout line endings. Unrelated pre-existing runtime formatting differences were left unchanged.
• Hosted CI has not run locally. Full-workspace aggregates, sidecar/DTS emulator E2E, Azure E2E, and sample validation were not run.

Manual validation (only if runtime/behavior changed)

• Environment (OS, Node.js version, components): Windows, Node.js v24.14.0, freshly built local core SDK with the public TestOrchestrationClient, TestOrchestrationWorker, and in-memory backend; no external service.
• Steps + observed results:
  1. Run ordinary async generator orchestrators for both arrival orders with constructor, Constructor, __proto__, and normal/mixed-case controls. All completed with the exact raised payload; the original constructor and early-event failures are gone.
  2. Fence event application in committed history, exercise FIFO with [false, 0], and carry events into a new execution before a fresh event. Results preserve order and once-only consumption: [false, 0] and [false, 0, "fresh"].
  3. Complete all 19 compiled-runtime cases, stop the worker/client, and reset the backend. No pending work or active timers remained, and the process exited naturally.
• Evidence (optional): Local proof artifacts record the committed source/module provenance, public terminal states, event ordering, and cleanup.

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Notes for reviewers

• The production change is limited to the two event dictionaries. No dependency, generated protobuf, entity registry/dispatch, or language-adapter changes.
• The simple __proto__ listener-first case already worked before the fix and remains covered; the failing __proto__ case was event-before-listener routing.
• Event names are protobuf string fields. The documented failure-properties protobuf map-key limitation is unrelated.

[Copilot]

🟢 Approval recommended

The focused implementation correctly addresses prototype collisions and is backed by comprehensive tests.

0 open findings

What changed in this PR

Fixes external-event routing for names that collide with JavaScript object properties.

Changes:

• Uses prototype-free event dictionaries.
• Adds routing, FIFO, falsy-payload, replay, and continue-as-new regressions.
• Documents the fix in the changelog.

File	Description
runtime-orchestration-context.ts	Creates prototype-free event dictionaries.
external-event-routing.spec.ts	Adds comprehensive regression coverage.
CHANGELOG.md	Records the external-event fix.

🧠 Review effort: Balanced

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