TypeScript Null Safety Guardrails SKILL.md skillA
TypeScript Null Safety Guardrails from s977043/river-review is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add s977043/river-review/TypeScript Null Safety Guardrails@v0.1.0Pins v0.1.0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- s977043/river-review
- Path
skills/midstream/typescript-nullcheck/SKILL.md- Versions recorded
- 2
- Latest version
- v0.1.0, committed Jun 29, 2026
- First version recorded
- Jun 29, 2026
- Size
- 3,405 bytes
- Repository stars
- 7
- License
- MIT
Enforce null/undefined safety for changed TypeScript code and suggest safer patterns.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
## Pattern declaration
Primary pattern: Reviewer
Secondary patterns: Inversion
Why: TypeScriptコードの差分からnull/undefinedの安全性をレビューし、実行時エラーシナリオを逆照射する。
## Rule / ルール
- 非同期・外部入力・オプショナル値には null/undefined ガードを設ける。
- 非 null アサーション（`!`）や型アサーション（`as Foo`）に頼らず安全な分岐/early return を使う。
- ユニオン型は網羅的にハンドリングし、`never` 到達をチェックする。
## Heuristics / 判定の手がかり
- `foo!` や `as Type` で未定義かもしれない値を強制している。
- API レスポンス/環境変数/クエリパラメータをノーチェックで使用。
- `switch`/`if` でユニオン型の全ケースをカバーしていない（defaultで握りつぶし）。
- Promise 戻りを `await` せずに使い、`undefined` アクセスの可能性がある。
## Good / Bad Examples
- Good: `if (!value) return err('missing value');` のように early return でガード。
- Bad: `value!.length` のような非 null アサーション。
- Good: `switch (state.kind)` で各 kind を列挙し、`default: assertNever(state)` を置く。
## Actions / 改善案
- 外部入力やオプショナル値に対して null/undefined チェックを追加し、早期 return/throw で制御を明確化する。
- 非 null アサーションを排除し、undefined を許容する型定義やパーサーを導入する。
- ユニオン型を網羅する switch/if を書き、`assertNever` などで漏れを検知する。
## Non-goals / 扱わないこと
- 全コードベースの型定義や API 契約の再設計。
- `strict` モードの導入可否判断。
- ライブラリ側の型定義バグの修正。
## Pre-execution Gate / 実行前ゲート
このスキルは以下の条件がすべて満たされない限り`NO_REVIEW`を返す。
- [ ] 差分にTypeScriptファイル（`*.ts` または `*.tsx`）が含まれている
- [ ] inputContextにdiffが含まれている
…Read the whole file at its exact version.
How to install
mdr add s977043/river-review/TypeScript Null Safety Guardrails@sha256:ccb1a535edbf69b6The line at the top of this page pins the label v0.1.0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_jsr6siac7jps5fhl)
5 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, all committed on Jun 29, 2026.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| v0.1.0 latest | 2026-06-29 | 45e66bc | 3,405 B | A | view · diff |
| v0.1.0 | 2026-06-29 | b988700 | 3,422 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (3405 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
s977043/river-review · 7 stars · license MIT · pushed 2026-11-08 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_jsr6siac7jps5fhl GET https://markdownregistry.com/api/v1/resolve?ref=s977043/river-review/TypeScript Null Safety Guardrails GET https://markdownregistry.com/api/v1/blob/ccb1a535edbf69b61098beb61449267d461efd66a13c6891678d08cf8aa6bd6d
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Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.
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