migrate-to-shoehorn

skills/misc/migrate-to-shoehorn/SKILL.md · 2.7 KB · View on GitHub at 4ae2317

Summary written at import

Migrates TypeScript test files from as type assertions to fromPartial, fromAny, and fromExact from @total-typescript/shoehorn. Model-invoked; in the frozen misc bucket.

Files in this skill

File	What it does	Flags
agents/openai.yaml	Codex metadata for the skill: display name “Migrate to Shoehorn” and short description “Replace test assertions with shoehorn”.

Frontmatter

name: migrate-to-shoehorn
description: Migrate test files from `as` type assertions to @total-typescript/shoehorn. Use when user mentions shoehorn, wants to replace `as` in tests, or needs partial test data.

Migrate to Shoehorn

Why shoehorn?

shoehorn lets you pass partial data in tests while keeping TypeScript happy. It replaces as assertions with type-safe alternatives.

Test code only. Never use shoehorn in production code.

Problems with as in tests:

• Trained not to use it
• Must manually specify target type
• Double-as (as unknown as Type) for intentionally wrong data

Install

npm i @total-typescript/shoehorn

Migration patterns

Large objects with few needed properties

Before:

type Request = {
  body: { id: string };
  headers: Record<string, string>;
  cookies: Record<string, string>;
  // ...20 more properties
};

it("gets user by id", () => {
  // Only care about body.id but must fake entire Request
  getUser({
    body: { id: "123" },
    headers: {},
    cookies: {},
    // ...fake all 20 properties
  });
});

After:

import { fromPartial } from "@total-typescript/shoehorn";

it("gets user by id", () => {
  getUser(
    fromPartial({
      body: { id: "123" },
    }),
  );
});

as Type → fromPartial()

Before:

getUser({ body: { id: "123" } } as Request);

After:

import { fromPartial } from "@total-typescript/shoehorn";

getUser(fromPartial({ body: { id: "123" } }));

as unknown as Type → fromAny()

Before:

getUser({ body: { id: 123 } } as unknown as Request); // wrong type on purpose

After:

import { fromAny } from "@total-typescript/shoehorn";

getUser(fromAny({ body: { id: 123 } }));

When to use each

Function	Use case
fromPartial()	Pass partial data that still type-checks
fromAny()	Pass intentionally wrong data (keeps autocomplete)
fromExact()	Force full object (swap with fromPartial later)

Workflow

1. Gather requirements - ask user:

   • What test files have as assertions causing problems?
   • Are they dealing with large objects where only some properties matter?
   • Do they need to pass intentionally wrong data for error testing?

2. Install and migrate:

   • Install: npm i @total-typescript/shoehorn
   • Find test files with as assertions: grep -r " as [A-Z]" --include="*.test.ts" --include="*.spec.ts"
   • Replace as Type with fromPartial()
   • Replace as unknown as Type with fromAny()
   • Add imports from @total-typescript/shoehorn
   • Run type check to verify

Original Markdown source

SKILL.md

---
name: migrate-to-shoehorn
description: Migrate test files from `as` type assertions to @total-typescript/shoehorn. Use when user mentions shoehorn, wants to replace `as` in tests, or needs partial test data.
---

# Migrate to Shoehorn

## Why shoehorn?

`shoehorn` lets you pass partial data in tests while keeping TypeScript happy. It replaces `as` assertions with type-safe alternatives.

**Test code only.** Never use shoehorn in production code.

Problems with `as` in tests:

- Trained not to use it
- Must manually specify target type
- Double-as (`as unknown as Type`) for intentionally wrong data

## Install

```bash
npm i @total-typescript/shoehorn
```

## Migration patterns

### Large objects with few needed properties

Before:

```ts
type Request = {
  body: { id: string };
  headers: Record<string, string>;
  cookies: Record<string, string>;
  // ...20 more properties
};

it("gets user by id", () => {
  // Only care about body.id but must fake entire Request
  getUser({
    body: { id: "123" },
    headers: {},
    cookies: {},
    // ...fake all 20 properties
  });
});
```

After:

```ts
import { fromPartial } from "@total-typescript/shoehorn";

it("gets user by id", () => {
  getUser(
    fromPartial({
      body: { id: "123" },
    }),
  );
});
```

### `as Type` → `fromPartial()`

Before:

```ts
getUser({ body: { id: "123" } } as Request);
```

After:

```ts
import { fromPartial } from "@total-typescript/shoehorn";

getUser(fromPartial({ body: { id: "123" } }));
```

### `as unknown as Type` → `fromAny()`

Before:

```ts
getUser({ body: { id: 123 } } as unknown as Request); // wrong type on purpose
```

After:

```ts
import { fromAny } from "@total-typescript/shoehorn";

getUser(fromAny({ body: { id: 123 } }));
```

## When to use each

| Function        | Use case                                           |
| --------------- | -------------------------------------------------- |
| `fromPartial()` | Pass partial data that still type-checks           |
| `fromAny()`     | Pass intentionally wrong data (keeps autocomplete) |
| `fromExact()`   | Force full object (swap with fromPartial later)    |

## Workflow

1. **Gather requirements** - ask user:
   - What test files have `as` assertions causing problems?
   - Are they dealing with large objects where only some properties matter?
   - Do they need to pass intentionally wrong data for error testing?

2. **Install and migrate**:
   - [ ] Install: `npm i @total-typescript/shoehorn`
   - [ ] Find test files with `as` assertions: `grep -r " as [A-Z]" --include="*.test.ts" --include="*.spec.ts"`
   - [ ] Replace `as Type` with `fromPartial()`
   - [ ] Replace `as unknown as Type` with `fromAny()`
   - [ ] Add imports from `@total-typescript/shoehorn`
   - [ ] Run type check to verify