Migrate To Shoehorn

# 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