TS · architecture

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prefer-minimal-parameter-contract

Prefer the proven read-only subset for a private consumer parameter.

minimal Rule source Tests Catalog JSON

Why

A private scalar consumer can unnecessarily require data it never reads. Removing unused required fields accepts more structural values while preserving the original runtime object and producer information.

Fix

Review a smaller existing contract, Pick or interface containing the read fields and preserving readonly and optional modifiers. Change the consumer annotation; a new runtime projection has different identity and allocation costs. The safe fix removes only proven unused required property signatures from the private inline annotation; producer objects, calls and function bodies remain unchanged.

Examples

Before — flagged A scalar prefix does not require the object's unread email

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
const prefix = "Hello ";
function label(prefix: string, user: { email: string; name: string }): string {
  return prefix + user.name;
}
label(prefix, account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

After — preferred Reading both object fields retains their requirements

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
const prefix = "Hello ";
function label(prefix: string, user: { email: string; name: string }): string {
  return prefix + user.name + user.email;
}
label(prefix, account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

Autofix output

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
const prefix = "Hello ";
function label(prefix: string, user: { name: string }): string {
  return prefix + user.name;
}
label(prefix, account);

Before — flagged Only the name crosses a local scalar helper call

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
function formatName(name: string): string {
  return name.toUpperCase();
}
function label(user: { email: string; name: string }): string {
  return formatName(user.name);
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

After — preferred The consumer still requires a separately read field

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
function formatName(name: string): string {
  return name.toUpperCase();
}
function label(user: { email: string; name: string }): string {
  return formatName(user.name) + user.email;
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

Autofix output

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
function formatName(name: string): string {
  return name.toUpperCase();
}
function label(user: { name: string }): string {
  return formatName(user.name);
}
label(account);

Before — flagged A required nullable field is never inspected

src/case.ts

export {};
const account = { name: "Ada", email: null };
function label(user: { email: string | null; name: string }): string {
  return user.name;
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

After — preferred An inspected nullable field keeps its contract

src/case.ts

export {};
const account = { name: "Ada", email: null };
function label(user: { email: string | null; name: string }): string {
  return user.email ?? user.name;
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

Autofix output

src/case.ts

export {};
const account = { name: "Ada", email: null };
function label(user: { name: string }): string {
  return user.name;
}
label(account);

Before — flagged A nullable name remains while an unread email requirement is removed

src/case.ts

export {};
const account = { name: null, email: "a" };
function label(user: { readonly email: string; readonly name: string | null }): string {
  return user.name ?? "";
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

After — preferred Both requirements remain when the nullable view reads email too

src/case.ts

export {};
const account = { name: null, email: "a" };
function label(user: { readonly email: string; readonly name: string | null }): string {
  return user.name ?? user.email;
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

Autofix output

src/case.ts

export {};
const account = { name: null, email: "a" };
function label(user: { readonly name: string | null }): string {
  return user.name ?? "";
}
label(account);

Before — flagged A private name consumer unnecessarily requires email

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
function label(user: { readonly email: string; readonly name: string }): string {
  return user.name;
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

After — preferred Every required dependency is read

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
function label(user: { readonly email: string; readonly name: string }): string {
  return user.name + user.email;
}
label(account);

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "Bundler"
  }
}

Autofix output

src/case.ts

export {};
const account = { name: "Ada", email: "a" };
function label(user: { readonly name: string }): string {
  return user.name;
}
label(account);