What is dittory?

dittory is a static analysis CLI tool that detects parameters that always receive the same value.

Supported Targets

Target	Description
React Components	Props passed to JSX elements (<Button variant="primary" />)
Functions	Arguments passed to exported functions
Class Methods	Arguments passed to methods of exported classes

The Problem

In large codebases, it's common to find patterns like this:

// Used in 20 different places, always with variant="primary"
<Button variant="primary" onClick={handleClick}>Submit</Button>
<Button variant="primary" onClick={handleSave}>Save</Button>
<Button variant="primary" onClick={handleCancel}>Cancel</Button>

Or function calls like:

// Called 15 times, always with cache: false
const data = await fetchData(id, { cache: false });

These patterns indicate:

• The parameter could be removed and replaced with a default value
• The API could be simplified by eliminating unnecessary options
• There's copy-paste code that should be refactored

How It Works

1. Parses your TypeScript/TSX codebase using ts-morph
2. Collects all exported React components, functions, and class methods
3. Finds all usages (JSX elements, function calls, method calls)
4. Analyzes each parameter to check if it always receives the same value
5. Reports parameters that are constant across all usages

Parameter Propagation (Call Graph Analysis)

dittory can track values through component/function chains:

// App passes "42" to Parent, Parent passes props.number to Child
// → Child.number is detected as constant "42"

const Child = ({ number }) => <div>{number}</div>;
const Parent = ({ number }) => <Child number={number} />;
export const App = () => <Parent number="42" />;

Pattern	Example	Supported
Direct props access	props.value	✅
Destructured props	({ value }) => ...	✅
Nested access	props.user.name	✅
Multi-level chains	A → B → C propagation	✅
Circular reference protection	Prevents infinite loops	✅

Example Output

Button src/components/Button.tsx:15
Constant Arguments:
  - variant = "primary"
Usages (5):
  - src/pages/Home.tsx:23
  - src/pages/About.tsx:45
  - src/pages/Contact.tsx:12
  - src/features/auth/Login.tsx:67
  - src/features/auth/Register.tsx:89


fetchUser src/api/users.ts:42
Constant Arguments:
  - includeProfile = true
  - cache = false
Usages (3):
  - src/hooks/useUser.ts:18
  - src/pages/Profile.tsx:31
  - src/components/UserCard.tsx:55


---
Found 2 function(s) with constant arguments out of 24 function(s).

Use Cases

Simplify Component APIs

// Before: variant is always "primary" across 20 usages
<Button variant="primary" onClick={handleClick}>Submit</Button>

// After: make "primary" the default
<Button onClick={handleClick}>Submit</Button>

Remove Unnecessary Flexibility

// Before: cache is always false in all 15 call sites
const data = await fetchData(id, { cache: false });

// After: remove the option or change the default
const data = await fetchData(id);

Identify Copy-Paste Patterns

When multiple unrelated files pass the same hardcoded values, it might indicate:

• Missing abstractions
• Configuration that should be centralized
• Dead code paths that were never actually used differently

Requirements

• Node.js >= 18
• TypeScript project with a tsconfig.json