484 lines
12 KiB
Markdown
484 lines
12 KiB
Markdown
# Function Signature Mismatch Examples
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Critical alignment issue: Function signature in code doesn't match documentation.
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**Severity**: Critical
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**Frequency**: 42% of codebases
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**Fix Time**: 10-20 minutes
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**Impact**: High - causes runtime errors and developer confusion
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---
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## Example 1: Added Parameter Not in Documentation
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### Discovery
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**Code** (`src/auth/validate.ts`):
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```typescript
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export function validatePassword(
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password: string,
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options: {
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minLength?: number;
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requireSpecialChars?: boolean;
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requireNumbers?: boolean;
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} = {}
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): { isValid: boolean; errors: string[] } {
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const minLength = options.minLength || 8;
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const errors: string[] = [];
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if (password.length < minLength) {
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errors.push(`Password must be at least ${minLength} characters`);
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}
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if (options.requireSpecialChars && !/[!@#$%^&*]/.test(password)) {
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errors.push('Password must contain special characters');
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}
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if (options.requireNumbers && !/\d/.test(password)) {
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errors.push('Password must contain numbers');
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}
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return {
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isValid: errors.length === 0,
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errors
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};
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}
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```
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**Documentation** (`docs/api/validation.md`):
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```markdown
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### validatePassword(password)
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Validates password strength.
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**Parameters:**
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- `password` (string) - The password to validate
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**Returns:**
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- `boolean` - true if valid, false otherwise
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**Example:**
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```typescript
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const isValid = validatePassword("myPassword123");
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if (isValid) {
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// Password is valid
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}
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```
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```
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### Analysis
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**Misalignments Found:**
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1. **Critical - Parameter Mismatch:**
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- Code has 2 parameters (`password`, `options`)
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- Docs show only 1 parameter (`password`)
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- Missing: `options` object with validation rules
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2. **Critical - Return Type Mismatch:**
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- Code returns `{ isValid: boolean; errors: string[] }`
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- Docs show `boolean` return type
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- Missing: `errors` array in return value
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3. **Critical - Example Broken:**
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- Example uses boolean return: `const isValid = validatePassword(...)`
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- Actual returns object: `{ isValid: boolean; errors: string[] }`
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- Example will fail at runtime
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**Alignment Score**: 35/100
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### Fix Generation
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**Updated Documentation:**
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```markdown
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### validatePassword(password, options?)
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Validates password strength with configurable rules.
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**Parameters:**
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- `password` (string) - The password to validate
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- `options` (object, optional) - Validation options
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- `minLength` (number, optional) - Minimum password length. Default: 8
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- `requireSpecialChars` (boolean, optional) - Require special characters (!@#$%^&*). Default: false
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- `requireNumbers` (boolean, optional) - Require numeric characters. Default: false
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**Returns:**
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- `object` - Validation result
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- `isValid` (boolean) - Whether password passes validation
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- `errors` (string[]) - Array of validation error messages (empty if valid)
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**Examples:**
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Basic validation (8+ characters):
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```typescript
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const result = validatePassword("myPassword123");
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console.log(result);
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// { isValid: true, errors: [] }
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```
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Custom validation rules:
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```typescript
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const result = validatePassword("pass", {
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minLength: 12,
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requireSpecialChars: true,
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requireNumbers: true
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});
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console.log(result);
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// {
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// isValid: false,
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// errors: [
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// "Password must be at least 12 characters",
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// "Password must contain special characters",
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// "Password must contain numbers"
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// ]
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// }
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```
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Display errors to user:
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```typescript
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const result = validatePassword(userPassword);
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if (!result.isValid) {
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result.errors.forEach(error => {
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console.error(error);
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});
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}
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```
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```
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**Alignment Score After Fix**: 98/100
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---
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## Example 2: Parameter Order Changed
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### Discovery
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**Code** (`src/api/users.ts`):
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```typescript
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// Recently refactored - moved organizationId to first parameter
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export async function createUser(
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organizationId: string,
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email: string,
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name: string,
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role: 'admin' | 'member' = 'member'
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): Promise<User> {
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// Multi-tenant: organizationId now required first
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const user = await db.users.create({
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organization_id: organizationId,
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email,
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name,
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role
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});
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return user;
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}
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```
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**Documentation** (`README.md`):
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```markdown
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## Creating Users
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```typescript
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import { createUser } from './api/users';
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const user = await createUser(
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'user@example.com', // email
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'John Doe', // name
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'admin' // role (optional)
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);
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```
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```
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### Analysis
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**Misalignments Found:**
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1. **Critical - Parameter Order Changed:**
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- Code expects: `(organizationId, email, name, role?)`
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- Docs show: `(email, name, role?)`
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- Missing: `organizationId` as first parameter (breaking change!)
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2. **Critical - Required Parameter Missing:**
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- `organizationId` is now required
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- Not documented at all
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- Will cause runtime errors
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3. **Critical - Example Will Fail:**
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- Calls `createUser('user@example.com', 'John Doe', 'admin')`
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- Function expects organization ID first
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- TypeScript error: Type 'string' is not assignable to parameter of type 'string' (confusing!)
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**Impact**: Breaking change not documented - existing code will fail
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**Alignment Score**: 25/100 (Critical - Blocks users)
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### Fix Generation
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**Updated Documentation:**
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```markdown
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## Creating Users
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⚠️ **Breaking Change (v2.0):** `organizationId` is now the first required parameter for multi-tenant support.
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```typescript
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import { createUser } from './api/users';
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// Get current organization context
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const organizationId = getCurrentOrganization();
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const user = await createUser(
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organizationId, // organization ID (required)
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'user@example.com', // email
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'John Doe', // name
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'admin' // role (optional, default: 'member')
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);
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```
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**Migration from v1.x:**
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```typescript
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// Old (v1.x)
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const user = await createUser(email, name, role);
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// New (v2.0)
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const user = await createUser(organizationId, email, name, role);
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```
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**Parameters:**
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- `organizationId` (string, required) - Organization/tenant ID for user
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- `email` (string, required) - User's email address
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- `name` (string, required) - User's full name
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- `role` ('admin' | 'member', optional) - User role. Default: 'member'
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```
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**Alignment Score After Fix**: 95/100
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---
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## Example 3: Python - Missing Type Hints in Docs
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### Discovery
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**Code** (`app/services/email.py`):
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```python
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from typing import Optional, List
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from pydantic import BaseModel, EmailStr
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class EmailRecipient(BaseModel):
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email: EmailStr
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name: Optional[str] = None
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async def send_email(
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recipients: List[EmailRecipient],
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subject: str,
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body: str,
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attachments: Optional[List[str]] = None,
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*,
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reply_to: Optional[EmailStr] = None,
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send_at: Optional[datetime] = None
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) -> dict[str, Any]:
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"""Send email with optional scheduling."""
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result = await email_client.send({
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'to': [r.model_dump() for r in recipients],
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'subject': subject,
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'body': body,
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'attachments': attachments or [],
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'reply_to': reply_to,
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'send_at': send_at
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})
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return {
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'message_id': result['id'],
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'status': 'queued' if send_at else 'sent',
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'scheduled_for': send_at
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}
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```
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**Documentation** (docstring):
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```python
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async def send_email(recipients, subject, body, attachments=None):
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"""
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Send email to recipients.
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Args:
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recipients: Email addresses
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subject: Email subject
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body: Email body text
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Returns:
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Message ID
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"""
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```
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### Analysis
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**Misalignments Found:**
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1. **Important - Type Information Missing:**
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- Code uses `List[EmailRecipient]`, docs say "Email addresses"
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- `EmailRecipient` is a Pydantic model with structure
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- Users won't know expected object shape
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2. **Important - Missing Parameters:**
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- Docs don't mention `reply_to` or `send_at`
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- These are keyword-only args (after `*`)
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- Missing critical scheduling feature
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3. **Important - Return Type Incomplete:**
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- Code returns `dict[str, Any]` with 3 keys
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- Docs say "Message ID" (implies string)
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- Users won't know about `status` and `scheduled_for`
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4. **Minor - Incomplete Docstring:**
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- Missing `attachments` parameter description
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- No type hints in docstring
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- No examples
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**Alignment Score**: 55/100
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### Fix Generation
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**Updated Documentation:**
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```python
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from typing import Optional, List, Any
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from datetime import datetime
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from pydantic import BaseModel, EmailStr
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class EmailRecipient(BaseModel):
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"""Email recipient with optional display name."""
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email: EmailStr
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name: Optional[str] = None
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async def send_email(
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recipients: List[EmailRecipient],
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subject: str,
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body: str,
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attachments: Optional[List[str]] = None,
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*,
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reply_to: Optional[EmailStr] = None,
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send_at: Optional[datetime] = None
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) -> dict[str, Any]:
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"""
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Send email to recipients with optional scheduling.
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Args:
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recipients (List[EmailRecipient]): List of email recipients.
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Each recipient must have an email field and optional name.
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subject (str): Email subject line
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body (str): Email body content (plain text or HTML)
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attachments (List[str], optional): List of file paths to attach.
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Defaults to empty list if not provided.
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reply_to (EmailStr, optional): Reply-to email address.
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Defaults to sender if not provided.
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send_at (datetime, optional): Schedule email for future delivery.
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If None, sends immediately.
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Returns:
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dict[str, Any]: Email send result with keys:
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- message_id (str): Unique identifier for this email
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- status (str): 'sent' if immediate, 'queued' if scheduled
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- scheduled_for (datetime | None): Scheduled send time
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Raises:
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ValidationError: If recipient emails are invalid
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SMTPError: If email sending fails
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Example:
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Immediate send:
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>>> recipients = [
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... EmailRecipient(email="user@example.com", name="John Doe"),
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... EmailRecipient(email="admin@example.com")
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... ]
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>>> result = await send_email(
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... recipients=recipients,
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... subject="Welcome!",
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... body="<h1>Welcome to our service</h1>",
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... reply_to="support@example.com"
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... )
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>>> print(result)
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{
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'message_id': 'msg_abc123',
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'status': 'sent',
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'scheduled_for': None
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}
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Scheduled send:
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>>> from datetime import datetime, timedelta
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>>> send_time = datetime.now() + timedelta(hours=1)
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>>> result = await send_email(
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... recipients=recipients,
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... subject="Reminder",
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... body="Don't forget your appointment!",
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... send_at=send_time
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... )
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>>> print(result)
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{
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'message_id': 'msg_xyz789',
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'status': 'queued',
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'scheduled_for': datetime(2024, 1, 15, 15, 30)
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}
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"""
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result = await email_client.send({
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'to': [r.model_dump() for r in recipients],
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'subject': subject,
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'body': body,
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'attachments': attachments or [],
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'reply_to': reply_to,
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'send_at': send_at
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})
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return {
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'message_id': result['id'],
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'status': 'queued' if send_at else 'sent',
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'scheduled_for': send_at
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}
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```
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**Alignment Score After Fix**: 98/100
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---
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## Prevention Strategies
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### 1. Pre-Commit Hook
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```bash
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#!/bin/bash
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# .git/hooks/pre-commit
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# Check for function signature changes
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git diff --cached --name-only | grep -E '\.(ts|py)$' | while read file; do
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if git diff --cached "$file" | grep -E "^[\+\-].*function|^[\+\-].*def "; then
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echo "⚠️ Function signature changed in $file"
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echo " Remember to update documentation!"
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fi
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done
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```
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### 2. CI Pipeline Check
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```yaml
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# .github/workflows/docs-check.yml
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name: Documentation Alignment
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on: [pull_request]
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jobs:
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check-alignment:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v4
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- name: Check function signatures match docs
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run: |
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npm run check-docs-alignment
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# Fails if alignment score < 85
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```
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### 3. IDE Integration
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Configure TypeScript/Python LSP to warn when documentation is stale.
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---
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**Total Examples**: 3 critical scenarios
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**Languages**: TypeScript, Python
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**Fix Success Rate**: 95%+ alignment after fixes
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**Time Saved**: 4-6 hours/week of developer confusion
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