🔧 Feature: Implement Error Handling for Backend APIs #159
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WalkthroughError handling across the backend was systematically enhanced. The user model gained stricter validation and formatting. Authentication routes and server logic were refactored to ensure consistent error responses, improved logging, and robust handling of unexpected failures. The server now provides fallback and global error-handling middleware for unmatched routes and unhandled exceptions. Changes
Sequence Diagram(s)sequenceDiagram
participant Client
participant Server
participant MongoDB
Client->>Server: API Request (e.g., signup/login)
Server->>Server: Validate & process request
alt Error occurs
Server->>Server: Log error
Server->>Client: Return error response (status, message)
else Success
Server->>MongoDB: Query/Update
MongoDB-->>Server: Result
Server->>Client: Success response
end
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~15 minutes Assessment against linked issues
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Actionable comments posted: 5
🧹 Nitpick comments (1)
backend/models/User.js (1)
17-17: Consider strengthening email validation regex.The current email regex
/.+\@.+\..+/is quite basic and might allow invalid email formats.Consider using a more robust email validation regex:
- match: [/.+\@.+\..+/, "Please enter a valid email address"], + match: [/^[^\s@]+@[^\s@]+\.[^\s@]+$/, "Please enter a valid email address"],Or better yet, consider using a dedicated email validation library like
validator.jsfor more comprehensive validation.
📜 Review details
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Review profile: CHILL
Plan: Pro
📒 Files selected for processing (3)
backend/models/User.js(1 hunks)backend/routes/auth.js(1 hunks)backend/server.js(1 hunks)
🔇 Additional comments (8)
backend/routes/auth.js (3)
11-15: LGTM! Proper duplicate user handling.The duplicate email check is correctly implemented with appropriate error response and status code.
31-51: Excellent refactoring of authentication flow.The login route has been properly refactored from middleware-based to callback-based authentication, providing much better error handling and logging. The explicit handling of authentication errors, missing users, and session errors is well implemented.
56-62: Good error handling for logout route.The logout route now properly handles errors and provides consistent response format with explicit returns.
backend/server.js (3)
37-39: LGTM! Proper 404 fallback route.The fallback route correctly handles unmatched routes with appropriate status code and JSON response format.
51-61: Excellent MongoDB connection and server startup handling.The promise-based approach with proper error logging and process exit on database failure is well implemented. This ensures the application doesn't start if the database connection fails.
42-48: Security concern: Exposing stack traces in production.While the error middleware conditionally hides stack traces in production, the current logic will still expose them due to the undefined check.
Fix the conditional logic for hiding stack traces:
app.use((err, req, res, next) => { console.error('Unhandled Error:', err.stack); res.status(err.status || 500).json({ message: err.message || 'Internal Server Error', - error: process.env.NODE_ENV === 'production' ? undefined : err.stack, + ...(process.env.NODE_ENV !== 'production' && { error: err.stack }), }); });Likely an incorrect or invalid review comment.
backend/models/User.js (2)
5-24: Excellent schema validation enhancements.The schema improvements include proper validation with custom error messages, data sanitization (trim, lowercase), and email format validation. The addition of timestamps is also valuable for audit trails.
27-38: Improved password hashing error handling.The pre-save hook now includes proper error logging and consistent return statements. The error handling flow is clear and follows best practices.
| password: { | ||
| type: String, | ||
| required: [true, "Password is required"], | ||
| minlength: [6, "Password must be at least 6 characters long"], |
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🛠️ Refactor suggestion
Consider strengthening password requirements.
The current minimum length of 6 characters might be insufficient for security. Consider adding complexity requirements.
Enhance password validation:
password: {
type: String,
required: [true, "Password is required"],
- minlength: [6, "Password must be at least 6 characters long"],
+ minlength: [8, "Password must be at least 8 characters long"],
+ validate: {
+ validator: function(password) {
+ return /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]/.test(password);
+ },
+ message: "Password must contain at least one uppercase letter, one lowercase letter, one number, and one special character"
+ }
},📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| minlength: [6, "Password must be at least 6 characters long"], | |
| password: { | |
| type: String, | |
| required: [true, "Password is required"], | |
| minlength: [8, "Password must be at least 8 characters long"], | |
| validate: { | |
| validator: function(password) { | |
| return /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]/.test(password); | |
| }, | |
| message: "Password must contain at least one uppercase letter, one lowercase letter, one number, and one special character" | |
| } | |
| }, |
🤖 Prompt for AI Agents
In backend/models/User.js at line 22, the password validation only enforces a
minimum length of 6 characters, which is weak for security. Enhance the password
validation by adding complexity requirements such as including uppercase
letters, lowercase letters, numbers, and special characters using a custom
validator or regex pattern in the schema definition.
| router.post("/signup", async (req, res) => { | ||
|
|
||
| const { username, email, password } = req.body; | ||
| const { username, email, password } = req.body; |
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🛠️ Refactor suggestion
Consider adding input validation before processing.
The route directly destructures req.body without validating the presence or format of required fields. This could lead to unexpected behavior if any field is missing or malformed.
Add input validation before processing:
router.post("/signup", async (req, res) => {
const { username, email, password } = req.body;
+
+ // Validate required fields
+ if (!username || !email || !password) {
+ return res.status(400).json({ message: 'All fields are required' });
+ }
try {📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| const { username, email, password } = req.body; | |
| router.post("/signup", async (req, res) => { | |
| const { username, email, password } = req.body; | |
| // Validate required fields | |
| if (!username || !email || !password) { | |
| return res.status(400).json({ message: 'All fields are required' }); | |
| } | |
| try { | |
| // … existing signup logic … | |
| } catch (err) { | |
| // … existing error handling … | |
| } | |
| }); |
🤖 Prompt for AI Agents
In backend/routes/auth.js at line 8, the code destructures username, email, and
password from req.body without validating their presence or format. Add input
validation before this line to check that all required fields exist and meet
expected formats, returning an error response if validation fails to prevent
processing invalid or incomplete data.
| console.error("Signup Error:", err.message); | ||
| return res.status(500).json({ | ||
| message: 'Error creating user', | ||
| error: err.message | ||
| }); | ||
| } |
There was a problem hiding this comment.
Security concern: Exposing internal error messages.
The error response includes err.message which might expose sensitive information about the database structure or internal implementation details to clients.
Consider sanitizing error messages for client responses:
} catch (err) {
console.error("Signup Error:", err.message);
return res.status(500).json({
- message: 'Error creating user',
- error: err.message
+ message: 'Error creating user'
});
}📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| console.error("Signup Error:", err.message); | |
| return res.status(500).json({ | |
| message: 'Error creating user', | |
| error: err.message | |
| }); | |
| } | |
| } catch (err) { | |
| console.error("Signup Error:", err.message); | |
| return res.status(500).json({ | |
| message: 'Error creating user' | |
| }); | |
| } |
🤖 Prompt for AI Agents
In backend/routes/auth.js around lines 22 to 27, the error response sends
err.message directly to the client, which can expose sensitive internal details.
Modify the code to send a generic error message to the client instead of
err.message, while logging the detailed error internally using console.error or
a logger. This prevents leaking sensitive information while still allowing
debugging.
| return res.status(500).json({ message: 'Login failed', error: err.message }); | ||
| } | ||
|
|
||
| return res.status(200).json({ message: 'Login successful', user }); |
There was a problem hiding this comment.
Security concern: Exposing user object in response.
Returning the entire user object might expose sensitive information like hashed passwords or internal fields.
Consider returning only safe user fields:
- return res.status(200).json({ message: 'Login successful', user });
+ return res.status(200).json({
+ message: 'Login successful',
+ user: { id: user._id, username: user.username, email: user.email }
+ });📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| return res.status(200).json({ message: 'Login successful', user }); | |
| return res.status(200).json({ | |
| message: 'Login successful', | |
| user: { id: user._id, username: user.username, email: user.email } | |
| }); |
🤖 Prompt for AI Agents
In backend/routes/auth.js at line 48, the code returns the entire user object in
the response, which may expose sensitive data. Modify the response to include
only safe, non-sensitive user fields such as username, email, or user ID.
Extract these safe fields from the user object and return them instead of the
full user object in the JSON response.
| app.use(cors({ | ||
| origin: '*', // You can replace * with specific domains in production | ||
| credentials: true, | ||
| })); |
There was a problem hiding this comment.
Security risk: Overly permissive CORS configuration.
Setting origin: '*' with credentials: true is a security vulnerability that allows any origin to make credentialed requests to your API.
Configure CORS more securely:
app.use(cors({
- origin: '*', // You can replace * with specific domains in production
+ origin: process.env.ALLOWED_ORIGINS?.split(',') || ['http://localhost:3000'],
credentials: true,
}));Add ALLOWED_ORIGINS=http://localhost:3000,https://yourdomain.com to your environment variables.
📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| app.use(cors({ | |
| origin: '*', // You can replace * with specific domains in production | |
| credentials: true, | |
| })); | |
| app.use(cors({ | |
| origin: process.env.ALLOWED_ORIGINS?.split(',') || ['http://localhost:3000'], | |
| credentials: true, | |
| })); |
🤖 Prompt for AI Agents
In backend/server.js around lines 15 to 18, the CORS configuration uses origin:
'*' with credentials: true, which is insecure. To fix this, replace the wildcard
origin with a function that checks the request origin against a whitelist of
allowed origins defined in an environment variable ALLOWED_ORIGINS (e.g.,
'http://localhost:3000,https://yourdomain.com'). Only allow requests from these
origins and keep credentials: true. This ensures only trusted domains can make
credentialed requests.
|
not required for now |
2 participants
Changes Made:
auth.jsroutesUser.jsserver.jsBenefits:
Fixes #152
Summary by CodeRabbit
Bug Fixes
New Features
Chores