Fix #712: Implement Global Error Handling & Standardized Response

[SatyamPandey-07]

Key Features Implemented:

Custom AppError Architecture: Created
utils/AppError.js
, which extends the native Node.js
Error
class and adds intelligent flagging for Operational vs. Programmer errors. This ensures that the system can distinguish between user-facing issues (like validation failures) and internal system crashes.
JSend Response Factory: Built
utils/ResponseFactory.js
, a centralized hub for all outgoing API traffic. It strictly enforces a standardized JSON structure (Success/Fail/Error), eliminating inconsistent data shapes across the codebase.
Global Hub Middleware: Implemented
middleware/globalErrorHandler.js
, a catch-all interceptor that processes every error in the application. It automatically normalizes complex database errors (Mongoose/MongoDB) and security exceptions into user-friendly messages.
Environment-Aware Logic: Created
controllers/errorController.js
to handle error delivery.
Development: Sends full stack traces and raw error objects for rapid debugging.
Production: Sanitizes all outputs to shield internal system logic and ensure high security.
ORM Error Normalization: The global handler now automatically detects and formats:
ValidationError (Input schema failures)
CastError (Invalid database IDs)
DuplicateKeyError (Unique constraint violations)
JWTError
& TokenExpiredError (Authentication failures)
Full Route Refactor: Updated multiple routes (e.g.,
users.js
,
expenses.js
) to transition from ad-hoc JSON responses to the new factory-driven system.
Standardization Docs: Created
ERROR_HANDLING_STANDARDS.md
, providing a technical guide for developers on how to throw and format standardized responses.

closes #712

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🎉 Thanks for the PR, @SatyamPandey-07!

We really appreciate you taking the time to contribute to ExpenseFlow! 💙

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Project	Deployment	Actions	Updated (UTC)
expenseflow	Ready	Preview, Comment	Feb 20, 2026 8:53am