feat: Error handler updates

* Ensure error details included in response for JSON Schema Validation errors
* Improve typings

src/app/common/errors.ts

@@ -14,6 +14,15 @@ export class HttpError extends BaseError {
 	) {
 		super(name, message);
 	}
+
+	toJSON(exposeServerErrors = false): Record<string, unknown> {
+		return {
+			status: this.status,
+			message: this.message,
+			type: this.name,
+			stack: exposeServerErrors ? this.stack : undefined
+		};
+	}
 }
 
 export class BadRequestError extends HttpError {
@@ -23,6 +32,12 @@ export class BadRequestError extends HttpError {
 	) {
 		super(StatusCodes.BAD_REQUEST, 'BadRequestError', message);
 	}
+
+	override toJSON(exposeServerErrors = false) {
+		const json = super.toJSON(exposeServerErrors);
+		json['errors'] = this.errors;
+		return json;
+	}
 }
 export class UnauthorizedError extends HttpError {
 	constructor(message: string) {
@@ -46,4 +61,12 @@ export class InternalServerError extends HttpError {
 	constructor(message: string) {
 		super(StatusCodes.INTERNAL_SERVER_ERROR, 'InternalServerError', message);
 	}
+
+	override toJSON(exposeServerErrors = false) {
+		const json = super.toJSON(exposeServerErrors);
+		if (exposeServerErrors) {
+			json['message'] = 'A server error has occurred.';
+		}
+		return json;
+	}
 }

src/app/common/express/error-handlers.ts

@@ -1,95 +1,69 @@
 import config from 'config';
+import { ErrorRequestHandler } from 'express';
 import { ValidationError } from 'express-json-validator-middleware';
 import _ from 'lodash';
-import { Error } from 'mongoose';
+import { Error as MongooseError } from 'mongoose';
 
 import { logger } from '../../../lib/logger';
-import { BadRequestError, HttpError, InternalServerError } from '../errors';
+import { BadRequestError, HttpError } from '../errors';
 
-const getStatus = (err) => {
-	logger.error(err.status < 400);
-	if (!err.status || err.status < 400 || err.status >= 600) {
-		return 500;
-	}
-	return err.status;
-};
-
-const getMessage = (
-	err: string | Error | { name: string; message?: unknown }
+export const mongooseValidationErrorHandler: ErrorRequestHandler = (
+	err,
+	req,
+	res,
+	next
 ) => {
-	if (_.isString(err)) {
-		return err;
-	}
-
-	if (err?.message) {
-		return `${err.name ?? 'Error'}: ${err.message}`;
-	}
-	return 'Error: Unknown error';
-};
-
-const getMongooseValidationErrors = (err) => {
-	const errors = [];
-
-	for (const field of Object.keys(err.errors ?? {})) {
-		if (err.errors[field].path) {
-			const message =
-				err.errors[field].type === 'required'
-					? `${field} is required`
-					: err.errors[field].message;
-			errors.push({ field: field, message: message });
-		}
-	}
-
-	return errors;
-};
-
-export const mongooseValidationErrorHandler = (err, req, res, next) => {
 	// Skip if not mongoose validation error
-	if (err.name !== 'ValidationError') {
+	if (!(err instanceof MongooseError.ValidationError)) {
 		return next(err);
 	}
 
 	// Map to format expected by default error handler and pass on
-	const errors = getMongooseValidationErrors(err);
+	const errors = Object.entries(err.errors ?? {})
+		.filter(
+			([, innerError]) => innerError instanceof MongooseError.ValidatorError
+		)
+		.map(([field, innerError]) => ({ field, message: innerError.message }));
+
 	return next(
 		new BadRequestError(errors.map((e) => e.message).join(', '), errors)
 	);
 };
 
-export const jsonSchemaValidationErrorHandler = (err, req, res, next) => {
+export const jsonSchemaValidationErrorHandler: ErrorRequestHandler = (
+	err: Error,
+	req,
+	res,
+	next
+) => {
+	// Skip if not json schema validation error
 	if (!(err instanceof ValidationError)) {
 		return next(err);
 	}
 
-	return next(new BadRequestError('Invalid submission', err.validationErrors));
+	return next(
+		new BadRequestError('Schema validation error', err.validationErrors)
+	);
 };
 
-export const defaultErrorHandler = (err, req, res, next) => {
+export const defaultErrorHandler: ErrorRequestHandler = (
+	err,
+	req,
+	res,
+	next
+) => {
 	if (res.headersSent) {
 		return next(err);
 	}
 
 	const exposeServerErrors = config.get<boolean>('exposeServerErrors');
 
-	if (err instanceof InternalServerError) {
-		return res.status(err.status).json({
-			status: err.status,
-			message: exposeServerErrors
-				? err.message
-				: 'A server error has occurred.',
-			type: err.name,
-			stack: exposeServerErrors ? err.stack : undefined
-		});
-	} else if (err instanceof HttpError) {
+	if (err instanceof HttpError) {
 		logger.error(req.url, err);
 
-		return res.status(err.status).json({
-			status: err.status,
-			message: err.message,
-			type: err.name,
-			stack: config.get<boolean>('exposeServerErrors') ? err.stack : undefined
-		});
+		return res.status(err.status).json(err.toJSON(exposeServerErrors));
 	}
+
 	const errorResponse = {
 		status: getStatus(err),
 		type: err.type ?? 'server-error',
@@ -102,7 +76,7 @@ export const defaultErrorHandler = (err, req, res, next) => {
 
 	if (errorResponse.status >= 500 && errorResponse.status < 600) {
 		// Swap the error message if `exposeServerErrors` is disabled
-		if (!config.get<boolean>('exposeServerErrors')) {
+		if (!exposeServerErrors) {
 			errorResponse.message = 'A server error has occurred.';
 			delete errorResponse.stack;
 		}
@@ -111,3 +85,22 @@ export const defaultErrorHandler = (err, req, res, next) => {
 	// Send the response
 	res.status(errorResponse.status).json(errorResponse);
 };
+
+const getStatus = (err: Parameters<ErrorRequestHandler>[0]) => {
+	if (!err.status || err.status < 400 || err.status >= 600) {
+		return 500;
+	}
+	return err.status;
+};
+
+const getMessage = (err: Parameters<ErrorRequestHandler>[0]) => {
+	if (_.isString(err)) {
+		return err;
+	}
+
+	if (err?.message) {
+		return `${err.name ?? 'Error'}: ${err.message}`;
+	}
+
+	return 'Error: Unknown error';
+};