chore: import upstream snapshot with attribution

api/src/plugins/error-handling.ts

@@ -0,0 +1,85 @@
+import type { FastifyError, FastifyPluginCallback } from 'fastify';
+import * as Sentry from '@sentry/node';
+import fp from 'fastify-plugin';
+
+import { getRedirectParams } from '../utils/redirection.js';
+import { clientNetInfo } from '../utils/logger.js';
+
+declare module 'fastify' {
+  interface FastifyInstance {
+    Sentry: typeof Sentry;
+  }
+}
+
+/**
+ * Plugin to handle errors and send them to Sentry.
+ *
+ * @param fastify The Fastify instance.
+ * @param _options Options passed to the plugin via `fastify.register(plugin, options)`.
+ * @param done Callback to signal that the logic has completed.
+ */
+export const isExpectedClientError = (error: unknown): boolean =>
+  typeof error === 'object' &&
+  error !== null &&
+  'statusCode' in error &&
+  typeof (error as { statusCode?: unknown }).statusCode === 'number' &&
+  (error as { statusCode: number }).statusCode < 500;
+
+const errorHandling: FastifyPluginCallback = (fastify, _options, done) => {
+  Sentry.setupFastifyErrorHandler(fastify, {
+    shouldHandleError: error => !isExpectedClientError(error)
+  });
+
+  fastify.decorate('Sentry', Sentry);
+
+  fastify.setErrorHandler((error: FastifyError, request, reply) => {
+    const accepts = request.accepts().type(['json', 'html']);
+    const { returnTo } = getRedirectParams(request);
+
+    if (!reply.statusCode || reply.statusCode === 200) {
+      const statusCode =
+        error.statusCode && error.statusCode >= 400 ? error.statusCode : 500;
+      reply.code(statusCode);
+    }
+
+    const isCSRFError =
+      error.code === 'FST_CSRF_INVALID_TOKEN' ||
+      error.code === 'FST_CSRF_MISSING_SECRET';
+
+    if (!isCSRFError) {
+      const context = { err: error, ...clientNetInfo(request) };
+      if (reply.statusCode >= 500) {
+        request.log.error(context, 'Error in request');
+      } else {
+        request.log.warn(context, 'Client error in request');
+      }
+    } else {
+      fastify.Sentry?.metrics?.count('security.csrf_rejected', 1, {
+        attributes: { reason: error.code }
+      });
+    }
+
+    const message =
+      reply.statusCode === 500 || isCSRFError
+        ? 'flash.generic-error'
+        : error.message;
+    if (accepts === 'json') {
+      void reply.send({
+        message,
+        type: 'danger'
+      });
+    } else {
+      void reply.status(302);
+      void reply.redirectWithMessage(returnTo, {
+        type: 'danger',
+        content: message
+      });
+    }
+  });
+
+  done();
+};
+
+export default fp(errorHandling, {
+  dependencies: ['redirect-with-message', '@fastify/accepts']
+});