212 error email by chnnick · Pull Request #227 · Code-4-Community/proj-bhchp

chnnick · 2026-04-01T05:33:18Z

ℹ️ Issue

Closes #212

📝 Description

Write a short summary of what you added. Why is it important? Any member of C4C should be able to read this and understand your contribution -- not just your team members.

Because the DTO already includes input validation, I added a filter on the controller that handles BadRequestExceptions and sends the user an email with the errors in human-readable format.

Example DTO with input validation:

Briefly list the changes made to the code:

Created logic for sending emails when a form validation error happens at the controller-level
Put logic in NestJS filter
Added Filter as a provider in the applications module
Put the filter as a decorator on POST route on the applications controller for creating new applications
Imported email services into applications module to allow for finding user names by application and sending emails
Matched the email to the template provided
Made the email error messages much more human readable by translating from camelCase
Created tests for newly-created filters, these run on the HTTP layer when endpoints first receive data regarding an application.

✔️ Verification

What steps did you take to verify your changes work? These should be clear enough for someone to be able to clone the branch and follow the steps themselves.

Example email:

🏕️ (Optional) Future Work / Notes

Got rid of input validation in service, as it is redundant and requests hitting the endpoint already get validated and error-handled by the controller. The filter handles errors thrown by controller-level validation errors, and sends emails from there

… email with hardcoded pandadoc links. sanitized output with escapeHTML

…on thrown by class validator in DTO

…-readable

SamNie2027

Please resolve the failing tests

SamNie2027 · 2026-04-01T11:48:47Z

apps/backend/src/applications/application-validation-email.filter.ts

+ * POST /api/applications endpoint fails due to validation errors.
+ *
+ * Applied at the controller-method level so it only intercepts
+ * BadRequestExceptions thrown during application creation.


It should intercept all error messages, not just BadRequestExceptions.
If the other Exceptions/ Errors aren't covered too, then a person will submit a Pandadoc and we will error out, causing their application not to be a part of our database, and the person who submitted it will never know that it failed.

SamNie2027 · 2026-04-01T11:50:21Z

apps/backend/src/applications/application-validation-email.filter.ts

+          'No email found in request body. Skipping error email.',
+        );
+      } else {
+        const applicant = await this.usersService.findOne(recipientEmail);


Don't check for applicant existing at this point - because at this point the user won't even exist yet, this is at step 1 when the user submits the pandadoc before any data about them is written in the backend

I am checking for this because I need to get the name of the applicant as per the email template. This name field does not exist in ApplicationDTO, but in Users which is tied to the application via its email? Should I fetch the name from somewhere else? or just Ignore the name field

SamNie2027 · 2026-04-01T11:50:34Z

apps/backend/src/applications/application-validation-email.filter.ts

+
+        if (!applicant) {
+          this.logger.warn(
+            `No user found for email: ${recipientEmail}. Skipping error email.`,


To the above point ^ don't have this check

SamNie2027 · 2026-04-01T11:51:02Z

apps/backend/src/applications/application-validation-email.filter.ts

+          );
+        } else {
+          const applicantName = `${escapeHtml(
+            applicant.firstName,


Get the firstname and lastname from the application data from pandadoc instead, not the applicant as previously discussed

SamNie2027 · 2026-04-01T11:52:26Z

apps/backend/src/applications/filters/application-validation-email.filter.ts

+import { UsersService } from '../users/users.service';
+import { FIELD_LABELS } from './types';
+
+function escapeHtml(text: string): string {


Documentation here would be nice

SamNie2027 · 2026-04-01T11:53:10Z

apps/backend/src/applications/filters/application-validation-email.filter.ts

+   *   "appStatus must be one of..." → "Application Status must be one of..."
+   *   "each value in interest must be one of..." → "Each value in Areas of Interest must be one of..."
+   */
+  private humanizeErrorMessage(message: string): string {


Remember to include info about the parameter when doing documentation

SamNie2027 · 2026-04-01T11:53:35Z

apps/backend/src/applications/filters/application-validation-email.filter.ts

+    applicantName: string,
+    requestBody: Record<string, unknown>,
+    errorMessages: string[],
+  ): string {


Remember to include info about parameter format when doing documentation and also include what it returns

SamNie2027 · 2026-04-01T11:54:00Z

apps/backend/src/applications/filters/application-validation-email.filter.ts

+   * Only includes fields that have a friendly label defined in FIELD_LABELS.
+   * Skips null/undefined values.
+   */
+  private formatSubmittedFields(body: Record<string, unknown>): string {


Again remember to put info about the parameters in the documentation

SamNie2027 · 2026-04-01T11:55:50Z

apps/backend/src/applications/types.ts

 }
+
+/** User-friendly labels for request body fields displayed in the error email. */
+export const FIELD_LABELS: Record<string, string> = {


My issue with this is that this is not the pandadoc fields - these are out database fields, which are in a different format than what the applicant submits.
Instead of fixing this, if alternatively you can find evidence that pandadoc can send a copy of their submission back to the user every time they submit, then that will negate the need for this

Yea i totally agree i think having a mapping is a bit impractical, ill go look around for functionality on how to get pandadoc to send a copy of the submission in human-readable format over

Can use this instead to fetch the fields:
https://developers.pandadoc.com/reference/document-details

Would require saving a formsubmission document ID, and using that ID to fetch

…ts to the name "Applicant"

…error, then sending submission-error-email

…error when processing email past the DTO validation stage + moved filters to filter folder

…ervice usage is moved to the filters

… before app validation (NestJS reverses the order) no longer need to check for badrequestexception in the second filter

…into 212-error-email

…ints receive DTO information

chnnick added 4 commits March 31, 2026 21:05

bring in users and email utility modules

c48bfeb

logic in between validation error caught and sending error, now sends…

331a5b1

… email with hardcoded pandadoc links. sanitized output with escapeHTML

created a filter, moved email logic to filter for bad-request-excepti…

e4c34ba

…on thrown by class validator in DTO

put mapping in types.ts, make error messages in email much more human…

2d7d1d9

…-readable

SamNie2027 self-requested a review April 1, 2026 11:44

SamNie2027 requested changes Apr 1, 2026

View reviewed changes

chnnick added 8 commits April 3, 2026 13:26

Documentation

5f4dd3c

No longer fetches for user + name in user module, instead just defaul…

fd48b32

…ts to the name "Applicant"

fully took out use of UserService, abstracted out logic for catching …

f39670a

…error, then sending submission-error-email

generic error filter that sends emails to recipients if they have an …

8f7896c

…error when processing email past the DTO validation stage + moved filters to filter folder

took out usersservice and emailsservice in application service emails…

31ae468

…ervice usage is moved to the filters

changed order of which filters run first, running badexception filter…

158859f

… before app validation (NestJS reverses the order) no longer need to check for badrequestexception in the second filter

Merge branch 'main' of https://github.com/Code-4-Community/proj-bhchp …

168d9fd

…into 212-error-email

tests for validation filters that run in the HTTP Pipeline when endpo…

648689b

…ints receive DTO information

chnnick requested a review from SamNie2027 April 5, 2026 02:51

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chnnick commented Apr 1, 2026 •

edited

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