Incorrect Error Message for Duplicate Module Name

backend/apps/mentorship/api/internal/mutations/module.py

@@ -6,7 +6,9 @@
 import strawberry
 from django.core.exceptions import ObjectDoesNotExist, PermissionDenied, ValidationError
 from django.db import transaction
+from django.db.utils import IntegrityError
 from django.utils import timezone
+from graphql import GraphQLError
 
 from apps.github.models import User as GithubUser
 from apps.mentorship.api.internal.nodes.module import (
@@ -114,18 +116,29 @@ def create_module(self, info: strawberry.Info, input_data: CreateModuleInput) ->
             program.ended_at,
         )
 
-        module = Module.objects.create(
-            name=input_data.name,
-            description=input_data.description,
-            experience_level=input_data.experience_level.value,
-            started_at=started_at,
-            ended_at=ended_at,
-            domains=input_data.domains,
-            labels=input_data.labels,
-            tags=input_data.tags,
-            program=program,
-            project=project,
-        )
+        try:
+            with transaction.atomic():
+                module = Module.objects.create(
+                    name=input_data.name,
+                    description=input_data.description,
+                    experience_level=input_data.experience_level.value,
+                    started_at=started_at,
+                    ended_at=ended_at,
+                    domains=input_data.domains,
+                    labels=input_data.labels,
+                    tags=input_data.tags,
+                    program=program,
+                    project=project,
+                )
+        except IntegrityError as e:
+            error_message = str(e)
+            if "unique_module_key_in_program" in error_message:
+                msg = "This module name already exists in this program."
+                raise GraphQLError(
+                    msg,
+                    extensions={"code": "VALIDATION_ERROR", "field": "name"},
+                ) from e
+            raise
 
         if module.experience_level not in program.experience_levels:
             program.experience_levels.append(module.experience_level)
@@ -392,7 +405,18 @@ def update_module(self, info: strawberry.Info, input_data: UpdateModuleInput) ->
             mentors_to_set = resolve_mentors_from_logins(input_data.mentor_logins)
             module.mentors.set(mentors_to_set)
 
-        module.save()
+        try:
+            with transaction.atomic():
+                module.save()
+        except IntegrityError as e:
+            error_message = str(e)
+            if "unique_module_key_in_program" in error_message:
+                msg = "This module name already exists in this program."
+                raise GraphQLError(
+                    msg,
+                    extensions={"code": "VALIDATION_ERROR", "field": "name"},
+                ) from e
+            raise
 
         if module.experience_level not in module.program.experience_levels:
             module.program.experience_levels.append(module.experience_level)

frontend/__tests__/unit/components/ModuleForm.test.tsx

@@ -466,7 +466,7 @@ describe('ModuleForm', () => {
       expect(mockOnSubmit).not.toHaveBeenCalled()
     })
 
-    it('calls onSubmit when all fields are valid', () => {
+    it('calls onSubmit when all fields are valid', async () => {
       const validFormData = {
         ...defaultFormData,
         name: 'Valid Module Name',
@@ -481,11 +481,15 @@ describe('ModuleForm', () => {
       renderModuleForm({ formData: validFormData })
 
       const form = document.querySelector('form')
-      if (form) {
-        fireEvent.submit(form)
-      }
+      await act(async () => {
+        if (form) {
+          fireEvent.submit(form)
+        }
+      })
 
-      expect(mockOnSubmit).toHaveBeenCalled()
+      await waitFor(() => {
+        expect(mockOnSubmit).toHaveBeenCalled()
+      })
     })
 
     it('sets all fields as touched on submit', () => {
@@ -523,6 +527,128 @@ describe('ModuleForm', () => {
       expect(screen.getByTestId('submit-button')).not.toBeDisabled()
     })
   })
+
+  describe('Mutation Error Display (validationErrors prop)', () => {
+    const validFormData = {
+      ...defaultFormData,
+      name: 'Test Module',
+      description: 'A valid description that is long enough',
+      startedAt: '2024-01-01',
+      endedAt: '2024-12-31',
+      projectId: 'project-123',
+      projectName: 'My Project',
+      experienceLevel: 'BEGINNER',
+    }
+
+    it('displays mutation error for name field after submission', () => {
+      const { rerender } = render(
+        <ModuleForm
+          formData={validFormData}
+          setFormData={mockSetFormData}
+          onSubmit={mockOnSubmit}
+          loading={false}
+          title="Create Module"
+        />
+      )
+
+      // Submit first to mark fields as touched
+      const form = document.querySelector('form')
+      fireEvent.submit(form!)
+
+      // Rerender with mutation errors (simulates page catching backend error)
+      rerender(
+        <ModuleForm
+          formData={validFormData}
+          setFormData={mockSetFormData}
+          onSubmit={mockOnSubmit}
+          loading={false}
+          title="Create Module"
+          validationErrors={{
+            name: 'This module name already exists in this program.',
+          }}
+        />
+      )
+
+      expect(screen.getByTestId('module-name-error')).toHaveTextContent(
+        'This module name already exists in this program.'
+      )
+    })
+
+    it('does not display mutation error when validationErrors is empty', () => {
+      renderModuleForm({
+        formData: validFormData,
+        validationErrors: {},
+      })
+
+      expect(screen.queryByTestId('module-name-error')).not.toBeInTheDocument()
+    })
+
+    it('allows resubmission even when validationErrors.name is set', async () => {
+      const { rerender } = render(
+        <ModuleForm
+          formData={validFormData}
+          setFormData={mockSetFormData}
+          onSubmit={mockOnSubmit}
+          loading={false}
+          title="Create Module"
+        />
+      )
+
+      // First submit to mark fields as touched
+      const form = document.querySelector('form')
+      fireEvent.submit(form!)
+      expect(mockOnSubmit).toHaveBeenCalledTimes(1)
+      mockOnSubmit.mockClear()
+
+      // Rerender with mutation errors
+      rerender(
+        <ModuleForm
+          formData={validFormData}
+          setFormData={mockSetFormData}
+          onSubmit={mockOnSubmit}
+          loading={false}
+          title="Create Module"
+          validationErrors={{
+            name: 'This module name already exists in this program.',
+          }}
+        />
+      )
+
+      // Second submit should still call onSubmit so parent can clear errors and retry
+      fireEvent.submit(form!)
+
+      await waitFor(() => {
+        expect(mockOnSubmit).toHaveBeenCalledTimes(1)
+      })
+    })
+
+    it('allows submission when validationErrors has no name error', async () => {
+      renderModuleForm({
+        formData: validFormData,
+        validationErrors: {},
+      })
+
+      const form = document.querySelector('form')
+      fireEvent.submit(form!)
+
+      await waitFor(() => {
+        expect(mockOnSubmit).toHaveBeenCalled()
+      })
+    })
+
+    it('allows submission when validationErrors is undefined', async () => {
+      renderModuleForm({
+        formData: validFormData,
+      })
+
+      const form = document.querySelector('form')
+      fireEvent.submit(form!)
+
+      await waitFor(() => {
+        expect(mockOnSubmit).toHaveBeenCalled()
+      })
+    })
+  })
 })
 
 describe('ProjectSelector', () => {

frontend/__tests__/unit/pages/CreateModule.test.tsx

@@ -255,7 +255,7 @@ describe('CreateModulePage', () => {
       expect(moduleForm).toBeInTheDocument()
     })
   })
-  it('handles form submission error gracefully', async () => {
+  it('handles form submission error by displaying inline error', async () => {
     const user = userEvent.setup({ delay: null })
 
     ;(useSession as jest.Mock).mockReturnValue({
@@ -300,16 +300,14 @@ describe('CreateModulePage', () => {
 
     await waitFor(() => {
       expect(mockCreateModuleError).toHaveBeenCalled()
-      expect(addToast).toHaveBeenCalledWith(
-        expect.objectContaining({
-          title: 'Creation Failed',
-          description: 'Network error',
-          color: 'danger',
-        })
+      // Error is displayed inline via validationErrors, not via addToast
+      expect(addToast).not.toHaveBeenCalledWith(
+        expect.objectContaining({ title: 'Creation Failed' })
       )
     })
   })
-  it('handles non-Error submission failure', async () => {
+  it('handles non-Error submission failure via handleAppError', async () => {
+    const { handleAppError } = jest.requireMock('app/global-error')
     const user = userEvent.setup({ delay: null })
 
     ;(useSession as jest.Mock).mockReturnValue({
@@ -353,11 +351,8 @@ describe('CreateModulePage', () => {
 
     await waitFor(() => {
       expect(mockCreateModuleError).toHaveBeenCalled()
-      expect(addToast).toHaveBeenCalledWith(
-        expect.objectContaining({
-          description: 'Something went wrong while creating the module.',
-        })
-      )
+      // Non-Error values fall through to handleAppError
+      expect(handleAppError).toHaveBeenCalledWith('String error')
     })
   }, 10000)
 })