Prevent duplicate captcha validation

company/forms.py

@@ -46,6 +46,7 @@ def clean_page(self):
 
 
 class ContactCompanyForm(forms.Form):
+
     error_css_class = 'input-field-container has-error'
     TERMS_CONDITIONS_MESSAGE = (
         'Tick the box to confirm you agree to the terms and conditions.'

exportopportunity/forms.py

@@ -190,6 +190,12 @@ class OpportunityNeedLegalForm(OpportunityNeedBaseForm):
 
 
 class OpportunityContactDetailsForm(forms.Form):
+
+    def __init__(self, skip_captcha_errors=False, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        if skip_captcha_errors:
+            del self.fields['captcha']
+
     error_css_class = 'input-field-container has-error'
     MESSAGE_TERMS_CONDITIONS = (
         'Tick the box to confirm you agree to the terms and conditions.'

exportopportunity/tests/test_views.py

@@ -237,9 +237,10 @@ def test_campaign_language_switcher(
 @patch.object(views.helpers, 'get_showcase_companies',
               return_value=showcase_companies)
 @patch.object(views.api_client.exportopportunity, 'create_opportunity_food')
+@patch('captcha.fields.ReCaptchaField.clean')
 def test_submit_export_opportunity_food(
-    mock_create_opportunity, mock_get_showcase_companies, client,
-    api_response_200, settings, captcha_stub, url, country
+    mock_clean_captcha, mock_create_opportunity, mock_get_showcase_companies,
+    client, api_response_200, settings, captcha_stub, url, country
 ):
     settings.FEATURE_EXPORT_OPPORTUNITY_LEAD_GENERATION_ENABLED = True
     mock_create_opportunity.return_value = api_response_200
@@ -296,7 +297,6 @@ def test_submit_export_opportunity_food(
             'additional_requirements': 'give me things',
             'business_model': ['distribution'],
             'business_model_other': 'things',
-            'captcha': None,
             'company_name': 'Jim corp',
             'company_website': 'http://www.example.com',
             'contact_preference': ['EMAIL', 'PHONE'],
@@ -321,6 +321,7 @@ def test_submit_export_opportunity_food(
     assert mock_get_showcase_companies.call_args == call(
         sector=sectors.FOOD_AND_DRINK
     )
+    assert mock_clean_captcha.call_count == 1
 
 
 @pytest.mark.parametrize('url,country', (
@@ -336,9 +337,10 @@ def test_submit_export_opportunity_food(
 @patch.object(views.helpers, 'get_showcase_companies',
               return_value=showcase_companies)
 @patch.object(views.api_client.exportopportunity, 'create_opportunity_legal')
+@patch('captcha.fields.ReCaptchaField.clean')
 def test_submit_export_opportunity_legal(
-    mock_create_opportunity, mock_get_showcase_companies, client,
-    api_response_200, settings, captcha_stub, url, country
+    mock_clean_captcha, mock_create_opportunity, mock_get_showcase_companies,
+    client, api_response_200, settings, captcha_stub, url, country
 ):
     settings.FEATURE_EXPORT_OPPORTUNITY_LEAD_GENERATION_ENABLED = True
     mock_create_opportunity.return_value = api_response_200
@@ -390,7 +392,6 @@ def test_submit_export_opportunity_legal(
     assert mock_create_opportunity.call_args == call(
         form_data={
            'company_name': 'Jim corp',
-           'captcha': None,
            'full_name': 'jim example',
            'phone_number': '07507605844',
            'advice_type_other': 'things',
@@ -414,3 +415,5 @@ def test_submit_export_opportunity_legal(
     assert mock_get_showcase_companies.call_args == call(
         campaign_tag=lead_generation.LEGAL_IS_GREAT,
     )
+
+    assert mock_clean_captcha.call_count == 1

exportopportunity/views.py

@@ -71,6 +71,8 @@ class BaseOpportunityWizardView(
 
     language_form_class = forms.LanguageLeadGeneartionForm
 
+    should_skip_captcha = False
+
     def dispatch(self, *args, **kwargs):
         if not settings.FEATURE_EXPORT_OPPORTUNITY_LEAD_GENERATION_ENABLED:
             raise Http404()
@@ -107,6 +109,21 @@ def done(self, *args, **kwargs):
             }
         )
 
+    def render_done(self, *args, **kwargs):
+        # django-forms runs form.is_valid() for all steps after the final step
+        # meaning the same captcha code is sent to google multiple times.
+        # Google rejects the code the second time as it's already seen it and
+        # thinks the second is a "replay attack" - so prevent formtools from
+        # validating the captcha twice.
+        self.should_skip_captcha = True
+        return super().render_done(*args, **kwargs)
+
+    def get_form_kwargs(self, step):
+        kwargs = super().get_form_kwargs(step=step)
+        if step == self.CONTACT and self.should_skip_captcha:
+            kwargs['skip_captcha_errors'] = True
+        return kwargs
+
 
 class FoodIsGreatOpportunityWizardView(BaseOpportunityWizardView):
     form_list = (