Merge pull request #729 from NHSDigital/dtoss-11446-support-exclusive-choices

Add param to mark options exclusive

Author: MatMoore

manage_breast_screening/nhsuk_forms/fields/choice_fields.py

@@ -1,6 +1,8 @@
 from django import forms
 from django.forms import widgets
 
+from manage_breast_screening.nhsuk_forms.validators import ExcludesOtherOptionsValidator
+
 
 class RadioSelectWithoutFieldset(widgets.RadioSelect):
     use_fieldset = False
@@ -23,6 +25,7 @@ def __init__(self, form: forms.Form, field: "ChoiceField", name: str):
 
         self._conditional_html = {}
         self.dividers = {}
+        self._exclusive_options = set()
 
     def add_conditional_html(self, value, html):
         if isinstance(self.field.widget, widgets.Select):
@@ -106,6 +109,7 @@ def __init__(
         label_classes="nhsuk-fieldset__legend--m",
         visually_hidden_label_prefix=None,
         visually_hidden_label_suffix=None,
+        exclusive_choices=(),
         classes=None,
         **kwargs,
     ):
@@ -116,5 +120,21 @@ def __init__(
         self.label_classes = label_classes
         self.visually_hidden_label_prefix = visually_hidden_label_prefix
         self.visually_hidden_label_suffix = visually_hidden_label_suffix
+        self.exclusive_choices = exclusive_choices
 
         super().__init__(*args, **kwargs)
+
+        choice_labels = {choice: label for choice, label in self.choices}
+
+        for exclusive_choice in self.exclusive_choices:
+            try:
+                label = choice_labels[exclusive_choice]
+            except KeyError:
+                raise ValueError(f"{exclusive_choice} is not in choices")
+
+            self.validators.append(
+                ExcludesOtherOptionsValidator(exclusive_choice, label)
+            )
+
+    def is_exclusive(self, value):
+        return value in self.exclusive_choices

manage_breast_screening/nhsuk_forms/jinja2/forms/checkboxes.jinja

@@ -12,6 +12,7 @@
     "value": value,
     "text": text,
     "checked": value in (field.value() or []),
+    "exclusive": unbound_field.is_exclusive(value),
     "conditional": {
       "html": conditional_html
     } if conditional_html else undefined

manage_breast_screening/nhsuk_forms/tests/fields/test_choice_fields.py

@@ -1,6 +1,7 @@
 import pytest
 from django.forms import Form
 from django.forms.widgets import CheckboxSelectMultiple, Select
+from django.http import QueryDict
 from pytest_django.asserts import assertHTMLEqual
 
 from manage_breast_screening.nhsuk_forms.fields.choice_fields import (
@@ -197,6 +198,9 @@ class TestForm(Form):
                 hint="Pick any number",
                 widget=CheckboxSelectMultiple,
             )
+            checkbox_field_with_exclusive_option = MultipleChoiceField(
+                label="Abc", choices=(("a", "A"), ("b", "B")), exclusive_choices={"b"}
+            )
             details = CharField(label="Abc", initial="")
 
         return TestForm
@@ -261,6 +265,44 @@ def test_renders_nhs_checkboxes_with_conditional_html(self, form_class):
             """,
         )
 
+    def test_renders_exclusive_options(self, form_class):
+        form = form_class()
+
+        assertHTMLEqual(
+            form["checkbox_field_with_exclusive_option"].as_field_group(),
+            """
+            <div class="nhsuk-form-group">
+                <fieldset class="nhsuk-fieldset">
+                    <legend class="nhsuk-fieldset__legend nhsuk-fieldset__legend--m">
+                        Abc
+                    </legend>
+                    <div class="nhsuk-checkboxes" data-module="nhsuk-checkboxes">
+                        <div class="nhsuk-checkboxes__item">
+                            <input class="nhsuk-checkboxes__input" id="id_checkbox_field_with_exclusive_option" name="checkbox_field_with_exclusive_option" type="checkbox" value="a">
+                            <label class="nhsuk-label nhsuk-checkboxes__label" for="id_checkbox_field_with_exclusive_option">A</label>
+                        </div>
+                        <div class="nhsuk-checkboxes__item">
+                            <input class="nhsuk-checkboxes__input" id="id_checkbox_field_with_exclusive_option-2" name="checkbox_field_with_exclusive_option" type="checkbox" value="b" data-checkbox-exclusive>
+                            <label class="nhsuk-label nhsuk-checkboxes__label" for="id_checkbox_field_with_exclusive_option-2">B</label>
+                        </div>
+                    </div>
+                </fieldset>
+            </div>
+            """,
+        )
+
+    def test_exclusive_options_are_validated(self, form_class):
+        form = form_class(
+            QueryDict(
+                "checkbox_field=a&details=abc&checkbox_field_with_exclusive_option=a&checkbox_field_with_exclusive_option=b"
+            )
+        )
+        assert form.errors == {
+            "checkbox_field_with_exclusive_option": [
+                'Unselect "B" in order to select other options'
+            ]
+        }
+
     def test_renders_without_fieldset(self, form_class):
         class TestForm(Form):
             checkbox_field = MultipleChoiceField(