Made fix for #9321 less buggy and more effective.

Don't try to be smart about building a good-looking help string
because it evaluates translations too early, simply use the same old
strategy as before. Thanks Donald Stufft for the report.

Also, actually fix the case reported by the OP by special-casing
CheckboxSelectMultiple.

Added tests.

Refs #9321.

django/forms/models.py

@@ -13,7 +13,7 @@ from django.forms.forms import BaseForm, get_declared_fields
 from django.forms.formsets import BaseFormSet, formset_factory
 from django.forms.util import ErrorList
 from django.forms.widgets import (SelectMultiple, HiddenInput,
-    MultipleHiddenInput, media_property)
+    MultipleHiddenInput, media_property, CheckboxSelectMultiple)
 from django.utils.encoding import smart_text, force_text
 from django.utils.datastructures import SortedDict
 from django.utils import six
@@ -1104,9 +1104,10 @@ class ModelMultipleChoiceField(ModelChoiceField):
         super(ModelMultipleChoiceField, self).__init__(queryset, None,
             cache_choices, required, widget, label, initial, help_text,
             *args, **kwargs)
-        if isinstance(self.widget, SelectMultiple):
+        # Remove this in Django 1.8
+        if isinstance(self.widget, SelectMultiple) and not isinstance(self.widget, CheckboxSelectMultiple):
             msg = _('Hold down "Control", or "Command" on a Mac, to select more than one.')
-            self.help_text = string_concat(self.help_text, ' ', msg) if self.help_text else msg
+            self.help_text = string_concat(self.help_text, ' ', msg)
 
     def clean(self, value):
         if self.required and not value:

docs/releases/1.6.txt

@@ -522,10 +522,10 @@ facilities together with Django built-in form :doc:`fields </ref/forms/fields>`
 and :doc:`widgets </ref/forms/widgets>` aren't affected but need to be aware of
 what's described in :ref:`m2m-help_text-deprecation` below.
 
-This is because, as an temporary backward-compatible provision, the described
-non-standard behavior has been preserved but moved to the model form field layer
-and occurs only when the associated widget is
-:class:`~django.forms.SelectMultiple` or a subclass.
+This is because, as an ad-hoc temporary backward-compatibility provision, the
+described non-standard behavior has been preserved but moved to the model form
+field layer and occurs only when the associated widget is
+:class:`~django.forms.SelectMultiple` or selected subclasses.
 
 QuerySet iteration
 ~~~~~~~~~~~~~~~~~~

tests/admin_widgets/tests.py

@@ -13,6 +13,7 @@ from django.core.files.uploadedfile import SimpleUploadedFile
 from django.db.models import CharField, DateField
 from django.test import TestCase as DjangoTestCase
 from django.test.utils import override_settings
+from django.utils import six
 from django.utils import translation
 from django.utils.html import conditional_escape
 from django.utils.unittest import TestCase
@@ -139,6 +140,17 @@ class AdminFormfieldForDBFieldTests(TestCase):
     def testInheritance(self):
         self.assertFormfield(models.Album, 'backside_art', widgets.AdminFileWidget)
 
+    def test_m2m_widgets(self):
+        """m2m fields help text as it applies to admin app (#9321)."""
+        class AdvisorAdmin(admin.ModelAdmin):
+            filter_vertical=['companies']
+
+        self.assertFormfield(models.Advisor, 'companies', widgets.FilteredSelectMultiple,
+                             filter_vertical=['companies'])
+        ma = AdvisorAdmin(models.Advisor, admin.site)
+        f = ma.formfield_for_dbfield(models.Advisor._meta.get_field('companies'), request=None)
+        self.assertEqual(six.text_type(f.help_text), ' Hold down "Control", or "Command" on a Mac, to select more than one.')
+
 
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
 class AdminFormfieldForDBFieldWithRequestTests(DjangoTestCase):

tests/model_forms/models.py

@@ -255,3 +255,7 @@ class Colour(models.Model):
 class ColourfulItem(models.Model):
     name = models.CharField(max_length=50)
     colours = models.ManyToManyField(Colour)
+
+class ArticleStatusNote(models.Model):
+    name = models.CharField(max_length=20)
+    status = models.ManyToManyField(ArticleStatus)

tests/model_forms/tests.py

@@ -24,7 +24,7 @@ from .models import (Article, ArticleStatus, BetterAuthor, BigInt,
     DerivedPost, ExplicitPK, FlexibleDatePost, ImprovedArticle,
     ImprovedArticleWithParentLink, Inventory, Post, Price,
     Product, TextFile, AuthorProfile, Colour, ColourfulItem,
-    test_images)
+    ArticleStatusNote, test_images)
 
 if test_images:
     from .models import ImageFile, OptionalImageFile
@@ -234,6 +234,20 @@ class ColourfulItemForm(forms.ModelForm):
         model = ColourfulItem
         fields = '__all__'
 
+# model forms for testing work on #9321:
+
+class StatusNoteForm(forms.ModelForm):
+    class Meta:
+        model = ArticleStatusNote
+        fields = '__all__'
+
+
+class StatusNoteCBM2mForm(forms.ModelForm):
+    class Meta:
+        model = ArticleStatusNote
+        fields = '__all__'
+        widgets = {'status': forms.CheckboxSelectMultiple}
+
 
 class ModelFormBaseTest(TestCase):
     def test_base_form(self):
@@ -1677,3 +1691,22 @@ class OldFormForXTests(TestCase):
         <option value="%(blue_pk)s">Blue</option>
         </select> <span class="helptext"> Hold down "Control", or "Command" on a Mac, to select more than one.</span></p>"""
             % {'blue_pk': colour.pk})
+
+
+class M2mHelpTextTest(TestCase):
+    """Tests for ticket #9321."""
+    def test_multiple_widgets(self):
+        """Help text of different widgets for ManyToManyFields model fields"""
+        dreaded_help_text = '<span class="helptext"> Hold down "Control", or "Command" on a Mac, to select more than one.</span>'
+
+        # Default widget (SelectMultiple):
+        std_form = StatusNoteForm()
+        self.assertInHTML(dreaded_help_text, std_form.as_p())
+
+        # Overridden widget (CheckboxSelectMultiple, a subclass of
+        # SelectMultiple but with a UI that doesn't involve Control/Command
+        # keystrokes to extend selection):
+        form = StatusNoteCBM2mForm()
+        html = form.as_p()
+        self.assertInHTML('<ul id="id_status">', html)
+        self.assertInHTML(dreaded_help_text, html, count=0)