From 5133f81104712611ef5c89722ebab1391f6b529f Mon Sep 17 00:00:00 2001
From: Richard Terry <git@radiac.net>
Date: Thu, 15 Aug 2024 01:38:06 +0100
Subject: [PATCH] Fix form field ``has_changed``

refs #185
---
 docs/changelog.rst        | 13 +++++++
 tagulous/forms.py         | 13 +++++++
 tagulous/models/fields.py | 81 ++++++++++++++++++++-------------------
 tagulous/utils.py         |  2 +-
 4 files changed, 68 insertions(+), 41 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 2fec9db..d9b17fe 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -13,6 +13,19 @@ Changes for upcoming releases will be listed without a release date - these
 are available by installing the develop branch from github.
 
 
+2.1.0, TBC
+----------
+
+Bugfix:
+
+* Form field ``has_changed`` now correctly detects if a TagField has changed (#185)
+
+Thanks to:
+
+* Christian Schneider (cnschn) for help fixing ``has_changed`` (#185)
+
+
+
 2.0.0, 2024-08-13
 -----------------
 
diff --git a/tagulous/forms.py b/tagulous/forms.py
index d4afbaf..a6947b6 100644
--- a/tagulous/forms.py
+++ b/tagulous/forms.py
@@ -12,6 +12,7 @@
 
 from . import settings
 from .models import options
+from .models.fields import FakeQuerySet
 from .models.models import BaseTagModel, TagModelQuerySet
 from .utils import parse_tags, render_tags
 
@@ -324,6 +325,18 @@ def prepare_value(self, value):
         # Deal with it as normal
         return super(TagField, self).prepare_value(value)
 
+    def _coerce(self, value):
+        """
+        Standardise the value - it could be a fake queryset from the database object, or
+        a tag string from the form field. Split and sort the tags.
+        """
+        if isinstance(value, FakeQuerySet):
+            tag_string = value[0]
+        else:
+            tag_string = value
+        tags = parse_tags(tag_string)
+        return render_tags(sorted(tags))
+
 
 # ##############################################################################
 # ###### Inline tagged formset
diff --git a/tagulous/models/fields.py b/tagulous/models/fields.py
index 25c6b88..c015944 100644
--- a/tagulous/models/fields.py
+++ b/tagulous/models/fields.py
@@ -385,6 +385,47 @@ def formfield(self, form_class=None, **kwargs):
 # ##############################################################################
 
 
+class FakeObject(object):
+    """
+    FakeObject so m2d can check obj.pk
+    """
+
+    def __init__(self, value):
+        self.pk = value
+
+    def __str__(self):
+        return self.pk
+
+
+class FakeQuerySet(object):
+    """
+    FakeQuerySet so m2d can call qs.values_list()
+    Only contains one FakeObject instance
+    """
+
+    def __init__(self, obj):
+        self.obj = obj
+        self._result_cache = None
+
+    def __iter__(self):
+        """
+        Iterable so m2d can use in list comprehension
+        """
+        yield self.obj
+
+    def __len__(self):
+        return 1
+
+    def __getitem__(self, key):
+        return self.obj
+
+    def values_list(self, *fields, **kwargs):
+        """
+        Ignores arguments and returns an empty list with the object.pk
+        """
+        return [self.obj.pk]
+
+
 class TagField(BaseTagField, models.ManyToManyField):
     """
     Build the tag model and register the TagManyToManyField
@@ -464,46 +505,6 @@ def value_from_object(self, obj):
         where the pk attribute is the tag string - a bit of a hack, but avoids
         monkey-patching Django.
         """
-
-        class FakeObject(object):
-            """
-            FakeObject so m2d can check obj.pk
-            """
-
-            def __init__(self, value):
-                self.pk = value
-
-            def __str__(self):
-                return self.pk
-
-        class FakeQuerySet(object):
-            """
-            FakeQuerySet so m2d can call qs.values_list()
-            Only contains one FakeObject instance
-            """
-
-            def __init__(self, obj):
-                self.obj = obj
-                self._result_cache = None
-
-            def __iter__(self):
-                """
-                Iterable so m2d can use in list comprehension
-                """
-                yield self.obj
-
-            def __len__(self):
-                return 1
-
-            def __getitem__(self, key):
-                return self.obj
-
-            def values_list(self, *fields, **kwargs):
-                """
-                Ignores arguments and returns an empty list with the object.pk
-                """
-                return [self.obj.pk]
-
         return FakeQuerySet(FakeObject(getattr(obj, self.attname).get_tag_string()))
 
     def formfield(self, form_class=None, **kwargs):
diff --git a/tagulous/utils.py b/tagulous/utils.py
index 3a71ea0..58b842a 100644
--- a/tagulous/utils.py
+++ b/tagulous/utils.py
@@ -13,7 +13,7 @@
 # ##############################################################################
 
 
-def parse_tags(tag_string, max_count=0, space_delimiter=True):
+def parse_tags(tag_string: str, max_count=0, space_delimiter=True) -> list[str]:
     """
     Tag parser