WIP: Fix #148 add a compare fallback

work-a-round for: etianen/django-reversion#859

reversion_compare/admin.py

@@ -4,11 +4,9 @@
 
     Admin extensions for django-reversion-compare
 
-    :copyleft: 2012-2019 by the django-reversion-compare team, see AUTHORS for more details.
+    :copyleft: 2012-2021 by the django-reversion-compare team, see AUTHORS for more details.
     :license: GNU GPL v3 or above, see LICENSE for more details.
 """
-
-
 import logging
 
 from django.conf import settings
@@ -19,10 +17,13 @@
 from django.urls import path, reverse
 from django.utils.text import capfirst
 from django.utils.translation import ugettext as _
+from reversion import RevertError
 from reversion.admin import VersionAdmin
 from reversion.models import Revision, Version
 
+from reversion_compare.compare_raw import get_version_data, pformat
 from reversion_compare.forms import SelectDiffForm
+from reversion_compare.helpers import html_diff
 from reversion_compare.mixins import CompareMethodsMixin, CompareMixin
 
 
@@ -72,6 +73,7 @@ def compare_sub_text(self, obj, version1, version2, value1, value2):
 
     # Template file used for the compare view:
     compare_template = "reversion-compare/compare.html"
+    compare_raw_template = "reversion-compare/compare_raw.html"
 
     # change template from django-reversion to add compare selection form:
     object_history_template = "reversion-compare/object_history.html"
@@ -163,7 +165,15 @@ def compare_view(self, request, object_id, extra_context=None):
         next_version = queryset.filter(pk__gt=version_id2).last()
         prev_version = queryset.filter(pk__lt=version_id1).first()
 
-        compare_data, has_unfollowed_fields = self.compare(obj, version1, version2)
+        try:
+            compare_data, has_unfollowed_fields = self.compare(obj, version1, version2)
+        except RevertError as err:
+            logger.exception('Fallback compare caused by: %s', err)
+            # A old version can't be loaded.
+            # e.g.: model was migrated and version JSON data not, see:
+            # https://github.com/etianen/django-reversion/issues/859
+            # Fallback to JSON compare
+            return self.compare_raw(request, obj, version1, version2, compare_error=err, extra_context=extra_context)
 
         opts = self.model._meta
 
@@ -201,6 +211,44 @@ def compare_view(self, request, object_id, extra_context=None):
         context.update(extra_context or {})
         return render(request, self.compare_template or self._get_template_list("compare.html"), context)
 
+    def compare_raw(self, request, obj, version1, version2, compare_error, extra_context=None):
+        """
+        Fallback: compare the raw json data.
+        """
+        version1data = get_version_data(version1)
+        version2data = get_version_data(version2)
+
+        version1pformat = pformat(version1data)
+        version2pformat = pformat(version2data)
+
+        # TODO: Generate a nicer diff ;)
+        diff_html = html_diff(version1pformat, version2pformat)
+
+        opts = self.model._meta
+        context = {
+            **self.admin_site.each_context(request),
+            "opts": opts,
+            "app_label": opts.app_label,
+            "model_name": capfirst(opts.verbose_name),
+            "title": _("Compare %(name)s") % {"name": version1.object_repr},
+            "obj": obj,
+            "compare_error": compare_error,
+            "diff_html": diff_html,
+            "version1": version1,
+            "version2": version2,
+            "changelist_url": reverse(f"{self.admin_site.name}:{opts.app_label}_{opts.model_name}_changelist"),
+            "original": obj,
+            "history_url": reverse(
+                f"{self.admin_site.name}:{opts.app_label}_{opts.model_name}_history", args=(quote(obj.pk),)
+            ),
+            "save_url": reverse(
+                f"{self.admin_site.name}:{opts.app_label}_{opts.model_name}_revision",
+                args=(quote(version1.object_id), version1.id),
+            ),
+        }
+        context.update(extra_context or {})
+        return render(request, self.compare_raw_template or self._get_template_list("compare_raw.html"), context)
+
 
 class CompareVersionAdmin(CompareMethodsMixin, BaseCompareVersionAdmin):
     """

reversion_compare/compare_raw.py

@@ -0,0 +1,42 @@
+"""
+    Helper to compare raw version data.
+    see: https://github.com/etianen/django-reversion/issues/859
+
+    :copyleft: 2021 by the django-reversion-compare team, see AUTHORS for more details.
+    :license: GNU GPL v3 or above, see LICENSE for more details.
+"""
+
+
+import json
+import pprint
+
+from django.core.serializers.json import DjangoJSONEncoder
+from reversion.models import Version
+
+
+def get_version_data(version):
+    """
+    Get field data from a Version instance.
+    """
+    assert isinstance(version, Version)
+    assert version.format == 'json', f'{version.format!r} not supported (only JSON)'
+
+    json_string = version.serialized_data
+    version_data = json.loads(json_string)
+    # version_data looks like:
+    # [{'fields': {'info': 'Migration state 2 - version 4',
+    #              'number_then_text': 111,
+    #              'text': 'Now this is a short text!!!'},
+    #   'model': 'reversion_compare_tests.migrationmodel',
+    #   'pk': 1}]
+    assert len(version_data) == 1
+    fields_data = version_data[0]['fields']
+    return fields_data
+
+
+def pformat(value):
+    try:
+        return DjangoJSONEncoder(indent=4, sort_keys=True, ensure_ascii=False).encode(value)
+    except TypeError:
+        # Fallback if values are not serializable with JSON:
+        return pprint.pformat(value, width=120)

reversion_compare/templates/reversion-compare/compare_raw.html

@@ -0,0 +1,69 @@
+{% extends "admin/base_site.html" %}
+{% load i18n %}
+
+{% block extrastyle %}{{ block.super }}
+<style type="text/css">
+    /* minimal style for the diffs */
+    pre.highlight {
+        max-width: 900px;
+    }
+    del, ins {
+        color: #000;
+        text-decoration: none;
+    }
+    del { background-color: #fdb8c0 }
+    ins { background-color: #acf2bd; }
+    sup.follow { color: #5555ff; }
+    .diff-line {
+      display: inline-block;
+      width: 100%;
+      margin-left: -1.0em;
+      padding-left: 0.5em;
+      background-color: #f6f6f6;
+      color: #222;
+    }
+    .diff-line.diff-ins { border-left: 0.5em solid #bef5cb; background-color: #e6ffed; }
+    .diff-line.diff-del { border-left: 0.5em solid #fdaeb7; background-color: #ffeef0; }
+    .diff-line.diff-ins.diff-del { border-left: 0.5em solid #bef5cb; background-color: #e6ffed; } /* mixed del/ins == green */
+</style>
+{% endblock %}
+
+{% block breadcrumbs %}
+    <div class="breadcrumbs">
+        <a href="{% url 'admin:index' %}">{% trans 'Home' %}</a> &rsaquo;
+        <a href="{% url 'admin:app_list' app_label %}">{{app_label|capfirst|escape}}</a> &rsaquo;
+        <a href="{{changelist_url}}">{{opts.verbose_name_plural|capfirst}}</a> &rsaquo;
+        <a href="{{history_url}}">{% trans "History" %}</a> &rsaquo;
+        {% blocktrans with opts.verbose_name_plural|escape as name %}Compare {{name}}{% endblocktrans %}
+        {{title}}
+    </div>
+{% endblock %}
+
+
+{% block content %}
+    <div id="content-main">
+
+        {% block object-tools %}
+            <ul class="object-tools">
+              {% block object-tools-items %}
+                {% include "reversion-compare/compare_links_partial.html"  %}
+              {% endblock %}
+            </ul>
+        {% endblock %}
+
+        <p class="help">
+            {% blocktrans with date1=version1.revision.date_created|date:_("DATETIME_FORMAT") date2=version2.revision.date_created|date:_("DATETIME_FORMAT") %}
+                Compare <strong>{{ date1 }}</strong> with <strong>{{ date2 }}</strong>:
+            {% endblocktrans %}
+        </p>
+        &lsaquo; <a href="{{history_url}}">{% trans "Go back to history list" %}</a>
+        &vert;
+        <a href="{{save_url}}">{% trans "Revert to this version" %}</a> &rsaquo;
+
+        {% include "reversion-compare/compare_raw_partial.html"  %}
+
+        &lsaquo; <a href="{{history_url}}">{% trans "Go back to history list" %}</a>
+        &vert;
+        <a href="{{save_url}}">{% trans "Revert to this version" %}</a> &rsaquo;
+    </div>
+{% endblock %}

reversion_compare/templates/reversion-compare/compare_raw_partial.html

@@ -0,0 +1,17 @@
+{% load i18n %}
+
+{{ diff_html }}
+
+<h4>{% trans "Edit comment:" %}</h4>
+<blockquote>{{ version2.revision.comment|default:_("(no comment exists)") }}</blockquote>
+
+<h4>{% trans "Note:" %}</h4>
+<p>
+    This is the fallback compare, because the normal compare can't be applied
+    between the two selected version:
+</p>
+<pre>{{ compare_error }}</pre>
+<p>
+    (More info: <a href="https://github.com/etianen/django-reversion/issues/859">
+    django-reversion issues #859</a>)
+</p>

reversion_compare_tests/admin.py

@@ -17,6 +17,7 @@
     CustomModel,
     Factory,
     Identity,
+    MigrationModel,
     Person,
     Pet,
     SimpleModel,
@@ -32,6 +33,13 @@ class SimpleModelAdmin(CompareVersionAdmin):
 admin.site.register(SimpleModel, SimpleModelAdmin)
 
 
+class MigrationModelAdmin(CompareVersionAdmin):
+    pass
+
+
+admin.site.register(MigrationModel, MigrationModelAdmin)
+
+
 class FactoryAdmin(CompareVersionAdmin):
     pass
 

reversion_compare_tests/management/commands/fill_migration_model.py

@@ -0,0 +1,54 @@
+"""
+    :copyleft: 2015-2016 by the django-reversion-compare team, see AUTHORS for more details.
+    :created: 2015 by JensDiemer.de
+    :license: GNU GPL v3 or above, see LICENSE for more details.
+"""
+
+
+from django.core.management import BaseCommand, call_command
+from reversion import create_revision, set_comment
+
+from reversion_compare_tests.models import MigrationModel
+
+
+lorem_ipsum = (
+    'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor'
+    ' invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et'
+    ' accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata'
+    ' sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing'
+    ' elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,'
+    ' sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita'
+    ' kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.'
+)
+
+
+class Command(BaseCommand):
+    help = "Run Unittest-Server"
+
+    def verbose_call(self, command, **kwargs):
+        self.stdout.write("\n")
+        self.stdout.write("_" * 79)
+        self.stdout.write(self.style.NOTICE(f" *** call '{command}' command:"))
+        self.stdout.write("\n")
+        call_command(command, **kwargs)
+
+    def handle(self, *args, **options):
+        # Migration state 1:
+        # number_then_text = models.CharField()
+        # text = models.TextField()
+        with create_revision():
+            info = 'Migration state 1 - version 1'
+            item = MigrationModel.objects.create(
+                info=info,
+                number_then_text='123',
+                text=lorem_ipsum
+            )
+            set_comment(f'Reversion comment: {info}')
+
+        if self.verbose:
+            print("version 1:", item1)
+
+        with create_revision():
+            item1.text = "version two"
+            item1.save()
+            set_comment("simply change the CharField text.")