tests/test_formdata.py

@@ -5440,3 +5440,101 @@ def test_page_field_var(pub, formdef):
 
     assert 'form_var_page' not in formdata.get_substitution_variables()
     assert 'page' not in LazyFormData(formdata).var.inspect_keys()
+
+
+def test_reverse_links(pub):
+    CardDef.wipe()
+    carddef1 = CardDef()
+    carddef1.name = 'Card 1'
+    carddef1.digest_templates = {'default': '{{form_var_name1}}'}
+    carddef1.fields = [
+        fields.StringField(id='0', label='string', varname='name1'),
+    ]
+    carddef1.store()
+    carddata1 = carddef1.data_class()()
+    carddata1.data = {
+        '0': 'foo1',
+    }
+    carddata1.just_created()
+    carddata1.store()
+
+    ds = {'type': 'carddef:%s' % carddef1.url_name}
+
+    carddef2 = CardDef()
+    carddef2.name = 'Card 2'
+    carddef2.digest_templates = {'default': '{{form_var_name2}}'}
+    carddef2.fields = [
+        fields.StringField(id='0', label='string', varname='name2'),
+        fields.ItemField(id='1', label='string', varname='foo', data_source=ds),
+    ]
+    carddef2.store()
+    carddata2 = carddef2.data_class()()
+    carddata2.data = {
+        '0': 'foo2',
+        '1': str(carddata1.id),
+    }
+    carddata2.data['1_display'] = carddef2.fields[1].store_display_value(carddata1.data, '0')
+    carddata2.data['1_structured'] = carddef2.fields[1].store_structured_value(carddata1.data, '0')
+    carddata2.just_created()
+    carddata2.store()
+
+    FormDef.wipe()
+    formdef = FormDef()
+    formdef.name = 'foobar'
+    formdef.fields = [fields.ItemField(id='0', label='string', varname='bar', data_source=ds)]
+    formdef.store()
+    formdata1 = formdef.data_class()()
+    formdata1.data = {
+        '0': str(carddata1.id),
+    }
+    formdata1.data['0_display'] = formdef.fields[0].store_display_value(carddata1.data, '0')
+    formdata1.data['0_structured'] = formdef.fields[0].store_structured_value(carddata1.data, '0')
+    formdata1.just_created()
+    formdata1.store()
+    formdata2 = formdef.data_class()()
+    formdata2.data = {
+        '0': str(carddata1.id),
+    }
+    formdata2.data['0_display'] = formdef.fields[0].store_display_value(carddata1.data, '0')
+    formdata2.data['0_structured'] = formdef.fields[0].store_structured_value(carddata1.data, '0')
+    formdata2.just_created()
+    formdata2.store()
+
+    # test reverse relation
+    carddef1.store()  # build & store reverse_relations
+    pub.substitutions.reset()
+    pub.substitutions.feed(pub)
+    pub.substitutions.feed(carddef1)
+    pub.substitutions.feed(carddata1)
+    context = pub.substitutions.get_context_variables(mode='lazy')
+    assert len(context['form_reverse_links_formdef_foobar_bar']) == 2
+    assert context['form_reverse_links_formdef_foobar_bar_0_form_internal_id'] == formdata1.id
+    assert context['form_reverse_links_formdef_foobar_bar_1_form_internal_id'] == formdata2.id
+    assert len(context['form_reverse_links_carddef_card_2_foo']) == 1
+    assert context['form_reverse_links_carddef_card_2_foo_0_form_internal_id'] == carddata2.id
+
+    # test with natural id
+    carddef1.id_template = 'X{{ form_var_name1 }}Y'
+    carddef1.store()
+    carddata1.store()
+    assert carddata1.id_display == 'Xfoo1Y'
+    carddata2.data['1'] = carddata1.get_natural_key()
+    carddata2.store()
+    formdata1.data['0'] = carddata1.get_natural_key()
+    formdata1.just_created()
+    formdata1.store()
+    formdata2 = formdef.data_class()()
+    formdata2.data['0'] = carddata1.get_natural_key()
+    formdata2.just_created()
+    formdata2.store()
+
+    pub.substitutions.reset()
+    pub.substitutions.feed(pub)
+    pub.substitutions.feed(carddef1)
+    pub.substitutions.feed(carddata1)
+    context = pub.substitutions.get_context_variables(mode='lazy')
+    assert len(context['form_reverse_links_formdef_foobar_bar']) == 2
+    assert context['form_reverse_links_formdef_foobar_bar_0_form_internal_id'] == formdata1.id
+    assert context['form_reverse_links_formdef_foobar_bar_1_form_internal_id'] == formdata2.id
+    assert len(context['form_reverse_links_carddef_card_2_foo']) == 1
+    assert context['form_reverse_links_carddef_card_2_foo_0_form_internal_id'] == carddata2.id

wcs/variables.py

@@ -991,6 +991,10 @@ class LazyFormData(LazyFormDef):
 
         return LazyFormDataLinks(self._formdata)
 
+    @property
+    def reverse_links(self):
+        return LazyFormDataReverseLinks(self._formdata)
+
     @property
     def workflow_email(self):
         # form_ workflow_email_ <slug (action varname)> _ <index> _ etc.
@@ -1057,6 +1061,97 @@ class LazyFormData(LazyFormDef):
             raise
 
 
+class LazyFormDataReverseLinks:
+    def __init__(self, formdata):
+        self._formdata = formdata
+
+    _relations = None
+
+    @property
+    def relations(self):
+        if self._relations is not None:
+            return self._relations
+        self._relations = {}
+        for relation in self._formdata.formdef.reverse_relations:
+            if not relation['varname']:
+                continue
+            key = '%s_%s' % (relation['obj'], relation['varname'])
+            key = key.replace(':', '_').replace('-', '_')
+            self._relations[key] = relation
+        return self._relations
+
+    def inspect_keys(self):
+        return self.relations.keys()
+
+    def __getitem__(self, key):
+        if not isinstance(key, str):
+            raise KeyError(str(key))
+
+        relation = self.relations[key]
+
+        formdef_type, formdef_slug = relation['obj'].split(':')
+        formdef_class = FormDef
+        if formdef_type == 'carddef':
+            formdef_class = CardDef
+        formdef = formdef_class.get_by_slug(formdef_slug, ignore_errors=True)
+        if formdef is None:
+            return None
+        lazy_manager = LazyFormDefObjectsManager(formdef=formdef)
+        formdatas = [
+            LazyFormDataReverseLinksItem(formdata)
+            for formdata in lazy_manager.filter_by(relation['varname']).apply_filter_value(
+                str(self._formdata.get_natural_key())
+            )
+        ]
+        if not formdatas:
+            return []
+        return LazyFormDataReverseLinksItems(formdatas)
+
+
+class LazyFormDataReverseLinksItems:
+    inspect_collapse = True
+
+    def __init__(self, formdatas):
+        self._formdatas = formdatas
+
+    def inspect_keys(self):
+        return [str(x) for x in range(len(self._formdatas))]
+
+    def __getitem__(self, key):
+        try:
+            key = int(key)
+        except ValueError:
+            raise KeyError
+        return self._formdatas[key]
+
+    def __len__(self):
+        return len(self._formdatas)
+
+    def __iter__(self):
+        yield from self._formdatas
+
+
+class LazyFormDataReverseLinksItem:
+    inspect_collapse = True
+
+    def __init__(self, formdata):
+        self._formdata = formdata
+
+    def inspect_keys(self):
+        return ['form']
+
+    @property
+    def form(self):
+        return self._formdata
+
+    def __getitem__(self, key):
+        try:
+            return getattr(self, key)
+        except AttributeError:
+            compat_dict = CompatibilityNamesDict({'form': self._formdata})
+            return compat_dict[key]
+
+
 class LazyFormDataVar:
     def __init__(self, fields, data, formdata=None, base_formdata=None):
         self._fields = fields