Keep "translated" attribute on translated nodes

`sphinx.transforms.Locale` iterates over all the nodes to replace its content
with the translated version of the text if found. Since the process works in two
phases, it adds an "internal" `translated: True` attribute to the docutils node
when the translated text is found in phase 1, allowing phase 2 to skip this
nodes and avoid re-processing them. Finally, this "internal" `translated`
attribute is removed from all the nodes.

This particular commit deletes the code that removes the `translated` attribute
from the nodes so developers can use it to improve the experience on
translations. This attribute can be useful to calculate the translated
percentage of a particular document, to visually mark paragraphs as not
translated and many other applications.

Closes sphinx-doc#11157

sphinx/transforms/i18n.py

@@ -512,11 +512,6 @@ def apply(self, **kwargs: Any) -> None:
                 node['raw_entries'] = entries
                 node['entries'] = new_entries
 
-        # remove translated attribute that is used for avoiding double translation.
-        matcher = NodeMatcher(translated=Any)
-        for translated in self.document.findall(matcher):  # type: nodes.Element
-            translated.delattr('translated')
-
 
 class RemoveTranslatableInline(SphinxTransform):
     """

tests/test_intl.py

@@ -615,6 +615,21 @@ def test_gettext_buildr_ignores_only_directive(app):
         assert expect_msg.id in [m.id for m in actual if m.id]
 
 
+@sphinx_intl
+@pytest.mark.test_params(shared_result='test_intl_gettext')
+def test_node_translated_attribute(app):
+    app.build()
+
+    expected = 23
+    translated_nodes = 0
+
+    doctree = app.env.get_doctree('admonitions')
+    for node in doctree.traverse():
+        if hasattr(node, 'get') and node.get('translated', False):
+            translated_nodes += 1
+    assert translated_nodes == expected
+
+
 @sphinx_intl
 # use individual shared_result directory to avoid "incompatible doctree" error
 @pytest.mark.sphinx(testroot='builder-gettext-dont-rebuild-mo')