std domain: Generate node_id for generic objects in the right way

3 files changed, 28 insertions, 9 deletions

diff --git a/sphinx/domains/std.py b/sphinx/domains/std.py
index abf3be716..d7239f79d 100644
--- a/sphinx/domains/std.py
+++ b/sphinx/domains/std.py
@@ -66,9 +66,17 @@ class GenericObject(ObjectDescription):
         return name
 
     def add_target_and_index(self, name: str, sig: str, signode: desc_signature) -> None:
-        targetname = '%s-%s' % (self.objtype, name)
-        signode['ids'].append(targetname)
+        node_id = make_id(self.env, self.state.document, self.objtype, name)
+        signode['ids'].append(node_id)
+
+        # Assign old styled node_id not to break old hyperlinks (if possible)
+        # Note: Will be removed in Sphinx-5.0 (RemovedInSphinx50Warning)
+        old_node_id = self.make_old_id(name)
+        if old_node_id not in self.state.document.ids and old_node_id not in signode['ids']:
+            signode['ids'].append(old_node_id)
+
         self.state.document.note_explicit_target(signode)
+
         if self.indextemplate:
             colon = self.indextemplate.find(':')
             if colon != -1:
@@ -77,11 +85,18 @@ class GenericObject(ObjectDescription):
             else:
                 indextype = 'single'
                 indexentry = self.indextemplate % (name,)
-            self.indexnode['entries'].append((indextype, indexentry,
-                                              targetname, '', None))
+            self.indexnode['entries'].append((indextype, indexentry, node_id, '', None))
 
         std = cast(StandardDomain, self.env.get_domain('std'))
-        std.note_object(self.objtype, name, targetname, location=signode)
+        std.note_object(self.objtype, name, node_id, location=signode)
+
+    def make_old_id(self, name: str) -> str:
+        """Generate old styled node_id for generic objects.
+
+        .. note:: Old Styled node_id was used until Sphinx-3.0.
+                  This will be removed in Sphinx-5.0.
+        """
+        return self.objtype + '-' + name
 
 
 class EnvVar(GenericObject):
diff --git a/tests/test_build_epub.py b/tests/test_build_epub.py
index a5780b04f..a61c3cbbb 100644
--- a/tests/test_build_epub.py
+++ b/tests/test_build_epub.py
@@ -320,9 +320,13 @@ def test_epub_anchor_id(app):
     app.build()
 
     html = (app.outdir / 'index.xhtml').read_text()
-    assert '<p id="std-setting-STATICFILES_FINDERS">blah blah blah</p>' in html
-    assert '<span id="std-setting-STATICFILES_SECTION"></span><h1>blah blah blah</h1>' in html
-    assert 'see <a class="reference internal" href="#std-setting-STATICFILES_FINDERS">' in html
+    assert ('<p id="std-setting-staticfiles-finders">'
+            '<span id="std-setting-STATICFILES_FINDERS"></span>'
+            'blah blah blah</p>' in html)
+    assert ('<span id="std-setting-staticfiles-section"></span>'
+            '<span id="std-setting-STATICFILES_SECTION"></span>'
+            '<h1>blah blah blah</h1>' in html)
+    assert 'see <a class="reference internal" href="#std-setting-staticfiles-finders">' in html
 
 
 @pytest.mark.sphinx('epub', testroot='html_assets')
diff --git a/tests/test_build_html.py b/tests/test_build_html.py
index c53d0b97d..4c2618af9 100644
--- a/tests/test_build_html.py
+++ b/tests/test_build_html.py
@@ -218,7 +218,7 @@ def test_html4_output(app, status, warning):
          "[@class='rfc reference external']/strong", 'RFC 1'),
         (".//a[@href='https://tools.ietf.org/html/rfc1.html']"
          "[@class='rfc reference external']/strong", 'Request for Comments #1'),
-        (".//a[@href='objects.html#envvar-HOME']"
+        (".//a[@href='objects.html#envvar-home']"
          "[@class='reference internal']/code/span[@class='pre']", 'HOME'),
         (".//a[@href='#with']"
          "[@class='reference internal']/code/span[@class='pre']", '^with$'),