From 5f696ed119fc77e5c57649d67984e691e59fc8ed Mon Sep 17 00:00:00 2001
From: Takeshi KOMIYA <i.tkomiya@gmail.com>
Date: Tue, 11 May 2021 23:25:21 +0900
Subject: [PATCH 1/2] Fix #9210: viewcode: crashed if non importable modules
 found on parallel build

---
 CHANGES                | 2 ++
 sphinx/ext/viewcode.py | 9 +++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/CHANGES b/CHANGES
index 8cb39f2672f..45a959e3923 100644
--- a/CHANGES
+++ b/CHANGES
@@ -16,6 +16,8 @@ Features added
 Bugs fixed
 ----------
 
+* #9210: viewcode: crashed if non importable modules found on parallel build
+
 Testing
 --------
 
diff --git a/sphinx/ext/viewcode.py b/sphinx/ext/viewcode.py
index f2a42f33f82..5728f607761 100644
--- a/sphinx/ext/viewcode.py
+++ b/sphinx/ext/viewcode.py
@@ -150,10 +150,11 @@ def env_merge_info(app: Sphinx, env: BuildEnvironment, docnames: Iterable[str],
         if modname not in env._viewcode_modules:  # type: ignore
             env._viewcode_modules[modname] = entry  # type: ignore
         else:
-            used = env._viewcode_modules[modname][2]  # type: ignore
-            for fullname, docname in entry[2].items():
-                if fullname not in used:
-                    used[fullname] = docname
+            if env._viewcode_modules[modname]:  # type: ignore
+                used = env._viewcode_modules[modname][2]  # type: ignore
+                for fullname, docname in entry[2].items():
+                    if fullname not in used:
+                        used[fullname] = docname
 
 
 def env_purge_doc(app: Sphinx, env: BuildEnvironment, docname: str) -> None:

From d18840b38d3627880b6af71d8d23552a9daf7e10 Mon Sep 17 00:00:00 2001
From: Takeshi KOMIYA <i.tkomiya@gmail.com>
Date: Thu, 13 May 2021 01:40:45 +0900
Subject: [PATCH 2/2] Fix test: the result of stringify_signature() has been
 changed randomly in py36

---
 tests/test_util_inspect.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/test_util_inspect.py b/tests/test_util_inspect.py
index 7b86c6ade36..5e35df762e9 100644
--- a/tests/test_util_inspect.py
+++ b/tests/test_util_inspect.py
@@ -198,7 +198,11 @@ def test_signature_annotations():
 
     # optional union
     sig = inspect.signature(f20)
-    assert stringify_signature(sig) == '() -> Optional[Union[int, str]]'
+    if sys.version_info < (3, 7):
+        assert stringify_signature(sig) in ('() -> Optional[Union[int, str]]',
+                                            '() -> Optional[Union[str, int]]')
+    else:
+        assert stringify_signature(sig) == '() -> Optional[Union[int, str]]'
 
     # Any
     sig = inspect.signature(f14)