refactor: Add Optional to type annotations

10 files changed, 30 insertions, 27 deletions

diff --git a/sphinx/config.py b/sphinx/config.py
index 418ecf4fb..5e265f576 100644
--- a/sphinx/config.py
+++ b/sphinx/config.py
@@ -309,7 +309,7 @@ class Config:
         self.__dict__.update(state)
 
 
-def eval_config_file(filename: str, tags: Tags) -> Dict[str, Any]:
+def eval_config_file(filename: str, tags: Optional[Tags]) -> Dict[str, Any]:
     """Evaluate a config file."""
     namespace: Dict[str, Any] = {}
     namespace['__file__'] = filename
diff --git a/sphinx/environment/adapters/toctree.py b/sphinx/environment/adapters/toctree.py
index 3ee2f9ff0..6822c42c9 100644
--- a/sphinx/environment/adapters/toctree.py
+++ b/sphinx/environment/adapters/toctree.py
@@ -8,7 +8,7 @@
     :license: BSD, see LICENSE for details.
 """
 
-from typing import TYPE_CHECKING, Any, Iterable, List, cast
+from typing import TYPE_CHECKING, Any, Iterable, List, Optional, cast
 
 from docutils import nodes
 from docutils.nodes import Element, Node
@@ -48,7 +48,7 @@ class TocTree:
 
     def resolve(self, docname: str, builder: "Builder", toctree: addnodes.toctree,
                 prune: bool = True, maxdepth: int = 0, titles_only: bool = False,
-                collapse: bool = False, includehidden: bool = False) -> Element:
+                collapse: bool = False, includehidden: bool = False) -> Optional[Element]:
         """Resolve a *toctree* node into individual bullet lists with titles
         as items, returning None (if no containing titles are found) or
         a new node.
diff --git a/sphinx/project.py b/sphinx/project.py
index bb2314c63..d4293cdc4 100644
--- a/sphinx/project.py
+++ b/sphinx/project.py
@@ -10,7 +10,7 @@
 
 import os
 from glob import glob
-from typing import Dict, List, Set
+from typing import Dict, List, Optional, Set
 
 from sphinx.locale import __
 from sphinx.util import get_matching_files, logging, path_stabilize
@@ -60,7 +60,7 @@ class Project:
 
         return self.docnames
 
-    def path2doc(self, filename: str) -> str:
+    def path2doc(self, filename: str) -> Optional[str]:
         """Return the docname for the filename if the file is document.
 
         *filename* should be absolute or relative to the source directory.
diff --git a/sphinx/transforms/__init__.py b/sphinx/transforms/__init__.py
index 213742636..66882e2b2 100644
--- a/sphinx/transforms/__init__.py
+++ b/sphinx/transforms/__init__.py
@@ -10,7 +10,7 @@
 
 import re
 import warnings
-from typing import TYPE_CHECKING, Any, Dict, Generator, List, Tuple
+from typing import TYPE_CHECKING, Any, Dict, Generator, List, Optional, Tuple
 
 from docutils import nodes
 from docutils.nodes import Element, Node, Text
@@ -72,8 +72,8 @@ class SphinxTransformer(Transformer):
     A transformer for Sphinx.
     """
 
-    document: nodes.document = None
-    env: "BuildEnvironment" = None
+    document: nodes.document
+    env: Optional["BuildEnvironment"] = None
 
     def set_environment(self, env: "BuildEnvironment") -> None:
         self.env = env
diff --git a/sphinx/util/docfields.py b/sphinx/util/docfields.py
index f74f03265..3a3367ebe 100644
--- a/sphinx/util/docfields.py
+++ b/sphinx/util/docfields.py
@@ -209,7 +209,7 @@ class DocFieldTransformer:
     Transforms field lists in "doc field" syntax into better-looking
     equivalents, using the field type definitions given on a domain.
     """
-    typemap: Dict[str, Tuple[Field, bool]] = None
+    typemap: Dict[str, Tuple[Field, bool]]
 
     def __init__(self, directive: "ObjectDescription") -> None:
         self.directive = directive
diff --git a/sphinx/util/docutils.py b/sphinx/util/docutils.py
index 44483bdd8..c2e12e152 100644
--- a/sphinx/util/docutils.py
+++ b/sphinx/util/docutils.py
@@ -176,8 +176,8 @@ class sphinx_domains:
     """
     def __init__(self, env: "BuildEnvironment") -> None:
         self.env = env
-        self.directive_func: Callable = None
-        self.roles_func: Callable = None
+        self.directive_func: Callable = lambda *args: (None, [])
+        self.roles_func: Callable = lambda *args: (None, [])
 
     def __enter__(self) -> None:
         self.enable()
@@ -372,7 +372,7 @@ class SphinxRole:
         if name:
             self.name = name.lower()
         else:
-            self.name = self.env.temp_data.get('default_role')
+            self.name = self.env.temp_data.get('default_role', '')
             if not self.name:
                 self.name = self.env.config.default_role
             if not self.name:
@@ -491,7 +491,7 @@ class SphinxTranslator(nodes.NodeVisitor):
 
 # cache a vanilla instance of nodes.document
 # Used in new_document() function
-__document_cache__: nodes.document = None
+__document_cache__: Optional[nodes.document] = None
 
 
 def new_document(source_path: str, settings: Any = None) -> nodes.document:
diff --git a/sphinx/util/logging.py b/sphinx/util/logging.py
index 64b7d8fb4..e0f4f0e70 100644
--- a/sphinx/util/logging.py
+++ b/sphinx/util/logging.py
@@ -320,8 +320,8 @@ def prefixed_warnings(prefix: str) -> Generator[None, None, None]:
             prefix_filter.prefix = previous
     else:
         # not prefixed yet
+        prefix_filter = MessagePrefixFilter(prefix)
         try:
-            prefix_filter = MessagePrefixFilter(prefix)
             warning_handler.addFilter(prefix_filter)
             yield
         finally:
@@ -472,7 +472,7 @@ class SphinxLogRecordTranslator(logging.Filter):
     * Make a instance of SphinxLogRecord
     * docname to path if location given
     """
-    LogRecordClass: Type[logging.LogRecord] = None
+    LogRecordClass: Type[logging.LogRecord]
 
     def __init__(self, app: "Sphinx") -> None:
         self.app = app
diff --git a/sphinx/util/nodes.py b/sphinx/util/nodes.py
index 44eb5d303..36db149b9 100644
--- a/sphinx/util/nodes.py
+++ b/sphinx/util/nodes.py
@@ -10,7 +10,8 @@
 
 import re
 import unicodedata
-from typing import TYPE_CHECKING, Any, Callable, Iterable, List, Set, Tuple, Type, Union, cast
+from typing import (TYPE_CHECKING, Any, Callable, Iterable, List, Optional, Set, Tuple, Type,
+                    Union, cast)
 
 from docutils import nodes
 from docutils.nodes import Element, Node
@@ -170,7 +171,7 @@ def apply_source_workaround(node: Element) -> None:
     ))):
         logger.debug('[i18n] PATCH: %r to have source and line: %s',
                      get_full_module_name(node), repr_domxml(node))
-        node.source = get_node_source(node)
+        node.source = get_node_source(node) or ''
         node.line = 0  # need fix docutils to get `node.line`
         return
 
@@ -266,7 +267,7 @@ def extract_messages(doctree: Element) -> Iterable[Tuple[Element, str]]:
             if node.get('translatable'):
                 msg = '.. image:: %s' % node['uri']
             else:
-                msg = None
+                msg = ''
         elif isinstance(node, META_TYPE_NODES):
             msg = node.rawcontent
         elif isinstance(node, nodes.pending) and is_pending_meta(node):
@@ -279,14 +280,14 @@ def extract_messages(doctree: Element) -> Iterable[Tuple[Element, str]]:
             yield node, msg
 
 
-def get_node_source(node: Element) -> str:
+def get_node_source(node: Element) -> Optional[str]:
     for pnode in traverse_parent(node):
         if pnode.source:
             return pnode.source
     return None
 
 
-def get_node_line(node: Element) -> int:
+def get_node_line(node: Element) -> Optional[int]:
     for pnode in traverse_parent(node):
         if pnode.line:
             return pnode.line
@@ -300,7 +301,7 @@ def traverse_parent(node: Element, cls: Any = None) -> Iterable[Element]:
         node = node.parent
 
 
-def get_prev_node(node: Node) -> Node:
+def get_prev_node(node: Node) -> Optional[Node]:
     pos = node.parent.index(node)
     if pos > 0:
         return node.parent[pos - 1]
@@ -360,10 +361,11 @@ indextypes = [
 ]
 
 
-def process_index_entry(entry: str, targetid: str) -> List[Tuple[str, str, str, str, str]]:
+def process_index_entry(entry: str, targetid: str
+                        ) -> List[Tuple[str, str, str, str, Optional[str]]]:
     from sphinx.domains.python import pairindextypes
 
-    indexentries: List[Tuple[str, str, str, str, str]] = []
+    indexentries: List[Tuple[str, str, str, str, Optional[str]]] = []
     entry = entry.strip()
     oentry = entry
     main = ''
@@ -531,7 +533,8 @@ def make_id(env: "BuildEnvironment", document: nodes.document,
     return node_id
 
 
-def find_pending_xref_condition(node: addnodes.pending_xref, condition: str) -> Element:
+def find_pending_xref_condition(node: addnodes.pending_xref, condition: str
+                                ) -> Optional[Element]:
     """Pick matched pending_xref_condition node up from the pending_xref."""
     for subnode in node:
         if (isinstance(subnode, addnodes.pending_xref_condition) and
diff --git a/sphinx/util/parallel.py b/sphinx/util/parallel.py
index 2d6b4bddb..2a83d6297 100644
--- a/sphinx/util/parallel.py
+++ b/sphinx/util/parallel.py
@@ -14,7 +14,7 @@ import sys
 import time
 import traceback
 from math import sqrt
-from typing import Any, Callable, Dict, List, Sequence
+from typing import Any, Callable, Dict, List, Optional, Sequence
 
 try:
     import multiprocessing
@@ -62,7 +62,7 @@ class ParallelTasks:
         # (optional) function performed by each task on the result of main task
         self._result_funcs: Dict[int, Callable] = {}
         # task arguments
-        self._args: Dict[int, List[Any]] = {}
+        self._args: Dict[int, Optional[List[Any]]] = {}
         # list of subprocesses (both started and waiting)
         self._procs: Dict[int, multiprocessing.Process] = {}
         # list of receiving pipe connections of running subprocesses
diff --git a/sphinx/util/typing.py b/sphinx/util/typing.py
index 957f8a332..fb8daa623 100644
--- a/sphinx/util/typing.py
+++ b/sphinx/util/typing.py
@@ -64,7 +64,7 @@ RoleFunction = Callable[[str, str, str, int, Inliner, Dict[str, Any], List[str]]
                         Tuple[List[nodes.Node], List[nodes.system_message]]]
 
 # A option spec for directive
-OptionSpec = Dict[str, Callable[[Optional[str]], Any]]
+OptionSpec = Dict[str, Callable[[str], Any]]
 
 # title getter functions for enumerable nodes (see sphinx.domains.std)
 TitleGetter = Callable[[nodes.Node], str]