MAINT: refactor/please mypy.

With this mypy should be happier, and some files should be properly
typed.

.github/workflows/mypy.yml

@@ -26,14 +26,11 b' jobs:'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install mypy pyflakes flake8
+        pip install mypy pyflakes flake8 types-decorator
     - name: Lint with mypy
       run: |
         set -e
-        mypy -p IPython.terminal
-        mypy -p IPython.core.magics
-        mypy -p IPython.core.guarded_eval
-        mypy -p IPython.core.completer
+        mypy IPython
     - name: Lint with pyflakes
       run: |
         set -e

IPython/core/formatters.py

@@ -29,6 +29,8 b' from traitlets import ('
     default, observe,
 )
 
+from typing import Any
+
 
 class DisplayFormatter(Configurable):
 
@@ -306,8 +308,8 b' class BaseFormatter(Configurable):'
     returned and this format type is not used.
     """
 
-    format_type = Unicode('text/plain')
-    _return_type = str
+    format_type = Unicode("text/plain")
+    _return_type: Any = str
 
     enabled = Bool(True).tag(config=True)
 

IPython/core/inputsplitter.py

@@ -31,6 +31,8 b' import sys'
 import tokenize
 import warnings
 
+from typing import List
+
 from IPython.core.inputtransformer import (leading_indent,
                                            classic_prompt,
                                            ipy_prompt,
@@ -319,17 +321,16 b' class InputSplitter(object):'
     # Private attributes
 
     # List with lines of input accumulated so far
-    _buffer = None
+    _buffer: List[str]
     # Command compiler
-    _compile = None
+    _compile: codeop.CommandCompiler
     # Boolean indicating whether the current block is complete
     _is_complete = None
     # Boolean indicating whether the current block has an unrecoverable syntax error
     _is_invalid = False
 
-    def __init__(self):
-        """Create a new InputSplitter instance.
-        """
+    def __init__(self) -> None:
+        """Create a new InputSplitter instance."""
         self._buffer = []
         self._compile = codeop.CommandCompiler()
         self.encoding = get_input_encoding()
@@ -483,7 +484,7 b' class InputSplitter(object):'
                 return False
             
             try:
-                code_ast = ast.parse(u''.join(self._buffer))
+                code_ast = ast.parse("".join(self._buffer))
             except Exception:
                 #print("Can't parse AST")  # debug
                 return False

IPython/core/interactiveshell.py

@@ -33,7 +33,7 b' from logging import error'
 from pathlib import Path
 from typing import Callable
 from typing import List as ListType, Dict as DictType, Any as AnyType
-from typing import Optional, Tuple
+from typing import Optional, Sequence, Tuple
 from warnings import warn
 
 from pickleshare import PickleShareDB
@@ -1563,7 +1563,7 b' class InteractiveShell(SingletonConfigurable):'
     # Things related to object introspection
     #-------------------------------------------------------------------------
     @staticmethod
-    def _find_parts(oname: str) -> ListType[str]:
+    def _find_parts(oname: str) -> Tuple[bool, ListType[str]]:
         """
         Given an object name, return a list of parts of this object name.
 
@@ -1607,7 +1607,9 b' class InteractiveShell(SingletonConfigurable):'
 
         return parts_ok, parts
 
-    def _ofind(self, oname: str, namespaces: DictType[str, AnyType] = None):
+    def _ofind(
+        self, oname: str, namespaces: Optional[Sequence[Tuple[str, AnyType]]] = None
+    ):
         """Find an object in the available namespaces.
 
         self._ofind(oname) -> dict with keys: found,obj,ospace,ismagic
@@ -1627,7 +1629,7 b' class InteractiveShell(SingletonConfigurable):'
                 isalias=False,
                 found=False,
                 obj=None,
-                namespace="",
+                namespace=None,
                 parent=None,
             )
 
@@ -1710,14 +1712,12 b' class InteractiveShell(SingletonConfigurable):'
             ospace = 'Interactive'
 
         return OInfo(
-            **{
-                "obj": obj,
-                "found": found,
-                "parent": parent,
-                "ismagic": ismagic,
-                "isalias": isalias,
-                "namespace": ospace,
-            }
+            obj=obj,
+            found=found,
+            parent=parent,
+            ismagic=ismagic,
+            isalias=isalias,
+            namespace=ospace,
         )
 
     @staticmethod
@@ -3110,7 +3110,7 b' class InteractiveShell(SingletonConfigurable):'
         shell_futures=True,
         *,
         transformed_cell: Optional[str] = None,
-        preprocessing_exc_tuple: Optional[Any] = None,
+        preprocessing_exc_tuple: Optional[AnyType] = None,
         cell_id=None,
     ) -> ExecutionResult:
         """Run a complete IPython cell asynchronously.
@@ -3425,7 +3425,7 b' class InteractiveShell(SingletonConfigurable):'
                 if mode == "exec":
                     mod = Module([node], [])
                 elif mode == "single":
-                    mod = ast.Interactive([node])
+                    mod = ast.Interactive([node])  # type: ignore
                 with compiler.extra_flags(
                     getattr(ast, "PyCF_ALLOW_TOP_LEVEL_AWAIT", 0x0)
                     if self.autoawait

IPython/core/magic_arguments.py

@@ -251,7 +251,7 b' class ArgMethodWrapper(ArgDecorator):'
 
     """
 
-    _method_name = None
+    _method_name: str
 
     def __init__(self, *args, **kwds):
         self.args = args

IPython/core/oinspect.py

@@ -46,7 +46,7 b' from pygments import highlight'
 from pygments.lexers import PythonLexer
 from pygments.formatters import HtmlFormatter
 
-from typing import Any
+from typing import Any, Optional
 from dataclasses import dataclass
 
 
@@ -55,7 +55,7 b' class OInfo:'
     ismagic: bool
     isalias: bool
     found: bool
-    namespace: str
+    namespace: Optional[str]
     parent: Any
     obj: Any
 
@@ -173,7 +173,10 b" def getsource(obj, oname='') -> Union[str,None]:"
                 oname_prefix = ('%s.' % oname) if oname else ''
                 sources.append(''.join(('# ', oname_prefix, attrname)))
                 if inspect.isfunction(fn):
-                    sources.append(dedent(getsource(fn)))
+                    _src = getsource(fn)
+                    if _src:
+                        # assert _src is not None, "please mypy"
+                        sources.append(dedent(_src))
                 else:
                     # Default str/repr only prints function name,
                     # pretty.pretty prints module name too.
@@ -797,9 +800,11 b' class Inspector(Colorable):'
                 if obj.__doc__:
                     ds += "\nDocstring:\n" + obj.__doc__
         else:
-            ds = getdoc(obj)
-            if ds is None:
+            ds_or_None = getdoc(obj)
+            if ds_or_None is None:
                 ds = '<no docstring>'
+            else:
+                ds = ds_or_None
 
         # store output in a dict, we initialize it here and fill it as we go
         out = dict(name=oname, found=True, isalias=isalias, ismagic=ismagic, subclasses=None)
@@ -1060,15 +1065,15 b' def _render_signature(obj_signature, obj_name) -> str:'
     pos_only = False
     kw_only = True
     for param in obj_signature.parameters.values():
-        if param.kind == inspect._POSITIONAL_ONLY:
+        if param.kind == inspect.Parameter.POSITIONAL_ONLY:
             pos_only = True
         elif pos_only:
             result.append('/')
             pos_only = False
 
-        if param.kind == inspect._VAR_POSITIONAL:
+        if param.kind == inspect.Parameter.VAR_POSITIONAL:
             kw_only = False
-        elif param.kind == inspect._KEYWORD_ONLY and kw_only:
+        elif param.kind == inspect.Parameter.KEYWORD_ONLY and kw_only:
             result.append('*')
             kw_only = False
 

IPython/core/tests/test_interactiveshell.py

@@ -449,7 +449,7 b' class InteractiveShellTestCase(unittest.TestCase):'
         self.assertEqual(found, info)
 
         found = ip._ofind("a.bar", [("locals", locals())])
-        info = OInfo(
+        expected = OInfo(
             found=False,
             isalias=False,
             ismagic=False,
@@ -457,7 +457,7 b' class InteractiveShellTestCase(unittest.TestCase):'
             obj=None,
             parent=a,
         )
-        self.assertEqual(found, info)
+        assert found == expected
 
     def test_ofind_prefers_property_to_instance_level_attribute(self):
         class A(object):

IPython/core/ultratb.py

@@ -391,7 +391,12 b' class TBTools(colorable.Colorable):'
         return self.stb2text(tb_list)
 
     def structured_traceback(
-        self, etype, evalue, tb, tb_offset: Optional[int] = None, context=5, mode=None
+        self,
+        etype: type,
+        evalue: Optional[BaseException],
+        etb: Optional[TracebackType] = None,
+        tb_offset: Optional[int] = None,
+        context=5,
     ):
         """Return a list of traceback frames.
 
@@ -435,7 +440,7 b' class ListTB(TBTools):'
     def structured_traceback(
         self,
         etype: type,
-        evalue: BaseException,
+        evalue: Optional[BaseException],
         etb: Optional[TracebackType] = None,
         tb_offset: Optional[int] = None,
         context=5,
@@ -493,8 +498,11 b' class ListTB(TBTools):'
         exception = self.get_parts_of_chained_exception(evalue)
 
         if exception and not id(exception[1]) in chained_exc_ids:
-            chained_exception_message = self.prepare_chained_exception_message(
-                evalue.__cause__)[0]
+            chained_exception_message = (
+                self.prepare_chained_exception_message(evalue.__cause__)[0]
+                if evalue is not None
+                else ""
+            )
             etype, evalue, etb = exception
             # Trace exception to avoid infinite 'cause' loop
             chained_exc_ids.add(id(exception[1]))
@@ -872,7 +880,7 b' class VerboseTB(TBTools):'
             )
         return result
 
-    def prepare_header(self, etype, long_version=False):
+    def prepare_header(self, etype: str, long_version: bool = False):
         colors = self.Colors  # just a shorthand + quicker name lookup
         colorsnormal = colors.Normal  # used a lot
         exc = '%s%s%s' % (colors.excName, etype, colorsnormal)
@@ -882,15 +890,25 b' class VerboseTB(TBTools):'
             pyver = 'Python ' + sys.version.split()[0] + ': ' + sys.executable
             date = time.ctime(time.time())
 
-            head = '%s%s%s\n%s%s%s\n%s' % (colors.topline, '-' * width, colorsnormal,
-                                           exc, ' ' * (width - len(str(etype)) - len(pyver)),
-                                           pyver, date.rjust(width) )
-            head += "\nA problem occurred executing Python code.  Here is the sequence of function" \
-                    "\ncalls leading up to the error, with the most recent (innermost) call last."
+            head = "%s%s%s\n%s%s%s\n%s" % (
+                colors.topline,
+                "-" * width,
+                colorsnormal,
+                exc,
+                " " * (width - len(etype) - len(pyver)),
+                pyver,
+                date.rjust(width),
+            )
+            head += (
+                "\nA problem occurred executing Python code.  Here is the sequence of function"
+                "\ncalls leading up to the error, with the most recent (innermost) call last."
+            )
         else:
             # Simplified header
-            head = '%s%s' % (exc, 'Traceback (most recent call last)'. \
-                             rjust(width - len(str(etype))) )
+            head = "%s%s" % (
+                exc,
+                "Traceback (most recent call last)".rjust(width - len(etype)),
+            )
 
         return head
 
@@ -911,7 +929,7 b' class VerboseTB(TBTools):'
     def format_exception_as_a_whole(
         self,
         etype: type,
-        evalue: BaseException,
+        evalue: Optional[BaseException],
         etb: Optional[TracebackType],
         number_of_lines_of_context,
         tb_offset: Optional[int],
@@ -995,7 +1013,7 b' class VerboseTB(TBTools):'
         )
 
         # Let's estimate the amount of code we will have to parse/highlight.
-        cf = etb
+        cf: Optional[TracebackType] = etb
         max_len = 0
         tbs = []
         while cf is not None:

IPython/lib/display.py

@@ -8,7 +8,7 b' from os import walk, sep, fsdecode'
 
 from IPython.core.display import DisplayObject, TextDisplayObject
 
-from typing import Tuple, Iterable
+from typing import Tuple, Iterable, Optional
 
 __all__ = ['Audio', 'IFrame', 'YouTubeVideo', 'VimeoVideo', 'ScribdDocument',
            'FileLink', 'FileLinks', 'Code']
@@ -272,7 +272,9 b' class IFrame(object):'
         ></iframe>
         """
 
-    def __init__(self, src, width, height, extras: Iterable[str] = None, **kwargs):
+    def __init__(
+        self, src, width, height, extras: Optional[Iterable[str]] = None, **kwargs
+    ):
         if extras is None:
             extras = []
 

IPython/utils/tz.py

@@ -33,7 +33,9 b' class tzUTC(tzinfo):'
     def dst(self, d):
         return ZERO
 
-UTC = tzUTC()
+
+UTC = tzUTC()  # type: ignore[abstract]
+
 
 def utc_aware(unaware):
     """decorator for adding UTC tzinfo to datetime's utcfoo methods"""

pyproject.toml

@@ -1,3 +1,32 b''
 [build-system]
 requires = ["setuptools >= 51.0.0"]
 build-backend = "setuptools.build_meta"
+[tool.mypy]
+python_version = 3.8
+ignore_missing_imports = true
+follow_imports = 'silent'
+exclude = [
+   'test_\.+\.py',
+   'IPython.utils.tests.test_wildcard',
+   'testing',
+   'tests',
+   'PyColorize.py',
+   '_process_win32_controller.py',
+   'IPython/core/application.py',
+   'IPython/core/completerlib.py',
+   'IPython/core/displaypub.py',
+   'IPython/core/historyapp.py',
+   #'IPython/core/interactiveshell.py',
+   'IPython/core/magic.py',
+   'IPython/core/profileapp.py',
+   'IPython/core/ultratb.py',
+   'IPython/lib/deepreload.py',
+   'IPython/lib/pretty.py',
+   'IPython/sphinxext/ipython_directive.py',
+   'IPython/terminal/ipapp.py',
+   'IPython/utils/_process_win32.py',
+   'IPython/utils/path.py',
+   'IPython/utils/timing.py',
+   'IPython/utils/text.py'
+   ]
+