Convert some functions to static typing

.mypy.ini

@@ -1,2 +1,3 @@
 [mypy]
 warn_unused_ignores = True
+disallow_incomplete_defs = True

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Renamed application name from "Diffuse Merge Tool" to "Diffuse"
 - Linters can be run sooner (before installation)
 - Better messages when an error occurs while parsing the config file
+- Start converting the code to static types
 
 ### Fixed
 - Removed the lasting lint errors (i.e. in main.py)

src/diffuse/constants.py

@@ -18,11 +18,12 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 from gettext import gettext as _
+from typing import Final
 
-APP_NAME = 'Diffuse'
+APP_NAME: Final[str] = 'Diffuse'
-COPYRIGHT = '''{copyright} © 2006-2019 Derrick Moser
+COPYRIGHT: Final[str] = '''{copyright} © 2006-2019 Derrick Moser
 {copyright} © 2015-2021 Romain Failliot'''.format(copyright=_("Copyright"))
-WEBSITE = 'https://mightycreak.github.io/diffuse/'
+WEBSITE: Final[str] = 'https://mightycreak.github.io/diffuse/'
 
 # Constants are set in main()
-VERSION = '0.0.0'
+VERSION: str = '0.0.0'

src/diffuse/dialogs.py

@@ -32,7 +32,7 @@ from gi.repository import GObject, Gtk  # type: ignore # noqa: E402
 
 # the about dialog
 class AboutDialog(Gtk.AboutDialog):
-    def __init__(self):
+    def __init__(self) -> None:
         Gtk.AboutDialog.__init__(self)
         self.set_logo_icon_name('io.github.mightycreak.Diffuse')
         self.set_program_name(constants.APP_NAME)
@@ -104,13 +104,13 @@ class FileChooserDialog(Gtk.FileChooserDialog):
     def set_encoding(self, encoding):
         self.encoding.set_text(encoding)
 
-    def get_encoding(self):
+    def get_encoding(self) -> str:
         return self.encoding.get_text()
 
-    def get_revision(self):
+    def get_revision(self) -> str:
         return self.revision.get_text()
 
-    def get_filename(self):
+    def get_filename(self) -> str:
         # convert from UTF-8 string to unicode
         return Gtk.FileChooserDialog.get_filename(self)
 

src/diffuse/main.py

@@ -26,6 +26,7 @@ import stat
 import webbrowser
 
 from gettext import gettext as _
+from typing import Optional
 from urllib.parse import urlparse
 
 from diffuse import constants
@@ -33,6 +34,7 @@ from diffuse import utils
 from diffuse.dialogs import AboutDialog, FileChooserDialog, NumericDialog, SearchDialog
 from diffuse.preferences import Preferences
 from diffuse.resources import theResources
+from diffuse.utils import LineEnding
 from diffuse.vcs.vcs_registry import VcsRegistry
 from diffuse.widgets import FileDiffViewerBase
 from diffuse.widgets import createMenu, LINE_MODE, CHAR_MODE, ALIGN_MODE
@@ -118,7 +120,7 @@ class Diffuse(Gtk.Window):
     class FileDiffViewer(FileDiffViewerBase):
         # pane header
         class PaneHeader(Gtk.Box):
-            def __init__(self):
+            def __init__(self) -> None:
                 Gtk.Box.__init__(self, orientation=Gtk.Orientation.HORIZONTAL, spacing=0)
                 _append_buttons(self, Gtk.IconSize.MENU, [
                     [Gtk.STOCK_OPEN, self.button_cb, 'open', _('Open File...')],
@@ -171,7 +173,7 @@ class Diffuse(Gtk.Window):
 
         # pane footer
         class PaneFooter(Gtk.Box):
-            def __init__(self):
+            def __init__(self) -> None:
                 Gtk.Box.__init__(self, orientation=Gtk.Orientation.HORIZONTAL, spacing=0)
                 self.cursor = label = Gtk.Label.new()
                 self.cursor.set_size_request(-1, -1)
@@ -212,11 +214,11 @@ class Diffuse(Gtk.Window):
             # set the format label
             def setFormat(self, s):
                 v = []
-                if s & utils.DOS_FORMAT:
+                if s & LineEnding.DOS_FORMAT:
                     v.append('DOS')
-                if s & utils.MAC_FORMAT:
+                if s & LineEnding.MAC_FORMAT:
                     v.append('Mac')
-                if s & utils.UNIX_FORMAT:
+                if s & LineEnding.UNIX_FORMAT:
                     v.append('Unix')
                 self.format.set_text('/'.join(v))
 
@@ -1108,7 +1110,7 @@ class Diffuse(Gtk.Window):
             self.quit_cb(widget, data)
 
     # convenience method to request confirmation when closing the last tab
-    def _confirm_tab_close(self):
+    def _confirm_tab_close(self) -> bool:
         dialog = utils.MessageDialog(
             self.get_toplevel(),
             Gtk.MessageType.WARNING,
@@ -1193,7 +1195,7 @@ class Diffuse(Gtk.Window):
             self.setSyntax(s)
 
     # create an empty viewer with 'n' panes
-    def newFileDiffViewer(self, n):
+    def newFileDiffViewer(self, n: int) -> FileDiffViewer:
         self.viewer_count += 1
         tabname = _('File Merge %d') % (self.viewer_count, )
         tab = NotebookTab(tabname, Gtk.STOCK_FILE)
@@ -1338,13 +1340,13 @@ class Diffuse(Gtk.Window):
                     )
 
     # close all tabs without differences
-    def closeOnSame(self):
+    def closeOnSame(self) -> None:
         for i in range(self.notebook.get_n_pages() - 1, -1, -1):
             if not self.notebook.get_nth_page(i).hasDifferences():
                 self.notebook.remove_page(i)
 
     # returns True if the application can safely quit
-    def confirmQuit(self):
+    def confirmQuit(self) -> bool:
         nb = self.notebook
         return self.confirmCloseViewers([nb.get_nth_page(i) for i in range(nb.get_n_pages())])
 
@@ -1356,7 +1358,7 @@ class Diffuse(Gtk.Window):
         return True
 
     # returns the currently focused viewer
-    def getCurrentViewer(self):
+    def getCurrentViewer(self) -> Optional[Gtk.Widget]:
         return self.notebook.get_nth_page(self.notebook.get_current_page())
 
     # callback for the open file menu item
@@ -1570,7 +1572,7 @@ class Diffuse(Gtk.Window):
         self.getCurrentViewer().go_to_line_cb(widget, data)
 
     # notify all viewers of changes to the preferences
-    def preferences_updated(self):
+    def preferences_updated(self) -> None:
         n = self.notebook.get_n_pages()
         self.notebook.set_show_tabs(self.prefs.getBool('tabs_always_show') or n > 1)
         for i in range(n):
@@ -1712,7 +1714,7 @@ def _append_buttons(box, size, specs):
 
 
 # constructs a full URL for the named file
-def _path2url(path, proto='file'):
+def _path2url(path: str, proto: str = 'file') -> str:
     r = [proto, ':///']
     s = os.path.abspath(path)
     i = 0

src/diffuse/preferences.py

@@ -199,7 +199,7 @@ class Preferences:
         self.path = path
         if os.path.isfile(self.path):
             try:
-                with open(self.path, 'r',  encoding='utf-8') as f:
+                with open(self.path, 'r', encoding='utf-8') as f:
                     ss = utils.readconfiglines(f)
                 for j, s in enumerate(ss):
                     try:
@@ -342,7 +342,7 @@ class Preferences:
                 if tpl[0] in ['Font', 'Integer']:
                     entry = Gtk.Box.new(Gtk.Orientation.HORIZONTAL, 0)
                     if tpl[0] == 'Font':
-                        button = _FontButton()
+                        button = Gtk.FontButton()
                         button.set_font(self.string_prefs[tpl[1]])
                     else:
                         button = Gtk.SpinButton.new(
@@ -368,28 +368,28 @@ class Preferences:
         return table
 
     # get/set methods to manipulate the preference values
-    def getBool(self, name):
+    def getBool(self, name: str) -> bool:
         return self.bool_prefs[name]
 
-    def setBool(self, name, value):
+    def setBool(self, name: str, value: bool) -> None:
         self.bool_prefs[name] = value
 
-    def getInt(self, name):
+    def getInt(self, name: str) -> int:
         return self.int_prefs[name]
 
-    def getString(self, name):
+    def getString(self, name: str) -> str:
         return self.string_prefs[name]
 
-    def setString(self, name, value):
+    def setString(self, name: str, value: str) -> None:
         self.string_prefs[name] = value
 
     def getEncodings(self):
         return self.encodings
 
-    def _getDefaultEncodings(self):
+    def _getDefaultEncodings(self) -> list[str]:
         return self.string_prefs['encoding_auto_detect_codecs'].split()
 
-    def getDefaultEncoding(self):
+    def getDefaultEncoding(self) -> str:
         return self.string_prefs['encoding_default_codec']
 
     # attempt to convert a string to unicode from an unknown encoding
@@ -412,7 +412,7 @@ class Preferences:
 
     # cygwin and native applications can be used on windows, use this method
     # to convert a path to the usual form expected on sys.platform
-    def convertToNativePath(self, s):
+    def convertToNativePath(self, s: str) -> str:
         if utils.isWindows() and s.find('/') >= 0:
             # treat as a cygwin path
             s = s.replace(os.sep, '/')
@@ -436,15 +436,6 @@ class Preferences:
         return s
 
 
-# adaptor class to allow a Gtk.FontButton to be read like a Gtk.Entry
-class _FontButton(Gtk.FontButton):
-    def __init__(self):
-        Gtk.FontButton.__init__(self)
-
-    def get_text(self):
-        return self.get_font_name()
-
-
 # text entry widget with a button to help pick file names
 class _FileEntry(Gtk.Box):
     def __init__(self, parent, title):
@@ -475,8 +466,8 @@ class _FileEntry(Gtk.Box):
             self.entry.set_text(dialog.get_filename())
         dialog.destroy()
 
-    def set_text(self, s):
+    def set_text(self, s: str) -> None:
         self.entry.set_text(s)
 
-    def get_text(self):
+    def get_text(self) -> str:
         return self.entry.get_text()

src/diffuse/resources.py

@@ -31,6 +31,7 @@ import shlex
 
 from distutils import util
 from gettext import gettext as _
+from typing import Final
 
 from diffuse import utils
 
@@ -529,7 +530,7 @@ class Resources:
 
 # colour resources
 class _Colour:
-    def __init__(self, r, g, b, a=1.0):
+    def __init__(self, r: float, g: float, b: float, a: float = 1.0):
         # the individual colour components as floats in the range [0, 1]
         self.red = r
         self.green = g
@@ -601,4 +602,4 @@ class _SyntaxParser:
         return state_name, blocks
 
 
-theResources = Resources()
+theResources: Final[Resources] = Resources()

src/diffuse/utils.py

@@ -23,7 +23,9 @@ import locale
 import subprocess
 import traceback
 
+from enum import IntFlag
 from gettext import gettext as _
+from typing import Final, Optional, TextIO
 
 from diffuse import constants
 from diffuse.resources import theResources
@@ -74,38 +76,38 @@ class EncodingMenu(Gtk.Box):
         return self.encodings[i] if i >= 0 else None
 
 
-# platform test
+def isWindows() -> bool:
-def isWindows():
+    '''Returns true if OS is Windows; otherwise false.'''
     return os.name == 'nt'
 
 
-def _logPrintOutput(msg):
+def _logPrintOutput(msg: str) -> None:
     if theResources.getOptionAsBool('log_print_output'):
         print(msg, file=sys.stderr)
         if theResources.getOptionAsBool('log_print_stack'):
             traceback.print_stack()
 
 
-# convenience function to display debug messages
+def logDebug(msg: str) -> None:
-def logDebug(msg):
+    '''Report debug message.'''
     _logPrintOutput(f'DEBUG: {msg}')
 
 
-# report error messages
+def logError(msg: str) -> None:
-def logError(msg):
+    '''Report error message.'''
     _logPrintOutput(f'ERROR: {msg}')
 
 
-# report error messages and show dialog
+def logErrorAndDialog(msg: str, parent: Gtk.Widget = None) -> None:
-def logErrorAndDialog(msg, parent=None):
+    '''Report error message and show dialog.'''
     logError(msg)
     dialog = MessageDialog(parent, Gtk.MessageType.ERROR, msg)
     dialog.run()
     dialog.destroy()
 
 
-# create nested subdirectories and return the complete path
+def make_subdirs(p: str, ss: list[str]) -> str:
-def make_subdirs(p, ss):
+    '''Create nested subdirectories and return the complete path.'''
     for s in ss:
         p = os.path.join(p, s)
         if not os.path.exists(p):
@@ -116,16 +118,16 @@ def make_subdirs(p, ss):
     return p
 
 
-# returns the Windows drive or share from a from an absolute path
+def _drive_from_path(path: str) -> str:
-def _drive_from_path(path):
+    '''Returns the Windows drive or share from a from an absolute path.'''
     d = path.split(os.sep)
     if len(d) > 3 and d[0] == '' and d[1] == '':
-        return os.path.join(d[:4])
+        return os.path.join(*d[:4])
     return d[0]
 
 
-# constructs a relative path from 'a' to 'b', both should be absolute paths
+def relpath(a: str, b: str) -> str:
-def relpath(a, b):
+    '''Constructs a relative path from 'a' to 'b', both should be absolute paths.'''
     if isWindows():
         if _drive_from_path(a) != _drive_from_path(b):
             return b
@@ -151,12 +153,12 @@ def safeRelativePath(abspath1, name, prefs, cygwin_pref):
     return s
 
 
-# escape arguments for use with bash
+def _bash_escape(s: str) -> str:
-def _bash_escape(s):
+    '''Escape arguments for use with bash.'''
     return "'" + s.replace("'", "'\\''") + "'"
 
 
-def _use_flatpak():
+def _use_flatpak() -> bool:
     return theResources.getOptionAsBool('use_flatpak')
 
 
@@ -201,9 +203,8 @@ def popenRead(dn, cmd, prefs, bash_pref, success_results=None):
         return s
 
 
-# returns the number of characters in the string excluding any line ending
+def len_minus_line_ending(s: str) -> int:
-# characters
+    '''Returns the number of characters in the string excluding any line ending characters.'''
-def len_minus_line_ending(s):
     if s is None:
         return 0
     n = len(s)
@@ -214,15 +215,15 @@ def len_minus_line_ending(s):
     return n
 
 
-# returns the string without the line ending characters
+def strip_eol(s: str) -> str:
-def strip_eol(s):
+    '''Returns the string without the line ending characters.'''
     if s:
         s = s[:len_minus_line_ending(s)]
     return s
 
 
-# returns the list of strings without line ending characters
+def _strip_eols(ss: list[str]) -> list[str]:
-def _strip_eols(ss):
+    '''Returns the list of strings without line ending characters.'''
     return [strip_eol(s) for s in ss]
 
 
@@ -232,12 +233,12 @@ def popenReadLines(dn, cmd, prefs, bash_pref, success_results=None):
         dn, cmd, prefs, bash_pref, success_results).decode('utf-8', errors='ignore')))
 
 
-def readconfiglines(fd):
+def readconfiglines(fd: TextIO) -> list[str]:
     return fd.read().replace('\r', '').split('\n')
 
 
-# escape special glob characters
+def globEscape(s: str) -> str:
-def globEscape(s):
+    '''Escape special glob characters.'''
     m = {c: f'[{c}]' for c in '[]?*'}
     return ''.join([m.get(c, c) for c in s])
 
@@ -272,25 +273,25 @@ def splitlines(text: str) -> list[str]:
 
 
 # also recognize old Mac OS line endings
-def readlines(fd):
+def readlines(fd: TextIO) -> list[str]:
     return _strip_eols(splitlines(fd.read()))
 
 
-# map an encoding name to its standard form
+def norm_encoding(e: Optional[str]) -> Optional[str]:
-def norm_encoding(e):
+    '''Map an encoding name to its standard form.'''
     if e is not None:
         return e.replace('-', '_').lower()
     return None
 
 
-def null_to_empty(s):
+def null_to_empty(s: Optional[str]) -> str:
     if s is None:
         s = ''
     return s
 
 
 # utility method to step advance an adjustment
-def step_adjustment(adj, delta):
+def step_adjustment(adj: Gtk.Adjustment, delta: int) -> None:
     v = adj.get_value() + delta
     # clamp to the allowed range
     v = max(v, int(adj.get_lower()))
@@ -298,36 +299,43 @@ def step_adjustment(adj, delta):
     adj.set_value(v)
 
 
-# masks used to indicate the presence of particular line endings
+def _get_default_lang() -> Optional[str]:
-DOS_FORMAT = 1
+    lang = locale.getdefaultlocale()[0]
-MAC_FORMAT = 2
+    if isWindows():
-UNIX_FORMAT = 4
+        # gettext looks for the language using environment variables which
+        # are normally not set on Windows so we try setting it for them
+        for lang_env in 'LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE':
+            if lang_env in os.environ:
+                lang = os.environ[lang_env]
+                # remove any additional languages, encodings, or modifications
+                for c in ':.@':
+                    lang = lang.split(c)[0]
+                break
+        else:
+            if lang is not None:
+                os.environ['LANG'] = lang
+    return lang
+
+
+class LineEnding(IntFlag):
+    '''Enumeration of line endings.
+
+    Values can be used as flags in bitwise operations.'''
+
+    DOS_FORMAT = 1
+    MAC_FORMAT = 2
+    UNIX_FORMAT = 4
+
 
 # avoid some dictionary lookups when string.whitespace is used in loops
 # this is sorted based upon frequency to speed up code for stripping whitespace
-whitespace = ' \t\n\r\x0b\x0c'
+whitespace: Final[str] = ' \t\n\r\x0b\x0c'
 
 # use the program's location as a starting place to search for supporting files
 # such as icon and help documentation
-if hasattr(sys, 'frozen'):
+app_path: Final[str] = sys.executable if hasattr(sys, 'frozen') else os.path.realpath(sys.argv[0])
-    app_path = sys.executable
+bin_dir: Final[str] = os.path.dirname(app_path)
-else:
-    app_path = os.path.realpath(sys.argv[0])
-bin_dir = os.path.dirname(app_path)
 
 # translation location: '../share/locale/<LANG>/LC_MESSAGES/diffuse.mo'
 # where '<LANG>' is the language key
-lang = locale.getdefaultlocale()[0]
+lang: Final[Optional[str]] = _get_default_lang()
-if isWindows():
-    # gettext looks for the language using environment variables which
-    # are normally not set on Windows so we try setting it for them
-    for lang_env in 'LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE':
-        if lang_env in os.environ:
-            lang = os.environ[lang_env]
-            # remove any additional languages, encodings, or modifications
-            for c in ':.@':
-                lang = lang.split(c)[0]
-            break
-    else:
-        if lang is not None:
-            os.environ['LANG'] = lang

src/diffuse/vcs/git.py

@@ -20,6 +20,7 @@
 import os
 
 from diffuse import utils
+from diffuse.preferences import Preferences
 from diffuse.vcs.folder_set import FolderSet
 from diffuse.vcs.vcs_interface import VcsInterface
 
@@ -61,7 +62,7 @@ class Git(VcsInterface):
         # sort the results
         return [modified[k] for k in sorted(modified.keys())]
 
-    def _extractPath(self, s, prefs):
+    def _extractPath(self, s: str, prefs: Preferences) -> str:
         return os.path.join(self.root, prefs.convertToNativePath(s.strip()))
 
     def getFolderTemplate(self, prefs, names):

src/diffuse/vcs/hg.py

@@ -19,6 +19,8 @@
 
 import os
 
+from typing import Optional
+
 from diffuse import utils
 from diffuse.vcs.folder_set import FolderSet
 from diffuse.vcs.vcs_interface import VcsInterface
@@ -26,9 +28,9 @@ from diffuse.vcs.vcs_interface import VcsInterface
 
 # Mercurial support
 class Hg(VcsInterface):
-    def __init__(self, root):
+    def __init__(self, root: str):
         VcsInterface.__init__(self, root)
-        self.working_rev = None
+        self.working_rev: Optional[str] = None
 
     def _getPreviousRevision(self, prefs, rev):
         if rev is None:

src/diffuse/vcs/svk.py

@@ -25,21 +25,21 @@ from diffuse.vcs.svn import Svn
 
 class Svk(Svn):
     @staticmethod
-    def _getVcs():
+    def _getVcs() -> str:
         return 'svk'
 
     @staticmethod
-    def _getURLPrefix():
+    def _getURLPrefix() -> str:
         return 'Depot Path: '
 
     @staticmethod
-    def _parseStatusLine(s):
+    def _parseStatusLine(s: str) -> tuple[str, str]:
         if len(s) < 4 or s[0] not in 'ACDMR':
             return '', ''
         return s[0], s[4:]
 
     @staticmethod
-    def _getPreviousRevision(rev):
+    def _getPreviousRevision(rev: str) -> str:
         if rev is None:
             return 'HEAD'
         if rev.endswith('@'):

src/diffuse/vcs/svn.py

@@ -21,6 +21,7 @@ import os
 import glob
 
 from gettext import gettext as _
+from typing import Optional
 
 from diffuse import utils
 from diffuse.vcs.folder_set import FolderSet
@@ -30,20 +31,20 @@ from diffuse.vcs.vcs_interface import VcsInterface
 # Subversion support
 # SVK support subclasses from this
 class Svn(VcsInterface):
-    def __init__(self, root):
+    def __init__(self, root: str):
         VcsInterface.__init__(self, root)
-        self.url = None
+        self.url: Optional[str] = None
 
     @staticmethod
-    def _getVcs():
+    def _getVcs() -> str:
         return 'svn'
 
     @staticmethod
-    def _getURLPrefix():
+    def _getURLPrefix() -> str:
         return 'URL: '
 
     @staticmethod
-    def _parseStatusLine(s):
+    def _parseStatusLine(s: str) -> tuple[str, str]:
         if len(s) < 8 or s[0] not in 'ACDMR':
             return '', ''
         # subversion 1.6 adds a new column
@@ -53,7 +54,7 @@ class Svn(VcsInterface):
         return s[0], s[k:]
 
     @staticmethod
-    def _getPreviousRevision(rev):
+    def _getPreviousRevision(rev: str) -> str:
         if rev is None:
             return 'BASE'
         m = int(rev)

src/diffuse/vcs/vcs_interface.py

@@ -20,7 +20,7 @@
 class VcsInterface:
     """Interface for the VCSs."""
 
-    def __init__(self, root):
+    def __init__(self, root: str):
         """The object will initialized with the repository's root folder."""
         self.root = root
 

src/diffuse/vcs/vcs_registry.py

@@ -20,9 +20,12 @@
 import os
 
 from gettext import gettext as _
+from typing import Optional
 
 from diffuse import utils
+from diffuse.preferences import Preferences
 from diffuse.vcs.folder_set import FolderSet
+from diffuse.vcs.vcs_interface import VcsInterface
 from diffuse.vcs.bzr import Bzr
 from diffuse.vcs.cvs import Cvs
 from diffuse.vcs.darcs import Darcs
@@ -35,7 +38,7 @@ from diffuse.vcs.svn import Svn
 
 
 class VcsRegistry:
-    def __init__(self):
+    def __init__(self) -> None:
         # initialise the VCS objects
         self._get_repo = {
             'bzr': _get_bzr_repo,
@@ -50,7 +53,7 @@ class VcsRegistry:
         }
 
     # determines which VCS to use for files in the named folder
-    def findByFolder(self, path, prefs):
+    def findByFolder(self, path: str, prefs: Preferences) -> Optional[VcsInterface]:
         path = os.path.abspath(path)
         for vcs in prefs.getString('vcs_search_order').split():
             if vcs in self._get_repo:
@@ -60,14 +63,14 @@ class VcsRegistry:
         return None
 
     # determines which VCS to use for the named file
-    def findByFilename(self, name, prefs):
+    def findByFilename(self, name: str, prefs: Preferences) -> Optional[VcsInterface]:
         if name is not None:
             return self.findByFolder(os.path.dirname(name), prefs)
         return None
 
 
 # utility method to help find folders used by version control systems
-def _find_parent_dir_with(path, dir_name):
+def _find_parent_dir_with(path: str, dir_name: str) -> Optional[str]:
     while True:
         name = os.path.join(path, dir_name)
         if os.path.isdir(name):
@@ -76,28 +79,28 @@ def _find_parent_dir_with(path, dir_name):
         if newpath == path:
             break
         path = newpath
+    return None
 
 
-def _get_bzr_repo(path, prefs):
+def _get_bzr_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     p = _find_parent_dir_with(path, '.bzr')
     return Bzr(p) if p else None
 
 
-def _get_cvs_repo(path, prefs):
+def _get_cvs_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     return Cvs(path) if os.path.isdir(os.path.join(path, 'CVS')) else None
 
 
-def _get_darcs_repo(path, prefs):
+def _get_darcs_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     p = _find_parent_dir_with(path, '_darcs')
     return Darcs(p) if p else None
 
 
-def _get_git_repo(path, prefs):
+def _get_git_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     if 'GIT_DIR' in os.environ:
         try:
-            d = path
+            ss: list[str] = utils.popenReadLines(
-            ss = utils.popenReadLines(
+                path,
-                d,
                 [
                     prefs.getString('git_bin'),
                     'rev-parse',
@@ -107,20 +110,20 @@ def _get_git_repo(path, prefs):
                 'git_bash')
             if len(ss) > 0:
                 # be careful to handle trailing slashes
-                d = d.split(os.sep)
+                dirs = path.split(os.sep)
-                if d[-1] != '':
+                if dirs[-1] != '':
-                    d.append('')
+                    dirs.append('')
                 ss = utils.strip_eol(ss[0]).split('/')
                 if ss[-1] != '':
                     ss.append('')
                 n = len(ss)
-                if n <= len(d):
+                if n <= len(dirs):
-                    del d[-n:]
+                    del dirs[-n:]
-                if len(d) == 0:
+                if len(dirs) == 0:
-                    d = os.curdir
+                    path = os.curdir
                 else:
-                    d = os.sep.join(d)
+                    path = os.sep.join(dirs)
-            return Git(d)
+            return Git(path)
         except (IOError, OSError):
             # working tree not found
             pass
@@ -133,19 +136,20 @@ def _get_git_repo(path, prefs):
         if newpath == path:
             break
         path = newpath
+    return None
 
 
-def _get_hg_repo(path, prefs):
+def _get_hg_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     p = _find_parent_dir_with(path, '.hg')
     return Hg(p) if p else None
 
 
-def _get_mtn_repo(path, prefs):
+def _get_mtn_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     p = _find_parent_dir_with(path, '_MTN')
     return Mtn(p) if p else None
 
 
-def _get_rcs_repo(path, prefs):
+def _get_rcs_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     if os.path.isdir(os.path.join(path, 'RCS')):
         return Rcs(path)
 
@@ -162,12 +166,12 @@ def _get_rcs_repo(path, prefs):
     return None
 
 
-def _get_svn_repo(path, prefs):
+def _get_svn_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     p = _find_parent_dir_with(path, '.svn')
     return Svn(p) if p else None
 
 
-def _get_svk_repo(path, prefs):
+def _get_svk_repo(path: str, prefs: Preferences) -> Optional[VcsInterface]:
     name = path
     # parse the ~/.svk/config file to discover which directories are part of
     # SVK repositories
@@ -181,7 +185,7 @@ def _get_svk_repo(path, prefs):
         try:
             # find working copies by parsing the config file
             with open(svkconfig, 'r', encoding='utf-8') as f:
-                ss = utils.readlines(f)
+                ss: list[str] = utils.readlines(f)
             projs, sep = [], os.sep
             # find the separator character
             for s in ss:

src/diffuse/widgets.py

@@ -22,10 +22,11 @@ import os
 import unicodedata
 
 from gettext import gettext as _
-from typing import Dict
+from typing import Any, Dict, List
 
 from diffuse import utils
 from diffuse.resources import theResources
+from diffuse.utils import LineEnding
 
 import gi  # type: ignore
 gi.require_version('GObject', '2.0')
@@ -148,9 +149,9 @@ class ScrolledWindow(Gtk.Grid):
 class FileDiffViewerBase(Gtk.Grid):
     # class describing a text pane
     class Pane:
-        def __init__(self):
+        def __init__(self) -> None:
             # list of lines displayed in this pane (including spacing lines)
-            self.lines = []
+            self.lines: List[FileDiffViewerBase.Line] = []
             # high water mark for line length in Pango units (used to determine
             # the required horizontal scroll range)
             self.line_lengths = 0
@@ -160,11 +161,11 @@ class FileDiffViewerBase(Gtk.Grid):
             # self.syntax_cache[i] corresponds to self.lines[i]
             # the list is truncated when a change to a line invalidates a
             # portion of the cache
-            self.syntax_cache = []
+            self.syntax_cache: List[List[Any]] = []
             # cache of character differences for each line
             # self.diff_cache[i] corresponds to self.lines[i]
             # portion of the cache are cleared by setting entries to None
-            self.diff_cache = []
+            self.diff_cache: List[List[Any]] = []
             # mask indicating the type of line endings present
             self.format = 0
             # number of lines with edits
@@ -314,7 +315,7 @@ class FileDiffViewerBase(Gtk.Grid):
 
         # create panes
         self.dareas = []
-        self.panes = []
+        self.panes: List[FileDiffViewerBase.Pane] = []
         self.hadj = Gtk.Adjustment.new(0, 0, 0, 0, 0, 0)
         self.vadj = Gtk.Adjustment.new(0, 0, 0, 0, 0, 0)
         for i in range(n):
@@ -3539,15 +3540,15 @@ class FileDiffViewerBase(Gtk.Grid):
 
     # 'convert_to_dos' action
     def convert_to_dos(self):
-        self.convert_format(utils.DOS_FORMAT)
+        self.convert_format(LineEnding.DOS_FORMAT)
 
     # 'convert_to_mac' action
     def convert_to_mac(self):
-        self.convert_format(utils.MAC_FORMAT)
+        self.convert_format(LineEnding.MAC_FORMAT)
 
     # 'convert_to_unix' action
     def convert_to_unix(self):
-        self.convert_format(utils.UNIX_FORMAT)
+        self.convert_format(LineEnding.UNIX_FORMAT)
 
     # copies the selected range of lines from pane 'f_src' to 'f_dst'
     def merge_lines(self, f_dst, f_src):
@@ -3985,11 +3986,11 @@ def _get_format(ss):
     for s in ss:
         if s is not None:
             if _has_dos_line_ending(s):
-                flags |= utils.DOS_FORMAT
+                flags |= LineEnding.DOS_FORMAT
             elif _has_mac_line_ending(s):
-                flags |= utils.MAC_FORMAT
+                flags |= LineEnding.MAC_FORMAT
             elif _has_unix_line_ending(s):
-                flags |= utils.UNIX_FORMAT
+                flags |= LineEnding.UNIX_FORMAT
     return flags
 
 
@@ -4000,17 +4001,17 @@ def _convert_to_format(s, fmt):
         if old_format != 0 and (old_format & fmt) == 0:
             s = utils.strip_eol(s)
             # prefer the host line ending style
-            if (fmt & utils.DOS_FORMAT) and os.linesep == '\r\n':
+            if (fmt & LineEnding.DOS_FORMAT) and os.linesep == '\r\n':
                 s += os.linesep
-            elif (fmt & utils.MAC_FORMAT) and os.linesep == '\r':
+            elif (fmt & LineEnding.MAC_FORMAT) and os.linesep == '\r':
                 s += os.linesep
-            elif (fmt & utils.UNIX_FORMAT) and os.linesep == '\n':
+            elif (fmt & LineEnding.UNIX_FORMAT) and os.linesep == '\n':
                 s += os.linesep
-            elif fmt & utils.UNIX_FORMAT:
+            elif fmt & LineEnding.UNIX_FORMAT:
                 s += '\n'
-            elif fmt & utils.DOS_FORMAT:
+            elif fmt & LineEnding.DOS_FORMAT:
                 s += '\r\n'
-            elif fmt & utils.MAC_FORMAT:
+            elif fmt & LineEnding.MAC_FORMAT:
                 s += '\r'
     return s