implement lazy imports

changes/2547.feature.rst

@@ -0,0 +1 @@
+implements lazy loading for toga core and toga cocoa

cocoa/src/toga_cocoa/factory.py

@@ -1,90 +1,54 @@
-from toga import NotImplementedWarning
+import importlib
 
-from . import dialogs
-from .app import App, DocumentApp, MainWindow
-from .command import Command
-from .documents import Document
-from .fonts import Font
-from .hardware.camera import Camera
-from .hardware.location import Location
-from .icons import Icon
-from .images import Image
-from .paths import Paths
+from toga import NotImplementedWarning
 
-# Widgets
-from .widgets.activityindicator import ActivityIndicator
-from .widgets.box import Box
-from .widgets.button import Button
-from .widgets.canvas import Canvas
-from .widgets.detailedlist import DetailedList
-from .widgets.divider import Divider
-from .widgets.imageview import ImageView
-from .widgets.label import Label
-from .widgets.mapview import MapView
-from .widgets.multilinetextinput import MultilineTextInput
-from .widgets.numberinput import NumberInput
-from .widgets.optioncontainer import OptionContainer
-from .widgets.passwordinput import PasswordInput
-from .widgets.progressbar import ProgressBar
-from .widgets.scrollcontainer import ScrollContainer
-from .widgets.selection import Selection
-from .widgets.slider import Slider
-from .widgets.splitcontainer import SplitContainer
-from .widgets.switch import Switch
-from .widgets.table import Table
-from .widgets.textinput import TextInput
-from .widgets.tree import Tree
-from .widgets.webview import WebView
-from .window import Window
+toga_factory_imports = {
+    "toga.app": ["App", "DocumentApp", "MainWindow"],
+    "toga_cocoa": ["dialogs"],
+    "toga.command": ["Command"],
+    "toga.documents": ["Document"],
+    "toga.fonts": ["Font"],
+    "toga.hardware.camera": ["Camera"],
+    "toga.hardware.location": ["Location"],
+    "toga.icons": ["Icon"],
+    "toga.images": ["Image"],
+    "toga.paths": ["Paths"],
+    "toga.widgets.activityindicator": ["ActivityIndicator"],
+    "toga.widgets.box": ["Box"],
+    "toga.widgets.button": ["Button"],
+    "toga.widgets.canvas": ["Canvas"],
+    "toga.widgets.detailedlist": ["DetailedList"],
+    "toga.widgets.divider": ["Divider"],
+    "toga.widgets.imageview": ["ImageView"],
+    "toga.widgets.label": ["Label"],
+    "toga.widgets.mapview": ["MapView"],
+    "toga.widgets.multilinetextinput": ["MultilineTextInput"],
+    "toga.widgets.numberinput": ["NumberInput"],
+    "toga.widgets.optioncontainer": ["OptionContainer"],
+    "toga.widgets.passwordinput": ["PasswordInput"],
+    "toga.widgets.progressbar": ["ProgressBar"],
+    "toga.widgets.scrollcontainer": ["ScrollContainer"],
+    "toga.widgets.selection": ["Selection"],
+    "toga.widgets.slider": ["Slider"],
+    "toga.widgets.splitcontainer": ["SplitContainer"],
+    "toga.widgets.switch": ["Switch"],
+    "toga.widgets.table": ["Table"],
+    "toga.widgets.textinput": ["TextInput"],
+    "toga.widgets.tree": ["Tree"],
+    "toga.widgets.webview": ["WebView"],
+    "toga.window": ["Window"],
+}
+
+
+def __getattr__(name):
+    for module, names in toga_factory_imports.items():
+        if name in names:
+            module = importlib.import_module(module)
+            globals()[name] = getattr(module, name)
+            return getattr(module, name)
+    else:
+        raise NotImplementedError(f"Toga's Cocoa backend doesn't implement {name}")
 
 
 def not_implemented(feature):
     NotImplementedWarning.warn("Cocoa", feature)
-
-
-__all__ = [
-    "not_implemented",
-    "App",
-    "DocumentApp",
-    "MainWindow",
-    "Command",
-    "Document",
-    # Resources
-    "Font",
-    "Icon",
-    "Image",
-    "Paths",
-    "dialogs",
-    # Hardware
-    "Camera",
-    "Location",
-    # Widgets
-    "ActivityIndicator",
-    "Box",
-    "Button",
-    "Canvas",
-    "DetailedList",
-    "Divider",
-    "ImageView",
-    "Label",
-    "MapView",
-    "MultilineTextInput",
-    "NumberInput",
-    "OptionContainer",
-    "PasswordInput",
-    "ProgressBar",
-    "ScrollContainer",
-    "Selection",
-    "Slider",
-    "SplitContainer",
-    "Switch",
-    "Table",
-    "TextInput",
-    "Tree",
-    "WebView",
-    "Window",
-]
-
-
-def __getattr__(name):  # pragma: no cover
-    raise NotImplementedError(f"Toga's Cocoa backend doesn't implement {name}")

core/src/toga/__init__.py

@@ -1,47 +1,61 @@
+from __future__ import annotations
+
+import importlib
+import importlib.util
 import warnings
 
-from .app import App, DocumentApp, DocumentMainWindow, MainWindow
+toga_core_imports = {
+    "toga.app": ["App", "DocumentApp", "DocumentMainWindow", "MainWindow"],
+    "toga.colors": ["hsl", "hsla", "rgb", "rgba"],
+    "toga.command": ["Command", "Group"],
+    "toga.commands": ["Command", "Group"],
+    "toga.documents": ["Document"],
+    "toga.fonts": ["Font"],
+    "toga.icons": ["Icon"],
+    "toga.images": ["Image"],
+    "toga.keys": ["Key"],
+    "toga.types": ["LatLng"],
+    "toga.widgets.activityindicator": ["ActivityIndicator"],
+    "toga.widgets.base": ["Widget"],
+    "toga.widgets.box": ["Box"],
+    "toga.widgets.button": ["Button"],
+    "toga.widgets.canvas": ["Canvas"],
+    "toga.widgets.dateinput": ["DateInput", "DatePicker"],
+    "toga.widgets.detailedlist": ["DetailedList"],
+    "toga.widgets.divider": ["Divider"],
+    "toga.widgets.imageview": ["ImageView"],
+    "toga.widgets.label": ["Label"],
+    "toga.widgets.mapview": ["MapPin", "MapView"],
+    "toga.widgets.multilinetextinput": ["MultilineTextInput"],
+    "toga.widgets.numberinput": ["NumberInput"],
+    "toga.widgets.optioncontainer": ["OptionContainer", "OptionItem"],
+    "toga.widgets.passwordinput": ["PasswordInput"],
+    "toga.widgets.progressbar": ["ProgressBar"],
+    "toga.widgets.scrollcontainer": ["ScrollContainer"],
+    "toga.widgets.selection": ["Selection"],
+    "toga.widgets.slider": ["Slider"],
+    "toga.widgets.splitcontainer": ["SplitContainer"],
+    "toga.widgets.switch": ["Switch"],
+    "toga.widgets.table": ["Table"],
+    "toga.widgets.textinput": ["TextInput"],
+    "toga.widgets.timeinput": ["TimeInput", "TimePicker"],
+    "toga.widgets.tree": ["Tree"],
+    "toga.widgets.webview": ["WebView"],
+    "toga.window": ["Window"],
+}
 
-# Resources
-from .colors import hsl, hsla, rgb, rgba
-from .command import Command, Group
-from .documents import Document
-from .fonts import Font
-from .icons import Icon
-from .images import Image
-from .keys import Key
+__all__ = []
 
-# Types
-from .types import LatLng
 
-# Widgets
-from .widgets.activityindicator import ActivityIndicator
-from .widgets.base import Widget
-from .widgets.box import Box
-from .widgets.button import Button
-from .widgets.canvas import Canvas
-from .widgets.dateinput import DateInput, DatePicker
-from .widgets.detailedlist import DetailedList
-from .widgets.divider import Divider
-from .widgets.imageview import ImageView
-from .widgets.label import Label
-from .widgets.mapview import MapPin, MapView
-from .widgets.multilinetextinput import MultilineTextInput
-from .widgets.numberinput import NumberInput
-from .widgets.optioncontainer import OptionContainer, OptionItem
-from .widgets.passwordinput import PasswordInput
-from .widgets.progressbar import ProgressBar
-from .widgets.scrollcontainer import ScrollContainer
-from .widgets.selection import Selection
-from .widgets.slider import Slider
-from .widgets.splitcontainer import SplitContainer
-from .widgets.switch import Switch
-from .widgets.table import Table
-from .widgets.textinput import TextInput
-from .widgets.timeinput import TimeInput, TimePicker
-from .widgets.tree import Tree
-from .widgets.webview import WebView
-from .window import Window
+def __getattr__(name):
+    for module, names in toga_core_imports.items():
+        if name in names:
+            module = importlib.import_module(module)
+            globals()[name] = getattr(module, name)
+            __all__.append(name)
+            return getattr(module, name)
+    else:
+        raise AttributeError(f"module {__name__} has no attribute {name}")
 
 
 class NotImplementedWarning(RuntimeWarning):
@@ -54,66 +68,6 @@ def warn(self, platform, feature):
         warnings.warn(NotImplementedWarning(f"[{platform}] Not implemented: {feature}"))
 
 
-__all__ = [
-    "NotImplementedWarning",
-    # Applications
-    "App",
-    "DocumentApp",
-    "MainWindow",
-    "DocumentMainWindow",
-    # Commands
-    "Command",
-    "Group",
-    # Documents
-    "Document",
-    # Keys
-    "Key",
-    # Resources
-    "hsl",
-    "hsla",
-    "rgb",
-    "rgba",
-    "Font",
-    "Icon",
-    "Image",
-    # Types
-    "LatLng",
-    # Widgets
-    "ActivityIndicator",
-    "Box",
-    "Button",
-    "Canvas",
-    "DateInput",
-    "DetailedList",
-    "Divider",
-    "ImageView",
-    "Label",
-    "MapPin",
-    "MapView",
-    "MultilineTextInput",
-    "NumberInput",
-    "OptionContainer",
-    "OptionItem",
-    "PasswordInput",
-    "ProgressBar",
-    "ScrollContainer",
-    "Selection",
-    "Slider",
-    "SplitContainer",
-    "Switch",
-    "Table",
-    "TextInput",
-    "TimeInput",
-    "Tree",
-    "WebView",
-    "Widget",
-    "Window",
-    # Deprecated widget names
-    "DatePicker",
-    "TimePicker",
-]
-
-
 def _package_version(file, name):
     try:
         # Read version from SCM metadata