[robotpy] Mirror robotpy's commands-v2 (#8369)

Project import generated by Copybara.

GitOrigin-RevId: 715c8e8372d936f447f2937aab6b1a22dc619126

commandsv2/src/main/python/commands2/deferredcommand.py

@@ -0,0 +1,71 @@
+# validated: 2024-01-24 DS 192a28af4731 DeferredCommand.java
+from typing import Callable
+
+from wpiutil import SendableBuilder
+
+from .command import Command
+from .commandscheduler import CommandScheduler
+from .printcommand import PrintCommand
+from .subsystem import Subsystem
+
+
+class DeferredCommand(Command):
+    """
+    Defers Command construction to runtime. Runs the command returned by a supplier when this command
+    is initialized, and ends when it ends. Useful for performing runtime tasks before creating a new
+    command. If this command is interrupted, it will cancel the command.
+
+    Note that the supplier *must* create a new Command each call. For selecting one of a
+    preallocated set of commands, use :class:`commands2.SelectCommand`.
+    """
+
+    def __init__(self, supplier: Callable[[], Command], *requirements: Subsystem):
+        """
+
+        Creates a new DeferredCommand that directly runs the supplied command when initialized, and
+        ends when it ends. Useful for lazily creating commands when the DeferredCommand is initialized,
+        such as if the supplied command depends on runtime state. The Supplier will be called
+        each time this command is initialized. The Supplier *must* create a new Command each call.
+
+        :param supplier:     The command supplier
+        :param requirements: The command requirements.
+        """
+        super().__init__()
+
+        assert callable(supplier)
+
+        self._null_command = PrintCommand(
+            f"[DeferredCommand] Supplied command (from {supplier!r} was None!"
+        )
+        self._supplier = supplier
+        self._command = self._null_command
+        self.addRequirements(*requirements)
+
+    def initialize(self):
+        cmd = self._supplier()
+        if cmd is not None:
+            self._command = cmd
+            CommandScheduler.getInstance().registerComposedCommands([self._command])
+        self._command.initialize()
+
+    def execute(self):
+        self._command.execute()
+
+    def isFinished(self):
+        return self._command.isFinished()
+
+    def end(self, interrupted):
+        self._command.end(interrupted)
+        self._command = self._null_command
+
+    def initSendable(self, builder: SendableBuilder):
+        super().initSendable(builder)
+        builder.addStringProperty(
+            "deferred",
+            lambda: (
+                "null"
+                if self._command is self._null_command
+                else self._command.getName()
+            ),
+            lambda _: None,
+        )