Throw Physics::MovementStuck upon stuck movement

This allows the exception to be caught directly in bots

spec/integration/bot_spec.cr → spec/integration/movement_spec.cr

@@ -72,16 +72,24 @@ Spectator.describe Rosegold::Bot do
     end
   end
 
-  it "should select a different hotbar slot" do
-    client.join_game do |client|
-      Rosegold::Bot.new(client).try do |bot|
-        bot.chat "/tp 1 -60 1"
-
-        bot.hotbar_selection = 4
-        expect(bot.hotbar_selection).to eq 4
-
-        bot.hotbar_selection = 7
-        expect(bot.hotbar_selection).to eq 7
+  describe "#move_to" do
+    context "when movement is stuck" do
+      it "throws Physics::MovementStuck" do
+        client.join_game do |client|
+          Rosegold::Bot.new(client).try do |bot|
+            sleep 2 # load chunks
+            bot.chat "/fill 1 -60 2 1 -60 2 minecraft:stone"
+            bot.chat "/tp 1 -60 1"
+            sleep 1 # teleport
+
+            expect {
+              bot.move_to 1, 2
+            }.to raise_error(Rosegold::Physics::MovementStuck)
+
+            bot.chat "/fill 1 -60 2 1 -60 2 minecraft:air"
+            sleep 1
+          end
+        end
       end
     end
   end

src/rosegold/control/action.cr

@@ -1,23 +1,24 @@
 class Rosegold::Action(T)
-  SUCCESS = "" # TODO use unique symbol
-
-  # TODO try channel size 1 so #succeed/#fail aren't rendezvous
-  getter channel : Channel(String) = Channel(String).new
+  getter channel : Channel(Exception | Nil) = Channel(Exception | Nil).new
   getter target : T
 
   def initialize(@target : T); end
 
   def succeed
-    @channel.send(SUCCESS)
+    @channel.send nil
   end
 
   def fail(msg : String)
-    @channel.send(msg)
+    @channel.send Exception.new msg
+  end
+
+  def fail(exception : Exception)
+    @channel.send exception
   end
 
   # Throw error if it failed
   def join
     result = channel.receive
-    raise Exception.new(result) if result != Action::SUCCESS
+    raise result if result
   end
 end

src/rosegold/control/physics.cr

@@ -164,7 +164,10 @@ class Rosegold::Physics
     # TODO: this only works with gravity on
     on_ground = movement.y > input_velocity.y
 
-    @movement_action.try &.fail "Stuck at #{feet}" unless feet != player.feet
+    unless feet != player.feet
+      @movement_action.try &.fail MovementStuck.new "Stuck at #{feet}"
+      @movement_action = nil
+    end
 
     send_movement_packet feet, look, on_ground
     player.velocity = next_velocity
@@ -185,6 +188,8 @@ class Rosegold::Physics
     client.emit_event Event::PhysicsTick.new movement
   end
 
+  class MovementStuck < Exception; end
+
   private def send_movement_packet(feet : Vec3d, look : Look, on_ground : Bool)
     # anticheat requires sending these different packets
     if feet != player.feet