WIP require at least one of the two bodies attached to constraint be dynamic

Author: viblo

CHANGELOG.rst

@@ -1,6 +1,9 @@
 =========
 Changelog 
 =========
+.. Pymunk 7.0.0
+   Breaking: At least one of the two bodies attached to constraint/join must be dynamic. 
+
 
 .. Pymunk 6.12?????
    Changes....

TODO.txt

@@ -54,6 +54,10 @@ v6.x
 - Remove support for pyglet 1.5 in debug draw. Should be fine now that 2.x has been out for a long time. 
 - Think about if Pymunk should assert things that Chipmunk already asserts, like if a body can sleep when calling Body.sleep()?
 
+v7
+---
+- Require at least one body on constraint to be dynamic.
+
 v7+ (all potentially breaking changes)
 ---
 - Think about split between pymunk.util and pymunk modules

pymunk/body.py

@@ -619,6 +619,12 @@ def is_sleeping(self) -> bool:
         return bool(lib.cpBodyIsSleeping(self._body))
 
     def _set_type(self, body_type: _BodyType) -> None:
+        if body_type != Body.DYNAMIC:
+            for c in self.constraints:
+                assert (c.a != self and c.b.body_type == Body.DYNAMIC) or (
+                    c.b != self and c.a.body_type == Body.DYNAMIC
+                ), "Cannot set a non-dynamic body type when Body is connected to a constraint {c} with a non-dynamic other body."
+
         lib.cpBodySetType(self._body, body_type)
 
     def _get_type(self) -> _BodyType:

pymunk/space.py

@@ -138,9 +138,9 @@ def spacefree(cp_space: ffi.CData) -> None:
 
         self._space = ffi.gc(cp_space, spacefree)
 
-        self._handlers: Dict[
-            Any, CollisionHandler
-        ] = {}  # To prevent the gc to collect the callbacks.
+        self._handlers: Dict[Any, CollisionHandler] = (
+            {}
+        )  # To prevent the gc to collect the callbacks.
 
         self._post_step_callbacks: Dict[Any, Callable[["Space"], None]] = {}
         self._removed_shapes: Dict[int, Shape] = {}
@@ -450,6 +450,11 @@ def _add_constraint(self, constraint: "Constraint") -> None:
         """Adds a constraint to the space"""
         assert constraint not in self._constraints, "Constraint already added to space."
 
+        assert (
+            constraint.a.body_type == Body.DYNAMIC
+            or constraint.b.body_type == Body.DYNAMIC
+        ), "At leasts one of a constraint's bodies must be DYNAMIC."
+
         self._constraints[constraint] = None
         cp.cpSpaceAddConstraint(self._space, constraint._constraint)