Merge pull request #367 from gaphor/no-juggle-error

Remove JuggleError

gaphas/solver/__init__.py

@@ -1,5 +1,5 @@
 from gaphas.solver.constraint import BaseConstraint, Constraint, MultiConstraint
-from gaphas.solver.solver import JuggleError, Solver
+from gaphas.solver.solver import Solver
 from gaphas.solver.variable import (
     NORMAL,
     REQUIRED,

gaphas/solver/solver.py

@@ -44,11 +44,12 @@ class Solver:
     A constraint should have accompanying variables.
     """
 
-    def __init__(self) -> None:
+    def __init__(self, resolve_limit: int = 16) -> None:
         # a dict of constraint -> name/variable mappings
         self._constraints: Set[Constraint] = set()
         self._marked_cons: List[Constraint] = []
         self._solving = False
+        self._resolve_limit = resolve_limit
         self._handlers: Set[Callable[[Constraint], None]] = set()
 
     def add_handler(self, handler: Callable[[Constraint], None]) -> None:
@@ -129,12 +130,8 @@ def request_resolve_constraint(self, c: Constraint) -> None:
             if c in self._marked_cons:
                 self._marked_cons.remove(c)
             self._marked_cons.append(c)
-        else:
+        elif self._marked_cons.count(c) < self._resolve_limit:
             self._marked_cons.append(c)
-            if self._marked_cons.count(c) > 100:
-                raise JuggleError(
-                    f"Variable juggling detected, constraint {c} resolved {self._marked_cons.count(c)} times out of {len(self._marked_cons)}"
-                )
 
     def solve(self) -> None:
         """
@@ -199,11 +196,3 @@ def find_containing_constraint(
         ):
             return find_containing_constraint(cs, constraints)
     return None
-
-
-class JuggleError(AssertionError):
-    """Variable juggling exception.
-
-    Raised when constraint's variables are marking each other dirty
-    forever.
-    """

tests/test_solver.py

@@ -1,8 +1,7 @@
 """Test constraint solver."""
-import pytest
 
 from gaphas.constraint import EqualsConstraint, EquationConstraint, LessThanConstraint
-from gaphas.solver import REQUIRED, JuggleError, MultiConstraint, Solver, Variable
+from gaphas.solver import REQUIRED, MultiConstraint, Solver, Variable
 from gaphas.solver.constraint import Constraint, ContainsConstraints
 
 
@@ -79,7 +78,7 @@ def test_minimal_size_constraint():
     assert 10 == v3
 
 
-def test_juggle_error_is_raised_when_constraints_can_not_be_resolved():
+def test_constraints_can_not_be_resolved():
     solver = Solver()
     a = Variable()
     b = Variable()
@@ -90,8 +89,10 @@ def test_juggle_error_is_raised_when_constraints_can_not_be_resolved():
     solver.add_constraint(EqualsConstraint(a, c))
     solver.add_constraint(EqualsConstraint(b, d))
 
-    with pytest.raises(JuggleError):
-        solver.solve()
+    solver.solve()
+
+    assert a.value == 40.0
+    assert b.value == 30.0
 
 
 def test_notify_for_nested_constraint():