fix require statements inside loops

src/scenic/core/dynamics/scenarios.py

@@ -58,7 +58,7 @@ def __init__(self, *args, **kwargs):
         self._objects = []  # ordered for reproducibility
         self._sampledObjects = self._objects
         self._externalParameters = []
-        self._pendingRequirements = defaultdict(list)
+        self._pendingRequirements = []
         self._requirements = []
         # things needing to be sampled to evaluate the requirements
         self._requirementDeps = set()
@@ -409,9 +409,8 @@ def _registerObject(self, obj):
 
     def _addRequirement(self, ty, reqID, req, line, name, prob):
         """Save a requirement defined at compile-time for later processing."""
-        assert reqID not in self._pendingRequirements
         preq = PendingRequirement(ty, req, line, prob, name, self._ego)
-        self._pendingRequirements[reqID] = preq
+        self._pendingRequirements.append((reqID, preq))
 
     def _addDynamicRequirement(self, ty, req, line, name):
         """Add a requirement defined during a dynamic simulation."""
@@ -429,7 +428,7 @@ def _compileRequirements(self):
         namespace = self._dummyNamespace if self._dummyNamespace else self.__dict__
         requirementSyntax = self._requirementSyntax
         assert requirementSyntax is not None
-        for reqID, requirement in self._pendingRequirements.items():
+        for reqID, requirement in self._pendingRequirements:
             syntax = requirementSyntax[reqID] if requirementSyntax else None
 
             # Catch the simple case where someone has most likely forgotten the "monitor"

src/scenic/core/requirements.py

@@ -102,12 +102,14 @@ def compile(self, namespace, scenario, syntax=None):
 
         # Construct closure
         def closure(values, monitor=None):
-            # rebind any names referring to sampled objects
+            # rebind any names referring to sampled objects (for require statements,
+            # rebind all names, since we want their values at the time the requirement
+            # was created)
             # note: need to extract namespace here rather than close over value
             # from above because of https://github.com/uqfoundation/dill/issues/532
             namespace = condition.atomics()[0].closure.__globals__
             for name, value in bindings.items():
-                if value in values:
+                if ty == RequirementType.require or value in values:
                     namespace[name] = values[value]
             # rebind ego object, which can be referred to implicitly
             boundEgo = None if ego is None else values[ego]

src/scenic/syntax/compiler.py

@@ -1359,11 +1359,12 @@ def createRequirementLike(
         """Create a call to a function that implements requirement-like features, such as `record` and `terminate when`.
 
         Args:
-            functionName (str): Name of the requirement-like function to call. Its signature must be `(reqId: int, body: () -> bool, lineno: int, name: str | None)`
+            functionName (str): Name of the requirement-like function to call. Its signature
+                must be `(reqId: int, body: () -> bool, lineno: int, name: str | None)`
             body (ast.AST): AST node to evaluate for checking the condition
             lineno (int): Line number in the source code
-            name (Optional[str], optional): Optional name for requirements. Defaults to None.
-            prob (Optional[float], optional): Optional probability for requirements. Defaults to None.
+            name (Optional[str]): Optional name for requirements. Defaults to None.
+            prob (Optional[float]): Optional probability for requirements. Defaults to None.
         """
         propTransformer = PropositionTransformer(self.filename)
         newBody, self.nextSyntaxId = propTransformer.transform(body, self.nextSyntaxId)
@@ -1374,7 +1375,7 @@ def createRequirementLike(
             value=ast.Call(
                 func=ast.Name(functionName, loadCtx),
                 args=[
-                    ast.Constant(requirementId),  # requirement IDre
+                    ast.Constant(requirementId),  # requirement ID
                     newBody,  # body
                     ast.Constant(lineno),  # line number
                     ast.Constant(name),  # requirement name

tests/syntax/test_requirements.py

@@ -19,6 +19,18 @@ def test_requirement():
     assert all(0 <= x <= 10 for x in xs)
 
 
+def test_requirement_in_loop():
+    scenario = compileScenic(
+        """
+        ego = new Object at Range(-10, 10) @ Range(-10, 10)
+        for i in range(2):
+            require ego.position[i] >= 0
+        """
+    )
+    poss = [sampleEgo(scenario, maxIterations=150).position for i in range(60)]
+    assert all(0 <= pos.x <= 10 and 0 <= pos.y <= 10 for pos in poss)
+
+
 def test_soft_requirement():
     scenario = compileScenic(
         """