Non-strict var name check

cpmpy/expressions/variables.py

@@ -68,6 +68,7 @@
 _BV_PREFIX = "BV"
 _IV_PREFIX = "IV"
 _VAR_ERR  = f"Variable names starting with {_IV_PREFIX} or {_BV_PREFIX} are reserved for internal use only, chose a different name"
+_VAR_STRICT_NAME_CHECK = True
 
 def BoolVar(shape=1, name=None):
     """
@@ -790,5 +791,58 @@ def _genname(basename, idxs):
     return f"{basename}[{stridxs}]" # "<name>[<idx0>,<idx1>,...]"
 
 def _is_invalid_name(name):
-    return name.startswith(_IV_PREFIX) or name.startswith(_BV_PREFIX)
+    """
+    Check if a variable name is invalid.
+
+    In 'strict' mode, the name is invalid if it starts with {_IV_PREFIX} or {_BV_PREFIX}.
+    In 'non-strict' mode, the name is invalid if it starts with {_IV_PREFIX} or {_BV_PREFIX} 
+    and the variables' counter is greater than the index, i.e. the name is already in use.
 
+    Toggle the strict mode with `_enable_strict_variable_name_check()` and `_disable_strict_variable_name_check()`,
+    or use the context manager `_ignore_strict_variable_name_check()`.
+    """
+    if name.startswith(_IV_PREFIX):
+        if _VAR_STRICT_NAME_CHECK:
+            return True
+        else:
+            id = int(name[len(_IV_PREFIX):])
+            if _IntVarImpl.counter > id:
+                return True # TODO: better error message
+            else:
+                return False
+
+    elif name.startswith(_BV_PREFIX):
+        if _VAR_STRICT_NAME_CHECK:
+            return True
+        else:
+            id = int(name[len(_BV_PREFIX):])
+            if _BoolVarImpl.counter > id:
+                return True # TODO: better error message
+            else:
+                return False
+
+    else:
+        return False
+
+def _enable_strict_variable_name_check():
+    global _VAR_STRICT_NAME_CHECK
+    _VAR_STRICT_NAME_CHECK = True
+
+def _disable_strict_variable_name_check():
+    global _VAR_STRICT_NAME_CHECK
+    _VAR_STRICT_NAME_CHECK = False
+
+
+def _ignore_strict_variable_name_check():
+    """
+    Context manager to temporarily disable strict variable name check.
+    """
+    class IgnoreStrictVariableNameCheck:
+        def __enter__(self):
+            _disable_strict_variable_name_check()
+        def __exit__(self, exc_type, exc_value, traceback):
+            _enable_strict_variable_name_check()
+            # _update_variable_counters() # TODO: add automatic support for this later (different PR)
+            return False  # propagate exceptions
+
+    return IgnoreStrictVariableNameCheck()

cpmpy/model.py

@@ -25,6 +25,7 @@
 
         Model
 """
+from __future__ import annotations
 import copy
 import warnings
 from typing import Optional
@@ -40,6 +41,33 @@
 
 import pickle
 
+
+def _update_variable_counters(model: Model):
+    from cpmpy.transformations.get_variables import get_variables_model  # avoid circular import
+    from cpmpy.expressions.variables import _BoolVarImpl, _IntVarImpl, _BV_PREFIX, _IV_PREFIX # avoid circular import
+
+    vs = get_variables_model(model)
+    bv_counter = 0
+    iv_counter = 0
+    for v in vs:
+        if v.name.startswith(_BV_PREFIX):
+            try:
+                bv_counter = max(bv_counter, int(v.name[2:])+1)
+            except: # When name starts with _BV_PREFIX but is not a valid integer (user created name), ignore
+                pass
+        elif v.name.startswith(_IV_PREFIX):
+            try:
+                iv_counter = max(iv_counter, int(v.name[2:])+1)
+            except: # When name starts with _IV_PREFIX but is not a valid integer (user created name), ignore
+                pass
+
+    if (_BoolVarImpl.counter > 0 and bv_counter > 0) or \
+            (_IntVarImpl.counter > 0 and iv_counter > 0):
+        warnings.warn(f"Model contains auxiliary {_IV_PREFIX}*/{_BV_PREFIX}* variables with the same name as already created. Only add expressions created AFTER loadig this model to avoid issues with duplicate variables.")
+    _BoolVarImpl.counter = max(_BoolVarImpl.counter, bv_counter)
+    _IntVarImpl.counter = max(_IntVarImpl.counter, iv_counter)
+
+
 class Model(object):
     """
     CPMpy Model object, contains the constraint and objective expressions
@@ -284,28 +312,7 @@ def from_file(fname):
         with open(fname, "rb") as f:
             m = pickle.load(f)
             # bug 158, we should increase the boolvar/intvar counters to avoid duplicate names
-            from cpmpy.transformations.get_variables import get_variables_model  # avoid circular import
-            from cpmpy.expressions.variables import _BoolVarImpl, _IntVarImpl, _BV_PREFIX, _IV_PREFIX # avoid circular import
-            vs = get_variables_model(m)
-            bv_counter = 0
-            iv_counter = 0
-            for v in vs:
-                if v.name.startswith(_BV_PREFIX):
-                    try:
-                        bv_counter = max(bv_counter, int(v.name[2:])+1)
-                    except:
-                        pass
-                elif v.name.startswith(_IV_PREFIX):
-                    try:
-                        iv_counter = max(iv_counter, int(v.name[2:])+1)
-                    except:
-                        pass
-
-            if (_BoolVarImpl.counter > 0 and bv_counter > 0) or \
-                    (_IntVarImpl.counter > 0 and iv_counter > 0):
-                warnings.warn(f"from_file '{fname}': contains auxiliary {_IV_PREFIX}*/{_BV_PREFIX}* variables with the same name as already created. Only add expressions created AFTER loadig this model to avoid issues with duplicate variables.")
-            _BoolVarImpl.counter = max(_BoolVarImpl.counter, bv_counter)
-            _IntVarImpl.counter = max(_IntVarImpl.counter, iv_counter)
+            _update_variable_counters(m)
             return m
 
     def copy(self):