Handle the usage of Python keywords in MiniZinc

Author: Dekker1

CHANGELOG.rst

@@ -20,6 +20,9 @@ Fixed
   usage of generated solver configurations on Windows.
 - The DZN parser now constructs correct range objects. The parser was off by one due to
   the exclusive upper bound in Python range objects.
+- Rewrite MiniZinc fields that are keywords in Python. These names cannot be used
+  directly as members of a dataclass. Python keywords used in MiniZinc are rewritten to
+  ``"mzn_" + {keyword}`` and a warning is thrown.
 
 0.2.2_ - 2020-02-17
 -------------------

src/minizinc/CLI/instance.py

@@ -9,9 +9,11 @@
 import re
 import sys
 import tempfile
+import warnings
 from dataclasses import field, make_dataclass
 from datetime import datetime, timedelta
 from enum import EnumMeta
+from keyword import iskeyword
 from numbers import Number
 from pathlib import Path
 from typing import Any, Dict, Iterator, List, Optional, Type, cast
@@ -207,6 +209,13 @@ def analyse(self):
             for k, v in self._output.items():
                 if k in ["_output_item", "_checker"]:
                     fields.append((k, str, field(default="")))
+                elif iskeyword(k):
+                    warnings.warn(
+                        f"MiniZinc field '{k}' is a Python keyword. It has been "
+                        f"renamed to 'mzn_{k}'",
+                        SyntaxWarning,
+                    )
+                    fields.append(("mzn_" + k, v))
                 else:
                     fields.append((k, v))
 

src/minizinc/result.py

@@ -7,6 +7,7 @@
 from dataclasses import dataclass
 from datetime import timedelta
 from enum import Enum, auto
+from keyword import kwlist
 from typing import Any, Dict, Optional, Tuple, Type, Union
 
 from .instance import Method
@@ -336,6 +337,10 @@ def parse_solution(
             tmp["objective"] = tmp.pop("_objective")
         if "_output" in tmp:
             tmp["_output_item"] = tmp.pop("_output")
+        for k in kwlist:
+            if k in tmp:
+                tmp["mzn_" + k] = tmp.pop(k)
+
         solution = output_type(**tmp)
 
     return solution, statistics

tests/test_instance.py

@@ -30,6 +30,19 @@ def test_reassign(self):
             self.instance["n"] = 15
 
 
+class TestPythonConflict(InstanceTestCase):
+    code = """
+        include "globals.mzn";
+        var 1..2: return;
+        constraint return > 1;
+    """
+
+    def test_rename(self):
+        with pytest.warns(SyntaxWarning):
+            result = self.instance.solve()
+            assert result.solution.mzn_return == 2
+
+
 class TestBranch(InstanceTestCase):
     code = """
         include "globals.mzn";