Move dzn parser into dzn extra

Author: Dekker1

CHANGELOG.rst

@@ -16,6 +16,10 @@ Added
 
 Changed
 ^^^^^^^
+- The DZN parser functionality has been moved into the ``dzn`` extra. If your
+  application requires parsed ``dzn`` information, then you have to ensure your
+  MiniZinc Python is installed with this extra enabled:
+  ``pip install minizinc[dzn]``.
 - ``Solver`` has been turned into a ``dataclass`` and has been updated with all
   attributes used in the compiler.
 

docs/getting_started.rst

@@ -33,6 +33,12 @@ installing MiniZinc Python is using the following command:
     On machines that have both Python 2 and Python 3 installed you might have to
     use ``pip3`` instead of ``pip``
 
+..  note::
+
+    If you require the parsed information of ``.dzn`` files within your python
+    environment, then you have to install the ``dzn`` extra with the MiniZinc
+    package: ``pip install minizinc[dzn]``
+
 A basic example
 ---------------
 

setup.py

@@ -38,9 +38,10 @@
     ],
     install_requires=[
         "dataclasses>=0.6.0; python_version < '3.7'",
-        "lark-parser>=0.7.5",
-        "pygments>=2.5",
     ],
+    extras_require={
+        "dzn": ["lark-parser>=0.7.5"],
+    },
     entry_points='''
         [pygments.lexers]
         minizinclexer = minizinc.pygments:MiniZincLexer

src/minizinc/CLI/instance.py

@@ -19,11 +19,10 @@
 from typing import Any, Dict, Iterator, List, Optional, Type, cast
 
 import minizinc
-from minizinc.dzn import UnknownExpression
 from minizinc.error import parse_error
 from minizinc.instance import Instance
 from minizinc.json import MZNJSONEncoder
-from minizinc.model import Method, Model, ParPath
+from minizinc.model import Method, Model, ParPath, UnknownExpression
 from minizinc.result import Result, Status, parse_solution, set_stat
 from minizinc.solver import Solver
 

src/minizinc/dzn.py

@@ -7,6 +7,8 @@
 
 from lark import Lark, Transformer
 
+from minizinc.model import UnknownExpression
+
 dzn_grammar = r"""
     items: [item (";" item)* ";"?]
     item: ident "=" value | ident "=" unknown
@@ -39,10 +41,6 @@
 """
 
 
-class UnknownExpression(str):
-    pass
-
-
 def arg1_construct(cls):
     return lambda self, s: cls(s[0])
 

src/minizinc/model.py

@@ -9,10 +9,6 @@
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Type, Union
 
-from lark.exceptions import LarkError
-
-from .dzn import parse_dzn
-
 ParPath = Union[Path, str]
 
 
@@ -34,7 +30,7 @@ def from_string(cls, s: str):
         """Get Method represented by the string s.
 
         Args:
-            s:
+            s: String expected to contain either "sat", "min", or "max".
 
         Returns:
             Method: Method represented by s
@@ -51,6 +47,10 @@ def from_string(cls, s: str):
             )
 
 
+class UnknownExpression(str):
+    pass
+
+
 class Model:
     """The representation of a MiniZinc model in Python
 
@@ -150,7 +150,8 @@ def add_file(self, file: ParPath, parse_data: bool = True) -> None:
         Args:
             file (Union[Path, str]): Path to the file to be added
             parse_data (bool): Signal if the data should be parsed for usage
-                within Python.
+                within Python. This option is ignored if the extra `dzn` is
+                not enabled.
         Raises:
             MiniZincError: when an error occurs during the parsing or
                 type checking of the model object.
@@ -166,8 +167,12 @@ def add_file(self, file: ParPath, parse_data: bool = True) -> None:
             data = json.load(file.open())
             for k, v in data.items():
                 self.__setitem__(k, v)
-        elif file.suffix == ".dzn":
+        elif file.suffix == ".dzn" and parse_data:
             try:
+                from lark.exceptions import LarkError
+
+                from .dzn import parse_dzn
+
                 data = parse_dzn(file)
                 for k, v in data.items():
                     self.__setitem__(k, v)
@@ -176,9 +181,12 @@ def add_file(self, file: ParPath, parse_data: bool = True) -> None:
                     f"Could not parse {file}. Parameters included within this file are "
                     f"not available in Python"
                 )
+            except ImportError:
+                pass
+            finally:
                 with self._lock:
                     self._includes.append(file)
-        elif file.suffix not in [".mzn", ".mzc"]:
+        elif file.suffix not in [".dzn", ".mzn", ".mzc"]:
             raise NameError("Unknown file suffix %s", file.suffix)
         else:
             with self._lock:

tests/test_dzn.py

@@ -2,7 +2,12 @@
 #  License, v. 2.0. If a copy of the MPL was not distributed with this
 #  file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-from minizinc.dzn import UnknownExpression, parse_dzn
+import pytest
+
+from minizinc.model import UnknownExpression
+
+lark = pytest.importorskip("lark")
+from minizinc.dzn import parse_dzn  # noqa: E402
 
 
 def test_dzn_empty():

tox.ini

@@ -10,6 +10,7 @@ envlist =
 [testenv]
 deps = pytest
 commands = pytest {posargs}
+extras = dzn
 
 [testenv:check]
 deps =