Add / execute variable converters (#92)

* add converter parameter to variable()

* maybe convert in variable property setter

* maybe convert input values

* add/update tests

* update release notes

doc/whats_new.rst

@@ -57,6 +57,9 @@ Enhancements
   in the class (:issue:`67`).
 - Added :func:`~xsimlab.validators.in_bounds` and
   :func:`~xsimlab.validators.is_subdtype` validators (:issue:`87`).
+- :func:`xsimlab.variable` has now a ``converter`` parameter that can be used to
+  convert any input value before (maybe) validating it and setting the variable
+  (:issue:`92`).
 
 Bug fixes
 ~~~~~~~~~

xsimlab/drivers.py

@@ -99,7 +99,10 @@ def _set_in_store(self, input_vars, check_static=True):
                     f"in process {p_name!r}"
                 )
 
-            self.store[key] = copy.copy(value)
+            if var.converter is not None:
+                self.store[key] = var.converter(value)
+            else:
+                self.store[key] = copy.copy(value)
 
     def initialize_store(self, input_vars):
         """Pre-populate the simulation active data store with input

xsimlab/process.py

@@ -145,6 +145,10 @@ def get_target_variable(var):
     return target_process_cls, target_var
 
 
+def _dummy_converter(value):
+    return value
+
+
 def _make_property_variable(var):
     """Create a property for a variable or a foreign variable (after
     some sanity checks).
@@ -157,6 +161,7 @@ def _make_property_variable(var):
 
     """
     var_name = var.name
+    var_converter = var.converter or _dummy_converter
 
     def get_from_store(self):
         key = self.__xsimlab_store_keys__[var_name]
@@ -169,7 +174,7 @@ def get_on_demand(self):
 
     def put_in_store(self, value):
         key = self.__xsimlab_store_keys__[var_name]
-        self.__xsimlab_store__[key] = value
+        self.__xsimlab_store__[key] = var_converter(value)
 
     target_process_cls, target_var = get_target_variable(var)
 
@@ -437,6 +442,7 @@ def _reset_attributes(self):
             new_attributes[k] = attr.attrib(
                 metadata=attrib.metadata,
                 validator=attrib.validator,
+                converter=attrib.converter,
                 default=attrib.default,
                 init=False,
                 repr=False,

xsimlab/tests/fixture_model.py

@@ -35,7 +35,9 @@ def _get_u_opposite(self):
 
 @xs.process
 class InitProfile:
-    n_points = xs.variable(description="nb. of profile points", static=True)
+    n_points = xs.variable(
+        description="nb. of profile points", converter=int, static=True
+    )
     u = xs.foreign(Profile, "u", intent="out")
 
     def initialize(self):

xsimlab/tests/fixture_process.py

@@ -33,7 +33,7 @@ class ExampleProcess:
 
     in_var = xs.variable(dims=["x", ("x", "y")], description="input variable")
     out_var = xs.variable(groups="example_group", intent="out")
-    inout_var = xs.variable(intent="inout")
+    inout_var = xs.variable(intent="inout", converter=int)
     od_var = xs.on_demand()
 
     in_foreign_var = xs.foreign(SomeProcess, "some_var")

xsimlab/tests/test_drivers.py

@@ -38,12 +38,21 @@ def test_set_store_ignore(self, base_driver):
         assert ("not-a-model", "input") not in base_driver.store
 
     def test_set_store_copy(self, base_driver):
-        n = np.array(10)
-        input_vars = {("init_profile", "n_points"): n}
+        n = np.array([1, 2, 3, 4])
+        input_vars = {("add", "offset"): n}
         base_driver.initialize_store(input_vars)
 
-        assert base_driver.store[("init_profile", "n_points")] == n
-        assert base_driver.store[("init_profile", "n_points")] is not n
+        actual = base_driver.store[("add", "offset")]
+        assert_array_equal(actual, n)
+        assert actual is not n
+
+    def test_set_store_converter(self, base_driver):
+        input_vars = {("init_profile", "n_points"): 10.2}
+        base_driver.initialize_store(input_vars)
+
+        actual = base_driver.store[("init_profile", "n_points")]
+        assert actual == 10
+        assert type(actual) is int
 
     def test_initialize_store(self, base_driver):
         input_vars = {("init_profile", "n_points"): 10}

xsimlab/tests/test_process.py

@@ -197,6 +197,14 @@ def test_process_properties_values(processes_with_store):
     assert set(example_process.group_var) == {1, 4}
 
 
+def test_process_properties_converter(processes_with_store):
+    _, _, example_process = processes_with_store
+
+    example_process.inout_var = 1.1
+    assert example_process.inout_var == 1
+    assert type(example_process.inout_var) is int
+
+
 def test_runtime_decorator_noargs():
     @xs.runtime
     def meth(self):

xsimlab/variable.py

@@ -99,6 +99,7 @@ def variable(
     groups=None,
     default=attr.NOTHING,
     validator=None,
+    converter=None,
     static=False,
     description="",
     attrs=None,
@@ -152,6 +153,11 @@ def variable(
         is given.
         If a ``list`` is passed, its items are all are treated as validators.
         The validator can also be set using decorator notation.
+    converter : callable, optional
+        Callable that is called when setting a value for this variable, and that
+        converts the value to the desired format. The callable must accept
+        one argument and return one value. The value is converted before being
+        passed to the validator, if any.
     static : bool, optional
         If True, the value of the (input) variable must be set once
         before the simulation starts and cannot be further updated
@@ -192,6 +198,7 @@ def variable(
         metadata=metadata,
         default=default,
         validator=validator,
+        converter=converter,
         init=_init,
         repr=_repr,
         kw_only=True,