change API for LSM and flow direction in component definition

Turn them into methods rather than properties, and add "requires" to them to be more explicit and to avoid confusion with SpaceDomain properties (land_sea_mask and flow_direction).

cm4twc/component.py

@@ -37,8 +37,8 @@ class MetaComponent(abc.ABCMeta):
     _states_info = None
     _outputs_info = None
     _solver_history = None
-    _land_sea_mask = None
-    _flow_direction = None
+    _requires_land_sea_mask = None
+    _requires_flow_direction = None
 
     @property
     def category(cls):
@@ -84,13 +84,11 @@ def outputs_metadata(cls):
     def solver_history(cls):
         return cls._solver_history
 
-    @property
-    def flow_direction(cls):
-        return cls._flow_direction
+    def requires_flow_direction(cls):
+        return cls._requires_flow_direction
 
-    @property
-    def land_sea_mask(cls):
-        return cls._land_sea_mask
+    def requires_land_sea_mask(cls):
+        return cls._requires_land_sea_mask
 
     def __str__(cls):
         info = [
@@ -109,8 +107,16 @@ def __str__(cls):
             + ["    category: {}".format(getattr(cls, '_category'))]
             + info
             + ["    solver history: {}".format(getattr(cls, '_solver_history'))]
-            + ["    land sea mask: {}".format(getattr(cls, '_land_sea_mask'))]
-            + ["    flow direction: {}".format(getattr(cls, '_flow_direction'))]
+            + [
+                "    requires land sea mask: {}".format(
+                    getattr(cls, '_requires_land_sea_mask')()
+                )
+            ]
+            + [
+                "    requires flow direction: {}".format(
+                    getattr(cls, '_requires_flow_direction')()
+                )
+            ]
             + [")"]
         )
 
@@ -128,8 +134,8 @@ class Component(metaclass=MetaComponent):
     _states_info = {}
     _outputs_info = {}
     _solver_history = 1
-    _land_sea_mask = False
-    _flow_direction = False
+    _requires_land_sea_mask = False
+    _requires_flow_direction = False
 
     def __init__(self, saving_directory, timedomain, spacedomain,
                  dataset=None, parameters=None, constants=None, records=None,
@@ -556,7 +562,7 @@ def _check_spacedomain(self, spacedomain):
                 "for spacedomain".format(Grid.__name__)
             )
 
-        if self._land_sea_mask:
+        if self._requires_land_sea_mask:
             if spacedomain.land_sea_mask is None:
                 raise RuntimeError(
                     "'land_sea_mask' must be set in {} of {} "
@@ -565,7 +571,7 @@ def _check_spacedomain(self, spacedomain):
                                             self.__class__.__name__)
                 )
 
-        if self._flow_direction:
+        if self._requires_flow_direction:
             if spacedomain.flow_direction is None:
                 raise RuntimeError(
                     "'flow_direction' must be set in {} of {} "

tests/components/surfacelayer/dummy.py

@@ -83,8 +83,8 @@ class Dummy(SurfaceLayerComponent):
         }
     }
     _solver_history = 1
-    _land_sea_mask = True
-    _flow_direction = True
+    _requires_land_sea_mask = True
+    _requires_flow_direction = True
 
     def initialise(self,
                    # component states