Add min computation period (#1329)

Author: clallemand

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+### 43.3.8 [#1329](https://github.com/openfisca/openfisca-core/pull/1329)
+
+#### New features
+
+- Add a parameter `start_computation_period` in simulation : if this parameter is not None, the simulation return the default value for all variable calculate before this period. The aim is to avoid computation of variables for period before the input  variables period.
+
 ### 43.3.7 [#1328](https://github.com/openfisca/openfisca-core/pull/1328)
 
 #### Technical changes

openfisca_core/simulations/simulation.py

@@ -59,6 +59,7 @@ def __init__(
         self.max_spiral_loops: int = 1
         self.memory_config = None
         self._data_storage_dir = None
+        self.start_computation_period = None
 
     @property
     def trace(self):
@@ -144,6 +145,13 @@ def _calculate(self, variable_name: str, period: periods.Period):
         array = None
 
         # First, try to run a formula
+        if self.start_computation_period is not None:
+            if not isinstance(self.start_computation_period, periods.Period):
+                self.start_computation_period = periods.period(
+                    self.start_computation_period
+                )
+            if period < self.start_computation_period:
+                return holder.default_array()
         try:
             self._check_for_cycle(variable.name, period)
             array = self._run_formula(variable, population, period)

setup.py

@@ -70,7 +70,7 @@
 
 setup(
     name="OpenFisca-Core",
-    version="43.3.7",
+    version="43.3.8",
     author="OpenFisca Team",
     author_email="[email protected]",
     classifiers=[