From 0ac58166c48e037df3344341aaf4fa59f42e0b56 Mon Sep 17 00:00:00 2001
From: Nikhil Woodruff <35577657+nikhilwoodruff@users.noreply.github.com>
Date: Thu, 8 Feb 2024 14:32:20 +0000
Subject: [PATCH] Add variable inheritance in declarations (#155)

* Format and improve error handling

* Allow inheritance in variable declarations
Fixes #154

* Changelog entry
---
 changelog_entry.yaml                    |  4 ++++
 policyengine_core/variables/variable.py | 15 +++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/changelog_entry.yaml b/changelog_entry.yaml
index e69de29bb..08abda926 100644
--- a/changelog_entry.yaml
+++ b/changelog_entry.yaml
@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    added:
+    - Variable inheritance in declarations.
diff --git a/policyengine_core/variables/variable.py b/policyengine_core/variables/variable.py
index 8fa44435e..0d02ffa34 100644
--- a/policyengine_core/variables/variable.py
+++ b/policyengine_core/variables/variable.py
@@ -136,6 +136,21 @@ def __init__(self, baseline_variable=None):
             for name, value in self.__class__.__dict__.items()
             if not name.startswith("__")
         }
+
+        # Allow inheritance for some properties
+        INHERITED_ALLOWED_PROPERTIES = (
+            "label",
+            "value_type",
+            "entity",
+            "definition_period",
+        )
+
+        for property_name in INHERITED_ALLOWED_PROPERTIES:
+            if not attr.get(property_name) and property_name in dir(
+                self.__class__
+            ):
+                attr[property_name] = getattr(self, property_name)
+
         self.baseline_variable = baseline_variable
         self.value_type = self.set(
             attr,