From dee954cf3ae31007786857a4e7e273a483ea85e4 Mon Sep 17 00:00:00 2001
From: Marnik Bercx <mbercx@gmail.com>
Date: Mon, 20 Nov 2023 11:36:43 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=91=8C=20Return=20`frozendict`=20for=20st?=
 =?UTF-8?q?ored=20`Dict`=20nodes?=
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---
 aiida/orm/nodes/data/dict.py | 17 ++++++++++++++++-
 environment.yml              |  1 +
 pyproject.toml               |  1 +
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/aiida/orm/nodes/data/dict.py b/aiida/orm/nodes/data/dict.py
index e0a975f916..df7b3e4fce 100644
--- a/aiida/orm/nodes/data/dict.py
+++ b/aiida/orm/nodes/data/dict.py
@@ -10,6 +10,8 @@
 """`Data` sub class to represent a dictionary."""
 import copy
 
+from frozendict import frozendict
+
 from aiida.common import exceptions
 
 from .base import to_aiida_type
@@ -62,15 +64,28 @@ def __init__(self, value=None, **kwargs):
             self.set_dict(dictionary)
 
     def __getitem__(self, key):
+        """Get the ``value`` of a key.
+
+        If the node is not stored, the value is returned as is (if present). Once the node is stored, we check if the
+        value is a dictionary and if so, we return a ``frozendict`` instance to prevent modifications. This is to
+        prevent the user from modifying the dictionary in place, which would not be reflected in the database.
+        """
         try:
-            return self.base.attributes.get(key)
+            value = self.base.attributes.get(key)
         except AttributeError as exc:
             raise KeyError from exc
 
+        if self.is_stored and isinstance(value, dict):
+            return frozendict(value)
+
+        return value
+
     def __setitem__(self, key, value):
+        """Set the ``value`` of a key."""
         self.base.attributes.set(key, value)
 
     def __eq__(self, other):
+        """Compare if the current node is equal to another node or to a dictionary."""
         if isinstance(other, Dict):
             return self.get_dict() == other.get_dict()
         return self.get_dict() == other
diff --git a/environment.yml b/environment.yml
index 7a8bd8a795..583873c264 100644
--- a/environment.yml
+++ b/environment.yml
@@ -14,6 +14,7 @@ dependencies:
 - click~=8.1
 - disk-objectstore~=1.0
 - docstring_parser
+- frozendict~=2.3
 - get-annotations~=0.1
 - python-graphviz~=0.19
 - ipython>=7
diff --git a/pyproject.toml b/pyproject.toml
index 7f1fe1ca9a..c978480a93 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,6 +33,7 @@ dependencies = [
     "click~=8.1",
     "disk-objectstore~=1.0",
     "docstring-parser",
+    "frozendict~=2.3",
     "get-annotations~=0.1;python_version<'3.10'",
     "graphviz~=0.19",
     "ipython>=7",