feat: implement merge function for MetaBase

2 files changed, 55 insertions, 1 deletions

diff --git a/meta/common/__init__.py b/meta/common/__init__.py
index 8e463f8448..ee294f00b3 100644
--- a/meta/common/__init__.py
+++ b/meta/common/__init__.py
@@ -49,3 +49,22 @@ def replace_old_launchermeta_url(url):
         return o._replace(netloc="piston-meta.mojang.com").geturl()
 
     return url
+
+
+def get_all_bases(cls, bases=None):
+    bases = bases or []
+    bases.append(cls)
+    for c in cls.__bases__:
+        get_all_bases(c, bases)
+    return tuple(bases)
+
+
+def merge_dict(base: dict, overlay: dict):
+    for k, v in base.items():
+        if isinstance(v, dict):
+            merge_dict(v, overlay.setdefault(k, {}))
+        else:
+            if k not in overlay:
+                overlay[k] = v
+
+    return overlay
diff --git a/meta/model/__init__.py b/meta/model/__init__.py
index b089040ee8..caa0e6d893 100644
--- a/meta/model/__init__.py
+++ b/meta/model/__init__.py
@@ -1,10 +1,11 @@
+import copy
 from datetime import datetime
 from typing import Optional, List, Dict, Any, Iterator
 
 import pydantic
 from pydantic import Field, validator
 
-from ..common import serialize_datetime, replace_old_launchermeta_url
+from ..common import serialize_datetime, replace_old_launchermeta_url, get_all_bases, merge_dict
 
 META_FORMAT_VERSION = 1
 
@@ -119,6 +120,40 @@ class MetaBase(pydantic.BaseModel):
         with open(file_path, "w") as f:
             f.write(self.json())
 
+    def merge(self, other):
+        """
+        Merge other object with self.
+        - Concatenates lists
+        - Combines sets
+        - Merges dictionaries (other takes priority)
+        - Recurses for all fields that are also MetaBase classes
+        - Overwrites for any other field type (int, string, ...)
+        """
+        assert type(other) is type(self)
+        for key, field in self.__fields__.items():
+            ours = getattr(self, key)
+            theirs = getattr(other, key)
+            if theirs is None:
+                continue
+            if ours is None:
+                setattr(self, key, theirs)
+                continue
+
+            if isinstance(ours, list):
+                ours += theirs
+            elif isinstance(ours, set):
+                ours |= theirs
+            elif isinstance(ours, dict):
+                result = merge_dict(ours, copy.deepcopy(theirs))
+                setattr(self, key, result)
+            elif MetaBase in get_all_bases(field.type_):
+                ours.merge(theirs)
+            else:
+                setattr(self, key, theirs)
+
+    def __hash__(self):
+        return hash(self.json())
+
     class Config:
         allow_population_by_field_name = True