Implement override and reset analog to docker-compose (https://docs.docker.com/compose/compose-file/13-merge/)

Signed-off-by: Sebastian Sellmeier <[email protected]>

Author: SebTM

podman_compose.py

@@ -1149,6 +1149,43 @@ def flat_deps(services, with_extends=False):
     for name, srv in services.items():
         rec_deps(services, name)
 
+###################
+# Override and reset tags
+###################
+
+class OverrideTag(yaml.YAMLObject):
+    yaml_tag = u'!override'
+
+    def __init__(self, value):
+        self.value = value
+
+    def __repr__(self):
+        return self.value
+
+    @classmethod
+    def from_yaml(cls, loader, node):
+        return OverrideTag(node.value)
+
+    @classmethod
+    def to_yaml(cls, dumper, data):
+        return dumper.represent_scalar(cls.yaml_tag, data.value)
+
+class ResetTag(yaml.YAMLObject):
+    yaml_tag = u'!reset'
+
+    def __repr__(self):
+        return
+
+    @classmethod
+    def from_yaml(cls, loader, node):
+        return ResetTag()
+
+    @classmethod
+    def to_yaml(cls, dumper, data):
+        return
+
+yaml.SafeLoader.add_constructor(OverrideTag.yaml_tag, OverrideTag.from_yaml)
+yaml.SafeLoader.add_constructor(ResetTag.yaml_tag, ResetTag.from_yaml)
 
 ###################
 # podman and compose classes
@@ -1330,6 +1367,8 @@ def rec_merge_one(target, source):
     update target from source recursively
     """
     done = set()
+    remove = set()
+
     for key, value in source.items():
         if key in target:
             continue
@@ -1340,10 +1379,18 @@ def rec_merge_one(target, source):
             continue
         if key not in source:
             continue
+
         value2 = source[key]
+
         if key in ("command", "entrypoint"):
             target[key] = clone(value2)
             continue
+        if isinstance(value, ResetTag) or isinstance(value2, ResetTag):
+            remove.add(key)
+            continue
+        if isinstance(value, OverrideTag) or isinstance(value2, OverrideTag):
+            target[key] = clone(value.value) if isinstance(value, OverrideTag) else clone(value2.value)
+            continue
         if not isinstance(value2, type(value)):
             value_type = type(value)
             value2_type = type(value2)
@@ -1368,6 +1415,10 @@ def rec_merge_one(target, source):
             rec_merge_one(value, value2)
         else:
             target[key] = value2
+
+    for key in remove:
+        del target[key]
+
     return target