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

Signed-off-by: Sebastian Sellmeier <mail@sebastian-sellmeier.de>

Author: SebTM

podman_compose.py

@@ -694,7 +694,7 @@ def port_dict_to_str(port_desc):
 
 
 def norm_ports(ports_in):
-    if not ports_in:
+    if not ports_in or isinstance(ports_in, ResetTag):
         ports_in = []
     if isinstance(ports_in, str):
         ports_in = [ports_in]
@@ -1149,6 +1149,51 @@ 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_dumper = yaml.Dumper
+    yaml_loader = yaml.SafeLoader
+    yaml_tag = u'!override'
+
+    def __init__(self, value):
+        values = list()
+
+        for item in value:
+            values.append(item.value)
+
+        self.value = values
+
+    @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_dumper = yaml.Dumper
+    yaml_loader = yaml.SafeLoader
+    yaml_tag = u'!reset'
+
+    @classmethod
+    def toJSON(self):
+        return self.yaml_tag
+
+    @classmethod
+    def from_yaml(cls, loader, node):
+        return ResetTag()
+
+    @classmethod
+    def to_yaml(cls, dumper, data):
+        return dumper.represent_scalar(cls.yaml_tag, '')
+
+class ResetTagEncoder(json.JSONEncoder):
+    def default(self, o):
+        return o.yaml_tag
 
 ###################
 # podman and compose classes
@@ -1293,6 +1338,9 @@ def normalize(compose):
     """
     services = compose.get("services", None) or {}
     for service in services.values():
+        if isinstance(service, ResetTag):
+            continue
+
         normalize_service(service)
     return compose
 
@@ -1330,6 +1378,8 @@ 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 +1390,18 @@ 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 +1426,10 @@ def rec_merge_one(target, source):
             rec_merge_one(value, value2)
         else:
             target[key] = value2
+
+    for key in remove:
+        del target[key]
+
     return target
 
 
@@ -1629,13 +1691,13 @@ def _parse_compose_file(self):
         compose["services"] = resolved_services
         if not getattr(args, "no_normalize", None):
             compose = normalize_final(compose, self.dirname)
-        self.merged_yaml = yaml.safe_dump(compose)
-        merged_json_b = json.dumps(compose, separators=(",", ":")).encode("utf-8")
+        self.merged_yaml = yaml.dump(compose)
+        merged_json_b = json.dumps(compose, separators=(",", ":"), cls=ResetTagEncoder).encode("utf-8")
         self.yaml_hash = hashlib.sha256(merged_json_b).hexdigest()
         compose["_dirname"] = dirname
         # debug mode
         if len(files) > 1:
-            log(" ** merged:\n", json.dumps(compose, indent=2))
+            log(" ** merged:\n", json.dumps(compose, indent=2, cls=ResetTagEncoder))
         # ver = compose.get('version', None)
 
         if not project_name: