Support deprecated message and fields (#126)

src/betterproto/plugin/models.py

@@ -33,6 +33,7 @@ import re
 from dataclasses import dataclass
 from dataclasses import field
 from typing import (
+    Iterator,
     Union,
     Type,
     List,
@@ -249,6 +250,13 @@ class OutputTemplate:
         """
         return [f.name for f in self.input_files]
 
+    @property
+    def python_module_imports(self) -> Set[str]:
+        imports = set()
+        if any(x for x in self.messages if any(x.deprecated_fields)):
+            imports.add("warnings")
+        return imports
+
 
 @dataclass
 class MessageCompiler(ProtoContentBase):
@@ -261,6 +269,7 @@ class MessageCompiler(ProtoContentBase):
     fields: List[Union["FieldCompiler", "MessageCompiler"]] = field(
         default_factory=list
     )
+    deprecated: bool = field(default=False, init=False)
 
     def __post_init__(self):
         # Add message to output file
@@ -269,6 +278,7 @@ class MessageCompiler(ProtoContentBase):
                 self.output_file.enums.append(self)
             else:
                 self.output_file.messages.append(self)
+        self.deprecated = self.proto_obj.options.deprecated
         super().__post_init__()
 
     @property
@@ -285,6 +295,12 @@ class MessageCompiler(ProtoContentBase):
             return f"List[{self.py_name}]"
         return self.py_name
 
+    @property
+    def deprecated_fields(self) -> Iterator[str]:
+        for f in self.fields:
+            if f.deprecated:
+                yield f.py_name
+
 
 def is_map(
     proto_field_obj: FieldDescriptorProto, parent_message: DescriptorProto

src/betterproto/templates/template.py.j2

@@ -1,6 +1,9 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # sources: {{ ', '.join(description.input_filenames) }}
 # plugin: python-betterproto
+{% for i in description.python_module_imports|sort %}
+import {{ i }}
+{% endfor %}
 from dataclasses import dataclass
 {% if description.datetime_imports %}
 from datetime import {% for i in description.datetime_imports|sort %}{{ i }}{% if not loop.last %}, {% endif %}{% endfor %}
@@ -50,6 +53,18 @@ class {{ message.py_name }}(betterproto.Message):
     pass
     {% endif %}
 
+    {% if message.deprecated or message.deprecated_fields %}
+    def __post_init__(self) -> None:
+        {% if message.deprecated %}
+        warnings.warn("{{ message.py_name }} is deprecated", DeprecationWarning)
+        {% endif %}
+        super().__post_init__()
+        {% for field in message.deprecated_fields %}
+        if self.{{ field }}:
+            warnings.warn("{{ message.py_name }}.{{ field }} is deprecated", DeprecationWarning)
+        {% endfor %}
+    {%  endif %}
+
 
 {% endfor %}
 {% for service in description.services %}