Generate pydantic validators

src/betterproto2_compiler/plugin/models.py

@@ -410,10 +410,43 @@ def py_type(self) -> str:
     def unwrapped_py_type(self) -> str:
         return self._py_type(wrap=False)
 
+    @property
+    def annotations(self) -> list[str]:
+        """List of the Pydantic annotation to add to the field."""
+        assert self.output_file.settings.pydantic_dataclasses
+
+        annotations = []
+
+        if self.proto_obj.type in (FieldType.TYPE_INT32, FieldType.TYPE_SFIXED32, FieldType.TYPE_SINT32):
+            annotations.append("pydantic.Field(ge=-2**31, le=2**31 - 1)")
+
+        elif self.proto_obj.type in (FieldType.TYPE_UINT32, FieldType.TYPE_FIXED32):
+            annotations.append("pydantic.Field(ge=0, le=2**32 - 1)")
+
+        elif self.proto_obj.type in (FieldType.TYPE_INT64, FieldType.TYPE_SFIXED64, FieldType.TYPE_SINT64):
+            annotations.append("pydantic.Field(ge=-2**63, le=2**63 - 1)")
+
+        elif self.proto_obj.type in (FieldType.TYPE_UINT64, FieldType.TYPE_FIXED64):
+            annotations.append("pydantic.Field(ge=0, le=2**64 - 1)")
+
+        elif self.proto_obj.type == FieldType.TYPE_FLOAT:
+            annotations.append("pydantic.AfterValidator(betterproto2.validators.validate_float32)")
+
+        elif self.proto_obj.type == FieldType.TYPE_STRING:
+            annotations.append("pydantic.AfterValidator(betterproto2.validators.validate_string)")
+
+        return annotations
+
     @property
     def annotation(self) -> str:
         py_type = self.py_type
 
+        # Add the pydantic annotation if needed
+        if self.output_file.settings.pydantic_dataclasses:
+            annotations = self.annotations
+            if annotations:
+                py_type = f"typing.Annotated[{py_type}, {', '.join(annotations)}]"
+
         if self.use_builtins:
             py_type = f"builtins.{py_type}"
         if self.repeated:

src/betterproto2_compiler/templates/header.py.j2

@@ -28,6 +28,7 @@ import typing
 from typing import TYPE_CHECKING
 
 {% if output_file.settings.pydantic_dataclasses %}
+import pydantic
 from pydantic.dataclasses import dataclass
 from pydantic import model_validator
 {%- else -%}

tests/inputs/validation/validation.proto

@@ -0,0 +1,20 @@
+syntax = "proto3";
+
+package validation;
+
+message Message {
+    int32 int32_value = 1;
+    int64 int64_value = 2;
+    uint32 uint32_value = 3;
+    uint64 uint64_value = 4;
+    sint32 sint32_value = 5;
+    sint64 sint64_value = 6;
+    fixed32 fixed32_value = 7;
+    fixed64 fixed64_value = 8;
+    sfixed32 sfixed32_value = 9;
+    sfixed64 sfixed64_value = 10;
+
+    float float_value = 11;
+
+    string string_value = 12;
+}