protos, python: use betterproto

protos/Makefile

@@ -4,7 +4,7 @@ go:
 
 # Creates the python libs in the python/ directory.
 python:
-	protoc --python_out=../python $(shell find ./in_toto_attestation -name "*.proto")
+	make -C ../python protos
 	make -C ../python reformat
 
 # Creates the java libs in the java/ directory.

python/Makefile

@@ -22,6 +22,8 @@ BUMP_ARGS :=
 # subset of development dependencies.
 INSTALL_EXTRA := dev
 
+PROTOS = $(shell find ../protos/in_toto_attestation -name "*.proto")
+
 .PHONY: all
 all:
 	@echo "Run my targets individually!"
@@ -61,3 +63,13 @@ package: $(VENV_STAMP)
 .PHONY: edit
 edit:
 	$(EDITOR) $(ALL_PY_SRCS)
+
+.PHONY: protos
+protos: $(VENV_STAMP)
+	@# TODO: Enable `--python_betterproto_opt=pydantic_dataclasses` once
+	@# Pydantic V2 is supported: https://github.com/danielgtaylor/python-betterproto/issues/530
+	protoc \
+		-I../protos \
+		--python_betterproto_out=./in_toto_attestation/_internal \
+		$(PROTOS)
+	$(MAKE) reformat

python/in_toto_attestation/__init__.py

@@ -1 +1 @@
-version = "0.9.3"
+__version__ = "0.9.3"