Allow configuring via pyproject.toml

Compilation of protocol buffer files sometimes need some extra
configuration, like location of include files for external dependencies.

These are available via command-line, but this is extremely
inconvenient.  This commit allow users to configure the compilation of
protocol buffer files using pyproject.toml.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

src/frequenz/repo/config/__init__.py

@@ -224,9 +224,26 @@
 recursive-include submodules/api-common-protos/google *.proto
 ```
 
-For now there is no way to customize where the protocol files are located,
-where the generated files should be placed, or which extra directories must be
-included when compiling the protocol files.
+If the defaults are not suitable for you (for example you need to use more or less
+submodules or your proto files are located somewhere else, you can customize how
+the protocol files are generated by adding the following section to your
+`pyproject.toml` file:
+
+```toml
+[tool.frequenz_repo_config.setuptools.grpc_tools]
+# Location of the proto files relative to the root of the repository (default: "proto")
+proto_path = "proto_files"
+# Glob pattern to use to find the proto files in the proto_path (default: "*.proto")
+proto_glob = "*.prt"  # Default: "*.proto"
+# List of paths to pass to the protoc compiler as include paths (default:
+# ["submodules/api-common-protos"])
+include_paths = []
+# Path where to generate the Python files (default: "py")
+py_path = "generated"
+```
+
+Please adapt the instructions above to your project structure if you need to change the
+defaults.
 """
 
 from . import nox, setuptools

src/frequenz/repo/config/setuptools/grpc_tools.py

@@ -13,6 +13,7 @@
 import pathlib as _pathlib
 import subprocess as _subprocess
 import sys as _sys
+import tomllib as _tomllib
 
 import setuptools as _setuptools
 
@@ -58,16 +59,69 @@ class CompileProto(_setuptools.Command):
     ]
     """Options of the command."""
 
+    DEFAULT_OPTIONS: dict[str, str] = {
+        "proto_path": "proto",
+        "proto_glob": "*.proto",
+        "include_paths": "submodules/api-common-protos",
+        "py_path": "py",
+    }
+
     def initialize_options(self) -> None:
         """Initialize options."""
-        self.proto_path = "proto"
-        self.proto_glob = "*.proto"
-        self.include_paths = "submodules/api-common-protos"
-        self.py_path = "py"
+        options = self._get_options_from_pyproject_toml(self.DEFAULT_OPTIONS)
+
+        self.proto_path = options["proto_path"]
+        self.proto_glob = options["proto_glob"]
+        self.include_paths = options["include_paths"]
+        self.py_path = options["py_path"]
 
     def finalize_options(self) -> None:
         """Finalize options."""
 
+    def _get_options_from_pyproject_toml(
+        self, defaults: dict[str, str]
+    ) -> dict[str, str]:
+        """Get the options from the pyproject.toml file.
+
+        The options are read from the `[tool.frequenz-repo-config.setuptools.grpc_tools]`
+        section of the pyproject.toml file.
+
+        Args:
+            defaults: The default values for the options.
+
+        Returns:
+            The options read from the pyproject.toml file.
+        """
+        try:
+            with _pathlib.Path("pyproject.toml").open("rb") as toml_file:
+                pyproject_toml = _tomllib.load(toml_file)
+        except FileNotFoundError:
+            return defaults
+        except (IOError, OSError) as err:
+            print(f"WARNING: Failed to load pyproject.toml: {err}")
+            return defaults
+
+        try:
+            config = pyproject_toml["tool"]["frequenz-repo-config"]["setuptools"][
+                "grpc_tools"
+            ]
+        except KeyError:
+            return defaults
+
+        known_keys = frozenset(defaults.keys())
+        config_keys = frozenset(config.keys())
+        if unknown_keys := config_keys - known_keys:
+            print(
+                "WARNING: There are some configuration keys in pyproject.toml we don't "
+                "know about and will be ignored: "
+                + ", ".join(f"'{k}'" for k in unknown_keys)
+            )
+
+        if "include_paths" in config:
+            config["include_paths"] = ",".join(config["include_paths"])
+
+        return dict(defaults, **{k: config[k] for k in (known_keys & config_keys)})
+
     def run(self) -> None:
         """Compile the Python protobuf files."""
         include_paths = self.include_paths.split(",")