Add support for global TOML configuration

src/furu/config.py

@@ -1,16 +1,44 @@
 import os
 from pathlib import Path
+from typing import Any
 
 from pydantic import BaseModel, ByteSize, ConfigDict, Field
 from pydantic_settings import (
     BaseSettings,
     JsonConfigSettingsSource,
     PydanticBaseSettingsSource,
     PyprojectTomlConfigSettingsSource,
+    SettingsError,
     SettingsConfigDict,
+    TomlConfigSettingsSource,
 )
 
 _WORKER_JSON_CONFIG_FILE_ENV_VAR = "_FURU_WORKER_JSON_CONFIG_FILE"
+_GLOBAL_CONFIG_KEYS = {
+    "worker": {
+        "connect_host",
+        "idle_timeout_seconds",
+        "max_failed_restarts",
+        "max_retries_per_object",
+    },
+    "provenance": {"max_snapshot_bytes"},
+}
+
+
+class _GlobalTomlConfigSettingsSource(TomlConfigSettingsSource):
+    def __call__(self) -> dict[str, Any]:
+        values = super().__call__()
+        unsupported = set(values) - _GLOBAL_CONFIG_KEYS.keys()
+        for section, allowed in _GLOBAL_CONFIG_KEYS.items():
+            if isinstance(section_values := values.get(section), dict):
+                unsupported |= {
+                    f"{section}.{key}" for key in section_values if key not in allowed
+                }
+        if unsupported:
+            raise SettingsError(
+                f"Unsupported global Furu setting(s): {', '.join(sorted(unsupported))}"
+            )
+        return values
 
 
 class _FuruDirectories(BaseModel):
@@ -84,6 +112,12 @@ def settings_customise_sources(
             env_settings,
             dotenv_settings,
             PyprojectTomlConfigSettingsSource(settings_cls),
+            _GlobalTomlConfigSettingsSource(
+                settings_cls,
+                Path(os.getenv("XDG_CONFIG_HOME", "~/.config")).expanduser()
+                / "furu"
+                / "furu.toml",
+            ),
             file_secret_settings,
         )
 

tests/test_config.py

@@ -2,6 +2,7 @@
 
 import pytest
 from pydantic import ValidationError
+from pydantic_settings import SettingsError
 
 from furu.config import (
     _Config,
@@ -137,6 +138,85 @@ def test_config_discovers_pyproject_toml_in_parent_directory(
     )
 
 
+def test_config_reads_global_toml(tmp_path, monkeypatch) -> None:
+    config_home = tmp_path / ".config"
+    config_file = config_home / "furu" / "furu.toml"
+    config_file.parent.mkdir(parents=True)
+    config_file.write_text(
+        """
+[worker]
+connect_host = "login01.cluster"
+idle_timeout_seconds = 120
+max_failed_restarts = 8
+max_retries_per_object = 5
+
+[provenance]
+max_snapshot_bytes = "1GiB"
+""",
+        encoding="utf-8",
+    )
+    monkeypatch.delenv("XDG_CONFIG_HOME", raising=False)
+    monkeypatch.setenv("HOME", str(tmp_path))
+
+    config = _Config()
+
+    assert config.worker.connect_host == "login01.cluster"
+    assert config.worker.idle_timeout_seconds == 120
+    assert config.worker.max_failed_restarts == 8
+    assert config.worker.max_retries_per_object == 5
+    assert config.provenance.max_snapshot_bytes == 1024**3
+
+
+def test_pyproject_toml_overrides_global_toml(tmp_path, monkeypatch) -> None:
+    config_home = tmp_path / "config"
+    config_file = config_home / "furu" / "furu.toml"
+    config_file.parent.mkdir(parents=True)
+    config_file.write_text(
+        """
+[worker]
+connect_host = "global.cluster"
+""",
+        encoding="utf-8",
+    )
+    (tmp_path / "pyproject.toml").write_text(
+        """
+[tool.furu.worker]
+connect_host = "project.cluster"
+""",
+        encoding="utf-8",
+    )
+    monkeypatch.setenv("XDG_CONFIG_HOME", str(config_home))
+    monkeypatch.chdir(tmp_path)
+
+    config = _Config()
+
+    assert config.worker.connect_host == "project.cluster"
+
+
+@pytest.mark.parametrize(
+    ("contents", "unsupported"),
+    [
+        ("debug_mode = true", "debug_mode"),
+        ('[directories]\nobjects = "/tmp/furu-objects"', "directories"),
+        ("[provenance]\nsnapshot = false", "provenance.snapshot"),
+        ("[worker]\nunknown_setting = 5", "worker.unknown_setting"),
+    ],
+)
+def test_global_toml_rejects_project_settings(
+    contents, unsupported, tmp_path, monkeypatch
+) -> None:
+    config_home = tmp_path / "config"
+    config_file = config_home / "furu" / "furu.toml"
+    config_file.parent.mkdir(parents=True)
+    config_file.write_text(contents, encoding="utf-8")
+    monkeypatch.setenv("XDG_CONFIG_HOME", str(config_home))
+
+    with pytest.raises(SettingsError) as error:
+        _Config()
+
+    assert unsupported in str(error.value)
+
+
 def test_environment_overrides_pyproject_toml(tmp_path, monkeypatch) -> None:
     pyproject = tmp_path / "pyproject.toml"
     pyproject.write_text(