feat: sketch of a new configuration manager

This will eventually fix
#397

datalad_next/config/__init__.py

@@ -2,11 +2,110 @@
 
 This modules provides the central ``ConfigManager`` class.
 
+.. todo::
+
+   Mention ``defaults``, ``manager``, and ``legacy_cfg``
+
+
+Validation of configuration item values
+
+There are two ways to do validation and type conversion.  on-access, or
+on-load. Doing it on-load would allow to reject invalid configuration
+immediately. But it might spend time on items that never get accessed.
+On-access might waste cycles on repeated checks, and possible complain later
+than useful. Here we nevertheless run a validator on-access in the default
+implementation. Particular sources may want to override this, or ensure that
+the stored value that is passed to a validator is already in the best possible
+form to make re-validation the cheapest.
+
 .. currentmodule:: datalad_next.config
 .. autosummary::
    :toctree: generated
 
    ConfigManager
+   LegacyConfigManager
+   LegacyEnvironment
+   GitConfig
+   SystemGitConfig
+   GlobalGitConfig
+   LocalGitConfig
+   ImplementationDefault
+   defaults
+   dialog
+   legacy_register_config
+   legacy_cfg
+"""
+
+__all__ = [
+    'ConfigManager',
+    'LegacyConfigManager',
+    'LegacyEnvironment',
+    'GitConfig',
+    'SystemGitConfig',
+    'GlobalGitConfig',
+    'LocalGitConfig',
+    'ImplementationDefault',
+    'defaults',
+    'dialog',
+    'legacy_register_config',
+    'legacy_cfg',
+]
+
+# TODO: eventually replace with
+# from .legacy import ConfigManager
+from datalad.config import ConfigManager  # type: ignore
+
+ConfigManager.__doc__ = """\
+Do not use anymore
+
+.. deprecated:: 1.6
+
+   The use of this class is discouraged. It is a legacy import from the
+   ``datalad`` package, and a near drop-in replacement is provided with
+   :class:`LegacyConfigManager`. Moreover, a :class:`LegacyConfigManager`-based
+   instance of a global configuration manager is available as a
+   :obj:`datalad_next.config.legacy_cfg` object in this module.
+
+   New implementation are encourage to use the
+   :obj:`datalad_next.config.manager` object (and instance of
+   :class:`MultiConfiguration`) to query and manipulate configuration items.
 """
 
-from datalad.config import ConfigManager
+from datasalad.settings import Settings
+
+from . import dialog
+from .default import (
+    ImplementationDefault,
+    legacy_register_config,
+)
+from .default import (
+    load_legacy_defaults as _load_legacy_defaults,
+)
+from .env import LegacyEnvironment
+from .git import (
+    GitConfig,
+    GlobalGitConfig,
+    LocalGitConfig,
+    SystemGitConfig,
+)
+from .legacy import ConfigManager as LegacyConfigManager
+
+# instance for registering all defaults
+defaults = ImplementationDefault()
+# load up with legacy registrations for now
+_load_legacy_defaults(defaults)
+
+manager = Settings({
+    # order reflects precedence rule, first source with a
+    # key takes precedence
+    'legacy-environment': LegacyEnvironment(),
+    #'git-local': ...,
+    'git-global': GlobalGitConfig(),
+    'git-system': SystemGitConfig(),
+    #'datalad-branch': ...,
+    'defaults': defaults,
+})
+
+legacy_cfg = LegacyConfigManager(
+    manager,
+)

datalad_next/config/default.py

@@ -0,0 +1,128 @@
+from __future__ import annotations
+
+import logging
+from typing import (
+    Any,
+    Callable,
+)
+
+# momentarily needed for the legacy_register_config()
+# implementation.
+from datalad.interface.common_cfg import definitions   # type: ignore
+from datalad.support.extensions import (   # type: ignore
+    register_config as _legacy_register_config,
+)
+from datasalad.settings import Defaults
+
+from datalad_next.config.dialog import get_dialog_class_from_legacy_ui_label
+from datalad_next.config.item import (
+    ConfigurationItem,
+    UnsetValue,
+)
+from datalad_next.constraints import (
+    Constraint,
+    EnsureNone,
+)
+
+lgr = logging.getLogger('datalad.config')
+
+
+class ImplementationDefault(Defaults):
+    def __str__(self):
+        return 'ImplementationDefaults'
+
+
+#
+# legacy support tooling from here.
+# non of this is executed by the code above. It has to be triggered manually
+# and pointed to an instance of ImplementationDefaults
+#
+
+def load_legacy_defaults(source: ImplementationDefault) -> None:
+    for name, cfg in definitions.items():
+        if 'default' not in cfg:
+            lgr.debug(
+                'Configuration %r has no default(_fn), not registering',
+                name
+            )
+            continue
+
+        cfg_props = cfg._props
+        ui = cfg_props.get('ui', None)
+        if ui is not None:
+            dialog = get_dialog_class_from_legacy_ui_label(ui[0])(
+                title=ui[1]['title'],
+                text=ui[1].get('text', ''),
+            )
+        else:
+            dialog = None
+
+        coercer = cfg_props.get('type')
+        if name == 'datalad.tests.temp.dir':
+            # https://github.com/datalad/datalad/issues/7662
+            coercer = coercer | EnsureNone()
+
+        default = cfg_props.get('default', UnsetValue)
+        default_fn = cfg_props.get('default_fn')
+
+        source[name] = ConfigurationItem(
+            default_fn if default_fn else default,
+            validator=coercer,
+            lazy=default_fn is not None,
+            dialog=dialog,
+            store_target=get_store_target_from_destination_label(
+                cfg_props.get('destination'),
+            ),
+        )
+
+
+def legacy_register_config(
+    source: ImplementationDefault,
+    name: str,
+    title: str,
+    *,
+    default: Any = UnsetValue,
+    default_fn: Callable | type[UnsetValue] = UnsetValue,
+    description: str | None = None,
+    type: Constraint | None = None,  # noqa: A002
+    dialog: str | None = None,
+    scope: str | type[UnsetValue] = UnsetValue,
+):
+    source[name] = ConfigurationItem(
+        default_fn if default_fn else default,
+        validator=type,
+        lazy=default_fn is not None,
+        dialog=None if dialog is None
+        else get_dialog_class_from_legacy_ui_label(dialog)(
+            title=title,
+            text=description or '',
+        ),
+        store_target=get_store_target_from_destination_label(scope),
+    )
+
+    # lastly trigger legacy registration
+    _legacy_register_config(
+        name=name,
+        title=title,
+        default=default,
+        default_fn=default_fn,
+        description=description,
+        type=type,
+        dialog=dialog,
+        scope=scope,
+    )
+
+
+def get_store_target_from_destination_label(
+    label: str | UnsetValue | None,
+) -> str | None:
+    if label in (None, UnsetValue):
+        return None
+    if label == 'global':
+        return 'GlobalGitConfig'
+    if label == 'local':
+        return 'LocalGitConfig'
+    if label == 'dataset':
+        return 'DatasetBranchConfig'
+    msg = f'unsupported configuration destination label {label!r}'
+    raise ValueError(msg)

datalad_next/config/dialog.py

@@ -0,0 +1,44 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+__all__ = [
+    'Dialog',
+    'Question',
+    'YesNo',
+    'Choice',
+]
+
+
+# only from PY3.10
+# @dataclass(kw_only=True)
+@dataclass
+class Dialog:
+    title: str
+    text: str
+
+
+@dataclass
+class Question(Dialog):
+    pass
+
+
+@dataclass
+class YesNo(Dialog):
+    pass
+
+
+@dataclass
+class Choice(Dialog):
+    pass
+
+
+def get_dialog_class_from_legacy_ui_label(label: str) -> type[Dialog]:
+    """Recode legacy `datalad.interface.common_cfg` UI type label"""
+    if label == 'yesno':
+        return YesNo
+    elif label == 'question':
+        return Question
+    else:
+        msg = f'unknown UI type label {label!r}'
+        raise ValueError(msg)

datalad_next/config/env.py

@@ -0,0 +1,53 @@
+from __future__ import annotations
+
+import json
+import logging
+from os import environ
+from typing import Any
+
+from datasalad.settings import CachingSource
+
+from datalad_next.config.item import ConfigurationItem
+
+lgr = logging.getLogger('datalad.config')
+
+
+class LegacyEnvironment(CachingSource):
+    """
+    All loaded items have a ``store_target`` of ``Environment``, assuming
+    that if they are loaded from the environment, a modification can
+    also target the environment again.
+    """
+    is_writable = False
+
+    def load(self) -> None:
+        # not resetting here, incremental load
+        for k, v in self._load_legacy_overrides().items():
+            self._items[k] = ConfigurationItem(value=v)
+        for k in environ:
+            if not k.startswith('DATALAD_'):
+                continue
+            # translate variable name to config item key
+            item_key = k.replace('__', '-').replace('_', '.').lower()
+            self._items[item_key] = ConfigurationItem(value=environ[k])
+
+    def _load_legacy_overrides(self) -> dict[str, Any]:
+        try:
+            return {
+                str(k): v
+                for k, v in json.loads(
+                    environ.get("DATALAD_CONFIG_OVERRIDES_JSON", '{}')
+                ).items()
+            }
+        except json.decoder.JSONDecodeError as exc:
+            lgr.warning(
+                "Failed to load DATALAD_CONFIG_OVERRIDES_JSON: %s",
+                exc,
+            )
+            return {}
+
+    def __str__(self):
+        return 'LegacyEnvironment'
+
+    def __repr__(self):
+        return 'LegacyEnvironment()'