refactor(config): add set_config_value for non-merge replacement

src/presa_mano/api/pose_3d_routes.py

@@ -8,9 +8,8 @@ from typing import Any, Literal, Optional
 from fastapi import APIRouter, HTTPException
 from pydantic import BaseModel, Field
 
-from .. import config as _config_mod
 from ..clients import G1Unavailable
-from ..config import get_config, update_config
+from ..config import get_config, set_config_value
 from ..geometry import normalize_quaternion
 from ..timing import Stopwatch
 from . import _deps
@@ -29,21 +28,6 @@ def _validate_name(name: str) -> None:
         )
 
 
-def _replace_named_poses(poses: dict[str, Any]) -> None:
-    """Wholesale replace pose_3d.named_poses.
-    update_config does a recursive deep-merge so a dict patch can't remove
-    keys from a nested dict. We bypass it by mutating the in-memory state
-    directly, then call update_config with an empty patch to persist."""
-    with _config_mod._LOCK:
-        if _config_mod._STATE["config"] is None:
-            _config_mod.load_config()
-        cfg = _config_mod._STATE["config"]
-        if "pose_3d" not in cfg or not isinstance(cfg["pose_3d"], dict):
-            cfg["pose_3d"] = {}
-        cfg["pose_3d"]["named_poses"] = poses
-    update_config({})  # persist to disk
-
-
 class WristPose(BaseModel):
     position: list[float]
     quaternion: list[float]
@@ -141,7 +125,7 @@ def put_pose(name: str, req: NamedPose) -> dict[str, Any]:
     cfg = get_config().get("pose_3d", {}) or {}
     poses = dict(cfg.get("named_poses") or {})
     poses[name] = pose
-    _replace_named_poses(poses)
+    set_config_value(["pose_3d", "named_poses"], poses)
     return {"name": name, "pose": pose}
 
 
@@ -153,5 +137,5 @@ def delete_pose(name: str) -> dict[str, Any]:
     if name not in poses:
         raise HTTPException(status_code=404, detail=f"pose '{name}' non trovata")
     del poses[name]
-    _replace_named_poses(poses)
+    set_config_value(["pose_3d", "named_poses"], poses)
     return {"deleted": name}

src/presa_mano/config.py

@@ -63,6 +63,36 @@ def update_config(patch: dict[str, Any]) -> dict[str, Any]:
         return deepcopy(merged)
 
 
+def set_config_value(path: list[str], value: Any) -> dict[str, Any]:
+    """Set a value at a nested path in config, REPLACING the existing value
+    (unlike update_config which deep-merges). Useful when you need to wholesale
+    replace a dict (e.g., to remove keys not present in the new value).
+
+    Example:
+        set_config_value(["pose_3d", "named_poses"], {"a": {...}, "b": {...}})
+
+    Walks the path creating intermediate dicts if missing. Persists to disk.
+    Returns the new full config (deep-copied)."""
+    if not path:
+        raise ValueError("path must be a non-empty list of keys")
+    with _LOCK:
+        if _STATE["config"] is None:
+            load_config()
+        cfg = _STATE["config"]
+        node = cfg
+        for key in path[:-1]:
+            child = node.get(key)
+            if not isinstance(child, dict):
+                child = {}
+                node[key] = child
+            node = child
+        node[path[-1]] = value
+        if _STATE["path"]:
+            with open(_STATE["path"], "w") as f:
+                yaml.safe_dump(cfg, f, sort_keys=False)
+        return deepcopy(cfg)
+
+
 def _deep_merge(base: dict[str, Any], patch: dict[str, Any]) -> dict[str, Any]:
     out = deepcopy(base)
     for k, v in patch.items():

tests/test_config_set_value.py

@@ -0,0 +1,45 @@
+"""Unit test for config.set_config_value (replaces, doesn't merge)."""
+from __future__ import annotations
+
+import yaml
+
+from presa_mano.config import (
+    set_config_value,
+    get_config,
+    load_config,
+    _STATE,
+    _default_config_path,
+)
+
+
+def test_replace_nested_dict_removes_old_keys(tmp_path, monkeypatch):
+    cfg_file = tmp_path / "cfg.yaml"
+    cfg_file.write_text(yaml.safe_dump({
+        "section": {"items": {"a": 1, "b": 2}},
+    }))
+    monkeypatch.setenv("PRESA_MANO_CONFIG", str(cfg_file))
+    # Reset in-memory singleton
+    _STATE["config"] = None
+    _STATE["path"] = None
+    load_config()
+
+    set_config_value(["section", "items"], {"c": 3})
+
+    out = get_config()
+    assert out["section"]["items"] == {"c": 3}
+    # File on disk also updated
+    on_disk = yaml.safe_load(cfg_file.read_text())
+    assert on_disk["section"]["items"] == {"c": 3}
+
+
+def test_create_intermediate_dicts(tmp_path, monkeypatch):
+    cfg_file = tmp_path / "cfg.yaml"
+    cfg_file.write_text(yaml.safe_dump({}))
+    monkeypatch.setenv("PRESA_MANO_CONFIG", str(cfg_file))
+    _STATE["config"] = None
+    _STATE["path"] = None
+    load_config()
+
+    set_config_value(["a", "b", "c"], 42)
+
+    assert get_config() == {"a": {"b": {"c": 42}}}