🚧 Add environment maneuverability

src/wago_sim/scenario/plantenv.py

@@ -23,6 +23,7 @@ constructed on an engine.
 
 from __future__ import annotations
 
+import os
 from collections.abc import Callable
 from dataclasses import dataclass, field
 from typing import TYPE_CHECKING
@@ -312,14 +313,29 @@ class PlantEnv:
 
 
 def load_env(ref: str, node: VirtualNode | None = None, *,
-             engine=None) -> PlantEnv:
+             engine=None, reload: bool = False) -> PlantEnv:
     """Load an environment from a module reference (FR-8.2.17).
 
     Accepts ``pkg.mod.ClassName``, ``pkg.mod.factory_fn`` (returns a
     PlantEnv), or a bare ``pkg.mod`` whose module defines either a
     class named ``Env`` or a function ``make_env(...)``.
+
+    ``reload=True`` (FR-10.2.17) invalidates the cached module first:
+    Python keeps modules in ``sys.modules``, so re-importing an
+    edited file would silently reuse the old class. Used by the web
+    UI's start/restart; the CLI runners start a fresh process anyway
+    and pass the default.
     """
     import importlib
+    import sys
+
+    # environments resolve from the WORKING DIRECTORY by contract
+    # (``envs/`` is not part of the installed package). A console
+    # script puts its Scripts dir — not the cwd — on sys.path, so
+    # make the cwd importable before trying (idempotent).
+    cwd = os.getcwd()
+    if cwd not in sys.path:
+        sys.path.insert(0, cwd)
 
     parts = ref.split(":")
     attr_path = None
@@ -341,6 +357,12 @@ def load_env(ref: str, node: VirtualNode | None = None, *,
                         and leaf is None):
         raise ScenarioError(f"--env {ref!r}: reference must include a module path")
 
+    if reload and mod_name in sys.modules:
+        # hot reload (FR-10.2.17): drop the cached module so the
+        # import below reads the file from disk again
+        sys.modules.pop(mod_name, None)
+        mod = None
+
     if mod is None:
         try:
             mod = importlib.import_module(mod_name)