some fixes, need proper tests now

CHANGELOG.rst

@@ -104,11 +104,17 @@ Native multi agents support:
 - [FIXED] issue https://github.com/Grid2op/grid2op/issues/657
 - [FIXED] missing an import on the `MaskedEnvironment` class
 - [FIXED] a bug when trying to set the load_p, load_q, gen_p, gen_v by names.
+- [FIXED] the `obs.get_forecast_env` : in some cases the resulting first
+  observation (obtained from `for_env.reset()`) did not have the correct
+  topology.
 - [ADDED] possibility to set the "thermal limits" when calling `env.reset(..., options={"thermal limit": xxx})`
 - [ADDED] possibility to retrieve some structural information about elements with
   with `gridobj.get_line_info(...)`, `gridobj.get_load_info(...)`, `gridobj.get_gen_info(...)` 
   or , `gridobj.get_storage_info(...)` 
 - [ADDED] codacy badge on the readme
+- [ADDED] a method to check the KCL (`obs.check_kirchoff`) directly from the observation
+  (previously it was only possible to do it from the backend). This should 
+  be used for testing purpose only
 - [IMPROVED] possibility to set the injections values with names
   to be consistent with other way to set the actions (*eg* set_bus)
 - [IMPROVED] error messages when creating an action which changes the injections
@@ -122,6 +128,8 @@ Native multi agents support:
 - [IMPROVED] the classes inherited from `GreedyAgent` with the added possibility to 
   do the `obs.simulate` on a different time horizon (kwarg `simulated_time_step`)
 - [IMPROVED] some type hints for some agent class
+- [IMPROVED] the `backend.update_from_obs` function to work even when observation
+  does not have shunt information but there are not shunts on the grid.
 
 [1.10.4] - 2024-10-15
 -------------------------

grid2op/Backend/backend.py

@@ -2027,7 +2027,7 @@ def update_from_obs(self,
         }
 
         if cls.shunts_data_available and type(obs).shunts_data_available:
-            if "_shunt_bus" not in type(obs).attr_list_set:
+            if cls.n_shunt > 0 and "_shunt_bus" not in type(obs).attr_list_set:
                 raise BackendError(
                     "Impossible to set the backend to the state given by the observation: shunts data "
                     "are not present in the observation."

grid2op/Environment/environment.py

@@ -947,6 +947,10 @@ def reset_grid(self,
 
         self._backend_action = self._backend_action_class()
         self.nb_time_step = -1  # to have init obs at step 1 (and to prevent 'setting to proper state' "action" to be illegal)
+
+        if self._init_obs is not None:
+            self.backend.update_from_obs(self._init_obs)
+
         init_action = None
         if not self._parameters.IGNORE_INITIAL_STATE_TIME_SERIE:
             # load the initial state from the time series (default)
@@ -1293,7 +1297,6 @@ def reset(self,
             if ambiguous:
                 raise Grid2OpException("You provided an invalid (ambiguous) action to set the 'init state'") from except_tmp
             init_state.remove_change()
-
         super().reset(seed=seed, options=options)
 
         if options is not None and "max step" in options:                

grid2op/Observation/baseObservation.py

@@ -4845,3 +4845,174 @@ def get_back_to_ref_state(
         if self._is_done:
             raise Grid2OpException("Cannot use this function in a 'done' state.")
         return self.action_helper.get_back_to_ref_state(self, storage_setpoint, precision)
+
+    def _aux_kcl(self,
+                 n_el, # cst eg. cls.n_gen
+                 el_to_subid, # cst eg. cls.gen_to_subid
+                 el_bus,  # cst eg. gen_bus
+                 el_p,  # cst, eg. gen_p
+                 el_q,  # cst, eg. gen_q
+                 el_v,  # cst, eg. gen_v
+                 p_subs, q_subs,
+                 p_bus, q_bus,
+                 v_bus,
+                 load_conv=True  # whether the object is load convention (True) or gen convention (False)
+                 ):
+
+        # bellow i'm "forced" to do a loop otherwise, numpy do not compute the "+=" the way I want it to.
+        # for example, if two powerlines are such that line_or_to_subid is equal (eg both connected to substation 0)
+        # then numpy do not guarantee that `p_subs[self.line_or_to_subid] += p_or` will add the two "corresponding p_or"
+        # TODO this can be vectorized with matrix product, see example in obs.flow_bus_matrix (BaseObervation.py)
+        for i in range(n_el):
+            psubid = el_to_subid[i]
+            if el_bus[i] == -1:
+                # el is disconnected
+                continue
+
+            # for substations
+            if load_conv:
+                p_subs[psubid] += el_p[i]
+                q_subs[psubid] += el_q[i]
+            else:
+                p_subs[psubid] -= el_p[i]
+                q_subs[psubid] -= el_q[i]
+
+            # for bus
+            loc_bus = el_bus[i] - 1
+            if load_conv:
+                p_bus[psubid, loc_bus] += el_p[i]
+                q_bus[psubid, loc_bus] += el_q[i]
+            else:
+                p_bus[psubid, loc_bus] -= el_p[i]
+                q_bus[psubid, loc_bus] -= el_q[i]
+
+            # compute max and min values
+            if el_v[i]:
+                # but only if gen is connected
+                v_bus[psubid, loc_bus][0] = min(
+                    v_bus[psubid, loc_bus][0],
+                    el_v[i],
+                )
+                v_bus[psubid, loc_bus][1] = max(
+                    v_bus[psubid, loc_bus][1],
+                    el_v[i],
+                )
+
+    def check_kirchoff(self) -> Tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray, np.ndarray]:
+        """
+        Analogous to "backend.check_kirchoff" but from the observation
+
+        .. versionadded:: 1.11.0
+        
+        Returns
+        -------
+        p_subs ``numpy.ndarray``
+            sum of injected active power at each substations (MW)
+        q_subs ``numpy.ndarray``
+            sum of injected reactive power at each substations (MVAr)
+        p_bus ``numpy.ndarray``
+            sum of injected active power at each buses. It is given in form of a matrix, with number of substations as
+            row, and number of columns equal to the maximum number of buses for a substation (MW)
+        q_bus ``numpy.ndarray``
+            sum of injected reactive power at each buses. It is given in form of a matrix, with number of substations as
+            row, and number of columns equal to the maximum number of buses for a substation (MVAr)
+        diff_v_bus: ``numpy.ndarray`` (2d array)
+            difference between maximum voltage and minimum voltage (computed for each elements)
+            at each bus. It is an array of two dimension:
+
+            - first dimension represents the the substation (between 1 and self.n_sub)
+            - second element represents the busbar in the substation (0 or 1 usually)
+
+        """
+        cls = type(self)
+
+        # fist check the "substation law" : nothing is created at any substation
+        p_subs = np.zeros(cls.n_sub, dtype=dt_float)
+        q_subs = np.zeros(cls.n_sub, dtype=dt_float)
+
+        # check for each bus
+        p_bus = np.zeros((cls.n_sub, cls.n_busbar_per_sub), dtype=dt_float)
+        q_bus = np.zeros((cls.n_sub, cls.n_busbar_per_sub), dtype=dt_float)
+        v_bus = (
+            np.zeros((cls.n_sub, cls.n_busbar_per_sub, 2), dtype=dt_float) - 1.0
+        )  # sub, busbar, [min,max]
+
+        self._aux_kcl(
+            cls.n_line, # cst eg. cls.n_gen
+            cls.line_or_to_subid, # cst eg. cls.gen_to_subid
+            self.line_or_bus,
+            self.p_or,  # cst, eg. gen_p
+            self.q_or,  # cst, eg. gen_q
+            self.v_or,  # cst, eg. gen_v
+            p_subs, q_subs,
+            p_bus, q_bus,
+            v_bus,
+            )
+        self._aux_kcl(
+            cls.n_line, # cst eg. cls.n_gen
+            cls.line_ex_to_subid, # cst eg. cls.gen_to_subid
+            self.line_ex_bus,
+            self.p_ex,  # cst, eg. gen_p
+            self.q_ex,  # cst, eg. gen_q
+            self.v_ex,  # cst, eg. gen_v
+            p_subs, q_subs,
+            p_bus, q_bus,
+            v_bus,
+            )
+        self._aux_kcl(
+            cls.n_load, # cst eg. cls.n_gen
+            cls.load_to_subid, # cst eg. cls.gen_to_subid
+            self.load_bus,
+            self.load_p,  # cst, eg. gen_p
+            self.load_q,  # cst, eg. gen_q
+            self.load_v,  # cst, eg. gen_v
+            p_subs, q_subs,
+            p_bus, q_bus,
+            v_bus,
+            )
+        self._aux_kcl(
+            cls.n_gen, # cst eg. cls.n_gen
+            cls.gen_to_subid, # cst eg. cls.gen_to_subid
+            self.gen_bus,  # cst eg. self.gen_bus
+            self.gen_p,  # cst, eg. gen_p
+            self.gen_q,  # cst, eg. gen_q
+            self.gen_v,  # cst, eg. gen_v
+            p_subs, q_subs,
+            p_bus, q_bus,
+            v_bus,
+            load_conv=False
+            )
+        if cls.n_storage:
+            self._aux_kcl(
+                cls.n_storage, # cst eg. cls.n_gen
+                cls.storage_to_subid, # cst eg. cls.gen_to_subid
+                self.storage_bus,
+                self.storage_p,  # cst, eg. gen_p
+                self.storage_q,  # cst, eg. gen_q
+                self.storage_v,  # cst, eg. gen_v
+                p_subs, q_subs,
+                p_bus, q_bus,
+                v_bus,
+                )
+
+        if cls.shunts_data_available:
+            self._aux_kcl(
+                cls.n_shunt, # cst eg. cls.n_gen
+                cls.storage_to_subid, # cst eg. cls.gen_to_subid
+                self._shunt_bus,
+                self._shunt_p,  # cst, eg. gen_p
+                self._shunt_q,  # cst, eg. gen_q
+                self._shunt_v,  # cst, eg. gen_v
+                p_subs, q_subs,
+                p_bus, q_bus,
+                v_bus,
+                )
+        else:
+            warnings.warn(
+                "Observation.check_kirchoff Impossible to get shunt information. Reactive information might be "
+                "incorrect."
+            )
+        diff_v_bus = np.zeros((cls.n_sub, cls.n_busbar_per_sub), dtype=dt_float)
+        diff_v_bus[:, :] = v_bus[:, :, 1] - v_bus[:, :, 0]
+        return p_subs, q_subs, p_bus, q_bus, diff_v_bus
+