[FIX] The DataFrame is empty when no CDR method is selected.

tabs/tab1_inputs.py

@@ -289,8 +289,8 @@ def dialog_add_custom_resource(cost_sliders, edit_index: int | None = None, pres
             errors.append(f"**{batch_name}** already exists. Choose a different name.")
         if not batch_amount or batch_amount <= 0:
             errors.append("Available amount must be greater than 0.")
-        # if not method_configs:
-        #     errors.append("Select at least one CDR method.")
+        if not method_configs and not secondary_related:
+            errors.append("Select at least one CDR method.")
         for m, c in method_configs.items():
             if any(v is None for v in [c["min"], c["median"], c["max"]]):
                 errors.append(f"**{m}**: all coefficient fields (min, median, max) are required.")
@@ -496,18 +496,33 @@ def render_custom_batch_inline(global_idx, batch, cost_sliders, unit):
             }
             for m, c in batch["methods"].items()
         ]
-        st.dataframe(
-            pd.DataFrame(rows),
-            width='stretch',
-            hide_index=True,
-            key=f"batch_editor_{global_idx}",
-            column_config={
-                "Method": st.column_config.TextColumn(disabled=True),
-                col_min: st.column_config.NumberColumn(format="%.4f", min_value=0.0),
-                col_med: st.column_config.NumberColumn(format="%.4f", min_value=0.0),
-                col_max: st.column_config.NumberColumn(format="%.4f", min_value=0.0),
-            },
-        )
+        if rows:
+            st.dataframe(
+                pd.DataFrame(rows),
+                width='stretch',
+                hide_index=True,
+                key=f"batch_editor_{global_idx}",
+                column_config={
+                    "Method": st.column_config.TextColumn(disabled=True),
+                    col_min: st.column_config.NumberColumn(format="%.4f", min_value=0.0),
+                    col_med: st.column_config.NumberColumn(format="%.4f", min_value=0.0),
+                    col_max: st.column_config.NumberColumn(format="%.4f", min_value=0.0),
+                },
+            )
+        else:
+            secondary_methods = [
+                m for m in cost_sliders
+                if (m, batch["group"]) in secondary_resources
+            ]
+            if secondary_methods:
+                methods_list = ", ".join(f"**{m}**" for m in secondary_methods)
+                st.caption(
+                    f"*No CDR methods selected.*\n\n"
+                    f"This resource is available as an optional input for: {methods_list}.\n\n"
+                    f"Go to the **Resource Coefficients** tab to enable this resource for any of the methods above."
+                )
+            else:
+                st.caption("No CDR methods selected.")
 
         with st.container(key=f"container-button-{global_idx}"):
             if st.button("Delete", key=f"del_batch_{global_idx}",
@@ -720,7 +735,7 @@ def render_tab(cost_sliders):
 
                         if secondary_for_r:
                             st.caption(
-                                "Secondary methods that can be added in the **Resource Coefficient** tab:\n\n"
+                                "The following methods use this resource as secondary and may be assigned later in the **Resource Coefficients** tab:\n\n"
                                 + "\n".join(f"- {m}" for m in secondary_for_r)
                             )