fix: reload dataset tables when connection changes in tabs

Extract _sync_table_catalog on TableBrowser, add demo watcher cells so
Marimo reruns the datasets panel when the connection dropdown changes,
and improve empty-state hints.

Author: eddietejeda

examples/demo.py

@@ -56,11 +56,25 @@ def _(mo):
 
 
 @app.cell
-def _(browser, editor, history, mo, recent, status, workspace):
+def _(browser):
+    # Register connection/table widget deps so Marimo reruns layout cells on change.
+    if browser._conn_pick is not None:
+        _ = browser._conn_pick.value
+    _ = browser.table_pick.value
+    return
+
+
+@app.cell
+def _(browser):
+    return (browser.ui,)
+
+
+@app.cell
+def _(browser_ui, editor, history, mo, recent, status, workspace):
     mo.ui.tabs({
         "Workspaces": workspace.ui,
         "Connections": status,
-        "Datasets": browser.ui,
+        "Datasets": browser_ui,
         "SQL query": editor.ui,
         "Recent results": recent.ui,
         "Run history": history,

hotdata_marimo/table_browser.py

@@ -43,6 +43,7 @@ def __init__(
             )
 
         self._table_pick_ctx: str | None = None
+        self._rebuilt_table_pick_this_run = False
         self._init_table_pick()
 
     def _init_table_pick(self) -> None:
@@ -53,6 +54,7 @@ def _init_table_pick(self) -> None:
             )
             self._empty_catalog = True
             self._all_names = []
+            self._table_pick_ctx = ""
             return
 
         names = self._names_for_active_connection()
@@ -120,35 +122,42 @@ def selected_table(self) -> str | None:
         v = self.table_pick.value
         return v if v else None
 
-    @property
-    def ui(self):
-        self._rebuilt_table_pick_this_run = False
-
+    def _sync_table_catalog(self) -> None:
+        """Refresh the table dropdown when the active connection changes."""
         if self._conn_pick is not None:
-            _ = self._conn_pick.value
-
+            _ = self._conn_pick.value  # type: ignore[attr-defined]
         cid = self._active_connection_id()
-        names = self._names_for_active_connection()
+        if not cid:
+            return
+        if cid == self._table_pick_ctx:
+            return
+        self._rebuild_table_pick(self._names_for_active_connection())
 
-        if cid and cid != self._table_pick_ctx:
-            self._rebuild_table_pick(names)
+    @property
+    def ui(self):
+        self._rebuilt_table_pick_this_run = False
+        self._sync_table_catalog()
 
         if not self._rebuilt_table_pick_this_run:
             _ = self.table_pick.value
 
         sel = None if self._rebuilt_table_pick_this_run else self.selected_table
+        cid = self._active_connection_id()
         conn_header = (
             mo.md(f"**Connection** `{self._active_connection_id()}`")
             if self._active_connection_id()
             else None
         )
         if not sel:
-            hint = (
-                "_No tables returned from the information schema. "
-                "Try refreshing a connection in Hotdata._"
-                if self._empty_catalog
-                else "Choose a table below (search inside the dropdown when needed)."
-            )
+            if self._conn_pick is not None and not cid:
+                hint = "Choose a connection above to load tables."
+            elif self._empty_catalog:
+                hint = (
+                    "_No tables returned from the information schema. "
+                    "Try refreshing a connection in Hotdata._"
+                )
+            else:
+                hint = "Choose a table below (search inside the dropdown when needed)."
             stack = [
                 mo.md(
                     f"**Workspace** `{self._client.workspace_id}` — {hint}"

tests/test_hotdata_marimo.py

@@ -10,6 +10,7 @@
 from hotdata_marimo._options import connection_options, unique_label_options
 from hotdata_marimo.display import connections_panel
 from hotdata_marimo.sql_engine import HotdataMarimoEngine
+from hotdata_marimo.table_browser import TableBrowser
 from hotdata_marimo.workspace_selector import WorkspaceSelector, workspace_selector_from_env
 from marimo._types.ids import VariableName
 
@@ -127,6 +128,28 @@ def test_connections_panel_lists_connections(mock_client):
     assert panel is not None
 
 
+def test_table_browser_rebuilds_tables_when_connection_changes(mock_client):
+    pick = MagicMock()
+    pick.value = ""
+    mock_client.list_qualified_table_names.return_value = []
+
+    with patch(
+        "hotdata_marimo.table_browser.resolve_connection_picker",
+        return_value=(pick, None),
+    ):
+        browser = TableBrowser(mock_client)
+
+    browser._sync_table_catalog()
+    assert browser._table_pick_ctx == ""
+
+    pick.value = "conn_1"
+    mock_client.list_qualified_table_names.return_value = ["azure.public.customer"]
+    browser._sync_table_catalog()
+    assert browser._table_pick_ctx == "conn_1"
+    assert browser._all_names == ["azure.public.customer"]
+    assert not browser._empty_catalog
+
+
 def test_workspace_selector_from_env_requires_api_key(monkeypatch: pytest.MonkeyPatch):
     monkeypatch.delenv("HOTDATA_API_KEY", raising=False)
     with pytest.raises(RuntimeError, match="HOTDATA_API_KEY"):