Implement caching in AiidaNodeViewWidget

aiidalab_widgets_base/static/styles/global.css

@@ -0,0 +1,7 @@
+.aiida-node-view-widget {
+  border: var(--jp-widgets-border-width) solid var(--jp-border-color1);
+  padding: 12px;
+  margin: 2px;
+  height: auto;
+  width: auto;
+}

aiidalab_widgets_base/viewers.py

@@ -24,6 +24,7 @@
 from matplotlib.colors import to_rgb
 
 from .dicts import RGB_COLORS, Colors, Radius
+from .loaders import LoadingWidget
 from .misc import CopyToClipboardButton, ReversePolishNotation
 from .utils import ase2spglib, list_to_string_range, string_range_to_list
 
@@ -67,20 +68,29 @@ class AiidaNodeViewWidget(ipw.VBox):
 
     def __init__(self, **kwargs):
         self._output = ipw.Output()
-        super().__init__(
-            children=[
-                self._output,
-            ],
-            **kwargs,
-        )
+        self.node_views = {}
+        self.node_view_loading_message = LoadingWidget("Loading node view")
+        super().__init__(**kwargs)
+        self.add_class("aiida-node-view-widget")
 
     @tl.observe("node")
     def _observe_node(self, change):
-        if change["new"] != change["old"]:
+        if not ((node := change["new"]) and node != change["old"]):
+            return
+        if node.uuid in self.node_views:
+            self.children = [self.node_views[node.uuid]]
+            return
+        self.children = [self.node_view_loading_message]
+        node_view = viewer(node)
+        if isinstance(node_view, ipw.DOMWidget):
+            self.node_views[node.uuid] = node_view
+            self.children = [node_view]
+        else:
             with self._output:
                 clear_output()
                 if change["new"]:
-                    display(viewer(change["new"]))
+                    display(node_view)
+            self.children = [self._output]
 
 
 @register_viewer_widget("data.core.dict.Dict.")

tests/test_loaders.py

@@ -1,5 +1,6 @@
 from pathlib import Path
 
+from aiidalab_widgets_base.loaders import LoadingWidget
 from aiidalab_widgets_base.utils.loaders import load_css
 
 
@@ -8,3 +9,12 @@ def test_load_css():
     css_dir = Path("aiidalab_widgets_base/static/styles")
     load_css(css_path=css_dir)
     load_css(css_path=css_dir / "global.css")
+
+
+def test_loading_widget():
+    """Test `LoadingWidget`."""
+    widget = LoadingWidget(message="Loading some widget")
+    assert widget.message.value == "Loading some widget"
+    assert widget.children[0].value == "Loading some widget"
+    assert widget.children[1].value == "<i class='fa fa-spinner fa-spin fa-2x fa-fw'/>"
+    assert "loading" in widget._dom_classes

tests/test_viewers.py

@@ -313,3 +313,31 @@ def __init__(self, node=None):
         "Viewer is not an instance of the expected viewer class."
     )
     assert viewer.node == process, "Viewer's node does not match the test process node."
+
+
+def test_node_view_for_non_widget_viewer():
+    """Test that a node with no registered viewer is displayed in an output widget"""
+    import sys
+    from io import StringIO
+
+    # Intercepting stdout because `ipw.Output` does not
+    # store outputs in non-interactive environments.
+    captured = StringIO()
+    sys.stdout = captured
+
+    node_view = viewers.AiidaNodeViewWidget()
+    node = orm.Int(1)
+    node_view.node = node
+    assert node_view.children[0] is node_view._output
+    assert str(node) in sys.stdout.getvalue()
+
+
+def test_node_view_caching():
+    """Test that providing a given node a second time returns the cached viewer."""
+    node_view = viewers.AiidaNodeViewWidget()
+    node = orm.Int(1)
+    node_view.node = node
+    viewer = node_view.children[0]
+    node_view.node = None
+    node_view.node = node
+    assert node_view.children[0] is viewer