feat(explain): a click on a plan node shows every field the driver reported (#1164)

lib/features/workspace/plan_tree_view.dart

@@ -3,14 +3,23 @@ import 'package:querya_desktop/features/workspace/query_plan.dart';
 import 'package:querya_desktop/shared/widgets/widgets.dart';
 
 /// The plan as a tree, top-down. The node with the largest own cost is
-/// highlighted; each node shows its share of the total cost as a bar.
-class PlanTreeView extends material.StatelessWidget {
+/// highlighted; each node shows its share of the total cost as a bar. A click
+/// on a node shows every field the driver reported for it.
+class PlanTreeView extends material.StatefulWidget {
   const PlanTreeView({super.key, required this.root});
 
   final PlanNode root;
 
+  @override
+  material.State<PlanTreeView> createState() => _PlanTreeViewState();
+}
+
+class _PlanTreeViewState extends material.State<PlanTreeView> {
+  PlanNode? _selected;
+
   @override
   material.Widget build(material.BuildContext context) {
+    final root = widget.root;
     final hottest = QueryPlanParser.hottest(root);
     final total = root.cost ?? _sumOwn(root);
     final rows = <material.Widget>[];
@@ -19,19 +28,25 @@ class PlanTreeView extends material.StatelessWidget {
         node: node,
         depth: depth,
         hottest: identical(node, hottest),
+        selected: identical(node, _selected),
         total: total,
+        onTap: () => setState(() => _selected = identical(node, _selected) ? null : node),
       ));
       for (final child in node.children) {
         add(child, depth + 1);
       }
     }
 
     add(root, 0);
+    final selected = _selected;
     return material.SingleChildScrollView(
       padding: const material.EdgeInsets.all(8),
       child: material.Column(
         crossAxisAlignment: material.CrossAxisAlignment.start,
-        children: rows,
+        children: [
+          ...rows,
+          if (selected != null) _DetailsPanel(node: selected),
+        ],
       ),
     );
   }
@@ -50,13 +65,17 @@ class _PlanRow extends material.StatelessWidget {
     required this.node,
     required this.depth,
     required this.hottest,
+    required this.selected,
     required this.total,
+    required this.onTap,
   });
 
   final PlanNode node;
   final int depth;
   final bool hottest;
+  final bool selected;
   final double total;
+  final material.VoidCallback onTap;
 
   @override
   material.Widget build(material.BuildContext context) {
@@ -69,13 +88,20 @@ class _PlanRow extends material.StatelessWidget {
             '${node.actualRows == null ? '' : ' → ${node.actualRows!.round()}'}';
     return material.Padding(
       padding: material.EdgeInsets.only(left: depth * 18.0, bottom: 6),
-      child: material.Container(
+      child: material.GestureDetector(
+        behavior: material.HitTestBehavior.opaque,
+        onTap: onTap,
+        child: material.Container(
         padding: const material.EdgeInsets.symmetric(horizontal: 10, vertical: 6),
         decoration: material.BoxDecoration(
           color: hottest ? wb.accent.withValues(alpha: 0.12) : null,
           border: material.Border.all(
-            color: hottest ? wb.accent : wb.borderSubtle,
-            width: hottest ? 1.5 : 1,
+            color: selected
+                ? Theme.of(context).colorScheme.foreground
+                : hottest
+                    ? wb.accent
+                    : wb.borderSubtle,
+            width: hottest || selected ? 1.5 : 1,
           ),
           borderRadius: material.BorderRadius.circular(6),
         ),
@@ -107,6 +133,57 @@ class _PlanRow extends material.StatelessWidget {
             ],
           ],
         ),
+        ),
+      ),
+    );
+  }
+}
+
+/// Every field the driver reported for a node, in the order it reported them.
+class _DetailsPanel extends material.StatelessWidget {
+  const _DetailsPanel({required this.node});
+
+  final PlanNode node;
+
+  @override
+  material.Widget build(material.BuildContext context) {
+    final wb = context.workbench;
+    final fields = <String, String>{
+      'Operation': node.operation,
+      if (node.relation != null) 'Relation': node.relation!,
+      if (node.estimatedRows != null)
+        'Estimated rows': '${node.estimatedRows!.round()}',
+      if (node.actualRows != null) 'Actual rows': '${node.actualRows!.round()}',
+      if (node.cost != null) 'Cost': node.cost!.toStringAsFixed(2),
+      if (node.ownCost != null) 'Own cost': node.ownCost!.toStringAsFixed(2),
+      ...node.details,
+    };
+    return material.Container(
+      margin: const material.EdgeInsets.only(top: 8),
+      padding: const material.EdgeInsets.all(10),
+      decoration: material.BoxDecoration(
+        border: material.Border.all(color: wb.borderSubtle),
+        borderRadius: material.BorderRadius.circular(6),
+      ),
+      child: material.Column(
+        crossAxisAlignment: material.CrossAxisAlignment.start,
+        children: [
+          for (final e in fields.entries)
+            material.Padding(
+              padding: const material.EdgeInsets.symmetric(vertical: 2),
+              child: material.Row(
+                crossAxisAlignment: material.CrossAxisAlignment.start,
+                children: [
+                  material.SizedBox(
+                    width: 140,
+                    child: material.Text(e.key,
+                        style: material.TextStyle(color: wb.mutedForeground)),
+                  ),
+                  material.Expanded(child: material.SelectableText(e.value)),
+                ],
+              ),
+            ),
+        ],
       ),
     );
   }

test/features/workspace/plan_tree_view_test.dart

@@ -0,0 +1,47 @@
+import 'package:flutter/material.dart' as material;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/features/workspace/plan_tree_view.dart';
+import 'package:querya_desktop/features/workspace/query_plan.dart';
+
+import '../../support/querya_theme_test_shell.dart';
+
+void main() {
+  testWidgets('a click on a plan node shows every field it reported (#1164)',
+      (t) async {
+    final root = PlanNode(
+      operation: 'Hash Join',
+      cost: 500,
+      children: [
+        PlanNode(
+          operation: 'Seq Scan',
+          relation: 'orders',
+          cost: 300,
+          details: {'Startup Cost': '0.00', 'Filter': 'paid'},
+        ),
+      ],
+    );
+    await t.pumpWidget(queryaThemeTestShell(
+      child: material.SizedBox(
+        width: 600,
+        height: 600,
+        child: PlanTreeView(root: root),
+      ),
+    ));
+    await t.pump();
+
+    expect(find.text('Seq Scan'), findsOneWidget);
+    expect(find.text('Filter'), findsNothing);
+
+    // The name shows again in the panel, so tap the tree row (the first one).
+    await t.tap(find.text('Seq Scan').first);
+    await t.pump();
+    expect(find.text('Filter'), findsOneWidget);
+    expect(find.text('paid'), findsOneWidget);
+    expect(find.text('Startup Cost'), findsOneWidget);
+
+    // A second click closes the details again.
+    await t.tap(find.text('Seq Scan').first);
+    await t.pump();
+    expect(find.text('Filter'), findsNothing);
+  });
+}