fix(erd): a diagram with every table hidden says so, the empty state names the database (#1157)

lib/features/erd/erd_view.dart

@@ -678,14 +678,32 @@ class _ErdViewState extends material.State<ErdView> {
           onAction: _load,
         ),
       );
+    } else if (full != null && full.tables.isNotEmpty && schema!.isEmpty) {
+      // Every table was hidden from the diagram: they exist, so say so and
+      // offer them back instead of "No tables found".
+      body = material.Center(
+        child: QueryaEmptyState(
+          icon: material.Icon(material.Icons.visibility_off_outlined,
+              color: wb.mutedForeground),
+          title: 'All tables are hidden',
+          description: '${_hidden.length} '
+              '${_hidden.length == 1 ? 'table is' : 'tables are'} hidden '
+              'from the diagram.',
+          actionLabel: 'Show all tables',
+          onAction: _showAllTables,
+        ),
+      );
     } else if (schema == null || layout == null || schema.isEmpty) {
+      final db = widget.databaseName;
       body = material.Center(
         child: QueryaEmptyState(
           icon: material.Icon(material.Icons.table_chart_outlined,
               color: wb.mutedForeground),
           title: 'No tables found',
-          description:
-              'This schema has no tables, or this role cannot see them.',
+          description: db.isEmpty
+              ? 'This schema has no tables, or this role cannot see them.'
+              : 'The current schema of $db has no tables, or this role '
+                  'cannot see them.',
         ),
       );
     } else if (widget.neighbourhoodDepth != null &&

test/features/erd/erd_test.dart

@@ -749,6 +749,83 @@ void main() {
           closeTo(height, 0.5));
     });
 
+    testWidgets('Copy Mermaid puts the diagram on the clipboard', (t) async {
+      await t.binding.setSurfaceSize(const material.Size(1200, 800));
+      String? copied;
+      t.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+          SystemChannels.platform, (call) async {
+        if (call.method == 'Clipboard.setData') {
+          copied = (call.arguments as Map)['text'] as String?;
+        }
+        return null;
+      });
+      addTearDown(() => t.binding.defaultBinaryMessenger
+          .setMockMethodCallHandler(SystemChannels.platform, null));
+      await t.pumpWidget(queryaThemeTestShell(
+        child: ErdView(
+            source: SqlErdSource(delegate: delegate(), dialect: SqlDialect.sqlite)),
+      ));
+      await t.pump();
+      await t.pump();
+
+      await t.tap(find.byKey(const material.ValueKey('erd_export')));
+      await t.pump();
+      await t.tap(find.text('Copy Mermaid'));
+      await t.pump();
+      expect(copied, startsWith('erDiagram'));
+      expect(copied, contains('users ||--|{ orders'));
+      // The toast's 5 s timer starts after its entry animation: step the
+      // clock frame by frame until it has gone.
+      for (var i = 0; i < 10; i++) {
+        await t.pump(const Duration(seconds: 1));
+      }
+    });
+
+    testWidgets('hiding every table says so and offers them back',
+        variant: desktop, (t) async {
+      await t.binding.setSurfaceSize(const material.Size(1200, 800));
+      await t.pumpWidget(queryaThemeTestShell(
+        child: ErdView(
+            source: SqlErdSource(delegate: delegate(), dialect: SqlDialect.sqlite)),
+      ));
+      await t.pump();
+      await t.pump();
+
+      for (final table in ['users', 'orders']) {
+        await t.tap(find.byKey(material.ValueKey('erd_table_$table')),
+            buttons: kSecondaryButton);
+        await t.pump();
+        await t.pump(const Duration(milliseconds: 300));
+        await t.tap(find.text('Hide from diagram'));
+        // Let the menu popover close, or it takes the next tap.
+        await t.pumpAndSettle();
+      }
+      expect(find.text('All tables are hidden'), findsOneWidget);
+      expect(find.text('No tables found'), findsNothing);
+
+      await t.tap(find.text('Show all tables'));
+      await t.pump();
+      await t.pump();
+      expect(find.byKey(const material.ValueKey('erd_table_users')),
+          findsOneWidget);
+    });
+
+    testWidgets('an empty schema names the database', (t) async {
+      await t.pumpWidget(queryaThemeTestShell(
+        child: ErdView(
+          source: SqlErdSource(
+              delegate: FakeSqlExecutionDelegate(
+                  onExecute: (_) => const SqlExecutionResult()),
+              dialect: SqlDialect.postgres),
+          databaseName: 'shop',
+        ),
+      ));
+      await t.pump();
+      await t.pump();
+      expect(find.text('No tables found'), findsOneWidget);
+      expect(find.textContaining('shop'), findsOneWidget);
+    });
+
     testWidgets('a card can be dragged and Auto layout puts it back',
         (t) async {
       await t.binding.setSurfaceSize(const material.Size(1200, 800));