[SuperEditor] Fix text duplicated when a placeholder is inserted in a text with attributions (Resolves #2595)

Author: angelosilvestre

Diff for: super_editor/lib/src/infrastructure/attributed_text_styles.dart

@@ -63,13 +63,26 @@ extension ComputeTextSpan on AttributedText {
         }
       } else {
         // This section is text. The end of this text is either the
-        // end of the AttributedText, or the index of the next placeholder.
+        // end of the current span, or the index of the next placeholder.
         contentEnd = span.end + 1;
+
+        final nextSpan = spanIndex + 1 < collapsedSpans.length //
+            ? collapsedSpans[spanIndex + 1]
+            : null;
         for (final entry in placeholders.entries) {
-          if (entry.key > start) {
-            contentEnd = entry.key;
+          if (entry.key <= start) {
+            // This placeholder is before the current span.
+            continue;
+          }
+
+          if (nextSpan != null && entry.key >= nextSpan.start) {
+            // This placeholder is beyond the next span.
             break;
           }
+
+          // This placeholder is within the current span.
+          contentEnd = entry.key;
+          break;
         }
 
         inlineSpans.add(

Diff for: super_editor/test/infrastructure/inline_span_test.dart

@@ -0,0 +1,117 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:super_editor/super_editor.dart';
+
+void main() {
+  group('SuperEditor > computeInlineSpan >', () {
+    testWidgets('does not modify text with attributions and a placeholder at the beginning', (tester) async {
+      // Pump a widget because we need a BuildContext to compute the InlineSpan.
+      await tester.pumpWidget(
+        const MaterialApp(),
+      );
+
+      // Create an AttributedText with the words "Welcome" and "SuperEditor" in bold and with a leading placeholder.
+      final text = AttributedText(
+        'Welcome to SuperEditor',
+        AttributedSpans(
+          attributions: [
+            const SpanMarker(attribution: boldAttribution, offset: 0, markerType: SpanMarkerType.start),
+            const SpanMarker(attribution: boldAttribution, offset: 6, markerType: SpanMarkerType.end),
+            const SpanMarker(attribution: boldAttribution, offset: 11, markerType: SpanMarkerType.start),
+            const SpanMarker(attribution: boldAttribution, offset: 21, markerType: SpanMarkerType.end),
+          ],
+        ),
+        {0: const _ExamplePlaceholder()},
+      );
+
+      final inlineSpan = text.computeInlineSpan(
+        find.byType(MaterialApp).evaluate().first as BuildContext,
+        defaultStyleBuilder,
+        [_inlineWidgetBuilder],
+      );
+
+      // Ensure the text was not modified.
+      expect(
+        inlineSpan.toPlainText(includePlaceholders: false),
+        'Welcome to SuperEditor',
+      );
+    });
+
+    testWidgets('does not modify text with attributions and a placeholder at the middle', (tester) async {
+      // Pump a widget because we need a BuildContext to compute the InlineSpan.
+      await tester.pumpWidget(
+        const MaterialApp(),
+      );
+
+      // Create an AttributedText with the words "Welcome" and "SuperEditor" in bold and with a
+      // placeholder after the word "to".
+      final text = AttributedText(
+        'Welcome to SuperEditor',
+        AttributedSpans(
+          attributions: [
+            const SpanMarker(attribution: boldAttribution, offset: 0, markerType: SpanMarkerType.start),
+            const SpanMarker(attribution: boldAttribution, offset: 6, markerType: SpanMarkerType.end),
+            const SpanMarker(attribution: boldAttribution, offset: 11, markerType: SpanMarkerType.start),
+            const SpanMarker(attribution: boldAttribution, offset: 21, markerType: SpanMarkerType.end),
+          ],
+        ),
+        {10: const _ExamplePlaceholder()},
+      );
+
+      final inlineSpan = text.computeInlineSpan(
+        find.byType(MaterialApp).evaluate().first as BuildContext,
+        defaultStyleBuilder,
+        [_inlineWidgetBuilder],
+      );
+
+      // Ensure the text was not modified.
+      expect(
+        inlineSpan.toPlainText(includePlaceholders: false),
+        'Welcome to SuperEditor',
+      );
+    });
+
+    testWidgets('does not modify text with attributions and a placeholder at the end', (tester) async {
+      // Pump a widget because we need a BuildContext to compute the InlineSpan.
+      await tester.pumpWidget(
+        const MaterialApp(),
+      );
+
+      // Create an AttributedText with the word "Welcome" in bold and with a trailing placeholder.
+      // Create an AttributedText with the words "Welcome" and "SuperEditor" in bold and with a
+      // placeholder after the word "to".
+      final text = AttributedText(
+        'Welcome to SuperEditor',
+        AttributedSpans(
+          attributions: [
+            const SpanMarker(attribution: boldAttribution, offset: 0, markerType: SpanMarkerType.start),
+            const SpanMarker(attribution: boldAttribution, offset: 6, markerType: SpanMarkerType.end),
+            const SpanMarker(attribution: boldAttribution, offset: 11, markerType: SpanMarkerType.start),
+            const SpanMarker(attribution: boldAttribution, offset: 21, markerType: SpanMarkerType.end),
+          ],
+        ),
+        {22: const _ExamplePlaceholder()},
+      );
+
+      final inlineSpan = text.computeInlineSpan(
+        find.byType(MaterialApp).evaluate().first as BuildContext,
+        defaultStyleBuilder,
+        [_inlineWidgetBuilder],
+      );
+
+      // Ensure the text was not modified.
+      expect(
+        inlineSpan.toPlainText(includePlaceholders: false),
+        'Welcome to SuperEditor',
+      );
+    });
+  });
+}
+
+class _ExamplePlaceholder {
+  const _ExamplePlaceholder();
+}
+
+Widget? _inlineWidgetBuilder(BuildContext context, TextStyle textStyle, Object placeholder) {
+  return const SizedBox(width: 10);
+}