[SuperEditor][AttributedText] Fix placeholder breaking attribution behavior (Resolves #2565) (#2566)

Author: angelosilvestre

attributed_text/lib/src/attributed_text.dart

@@ -421,16 +421,20 @@ class AttributedText {
     final textEndCopyOffset =
         (endOffset ?? length) - placeholdersBeforeStartOffset.length - placeholdersAfterStartBeforeEndOffset.length;
 
+    // The span marker offsets are based on the text with placeholders, so we need
+    // to copy the text with placeholders to ensure the span markers are correct.
+    final textWithPlaceholders = toPlainText();
+
     // Note: -1 because copyText() uses an exclusive `start` and `end` but
     // _copyAttributionRegion() uses an inclusive `start` and `end`.
-    final startCopyOffset = startOffset < _text.length ? startOffset : _text.length - 1;
+    final startCopyOffset = startOffset < textWithPlaceholders.length ? startOffset : textWithPlaceholders.length - 1;
     int endCopyOffset;
     if (endOffset == startOffset) {
       endCopyOffset = startCopyOffset;
     } else if (endOffset != null) {
       endCopyOffset = endOffset - 1;
     } else {
-      endCopyOffset = _text.length - 1;
+      endCopyOffset = textWithPlaceholders.length - 1;
     }
     _log.fine('offsets, start: $startCopyOffset, end: $endCopyOffset');
 

attributed_text/test/attributed_text_placeholders_test.dart

@@ -440,6 +440,46 @@ void main() {
           }),
         );
       });
+
+      test("empty text with leading placeholder (with attributions)", () {
+        // Create an empty text containing a placeholder with an attribution around it.
+        final text = AttributedText(
+          '',
+          AttributedSpans(
+            attributions: [
+              const SpanMarker(
+                attribution: _bold,
+                offset: 0,
+                markerType: SpanMarkerType.start,
+              ),
+              const SpanMarker(
+                attribution: _bold,
+                offset: 0,
+                markerType: SpanMarkerType.end,
+              ),
+            ],
+          ),
+          {
+            0: const _FakePlaceholder('leading'),
+          },
+        );
+
+        expect(
+          text.copyText(0),
+          AttributedText(
+            "",
+            AttributedSpans(
+              attributions: const [
+                SpanMarker(attribution: _bold, offset: 0, markerType: SpanMarkerType.start),
+                SpanMarker(attribution: _bold, offset: 0, markerType: SpanMarkerType.end),
+              ],
+            ),
+            {
+              0: const _FakePlaceholder("leading"),
+            },
+          ),
+        );
+      });
     });
 
     group("copy and append >", () {

super_editor/test/super_editor/text_entry/inline_widgets_test.dart

@@ -133,6 +133,58 @@ void main() {
         ),
       );
     });
+
+    testWidgetsOnArbitraryDesktop("can insert an inline widget with attributions in an empty paragraph",
+        (tester) async {
+      final editor = await _pumpScaffold(tester);
+
+      // Insert an empty text containing a placeholder with an attribution around it.
+      editor.execute([
+        InsertStyledTextAtCaretRequest(
+          AttributedText(
+              '',
+              AttributedSpans(
+                attributions: [
+                  const SpanMarker(
+                    attribution: _emojiAttribution,
+                    offset: 0,
+                    markerType: SpanMarkerType.start,
+                  ),
+                  const SpanMarker(
+                    attribution: _emojiAttribution,
+                    offset: 0,
+                    markerType: SpanMarkerType.end,
+                  ),
+                ],
+              ),
+              {
+                0: const _TestPlaceholder(),
+              }),
+        ),
+      ]);
+      await tester.pump();
+
+      // Ensure we can type after the inline placeholder was added.
+      await tester.typeImeText('hello');
+
+      // Ensure the inline widget was kept, the text was inserted, and the attribution
+      // was not applied to the inserted characters.
+      expect(
+        SuperEditorInspector.findTextInComponent('1'),
+        AttributedText(
+          'hello',
+          AttributedSpans(
+            attributions: const [
+              SpanMarker(attribution: _emojiAttribution, offset: 0, markerType: SpanMarkerType.start),
+              SpanMarker(attribution: _emojiAttribution, offset: 0, markerType: SpanMarkerType.end),
+            ],
+          ),
+          {
+            0: const _TestPlaceholder(),
+          },
+        ),
+      );
+    });
   });
 }
 
@@ -165,3 +217,5 @@ Widget? _buildInlineTestWidget(BuildContext context, TextStyle style, Object pla
 class _TestPlaceholder {
   const _TestPlaceholder();
 }
+
+const _emojiAttribution = NamedAttribution('emoji');