[SuperEditor] Limit tag expansion to caret position (Resolves #2240, #2241, #2242)

super_editor/lib/src/default_editor/text.dart

@@ -1396,9 +1396,12 @@ class RemoveTextAttributionsCommand extends EditCommand {
 
         startOffset = (normalizedRange.start.nodePosition as TextPosition).offset;
 
-        // -1 because TextPosition's offset indexes the character after the
-        // selection, not the final character in the selection.
-        endOffset = (normalizedRange.end.nodePosition as TextPosition).offset - 1;
+        endOffset = normalizedRange.start != normalizedRange.end
+            // -1 because TextPosition's offset indexes the character after the
+            // selection, not the final character in the selection.
+            ? (normalizedRange.end.nodePosition as TextPosition).offset - 1
+            // The selection is collapsed. Don't decrement the offset.
+            : startOffset;
       } else if (textNode == nodes.first) {
         // Handle partial node selection in first node.
         editorDocLog.info(' - selecting part of the first node: ${textNode.id}');

super_editor/lib/src/default_editor/text_tokenizing/action_tags.dart

@@ -1,4 +1,7 @@
+import 'dart:math';
+
 import 'package:attributed_text/attributed_text.dart';
+import 'package:characters/characters.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:super_editor/src/core/document.dart';
@@ -132,12 +135,14 @@ class SubmitComposingActionTagCommand extends EditCommand {
 
     final textNode = document.getNodeById(extent.nodeId) as TextNode;
 
-    final tagAroundPosition = TagFinder.findTagAroundPosition(
+    final normalizedSelection = composer.selection!.normalize(document);
+    final tagAroundPosition = _findTag(
       // TODO: deal with these tag rules in requests and commands, should the user really pass them?
       tagRule: defaultActionTagRule,
       nodeId: composer.selection!.extent.nodeId,
       text: textNode.text,
       expansionPosition: extentPosition,
+      endPosition: normalizedSelection.end.nodePosition,
       isTokenCandidate: (attributions) => !attributions.contains(actionTagCancelledAttribution),
     );
 
@@ -214,23 +219,26 @@ class CancelComposingActionTagCommand extends EditCommand {
     TagAroundPosition? composingToken;
     TextNode? textNode;
 
+    final normalizedSelection = selection.normalize(document);
     if (base.nodePosition is TextNodePosition) {
       textNode = document.getNodeById(selection.base.nodeId) as TextNode;
-      composingToken = TagFinder.findTagAroundPosition(
+      composingToken = _findTag(
         tagRule: _tagRule,
         nodeId: textNode.id,
         text: textNode.text,
         expansionPosition: base.nodePosition as TextNodePosition,
+        endPosition: normalizedSelection.end.nodePosition,
         isTokenCandidate: (tokenAttributions) => tokenAttributions.contains(actionTagComposingAttribution),
       );
     }
     if (composingToken == null && extent.nodePosition is TextNodePosition) {
       textNode = document.getNodeById(selection.extent.nodeId) as TextNode;
-      composingToken = TagFinder.findTagAroundPosition(
+      composingToken = _findTag(
         tagRule: _tagRule,
         nodeId: textNode.id,
         text: textNode.text,
         expansionPosition: base.nodePosition as TextNodePosition,
+        endPosition: normalizedSelection.end.nodePosition,
         isTokenCandidate: (tokenAttributions) => tokenAttributions.contains(actionTagComposingAttribution),
       );
     }
@@ -300,23 +308,27 @@ class ActionTagComposingReaction extends EditReaction {
     TagAroundPosition? tagAroundPosition;
     TextNode? textNode;
 
+    final normalizedSelection = selection.normalize(document);
+
     if (base.nodePosition is TextNodePosition) {
       textNode = document.getNodeById(selection.base.nodeId) as TextNode;
-      tagAroundPosition = TagFinder.findTagAroundPosition(
+      tagAroundPosition = _findTag(
         tagRule: _tagRule,
         nodeId: textNode.id,
         text: textNode.text,
         expansionPosition: base.nodePosition as TextNodePosition,
+        endPosition: normalizedSelection.end.nodePosition,
         isTokenCandidate: (attributions) => !attributions.contains(actionTagCancelledAttribution),
       );
     }
     if (tagAroundPosition == null && extent.nodePosition is TextNodePosition) {
       textNode = document.getNodeById(selection.extent.nodeId) as TextNode;
-      tagAroundPosition = TagFinder.findTagAroundPosition(
+      tagAroundPosition = _findTag(
         tagRule: _tagRule,
         nodeId: textNode.id,
         text: textNode.text,
         expansionPosition: extent.nodePosition as TextNodePosition,
+        endPosition: normalizedSelection.end.nodePosition,
         isTokenCandidate: (attributions) => !attributions.contains(actionTagCancelledAttribution),
       );
     }
@@ -455,6 +467,91 @@ class ActionTagComposingReaction extends EditReaction {
   }
 }
 
+/// Finds a tag that touches the given [expansionPosition], constaining it
+/// to not cross the [endPosition].
+///
+/// If [endPosition] is not a `TextNodePosition`, it will be ignored .
+TagAroundPosition? _findTag({
+  required TagRule tagRule,
+  required String nodeId,
+  required AttributedText text,
+  required TextNodePosition expansionPosition,
+  required NodePosition endPosition,
+  required bool Function(Set<Attribution> tokenAttributions) isTokenCandidate,
+}) {
+  final rawText = text.text;
+  if (rawText.isEmpty) {
+    return null;
+  }
+
+  int splitIndex = min(expansionPosition.offset, rawText.length);
+  splitIndex = max(splitIndex, 0);
+
+  final endOffset = endPosition is TextNodePosition ? endPosition.offset : null;
+
+  // Create 2 splits of characters to navigate upstream and downstream the caret position.
+  // ex: "this is a very|long string"
+  // -> split around the caret into charactersBefore="this is a very" and charactersAfter="long string"
+  final charactersBefore = rawText.substring(0, splitIndex).characters;
+  final iteratorUpstream = charactersBefore.iteratorAtEnd;
+
+  final charactersAfter = rawText.substring(splitIndex, endOffset).characters;
+  final iteratorDownstream = charactersAfter.iterator;
+
+  if (charactersBefore.isNotEmpty && tagRule.excludedCharacters.contains(charactersBefore.last)) {
+    // The character where we're supposed to begin our expansion is a
+    // character that's not allowed in a tag. Therefore, no tag exists
+    // around the search offset.
+    return null;
+  }
+
+  // Move upstream until we find the trigger character or an excluded character.
+  while (iteratorUpstream.moveBack()) {
+    final currentCharacter = iteratorUpstream.current;
+    if (tagRule.excludedCharacters.contains(currentCharacter)) {
+      // The upstream character isn't allowed to appear in a tag. end the search.
+      return null;
+    }
+
+    if (currentCharacter == tagRule.trigger) {
+      // The character we are reading is the trigger.
+      // We move the iteratorUpstream one last time to include the trigger in the tokenRange and stop looking any further upstream
+      iteratorUpstream.moveBack();
+      break;
+    }
+  }
+
+  // Move downstream the caret position until we find excluded character or reach the end of the text.
+  while (iteratorDownstream.moveNext()) {
+    final current = iteratorDownstream.current;
+    if (tagRule.excludedCharacters.contains(current)) {
+      break;
+    }
+  }
+
+  final tokenStartOffset = splitIndex - iteratorUpstream.stringAfterLength;
+  final tokenRange = SpanRange(tokenStartOffset, splitIndex + iteratorDownstream.stringBeforeLength);
+
+  final tagText = text.substringInRange(tokenRange);
+  if (!tagText.startsWith(tagRule.trigger)) {
+    return null;
+  }
+
+  final tokenAttributions = text.getAttributionSpansInRange(attributionFilter: (a) => true, range: tokenRange);
+  if (!isTokenCandidate(tokenAttributions.map((span) => span.attribution).toSet())) {
+    return null;
+  }
+
+  return TagAroundPosition(
+    indexedTag: IndexedTag(
+      Tag(tagRule.trigger, tagText.substring(1)),
+      nodeId,
+      tokenStartOffset,
+    ),
+    searchOffset: expansionPosition.offset,
+  );
+}
+
 const _composingActionTagKey = "composing_action_tag";
 
 extension on EditContext {

super_editor/lib/src/default_editor/text_tokenizing/tags.dart

@@ -283,6 +283,9 @@ class IndexedTag {
   /// The [DocumentRange] from [start] to [end].
   DocumentRange get range => DocumentRange(start: start, end: end);
 
+  /// The length of the [tag]'s text.
+  int get length => tag.raw.length;
+
   /// Collects and returns all attributions in this tag's [TextNode], between the
   /// [start] of the tag and the [end] of the tag.
   AttributedSpans computeTagSpans(Document document) =>