fix: Cleaned up whitespace processing and added whitespace tests

lib/src/builtins/styled_element_builtin.dart

@@ -429,11 +429,12 @@ class StyledElementBuiltIn extends HtmlExtension {
               .entries
               .expandIndexed((i, child) => [
                     child.value,
-                    if (i != context.styledElement!.children.length - 1 &&
+                    if (context.parser.shrinkWrap &&
+                        i != context.styledElement!.children.length - 1 &&
                         child.key.style.display == Display.block &&
                         child.key.element?.localName != "html" &&
                         child.key.element?.localName != "body")
-                      const TextSpan(text: "\n"),
+                      const TextSpan(text: "\n", style: TextStyle(fontSize: 0)),
                   ])
               .toList(),
         ),
@@ -444,14 +445,16 @@ class StyledElementBuiltIn extends HtmlExtension {
       style: context.styledElement!.style.generateTextStyle(),
       children: buildChildren()
           .entries
-          .expand((child) => [
+          .expandIndexed((index, child) => [
                 child.value,
-                if (child.key.style.display == Display.block &&
+                if (context.parser.shrinkWrap &&
+                    child.key.style.display == Display.block &&
+                    index != context.styledElement!.children.length - 1 &&
                     child.key.element?.parent?.localName != "th" &&
                     child.key.element?.parent?.localName != "td" &&
                     child.key.element?.localName != "html" &&
                     child.key.element?.localName != "body")
-                  const TextSpan(text: "\n"),
+                  const TextSpan(text: "\n", style: TextStyle(fontSize: 0)),
               ])
           .toList(),
     );

lib/src/builtins/text_builtin.dart

@@ -22,10 +22,8 @@ class TextBuiltIn extends HtmlExtension {
   StyledElement prepare(
       ExtensionContext context, List<StyledElement> children) {
     if (context.elementName == "br") {
-      return TextContentElement(
-        text: '\n',
+      return LinebreakContentElement(
         style: Style(whiteSpace: WhiteSpace.pre),
-        element: context.node as dom.Element?,
         node: context.node,
       );
     }
@@ -45,6 +43,13 @@ class TextBuiltIn extends HtmlExtension {
   @override
   InlineSpan build(ExtensionContext context,
       Map<StyledElement, InlineSpan> Function() buildChildren) {
+    if (context.styledElement is LinebreakContentElement) {
+      return TextSpan(
+        text: '\n',
+        style: context.styledElement!.style.generateTextStyle(),
+      );
+    }
+
     final element = context.styledElement! as TextContentElement;
     return TextSpan(
       style: element.style.generateTextStyle(),

lib/src/processing/whitespace.dart

@@ -6,26 +6,30 @@ import 'package:html/dom.dart' as html;
 class WhitespaceProcessing {
   /// [processWhitespace] handles the removal of unnecessary whitespace from
   /// a StyledElement tree.
+  ///
+  /// The criteria for determining which whitespace is replaceable is outlined
+  /// at https://www.w3.org/TR/css-text-3/
+  /// and summarized at https://medium.com/@patrickbrosset/when-does-white-space-matter-in-html-b90e8a7cdd33
   static StyledElement processWhitespace(StyledElement tree) {
     tree = _processInternalWhitespace(tree);
     tree = _processInlineWhitespace(tree);
+    tree = _processBlockWhitespace(tree);
     tree = _removeEmptyElements(tree);
     return tree;
   }
 
   /// [_processInternalWhitespace] removes unnecessary whitespace from the StyledElement tree.
-  ///
-  /// The criteria for determining which whitespace is replaceable is outlined
-  /// at https://www.w3.org/TR/css-text-3/
-  /// and summarized at https://medium.com/@patrickbrosset/when-does-white-space-matter-in-html-b90e8a7cdd33
   static StyledElement _processInternalWhitespace(StyledElement tree) {
-    if ((tree.style.whiteSpace ?? WhiteSpace.normal) == WhiteSpace.pre) {
-      // Preserve this whitespace
-    } else if (tree is TextContentElement) {
+    if (tree.style.whiteSpace == WhiteSpace.pre) {
+      return tree;
+    }
+
+    if (tree is TextContentElement) {
       tree.text = _removeUnnecessaryWhitespace(tree.text!);
     } else {
       tree.children.forEach(_processInternalWhitespace);
     }
+
     return tree;
   }
 
@@ -36,13 +40,95 @@ class WhitespaceProcessing {
     return _processInlineWhitespaceRecursive(tree, Context(false));
   }
 
+  /// [_processBlockWhitespace] removes unnecessary whitespace from block
+  /// rendering contexts. Specifically, a space at the beginning and end of
+  /// each inline rendering context should be removed.
+  static StyledElement _processBlockWhitespace(StyledElement tree) {
+    if (tree.style.whiteSpace == WhiteSpace.pre) {
+      return tree;
+    }
+
+    bool isBlockContext = false;
+    for (final child in tree.children) {
+      if (child.style.display == Display.block || child.name == "br") {
+        isBlockContext = true;
+      }
+
+      _processBlockWhitespace(child);
+    }
+
+    if (isBlockContext) {
+      for (int i = 0; i < tree.children.length; i++) {
+        final lastChild = i != 0 ? tree.children[i - 1] : null;
+        final child = tree.children[i];
+        final nextChild =
+            (i + 1) != tree.children.length ? tree.children[i + 1] : null;
+
+        if (child.style.whiteSpace == WhiteSpace.pre) {
+          continue;
+        }
+
+        if (child.style.display == Display.block) {
+          _removeLeadingSpace(child);
+          _removeTrailingSpace(child);
+        }
+
+        if (lastChild?.style.display == Display.block ||
+            lastChild?.name == "br") {
+          _removeLeadingSpace(child);
+        }
+
+        if (nextChild?.style.display == Display.block ||
+            nextChild?.name == "br") {
+          _removeTrailingSpace(child);
+        }
+      }
+    }
+
+    return tree;
+  }
+
+  /// [_removeLeadingSpace] removes any leading space
+  /// from the text of the tree at this level, no matter how deep in the tree
+  /// it may be.
+  static void _removeLeadingSpace(StyledElement element) {
+    if (element.style.whiteSpace == WhiteSpace.pre) {
+      return;
+    }
+
+    if (element is TextContentElement) {
+      element.text = element.text?.trimLeft();
+    } else if (element.children.isNotEmpty) {
+      _removeLeadingSpace(element.children.first);
+    }
+  }
+
+  /// [_removeTrailingSpace] removes any leading space
+  /// from the text of the tree at this level, no matter how deep in the tree
+  /// it may be.
+  static void _removeTrailingSpace(StyledElement element) {
+    if (element.style.whiteSpace == WhiteSpace.pre) {
+      return;
+    }
+
+    if (element is TextContentElement) {
+      element.text = element.text?.trimRight();
+    } else if (element.children.isNotEmpty) {
+      _removeTrailingSpace(element.children.last);
+    }
+  }
+
   /// [_processInlineWhitespaceRecursive] analyzes the whitespace between and among different
   /// inline elements, and replaces any instance of two or more spaces with a single space, according
   /// to the w3's HTML whitespace processing specification linked to above.
   static StyledElement _processInlineWhitespaceRecursive(
     StyledElement tree,
     Context<bool> keepLeadingSpace,
   ) {
+    if (tree.style.whiteSpace == WhiteSpace.pre) {
+      return tree;
+    }
+
     if (tree is TextContentElement) {
       /// initialize indices to negative numbers to make conditionals a little easier
       int textIndex = -1;
@@ -62,9 +148,9 @@ class WhitespaceProcessing {
       final parentNodes = tree.element?.parent?.nodes;
 
       /// find the index of the tree itself in the parent nodes
-      if ((parentNodes?.length ?? 0) >= 1) {
+      if (parentNodes?.isNotEmpty ?? false) {
         elementIndex =
-            parentNodes?.indexWhere((element) => element == tree.element) ?? -1;
+            parentNodes!.indexWhere((element) => element == tree.element);
       }
 
       /// if the tree is any node except the last node in the node list and the
@@ -117,9 +203,7 @@ class WhitespaceProcessing {
       /// update the [Context] to signify to that next text node whether it should
       /// keep its whitespace. This is based on whether the current text ends with a
       /// whitespace.
-      if (textIndex ==
-              ((tree.element?.nodes.length ?? 0) -
-                  1) && //TODO is this the proper ??
+      if (textIndex == (tree.node.nodes.length - 1) &&
           tree.element?.localName != "br" &&
           parentAfterText.startsWith(' ')) {
         keepLeadingSpace.data = !tree.text!.endsWith(' ');
@@ -142,11 +226,11 @@ class WhitespaceProcessing {
   /// (4) Replace any instances of two or more spaces with a single space.
   static String _removeUnnecessaryWhitespace(String text) {
     return text
-        .replaceAll(RegExp("\\ *(?=\n)"), "\n")
-        .replaceAll(RegExp("(?:\n)\\ *"), "\n")
+        .replaceAll(RegExp(r" *(?=\n)"), "")
+        .replaceAll(RegExp(r"(?<=\n) *"), "")
         .replaceAll("\n", " ")
         .replaceAll("\t", " ")
-        .replaceAll(RegExp(" {2,}"), " ");
+        .replaceAll(RegExp(r" {2,}"), " ");
   }
 
   /// [_removeEmptyElements] recursively removes empty elements.
@@ -155,7 +239,7 @@ class WhitespaceProcessing {
   /// or any block-level [TextContentElement] that contains only whitespace and doesn't follow
   /// a block element or a line break.
   static StyledElement _removeEmptyElements(StyledElement tree) {
-    List<StyledElement> toRemove = <StyledElement>[];
+    Set<StyledElement> toRemove = <StyledElement>{};
     bool lastChildBlock = true;
     tree.children.forEachIndexed((index, child) {
       if (child is EmptyContentElement) {

lib/src/tree/replaced_element.dart

@@ -46,6 +46,13 @@ class TextContentElement extends ReplacedElement {
   }
 }
 
+class LinebreakContentElement extends ReplacedElement {
+  LinebreakContentElement({
+    required super.style,
+    required super.node,
+  }) : super(name: 'br', elementId: "[[No ID]]");
+}
+
 class EmptyContentElement extends ReplacedElement {
   EmptyContentElement({required super.node, String name = "empty"})
       : super(name: name, style: Style(), elementId: "[[No ID]]");

test/test_utils.dart

@@ -1,5 +1,7 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
-import 'package:flutter_html/src/css_box_widget.dart';
+import 'package:flutter_html/flutter_html.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 class TestApp extends StatelessWidget {
@@ -141,3 +143,86 @@ CssBoxWidget? findCssBox(Finder finder) {
     return found.first.widget as CssBoxWidget;
   }
 }
+
+Future<StyledElement> generateStyledElementTreeFromHtml(
+  WidgetTester tester, {
+  required String html,
+  bool applyStyleSteps = true,
+  bool applyProcessingSteps = true,
+  bool shrinkWrap = false,
+  List<HtmlExtension> extensions = const [],
+  Map<String, Style> styles = const {},
+}) async {
+  final completer = Completer<StyledElement>();
+
+  await tester.pumpWidget(TestApp(
+    child: Html(
+      data: html,
+      shrinkWrap: shrinkWrap,
+      extensions: [
+        ...extensions,
+        TestExtension(
+          beforeStyleCallback: (tree) {
+            if (!applyStyleSteps) {
+              completer.complete(tree);
+            }
+          },
+          beforeProcessingCallback: (tree) {
+            if (!completer.isCompleted && !applyProcessingSteps) {
+              completer.complete(tree);
+            }
+          },
+          finalCallback: (tree) {
+            if (!completer.isCompleted) {
+              completer.complete(tree);
+            }
+          },
+        ),
+      ],
+      style: styles,
+    ),
+  ));
+
+  return completer.future;
+}
+
+class TestExtension extends HtmlExtension {
+  final void Function(StyledElement)? beforeStyleCallback;
+  final void Function(StyledElement)? beforeProcessingCallback;
+  final void Function(StyledElement)? finalCallback;
+
+  TestExtension({
+    this.beforeStyleCallback,
+    this.beforeProcessingCallback,
+    this.finalCallback,
+  });
+
+  @override
+  Set<String> get supportedTags => {};
+
+  @override
+  bool matches(ExtensionContext context) {
+    return context.currentStep != CurrentStep.preparing &&
+        context.elementName == "html";
+  }
+
+  @override
+  void beforeStyle(ExtensionContext context) {
+    beforeStyleCallback?.call(context.styledElement!);
+  }
+
+  @override
+  void beforeProcessing(ExtensionContext context) {
+    beforeProcessingCallback?.call(context.styledElement!);
+  }
+
+  @override
+  InlineSpan build(ExtensionContext context, buildChildren) {
+    finalCallback?.call(context.styledElement!);
+    return context.parser.buildFromExtension(
+      context,
+      buildChildren,
+      extensionsToIgnore: {this},
+    );
+  }
+}