fix: a tag should not style as link if href is not provided

lib/src/builtins/interactive_element_builtin.dart

@@ -5,33 +5,32 @@ import 'package:flutter_html/src/utils.dart';
 import 'package:html/dom.dart' as dom;
 
 /// Defines the way an anchor ('a') element is lexed and parsed.
+///
+/// An `<a>` element with no `href` attribute is not interactive and is thus
+/// not handled by this BuiltIn.
 class InteractiveElementBuiltIn extends HtmlExtension {
   const InteractiveElementBuiltIn();
 
   @override
   Set<String> get supportedTags => {'a'};
 
+  @override
+  bool matches(ExtensionContext context) {
+    return supportedTags.contains(context.elementName) &&
+        context.attributes.containsKey("href");
+  }
+
   @override
   StyledElement prepare(
       ExtensionContext context, List<StyledElement> children) {
-    if (context.attributes.containsKey('href')) {
-      return InteractiveElement(
-        name: context.elementName,
-        children: children,
-        href: context.attributes['href'],
-        style: Style(
-          color: Colors.blue,
-          textDecoration: TextDecoration.underline,
-        ),
-        node: context.node,
-        elementId: context.id,
-      );
-    }
-    // When <a> tag have no href, it must be unclickable and without decoration.
-    return StyledElement(
+    return InteractiveElement(
       name: context.elementName,
       children: children,
-      style: Style(),
+      href: context.attributes['href'],
+      style: Style(
+        color: Colors.blue,
+        textDecoration: TextDecoration.underline,
+      ),
       node: context.node,
       elementId: context.id,
     );
@@ -72,10 +71,7 @@ class InteractiveElementBuiltIn extends HtmlExtension {
         child: MultipleTapGestureDetector(
           onTap: onTap,
           child: GestureDetector(
-            key: AnchorKey.of(
-                context.parser.key,
-                context
-                    .styledElement), //TODO this replaced context.key. Does it work?
+            key: AnchorKey.of(context.parser.key, context.styledElement),
             onTap: onTap,
             child: (childSpan as WidgetSpan).child,
           ),

lib/src/builtins/styled_element_builtin.dart

@@ -13,6 +13,7 @@ class StyledElementBuiltIn extends HtmlExtension {
 
   @override
   Set<String> get supportedTags => {
+        "a",
         "abbr",
         "acronym",
         "address",

lib/src/processing/relative_sizes.dart

@@ -12,6 +12,8 @@ class RelativeSizesProcessing {
   /// applies relative calculations
   static StyledElement _calculateRelativeValues(
       StyledElement tree, double devicePixelRatio) {
+    tree.style.fontSize ??= FontSize.medium;
+
     double remSize = (tree.style.fontSize?.value ?? FontSize.medium.value);
 
     //If the root element has a rem-based fontSize, then give it the default

test/elements/a_test.dart

@@ -0,0 +1,90 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_html/flutter_html.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../test_data.dart';
+
+void main() {
+  testWidgets('<a> test', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      TestApp(
+        child: Html(
+          data: """<a>Hello, world!</a>""",
+        ),
+      ),
+    );
+    expect(find.text("Hello, world!", findRichText: true), findsOneWidget);
+  });
+
+  testWidgets('<a> test with href', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      TestApp(
+        child: Html(
+          data: """<a href="https://example.com">Hello, world!</a>""",
+        ),
+      ),
+    );
+    expect(find.text("Hello, world!", findRichText: true), findsOneWidget);
+  });
+
+  testWidgets('<a> with widget child renders', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      TestApp(
+        child: Html(
+          data: """<a href="https://example.com"><icon></icon></a>""",
+          extensions: [
+            TagExtension(
+              tagsToExtend: {"icon"},
+              child: const Icon(Icons.check),
+            ),
+          ],
+        ),
+      ),
+    );
+    expect(find.byIcon(Icons.check), findsOneWidget);
+  });
+
+  testWidgets('Tapping <a> test', (WidgetTester tester) async {
+    String tappedUrl = "";
+
+    await tester.pumpWidget(
+      TestApp(
+        child: Html(
+          data: """<a href="https://example.com">Hello, world!</a>""",
+          onLinkTap: (url, _, __) {
+            tappedUrl = url ?? "";
+          },
+        ),
+      ),
+    );
+    expect(find.text("Hello, world!", findRichText: true), findsOneWidget);
+    expect(tappedUrl, equals(""));
+    await tester.tap(find.text("Hello, world!", findRichText: true));
+    expect(tappedUrl, equals("https://example.com"));
+  });
+
+  testWidgets('Tapping <a> with widget works', (WidgetTester tester) async {
+    String tappedUrl = "";
+
+    await tester.pumpWidget(
+      TestApp(
+        child: Html(
+          data: """<a href="https://example.com"><icon></icon></a>""",
+          onLinkTap: (url, _, __) {
+            tappedUrl = url ?? "";
+          },
+          extensions: [
+            TagExtension(
+              tagsToExtend: {"icon"},
+              child: const Icon(Icons.check),
+            ),
+          ],
+        ),
+      ),
+    );
+    expect(find.byIcon(Icons.check), findsOneWidget);
+    expect(tappedUrl, equals(""));
+    await tester.tap(find.byIcon(Icons.check));
+    expect(tappedUrl, equals("https://example.com"));
+  });
+}

test/test_data.dart

@@ -1,3 +1,20 @@
+import 'package:flutter/material.dart';
+
+class TestApp extends StatelessWidget {
+  final Widget child;
+
+  const TestApp({Key? key, required this.child}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Scaffold(
+        body: child,
+      ),
+    );
+  }
+}
+
 const testData = <String, String>{
   'a': '<a>Hello, World!</a>',
   'abbr': '<abbr>HLO-WRLD</abbr>',