Fix handling of mis-nested <a> tags

Sources/HTMLStreamer/AttributedStringConverter.swift

@@ -151,7 +151,7 @@ public struct AttributedStringConverter<Callbacks: AttributedStringCallbacks> {
     private mutating func handleEndTag(_ name: String) {
         switch name {
         case "a":
-            if case .link(.some(_)) = styleStack.last {
+            if case .link(.some(_)) = lastStyle(.link) {
                 finishRun()
             }
             removeLastStyle(.link)
@@ -186,7 +186,8 @@ public struct AttributedStringConverter<Callbacks: AttributedStringCallbacks> {
         }
     }
     
-    // needed to correctly handle mis-nested tags
+    // Finds the last currently-open style of the given type.
+    // We can't just use the last one because we need to handle mis-nested tags.
     private mutating func removeLastStyle(_ type: Style.StyleType) {
         var i = styleStack.index(before: styleStack.endIndex)
         while i >= styleStack.startIndex {
@@ -198,6 +199,10 @@ public struct AttributedStringConverter<Callbacks: AttributedStringCallbacks> {
         }
     }
     
+    private func lastStyle(_ type: Style.StyleType) -> Style? {
+        styleStack.last { $0.type == type }
+    }
+    
     private lazy var blockquoteParagraphStyle: NSParagraphStyle = {
         let style = configuration.paragraphStyle.mutableCopy() as! NSMutableParagraphStyle
         style.headIndent = 32

Tests/HTMLStreamerTests/AttributedStringConverterTests.swift

@@ -119,6 +119,21 @@ final class AttributedStringConverterTests: XCTestCase {
         XCTAssertEqual(convert("<strong>bold <em>both</strong> italic</em>"), result)
     }
     
+    func testMisnestedLink() {
+        let result = NSMutableAttributedString()
+        result.append(NSAttributedString(string: "hello ", attributes: [
+            .link: URL(string: "https://example.com")!,
+            .font: font,
+            .paragraphStyle: NSParagraphStyle.default,
+        ]))
+        result.append(NSAttributedString(string: "world", attributes: [
+            .link: URL(string: "https://example.com")!,
+            .font: boldFont,
+            .paragraphStyle: NSParagraphStyle.default,
+        ]))
+        XCTAssertEqual(convert("<a href='https://example.com'>hello <b>world</a></b>"), result)
+    }
+    
     func testDel() {
         XCTAssertEqual(convert("<del>blah</del>"), NSAttributedString(string: "blah", attributes: [
             .font: font,