Fix complex pattern hanging forever (SimonFairbairn#139).

Done by https://github.com/polqf

Sources/SwiftyMarkdown/SwiftyScanner.swift

@@ -259,20 +259,28 @@ class SwiftyScanner {
 		} else {
 			var remainingTags = min(openRange.upperBound - openRange.lowerBound, closeRange.upperBound - closeRange.lowerBound) + 1
 			while remainingTags > 0 {
-				if remainingTags >= self.rule.maxTags {
+                let shouldAppendStyle = remainingTags >= self.rule.maxTags
+                if shouldAppendStyle {
 					remainingTags -= self.rule.maxTags
 					if let style = self.rule.styles[ self.rule.maxTags ] {
 						if !styles.contains(where: { $0.isEqualTo(style)}) {
 							styles.append(style)
 						}
 					}
 				}
-				if let style = self.rule.styles[remainingTags] {
+
+
+                let remainingTagsStyle = self.rule.styles[remainingTags]
+                if let style = remainingTagsStyle {
 					remainingTags -= remainingTags
 					if !styles.contains(where: { $0.isEqualTo(style)}) {
 						styles.append(style)
 					}
 				}
+
+                if !shouldAppendStyle && remainingTagsStyle == nil {
+                    break
+                }
 			}
 
 			for idx in (openRange.upperBound)...(closeRange.lowerBound) {

Tests/SwiftyMarkdownTests/SwiftyMarkdownAttributedStringTests.swift

@@ -6,32 +6,37 @@
 //  Copyright © 2019 Voyage Travel Apps. All rights reserved.
 //
 
-import XCTest
 @testable import SwiftyMarkdown
+import XCTest
 
 class SwiftyMarkdownAttributedStringTests: XCTestCase {
-
-	func testThatAttributesAreAppliedCorrectly() {
-
-		let string = """
-# Heading 1
-
-A more *complicated* example. This one has **it all**. Here is a [link](http://voyagetravelapps.com/).
-
-## Heading 2
-
-## Heading 3
-
-> This one is a blockquote
-"""
-		let md = SwiftyMarkdown(string: string)
-		let attributedString = md.attributedString()
-
-		XCTAssertNotNil(attributedString)
-
-		XCTAssertEqual(attributedString.string, "Heading 1\n\nA more complicated example. This one has it all. Here is a link.\n\nHeading 2\n\nHeading 3\n\nThis one is a blockquote")
-
-
-	}
-
+    func testThatAttributesAreAppliedCorrectly() {
+        let string = """
+        # Heading 1
+
+        A more *complicated* example. This one has **it all**. Here is a [link](http://voyagetravelapps.com/).
+
+        ## Heading 2
+
+        ## Heading 3
+
+        > This one is a blockquote
+        """
+
+        let md = SwiftyMarkdown(string: string)
+        let attributedString = md.attributedString()
+
+        XCTAssertNotNil(attributedString)
+        XCTAssertEqual(attributedString.string, "Heading 1\n\nA more complicated example. This one has it all. Here is a link.\n\nHeading 2\n\nHeading 3\n\nThis one is a blockquote")
+    }
+
+    func testComplexPatternDoesNotHangForever() {
+        let string = "**~*~~~*~*~**~*~* h e a r d ***~*~*~**~*~~~*"
+
+        let md = SwiftyMarkdown(string: string)
+        let attributedString = md.attributedString()
+
+        XCTAssertNotNil(attributedString)
+        XCTAssertEqual(attributedString.string, "**~~*~**~~ h e a r d ***~~~**~")
+    }
 }