Fix #4913 - Email addresses are detected as URLs

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilder.swift

@@ -330,12 +330,17 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
         })
         
         matches.append(contentsOf: MatrixEntityRegex.linkRegex.matches(in: string).compactMap { match in
-            guard let matchRange = Range(match.range, in: string) else {
+            guard let matchRange = Range(match.range, in: string), let url = match.url else {
                 return nil
             }
             
-            let link = String(string[matchRange]).asSanitizedLink
+            // If the NSDataDetector found a hyperlink then sanitise it
-            return TextParsingMatch(type: .link(urlString: link), range: match.range)
+            if url.scheme?.contains("http") ?? false {
+                // Use the underlying string so it gets an `https` scheme if it didn't have any
+                return TextParsingMatch(type: .link(urlString: String(string[matchRange]).asSanitizedLink), range: match.range)
+            } else { // otherwise use it as it is e.g. mailto: (https://github.com/element-hq/element-x-ios/issues/4913)
+                return TextParsingMatch(type: .link(urlString: url.absoluteString), range: match.range)
+            }
         })
         
         matches.append(contentsOf: MatrixEntityRegex.allUsersRegex.matches(in: attributedString.string).map { match in

UnitTests/Sources/AttributedStringBuilderTests.swift

@@ -114,6 +114,18 @@ class AttributedStringBuilderTests: XCTestCase {
         XCTAssertEqual(link, "https://matrix.org")
     }
     
+    func testMailToLinks() {
+        let plainString = "Linking to email addresses like stefan@matrix.org should work as well"
+        
+        guard let attributedString = attributedStringBuilder.fromPlain(plainString) else {
+            XCTFail("Could not build the attributed string")
+            return
+        }
+        
+        let link = attributedString.runs.first { $0.link != nil }?.link
+        XCTAssertEqual(link, "mailto:stefan@matrix.org")
+    }
+    
     func testRenderHTMLStringWithLinkInHeader() {
         let h1HTMLString = "<h1><a href=\"https://matrix.org/\">Matrix.org</a></h1>"
         let h2HTMLString = "<h2><a href=\"https://matrix.org/\">Matrix.org</a></h2>"