Prevent using split by \.newLine for faster speed

Author: intitni

Pro

@@ -1,6 +1,7 @@
 import AppKit
 import Foundation
 import Highlightr
+import SuggestionModel
 import SwiftUI
 
 public func highlightedCodeBlock(
@@ -82,7 +83,7 @@ func convertToCodeLines(
         return false
     }
 
-    let separatedInput = input.split(omittingEmptySubsequences: false, whereSeparator: \.isNewline)
+    let separatedInput = input.splitByNewLine(omittingEmptySubsequences: false)
         .map { String($0) }
     let commonLeadingSpaceCount = {
         if !droppingLeadingSpaces { return 0 }

Tool/Sources/SharedUIComponents/SyntaxHighlighting.swift

@@ -2,23 +2,48 @@ import Foundation
 
 public extension String {
     /// The line ending of the string.
+    ///
+    /// We are pretty safe to just check the last character here, in most case, a line ending
+    /// will be in the end of the string.
+    ///
+    /// For other situations, we can assume that they are "\n".
     var lineEnding: Character? {
-        last(where: \.isNewline)
+        if let last, last.isNewline { return last }
+        return "\n"
+    }
+
+    func splitByNewLine(
+        omittingEmptySubsequences: Bool = true,
+        fast: Bool = true
+    ) -> [Substring] {
+        if fast {
+            let lineEndingInText = lineEnding ?? "\n"
+            return split(
+                separator: lineEndingInText,
+                omittingEmptySubsequences: omittingEmptySubsequences
+            )
+        }
+        return split(
+            omittingEmptySubsequences: omittingEmptySubsequences,
+            whereSeparator: \.isNewline
+        )
     }
 
     /// Break a string into lines.
     func breakLines(
         proposedLineEnding: String? = nil,
         appendLineBreakToLastLine: Bool = false
     ) -> [String] {
-        let lineEnding = proposedLineEnding ?? String(lineEnding ?? "\n")
-        let lines = split(omittingEmptySubsequences: false, whereSeparator: \.isNewline)
+        let lineEndingInText = lineEnding ?? "\n"
+        let lineEnding = proposedLineEnding ?? String(lineEndingInText)
+        // Split on character for better performance.
+        let lines = split(separator: lineEndingInText, omittingEmptySubsequences: false)
         var all = [String]()
         for (index, line) in lines.enumerated() {
             if !appendLineBreakToLastLine, index == lines.endIndex - 1 {
                 all.append(String(line))
             } else {
-                all.append(String(line) + String(lineEnding))
+                all.append(String(line) + lineEnding)
             }
         }
         return all

Tool/Sources/SuggestionModel/String+LineEnding.swift

@@ -0,0 +1,18 @@
+import Foundation
+import XCTest
+@testable import SuggestionModel
+
+final class BreakLinePerformanceTests: XCTestCase {
+    func test_breakLines() {
+        let string = String(repeating: """
+        Hello
+        World
+        
+        """, count: 50000)
+        
+        measure {
+            let _ = string.breakLines()
+        }
+    }
+}
+