Fix Overlapping Lines Method

Sources/CodeEditSourceEditor/Controller/TextViewController+IndentLines.swift

@@ -67,7 +67,7 @@ extension TextViewController {
         var selectionIndex = 0
         textView.editSelections { textView, selection in
             // get lineindex, i.e line-numbers+1
-            guard let lineIndexes = getHighlightedLines(for: selection.range) else { return }
+            guard let lineIndexes = getOverlappingLines(for: selection.range) else { return }
 
             adjustIndentation(lineIndexes: lineIndexes, inwards: inwards)
 
@@ -129,7 +129,24 @@ extension TextViewController {
         return false
     }
 
-    private func getHighlightedLines(for range: NSRange) -> ClosedRange<Int>? {
+    /// Find the range of lines overlapping a text range.
+    ///
+    /// Use this method to determine what lines to apply a text transformation on using a text selection. For instance,
+    /// when indenting a selected line.
+    ///
+    /// Does not determine the *visible* lines, which is a very slight change from most
+    /// ``CodeEditTextView/TextLayoutManager`` APIs.
+    /// Given the text:
+    /// ```
+    /// A
+    /// B
+    /// ```
+    /// This method will return lines `0...0` for the text range `0..<2`. The layout manager might return lines
+    /// `0...1`, as the text range contains the newline, which appears *visually* in line index `1`.
+    ///
+    /// - Parameter range: The text range in the document to find contained lines for.
+    /// - Returns: A closed range of line indexes (0-indexed) where each line is overlapping the given text range.
+    func getOverlappingLines(for range: NSRange) -> ClosedRange<Int>? {
         guard let startLineInfo = textView.layoutManager.textLineForOffset(range.lowerBound) else {
             return nil
         }
@@ -139,7 +156,16 @@ extension TextViewController {
             return startLineInfo.index...startLineInfo.index
         }
 
-        return startLineInfo.index...endLineInfo.index
+        // If we've selected up to the start of a line (just over the newline character), the layout manager tells us
+        // we've selected the next line. However, we aren't overlapping the *text line* with that range, so we
+        // decrement it if it's not the end of the document
+        var endLineIndex = endLineInfo.index
+        if endLineInfo.range.lowerBound == range.upperBound
+            && endLineInfo.index != textView.layoutManager.lineCount - 1 {
+            endLineIndex -= 1
+        }
+
+        return startLineInfo.index...endLineIndex
     }
 
     private func adjustIndentation(lineIndexes: ClosedRange<Int>, inwards: Bool) {

Tests/CodeEditSourceEditorTests/Controller/TextViewControllerTests.swift

@@ -461,5 +461,31 @@ final class TextViewControllerTests: XCTestCase {
         XCTAssertEqual(controller.minimapView.frame.width, MinimapView.maxWidth)
         XCTAssertEqual(controller.textViewInsets.right, MinimapView.maxWidth)
     }
+
+    // MARK: - Get Overlapping Lines
+
+    func test_getOverlappingLines() {
+        controller.setText("A\nB\nC")
+
+        // Select the entire first line, shouldn't include the second line
+        var lines = controller.getOverlappingLines(for: NSRange(location: 0, length: 2))
+        XCTAssertEqual(0...0, lines)
+
+        // Select the first char of the second line
+        lines = controller.getOverlappingLines(for: NSRange(location: 0, length: 3))
+        XCTAssertEqual(0...1, lines)
+
+        // Select the newline in the first line, and part of the second line
+        lines = controller.getOverlappingLines(for: NSRange(location: 1, length: 2))
+        XCTAssertEqual(0...1, lines)
+
+        // Select until the end of the document
+        lines = controller.getOverlappingLines(for: NSRange(location: 3, length: 2))
+        XCTAssertEqual(1...2, lines)
+
+        // Select just the last line of the document
+        lines = controller.getOverlappingLines(for: NSRange(location: 4, length: 1))
+        XCTAssertEqual(2...2, lines)
+    }
 }
 // swiftlint:enable all