test pretty printing macro expressions

Add a missing test case for pretty printing freestanding macro
expressions along with some basic tests checking that #542 has been
properly resolved in commit 7a43205.

The tests are by far not exhaustive and only cover the bug discovered in
issue #542.

Closes #542

Author: kimberninger

Tests/SwiftFormatPrettyPrintTests/MacroCallTests.swift

@@ -0,0 +1,117 @@
+import SwiftFormatConfiguration
+
+final class MacroCallTests: PrettyPrintTestCase {
+  func testNoWhiteSpaceAfterMacroWithoutTrailingClosure() {
+    let input =
+      """
+      func myFunction() {
+        print("Currently running \\(#function)")
+      }
+
+      """
+
+    let expected =
+      """
+      func myFunction() {
+        print("Currently running \\(#function)")
+      }
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 50)
+  }
+
+  func testKeepWhiteSpaceBeforeTrailingClosure() {
+    let input =
+      """
+      #Preview {}
+      #Preview("MyPreview") {
+        MyView()
+      }
+      let p = #Predicate<Int> { $0 == 0 }
+      """
+
+    let expected =
+      """
+      #Preview {}
+      #Preview("MyPreview") {
+        MyView()
+      }
+      let p = #Predicate<Int> { $0 == 0 }
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 40)
+  }
+
+  func testInsertWhiteSpaceBeforeTrailingClosure() {
+    let input =
+      """
+      #Preview{}
+      #Preview("MyPreview"){
+        MyView()
+      }
+      let p = #Predicate<Int>{ $0 == 0 }
+      """
+
+    let expected =
+      """
+      #Preview {}
+      #Preview("MyPreview") {
+        MyView()
+      }
+      let p = #Predicate<Int> { $0 == 0 }
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 40)
+  }
+
+  func testDiscretionaryLineBreakBeforeTrailingClosure() {
+    let input =
+      """
+      #Preview("MyPreview")
+      {
+        MyView()
+      }
+      #Preview(
+        "MyPreview", traits: .landscapeLeft
+      )
+      {
+        MyView()
+      }
+      #Preview("MyPreview", traits: .landscapeLeft, .sizeThatFitsLayout)
+      {
+        MyView()
+      }
+      #Preview("MyPreview", traits: .landscapeLeft) {
+        MyView()
+      }
+      """
+
+    let expected =
+      """
+      #Preview("MyPreview") {
+        MyView()
+      }
+      #Preview(
+        "MyPreview", traits: .landscapeLeft
+      ) {
+        MyView()
+      }
+      #Preview(
+        "MyPreview", traits: .landscapeLeft,
+        .sizeThatFitsLayout
+      ) {
+        MyView()
+      }
+      #Preview("MyPreview", traits: .landscapeLeft)
+      {
+        MyView()
+      }
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 45)
+  }
+}