Merge pull request #910 from TTOzzi/fix-NoEmptyLinesOpeningClosingBraces

Fix NoEmptyLinesOpeningClosingBraces to respect consecutive newlines when a function starts or ends with a comment

Author: allevato

Sources/SwiftFormat/Rules/NoEmptyLineOpeningClosingBraces.swift

@@ -69,7 +69,9 @@ public final class NoEmptyLinesOpeningClosingBraces: SyntaxFormatRule {
   }
 
   func rewritten(_ token: TokenSyntax) -> TokenSyntax {
-    let (trimmedLeadingTrivia, count) = token.leadingTrivia.trimmingSuperfluousNewlines()
+    let (trimmedLeadingTrivia, count) = token.leadingTrivia.trimmingSuperfluousNewlines(
+      fromClosingBrace: token.tokenKind == .rightBrace
+    )
     if trimmedLeadingTrivia.sourceLength != token.leadingTriviaLength {
       diagnose(.removeEmptyLinesBefore(count), on: token, anchor: .start)
       return token.with(\.leadingTrivia, trimmedLeadingTrivia)
@@ -83,7 +85,7 @@ public final class NoEmptyLinesOpeningClosingBraces: SyntaxFormatRule {
     if let first = collection.first, first.leadingTrivia.containsNewlines,
       let index = collection.index(of: first)
     {
-      let (trimmedLeadingTrivia, count) = first.leadingTrivia.trimmingSuperfluousNewlines()
+      let (trimmedLeadingTrivia, count) = first.leadingTrivia.trimmingSuperfluousNewlines(fromClosingBrace: false)
       if trimmedLeadingTrivia.sourceLength != first.leadingTriviaLength {
         diagnose(.removeEmptyLinesAfter(count), on: first, anchor: .leadingTrivia(0))
         var first = first
@@ -96,24 +98,49 @@ public final class NoEmptyLinesOpeningClosingBraces: SyntaxFormatRule {
 }
 
 extension Trivia {
-  func trimmingSuperfluousNewlines() -> (Trivia, Int) {
+  func trimmingSuperfluousNewlines(fromClosingBrace: Bool) -> (Trivia, Int) {
     var trimmmed = 0
+    var pendingNewlineCount = 0
     let pieces = self.indices.reduce([TriviaPiece]()) { (partialResult, index) in
       let piece = self[index]
       // Collapse consecutive newlines into a single one
       if case .newlines(let count) = piece {
-        if let last = partialResult.last, last.isNewline {
-          trimmmed += count
-          return partialResult
+        if fromClosingBrace {
+          if index == self.count - 1 {
+            // For the last index(newline right before the closing brace), collapse into a single newline
+            trimmmed += count - 1
+            return partialResult + [.newlines(1)]
+          } else {
+            pendingNewlineCount += count
+            return partialResult
+          }
         } else {
-          trimmmed += count - 1
-          return partialResult + [.newlines(1)]
+          if let last = partialResult.last, last.isNewline {
+            trimmmed += count
+            return partialResult
+          } else if index == 0 {
+            // For leading trivia not associated with a closing brace, collapse the first newline into a single one
+            trimmmed += count - 1
+            return partialResult + [.newlines(1)]
+          } else {
+            return partialResult + [piece]
+          }
         }
       }
       // Remove spaces/tabs surrounded by newlines
       if piece.isSpaceOrTab, index > 0, index < self.count - 1, self[index - 1].isNewline, self[index + 1].isNewline {
         return partialResult
       }
+      // Handle pending newlines if there are any
+      if pendingNewlineCount > 0 {
+        if index < self.count - 1 {
+          let newlines = TriviaPiece.newlines(pendingNewlineCount)
+          pendingNewlineCount = 0
+          return partialResult + [newlines] + [piece]
+        } else {
+          return partialResult + [.newlines(1)] + [piece]
+        }
+      }
       // Retain other trivia pieces
       return partialResult + [piece]
     }

Tests/SwiftFormatTests/Rules/NoEmptyLinesOpeningClosingBracesTests.swift

@@ -136,4 +136,60 @@ final class NoEmptyLinesOpeningClosingBracesTests: LintOrFormatRuleTestCase {
       ]
     )
   }
+
+  func testNoEmptyLinesOpeningClosingBracesInFunctionBeginningAndEndingWithComment() {
+    assertFormatting(
+      NoEmptyLinesOpeningClosingBraces.self,
+      input: """
+        func myFunc() {
+            // Some comment here
+
+            // Do a thing
+            var x = doAThing()
+
+            // Do a thing
+
+            var y = doAThing()
+
+            // Some other comment here
+        }
+        """,
+      expected: """
+        func myFunc() {
+            // Some comment here
+
+            // Do a thing
+            var x = doAThing()
+
+            // Do a thing
+
+            var y = doAThing()
+
+            // Some other comment here
+        }
+        """
+    )
+  }
+
+  func testNoEmptyLinesOpeningClosingBracesInFunctionWithEmptyLinesOnly() {
+    assertFormatting(
+      NoEmptyLinesOpeningClosingBraces.self,
+      input: """
+        func myFunc() {
+
+
+
+
+
+        1️⃣}
+        """,
+      expected: """
+        func myFunc() {
+        }
+        """,
+      findings: [
+        FindingSpec("1️⃣", message: "remove empty lines before '}'")
+      ]
+    )
+  }
 }