Be more comprehensive

Author: dduan

Sources/SwiftFormat/PrettyPrint/TokenStreamCreator.swift

@@ -1496,7 +1496,15 @@ private final class TokenStreamCreator: SyntaxVisitor {
 
   override func visit(_ node: IfConfigDeclSyntax) -> SyntaxVisitorContinueKind {
     // there has to be a break after an #endif
-    after(node.poundEndif, tokens: .break(.same, size: 0))
+    let newlines: NewlineBehavior
+    if node.parent?.is(AttributeListSyntax.self) == true {
+      newlines = .elective
+    } else if isNestedInPostfixIfConfig(node: Syntax(node)) {
+      newlines = config.respectsExistingLineBreaks ? .elective : .soft
+    } else {
+      newlines = .soft
+    }
+    after(node.poundEndif, tokens: .break(.same, size: 0, newlines: newlines))
     return .visitChildren
   }
 
@@ -4317,10 +4325,9 @@ private final class TokenStreamCreator: SyntaxVisitor {
       after(postfixIfExpr.lastToken(viewMode: .sourceAccurate), tokens: .contextualBreakingEnd)
 
       for clause in postfixIfExpr.config.clauses {
-        before(clause.poundKeyword, tokens: .break(.contextual, size: 0))
+        before(clause.poundKeyword, tokens: .break(.contextual, size: 0, newlines: .soft))
       }
-      before(postfixIfExpr.config.poundEndif, tokens: .break(.contextual, size: 0))
-      after(postfixIfExpr.config.poundEndif, tokens: .break(.same, size: 0))
+      before(postfixIfExpr.config.poundEndif, tokens: .break(.contextual, size: 0, newlines: .soft))
 
       return insertContextualBreaks(base, isTopLevel: false)
     } else if let callingExpr = expr.asProtocol(CallingExprSyntaxProtocol.self) {

Tests/SwiftFormatTests/PrettyPrint/RespectsExistingLineBreaksTests.swift

@@ -295,14 +295,30 @@ final class RespectsExistingLineBreaksTests: PrettyPrintTestCase {
     )
   }
 
-  func testDeclarationAfterTrailingIfConfigAttributeKeepsRequiredLineBreak() {
+  func testIfConfigKeepsRequiredLineBreakAfterEndif() {
     let input =
       """
       #if FLAG
       @frozen
       #endif
       struct S {}
 
+      switch x {
+      #if A
+      case 1: f()
+      #endif
+      #if B
+      case 2: g()
+      #endif
+      }
+
+      let x =
+        base
+        #if FLAG
+        .foo()
+        #endif
+        .bar()
+
       """
 
     let expected =
@@ -312,6 +328,20 @@ final class RespectsExistingLineBreaksTests: PrettyPrintTestCase {
       #endif
       struct S {}
 
+      switch x { #if A
+        case 1: f()
+      #endif
+      #if B
+        case 2: g()
+      #endif
+      }
+
+      let x = base
+        #if FLAG
+          .foo()
+        #endif
+        .bar()
+
       """
 
     assertPrettyPrintEqual(