Only disable wrapping in import decls when it is safe to do so.

The ImportDeclSyntax attributes might include IfConfigDecls, which
absolutely require line breaks in certain positions. The disable
breaking logic of ImportDecl was preventing these from being emitted.

Author: shawnhyam

Sources/SwiftFormat/PrettyPrint/TokenStreamCreator.swift

@@ -1492,7 +1492,7 @@ fileprivate 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))
+    after(node.poundEndif, tokens: .break(.same, size: 0, newlines: .soft))
     return .visitChildren
   }
 
@@ -1951,17 +1951,28 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
   }
 
   override func visit(_ node: ImportDeclSyntax) -> SyntaxVisitorContinueKind {
-    // Import declarations should never be wrapped.
-    before(
-      node.firstToken(viewMode: .sourceAccurate),
-      tokens: .printerControl(kind: .disableBreaking(allowDiscretionary: false))
-    )
+    // Import declarations ignore wrapping when it is safe to do so (no #if constructs)
+    let isSafeToIgnoreBreaking = !node.attributes.contains(where: { element in
+      return element.is(IfConfigDeclSyntax.self)
+    })
+
+    if isSafeToIgnoreBreaking {
+      before(
+        node.firstToken(viewMode: .sourceAccurate),
+        tokens: .printerControl(kind: .disableBreaking(allowDiscretionary: false))
+      )
+    }
 
     arrangeAttributeList(node.attributes)
     after(node.importKeyword, tokens: .space)
     after(node.importKindSpecifier, tokens: .space)
 
-    after(node.lastToken(viewMode: .sourceAccurate), tokens: .printerControl(kind: .enableBreaking))
+    if isSafeToIgnoreBreaking {
+      after(
+        node.lastToken(viewMode: .sourceAccurate),
+        tokens: .printerControl(kind: .enableBreaking)
+      )
+    }
     return .visitChildren
   }
 

Tests/SwiftFormatTests/PrettyPrint/IfConfigTests.swift

@@ -383,10 +383,10 @@ final class IfConfigTests: PrettyPrintTestCase {
           .toggleStyle(
             SwitchToggleStyle(tint: Color.blue))
         #endif
-        .accessibilityValue(
-          binding.wrappedValue == true
-            ? "On" : "Off"
-        )
+          .accessibilityValue(
+            binding.wrappedValue == true
+              ? "On" : "Off"
+          )
       }
 
       """
@@ -482,7 +482,7 @@ final class IfConfigTests: PrettyPrintTestCase {
       #if os(iOS)
         .iOSSpecificModifier()
       #endif
-      .commonModifier()
+        .commonModifier()
 
       """
 
@@ -510,7 +510,7 @@ final class IfConfigTests: PrettyPrintTestCase {
       #if os(iOS)
         .iOSSpecificModifier()
       #endif
-      .commonModifier()
+        .commonModifier()
 
       """
 
@@ -563,11 +563,16 @@ final class IfConfigTests: PrettyPrintTestCase {
       """
       #if os(Foo)
       @_spiOnly
+      #elseif os(Bar)
+      @_spiOnly
+      #else
+      @_spiOnly
       #endif
       @_spi(Foo) import Foundation
-      
+
       """
     var configuration = Configuration.forTesting
+    configuration.respectsExistingLineBreaks = false
     configuration.indentConditionalCompilationBlocks = false
     assertPrettyPrintEqual(input: input, expected: input, linelength: 80, configuration: configuration)