Do not affect indentation when formatMode is set to off

Make two changes:
- Don’t trim the expansions from a macro if `formatMode` is set to `off`. We want to keep all whitespace just as the macro provided it
- Don’t add indentation when collapsing a macro. Again, we want to keep the indentation as the macro provided it.

rdar://132597440
Fixes #2757

Author: ahoppen

Sources/SwiftCompilerPluginMessageHandling/Macros.swift

@@ -163,12 +163,18 @@ extension PluginProviderMessageHandler {
         in: context
       )
       if let expansions, hostCapability.hasExpandMacroResult {
+        let collapseIndentationWidth: Trivia?
+        switch macroDefinition.formatMode {
+        case .auto: collapseIndentationWidth = nil
+        case .disabled: collapseIndentationWidth = []
+        }
         // Make a single element array by collapsing the results into a string.
         expandedSources = [
           SwiftSyntaxMacroExpansion.collapse(
             expansions: expansions,
             for: role,
-            attachedTo: declarationNode
+            attachedTo: declarationNode,
+            indentationWidth: collapseIndentationWidth
           )
         ]
       } else {

Sources/SwiftSyntaxMacroExpansion/MacroExpansion.swift

@@ -398,27 +398,38 @@ public func expandAttachedMacro<Context: MacroExpansionContext>(
     in: context,
     indentationWidth: indentationWidth
   )
-  return expandedSources.map {
-    collapse(expansions: $0, for: macroRole, attachedTo: declarationNode, indentationWidth: indentationWidth)
+  if let expandedSources {
+    // If formatting is disabled we don't want to add any indentation while collapsing
+    let collapseIndentationWidth: Trivia?
+    switch definition.formatMode {
+    case .auto: collapseIndentationWidth = indentationWidth
+    case .disabled: collapseIndentationWidth = []
+    }
+    return collapse(
+      expansions: expandedSources,
+      for: macroRole,
+      attachedTo: declarationNode,
+      indentationWidth: collapseIndentationWidth
+    )
   }
+  return nil
 }
 
 fileprivate extension SyntaxProtocol {
   /// Perform a format if required and then trim any leading/trailing
   /// whitespace.
   func formattedExpansion(_ mode: FormatMode, indentationWidth: Trivia?) -> String {
-    let formatted: Syntax
     switch mode {
     case .auto:
-      formatted = self.formatted(using: BasicFormat(indentationWidth: indentationWidth))
+      return self.formatted(using: BasicFormat(indentationWidth: indentationWidth))
+        .trimmedDescription(matching: \.isWhitespace)
     case .disabled:
-      formatted = Syntax(self)
+      return Syntax(self).description
     #if RESILIENT_LIBRARIES
     @unknown default:
       fatalError()
     #endif
     }
-    return formatted.trimmedDescription(matching: { $0.isWhitespace })
   }
 }
 

Tests/SwiftSyntaxMacroExpansionTest/AccessorMacroTests.swift

@@ -157,7 +157,7 @@ final class AccessorMacroTests: XCTestCase {
       """,
       expandedSource: """
         var x: Int { // hello
-          get { 1 }
+        get { 1 }
         }
         """,
       macros: ["constantOne": ConstantOneSingleLineGetter.self],

Tests/SwiftSyntaxMacroExpansionTest/BodyMacroTests.swift

@@ -156,7 +156,7 @@ final class BodyMacroTests: XCTestCase {
     )
   }
 
-  func testBodyNodeLocationFromContext() {
+  func testDontAddIndentationWhenCollapsingBody() {
     struct SourceLocationMacro: BodyMacro {
       public static var formatMode: FormatMode { .disabled }
 
@@ -168,37 +168,35 @@ final class BodyMacroTests: XCTestCase {
         guard let statements = declaration.body?.statements else {
           return []
         }
-        let body =
-          if let location = context.location(of: statements, at: .afterLeadingTrivia, filePathMode: .filePath) {
+        if let location = context.location(of: statements, at: .afterLeadingTrivia, filePathMode: .filePath) {
+          return statements.flatMap { statement in
             CodeBlockItemListSyntax {
               "#sourceLocation(file: \(location.file), line: \(location.line))"
-              statements
+              statement.trimmed(matching: \.isNewline)
               "#sourceLocation()"
             }
-          } else {
-            statements
           }
-        return Array(body)
+        } else {
+          return Array(statements)
+        }
       }
     }
 
     assertMacroExpansion(
       """
       @SourceLocationMacro
       func f() {
-        let x: Int = 1
+              let x: Int = 1
       }
       """,
-      expandedSource:
-        """
+      expandedSource: """
         func f() {
-          #sourceLocation(file: "test.swift", line: 3)
-          let x: Int = 1
-          #sourceLocation()
+        #sourceLocation(file: "test.swift", line: 3)
+                let x: Int = 1
+        #sourceLocation()
         }
         """,
-      macros: ["SourceLocationMacro": SourceLocationMacro.self],
-      indentationWidth: indentationWidth
+      macros: ["SourceLocationMacro": SourceLocationMacro.self]
     )
   }
 }