Add new format rule for wrapping case bodies (#2476)

Sources/RuleRegistry.generated.swift

@@ -141,6 +141,7 @@ let ruleRegistry: [String: FormatRule] = [
     "wrap": .wrap,
     "wrapArguments": .wrapArguments,
     "wrapAttributes": .wrapAttributes,
+    "wrapCaseBodies": .wrapCaseBodies,
     "wrapConditionalBodies": .wrapConditionalBodies,
     "wrapEnumCases": .wrapEnumCases,
     "wrapFunctionBodies": .wrapFunctionBodies,

Sources/Rules/WrapCaseBodies.swift

@@ -0,0 +1,53 @@
+//
+//  WrapCaseBodies.swift
+//  SwiftFormat
+//
+//  Created by Kim de Vos on 3/23/26.
+//  Copyright © 2026 Nick Lockwood. All rights reserved.
+//
+
+import Foundation
+
+public extension FormatRule {
+    static let wrapCaseBodies = FormatRule(
+        help: "Wrap the bodies of inline switch cases onto a new line.",
+        disabledByDefault: true,
+        sharedOptions: ["linebreaks", "indent"]
+    ) { formatter in
+        formatter.forEach(.endOfScope("case")) { i, _ in
+            formatter.wrapCaseBody(at: i)
+        }
+        formatter.forEach(.endOfScope("default")) { i, _ in
+            formatter.wrapCaseBody(at: i)
+        }
+    } examples: {
+        """
+        ```diff
+        - case .foo: return bar
+        + case .foo:
+        +     return bar
+        ```
+        """
+    }
+}
+
+extension Formatter {
+    func wrapCaseBody(at caseIndex: Int) {
+        guard let colonIndex = index(of: .startOfScope(":"), after: caseIndex),
+              var firstTokenIndex = index(of: .nonSpaceOrComment, after: colonIndex),
+              !tokens[firstTokenIndex].isLinebreak,
+              !tokens[firstTokenIndex].isEndOfScope
+        else { return }
+
+        insertLinebreak(at: firstTokenIndex)
+
+        if tokens[firstTokenIndex - 1].isSpace {
+            removeToken(at: firstTokenIndex - 1)
+            firstTokenIndex -= 1
+        }
+
+        let movedTokenIndex = firstTokenIndex + 1
+        let indent = currentIndentForLine(at: caseIndex) + options.indent
+        insertSpace(indent, at: movedTokenIndex)
+    }
+}