SimplifyGenericConstraints: Add 40 character limit to protocol composition (#2254)

Sources/Rules/SimplifyGenericConstraints.swift

@@ -134,6 +134,16 @@ extension Formatter {
             constraintsByType[item.genericType.name, default: []].append(item.conformance)
         }
 
+        // Check if any combined protocol composition is over 40 characters
+        // If so, skip simplification for the entire declaration
+        for conformances in constraintsByType.values {
+            let protocolNames = conformances.map(\.name)
+            let combinedComposition = protocolNames.joined(separator: " & ")
+            if combinedComposition.count > 40 {
+                return
+            }
+        }
+
         // We perform modifications in reverse order to avoid invalidating indices
 
         // First, remove constraints from the where clause

Tests/Rules/SimplifyGenericConstraintsTests.swift

@@ -326,6 +326,21 @@ final class SimplifyGenericConstraintsTests: XCTestCase {
         testFormatting(for: input, output, rule: .simplifyGenericConstraints, exclude: [.unusedArguments, .indent])
     }
 
+    func testDoesNotSimplifyWhenCombinedCompositionIsTooLong() {
+        // When multiple constraints for the same type are combined with &,
+        // don't simplify if the result is over 40 characters
+        let input = """
+        func transform<A, B, C, D>(_ a: A, _ b: B, _ c: C, _ d: D)
+            where A: VeryLongProtocolName,
+                  A: AnotherVeryLongProtocolName,
+                  B: Collection,
+                  C: Comparable,
+                  D: Sequence
+        {}
+        """
+        testFormatting(for: input, rule: .simplifyGenericConstraints, exclude: [.unusedArguments, .indent])
+    }
+
     // MARK: - Constraints on generics not in parameter list
 
     func testPreserveConstraintsForGenericsNotInParameterList() {
@@ -398,4 +413,26 @@ final class SimplifyGenericConstraintsTests: XCTestCase {
         """
         testFormatting(for: input, rule: .simplifyGenericConstraints, exclude: [.indent, .emptyBraces])
     }
+
+    func testDoesNotSimplifyLongProtocolComposition() {
+        // Don't simplify when protocol composition is over 40 characters
+        // This prevents awkward line breaks when wrapArguments is applied
+        let input = """
+        enum Foo<T>: SomeProtocol where
+          T: ProtocolA & SomeModule.ProtocolB & ProtocolC
+        {
+        }
+        """
+        testFormatting(for: input, rule: .simplifyGenericConstraints, exclude: [.indent, .emptyBraces])
+    }
+
+    func testDoesNotSimplifySingleLongProtocolName() {
+        // Don't simplify when a single protocol name is over 40 characters
+        let input = """
+        enum Foo<T>: SomeProtocol where T: VeryLongProtocolNameThatIsOverFortyCharacters
+        {
+        }
+        """
+        testFormatting(for: input, rule: .simplifyGenericConstraints, exclude: [.indent, .emptyBraces, .braces])
+    }
 }