From a65ea804ca7f1debef94d852ec2e609e7ca60d60 Mon Sep 17 00:00:00 2001
From: Cameron Pulsford <cpulsfor@me.com>
Date: Wed, 11 Jun 2025 10:37:06 -0400
Subject: [PATCH] Add `--trailingcommas collections-only` option to opt out of
 Swift 6.1 trailing comma support (#2081)

Co-authored-by: Cal Stephens <cal.stephens@airbnb.com>
---
 PerformanceTests/PerformanceTests.swift |   2 +-
 Rules.md                                |   2 +-
 Sources/Inference.swift                 |   2 +-
 Sources/OptionDescriptor.swift          |  22 ++-
 Sources/Options.swift                   |  10 +-
 Sources/Rules/TrailingCommas.swift      |  47 ++++++-
 Tests/InferenceTests.swift              |   4 +-
 Tests/Rules/TrailingCommasTests.swift   | 175 ++++++++++++++++--------
 Tests/Rules/WrapArgumentsTests.swift    |  16 +--
 9 files changed, 200 insertions(+), 80 deletions(-)

diff --git a/PerformanceTests/PerformanceTests.swift b/PerformanceTests/PerformanceTests.swift
index f1814a26..4772be2e 100644
--- a/PerformanceTests/PerformanceTests.swift
+++ b/PerformanceTests/PerformanceTests.swift
@@ -77,7 +77,7 @@ class PerformanceTests: XCTestCase {
             spaceAroundOperatorDeclarations: .remove,
             useVoid: false,
             indentCase: true,
-            trailingCommas: false,
+            trailingCommas: .never,
             indentComments: false,
             truncateBlankLines: false,
             allmanBraces: true,
diff --git a/Rules.md b/Rules.md
index 5ac3eb95..18ac2bd3 100644
--- a/Rules.md
+++ b/Rules.md
@@ -3233,7 +3233,7 @@ Add or remove trailing commas in comma-separated lists.
 
 Option | Description
 --- | ---
-`--commas` | Commas in collection literals: "always" (default) or "inline"
+`--trailingcommas` | Trailing commas: "always" (default), "never", or "collections-only"
 
 <details>
 <summary>Examples</summary>
diff --git a/Sources/Inference.swift b/Sources/Inference.swift
index 279a6552..e4d55ef2 100644
--- a/Sources/Inference.swift
+++ b/Sources/Inference.swift
@@ -235,7 +235,7 @@ private struct Inference {
                 noTrailing += 1
             }
         }
-        options.trailingCommas = (trailing >= noTrailing)
+        options.trailingCommas = (trailing >= noTrailing) ? .always : .never
     }
 
     let truncateBlankLines = OptionInferrer { formatter, options in
diff --git a/Sources/OptionDescriptor.swift b/Sources/OptionDescriptor.swift
index 9747442f..b7b48ef7 100644
--- a/Sources/OptionDescriptor.swift
+++ b/Sources/OptionDescriptor.swift
@@ -516,12 +516,10 @@ struct _Descriptors {
         falseValues: ["false"]
     )
     let trailingCommas = OptionDescriptor(
-        argumentName: "commas",
-        displayName: "Commas",
-        help: "Commas in collection literals: \"always\" (default) or \"inline\"",
-        keyPath: \.trailingCommas,
-        trueValues: ["always", "true"],
-        falseValues: ["inline", "false"]
+        argumentName: "trailingcommas",
+        displayName: "Trailing commas",
+        help: "Trailing commas: \"always\" (default), \"never\", or \"collections-only\"",
+        keyPath: \.trailingCommas
     )
     let truncateBlankLines = OptionDescriptor(
         argumentName: "trimwhitespace",
@@ -1361,6 +1359,18 @@ struct _Descriptors {
         deprecationMessage: "Use with `--storedvarattributes` or `--computedvarattributes` instead.",
         keyPath: \.varAttributes
     )
+    let commas = OptionDescriptor(
+        argumentName: "commas",
+        displayName: "Trailing commas",
+        help: "deprecated",
+        deprecationMessage: "Use '--trailingcommas' instead",
+        keyPath: \.trailingCommas,
+        altOptions: [
+            "inline": .never,
+            "false": .never,
+            "true": .always,
+        ]
+    )
 
     // MARK: - RENAMED
 
diff --git a/Sources/Options.swift b/Sources/Options.swift
index 13f4cf74..07d80c25 100644
--- a/Sources/Options.swift
+++ b/Sources/Options.swift
@@ -178,6 +178,12 @@ public enum ClosureVoidReturn: String, CaseIterable {
     case preserve
 }
 
+public enum TrailingCommas: String, CaseIterable {
+    case never
+    case always
+    case collectionsOnly = "collections-only"
+}
+
 /// Whether to insert, remove, or preserve spaces around operators
 public enum OperatorSpacingMode: String, CaseIterable {
     case insert = "spaced"
@@ -651,7 +657,7 @@ public struct FormatOptions: CustomStringConvertible {
     public var spaceAroundOperatorDeclarations: OperatorSpacingMode
     public var useVoid: Bool
     public var indentCase: Bool
-    public var trailingCommas: Bool
+    public var trailingCommas: TrailingCommas
     public var truncateBlankLines: Bool
     public var insertBlankLines: Bool
     public var removeBlankLines: Bool
@@ -782,7 +788,7 @@ public struct FormatOptions: CustomStringConvertible {
                 spaceAroundOperatorDeclarations: OperatorSpacingMode = .insert,
                 useVoid: Bool = true,
                 indentCase: Bool = false,
-                trailingCommas: Bool = true,
+                trailingCommas: TrailingCommas = .always,
                 indentComments: Bool = true,
                 truncateBlankLines: Bool = true,
                 insertBlankLines: Bool = true,
diff --git a/Sources/Rules/TrailingCommas.swift b/Sources/Rules/TrailingCommas.swift
index 7470786e..90967dc1 100644
--- a/Sources/Rules/TrailingCommas.swift
+++ b/Sources/Rules/TrailingCommas.swift
@@ -11,7 +11,7 @@ import Foundation
 public extension FormatRule {
     static let trailingCommas = FormatRule(
         help: "Add or remove trailing commas in comma-separated lists.",
-        options: ["commas"]
+        options: ["trailingcommas"]
     ) { formatter in
         formatter.forEachToken { i, token in
             switch token {
@@ -20,7 +20,18 @@ public extension FormatRule {
                 case .array, .dictionary:
                     formatter.addOrRemoveTrailingComma(before: i, trailingCommaSupported: true)
                 case .subscript, .captureList:
-                    formatter.addOrRemoveTrailingComma(before: i, trailingCommaSupported: formatter.options.swiftVersion >= "6.1")
+                    var trailingCommaSupported = false
+
+                    if formatter.options.swiftVersion >= "6.1" {
+                        switch formatter.options.trailingCommas {
+                        case .always:
+                            trailingCommaSupported = true
+                        case .never, .collectionsOnly:
+                            break
+                        }
+                    }
+
+                    formatter.addOrRemoveTrailingComma(before: i, trailingCommaSupported: trailingCommaSupported)
                 default:
                     return
                 }
@@ -84,6 +95,13 @@ public extension FormatRule {
                     }
                 }
 
+                switch formatter.options.trailingCommas {
+                case .always:
+                    break
+                case .never, .collectionsOnly:
+                    trailingCommaSupported = false
+                }
+
                 formatter.addOrRemoveTrailingComma(before: i, trailingCommaSupported: trailingCommaSupported)
 
             case .endOfScope(">"):
@@ -104,6 +122,13 @@ public extension FormatRule {
                     trailingCommaSupported = true
                 }
 
+                switch formatter.options.trailingCommas {
+                case .always:
+                    break
+                case .never, .collectionsOnly:
+                    trailingCommaSupported = false
+                }
+
                 formatter.addOrRemoveTrailingComma(before: i, trailingCommaSupported: trailingCommaSupported)
 
             default:
@@ -154,7 +179,8 @@ public extension FormatRule {
 extension Formatter {
     /// Adds or removes a trailing comma before the given index that marks the end of a comma-separated list.
     /// Trailing commas can always be removed. `trailingCommaSupported` indicates whether or not a trailing
-    /// comma is allowed at this position.
+    /// comma is allowed at this position. A comma being supported is a combination of language support
+    /// and enabled options.
     func addOrRemoveTrailingComma(before endOfListIndex: Int, trailingCommaSupported: Bool) {
         guard let prevTokenIndex = index(of: .nonSpaceOrComment, before: endOfListIndex) else { return }
 
@@ -169,11 +195,11 @@ extension Formatter {
             case .startOfScope("["), .delimiter(":"), .startOfScope("("):
                 break // do nothing
             case .delimiter(","):
-                if !options.trailingCommas {
+                if !options.trailingCommas.enabled || !trailingCommaSupported {
                     removeToken(at: prevTokenIndex)
                 }
             default:
-                if options.trailingCommas, trailingCommaSupported {
+                if options.trailingCommas.enabled, trailingCommaSupported {
                     insert(.delimiter(","), at: prevTokenIndex + 1)
                 }
             }
@@ -184,3 +210,14 @@ extension Formatter {
         }
     }
 }
+
+extension TrailingCommas {
+    var enabled: Bool {
+        switch self {
+        case .never:
+            return false
+        case .always, .collectionsOnly:
+            return true
+        }
+    }
+}
diff --git a/Tests/InferenceTests.swift b/Tests/InferenceTests.swift
index fc6f7ca9..7fcd1047 100644
--- a/Tests/InferenceTests.swift
+++ b/Tests/InferenceTests.swift
@@ -149,13 +149,13 @@ class InferenceTests: XCTestCase {
     func testInferTrailingCommas() {
         let input = "let foo = [\nbar,\n]\n let baz = [\nquux\n]"
         let options = inferFormatOptions(from: tokenize(input))
-        XCTAssertTrue(options.trailingCommas)
+        XCTAssertEqual(options.trailingCommas, .always)
     }
 
     func testInferNoTrailingCommas() {
         let input = "let foo = [\nbar\n]\n let baz = [\nquux\n]"
         let options = inferFormatOptions(from: tokenize(input))
-        XCTAssertFalse(options.trailingCommas)
+        XCTAssertEqual(options.trailingCommas, .never)
     }
 
     // MARK: truncateBlankLines
diff --git a/Tests/Rules/TrailingCommasTests.swift b/Tests/Rules/TrailingCommasTests.swift
index 82d41b0e..5ebf1267 100644
--- a/Tests/Rules/TrailingCommasTests.swift
+++ b/Tests/Rules/TrailingCommasTests.swift
@@ -22,6 +22,13 @@ class TrailingCommasTests: XCTestCase {
         testFormatting(for: input, output, rule: .trailingCommas)
     }
 
+    func testCommaAddedToLastItemCollectionsOnly() {
+        let input = "[\n    foo,\n    bar\n]"
+        let output = "[\n    foo,\n    bar,\n]"
+        let options = FormatOptions(trailingCommas: .collectionsOnly)
+        testFormatting(for: input, output, rule: .trailingCommas, options: options)
+    }
+
     func testCommaAddedToDictionary() {
         let input = "[\n    foo: bar\n]"
         let output = "[\n    foo: bar,\n]"
@@ -262,14 +269,14 @@ class TrailingCommasTests: XCTestCase {
 
     func testCommaNotAddedToLastItem() {
         let input = "[\n    foo,\n    bar\n]"
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
     func testCommaRemovedFromLastItem() {
         let input = "[\n    foo,\n    bar,\n]"
         let output = "[\n    foo,\n    bar\n]"
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -294,7 +301,7 @@ class TrailingCommasTests: XCTestCase {
             }
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -304,7 +311,7 @@ class TrailingCommasTests: XCTestCase {
             bar _: Int
         ) {}
         """
-        let options = FormatOptions(trailingCommas: true)
+        let options = FormatOptions(trailingCommas: .always)
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -319,7 +326,7 @@ class TrailingCommasTests: XCTestCase {
             bar _: Int
         ) {}
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -336,7 +343,7 @@ class TrailingCommasTests: XCTestCase {
             baaz _: Int)
         {}
         """
-        let options = FormatOptions(trailingCommas: false, closingParenPosition: .sameLine)
+        let options = FormatOptions(trailingCommas: .never, closingParenPosition: .sameLine)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -353,7 +360,7 @@ class TrailingCommasTests: XCTestCase {
             baaz _: Int)
         {}
         """
-        let options = FormatOptions(trailingCommas: true, closingParenPosition: .sameLine)
+        let options = FormatOptions(trailingCommas: .always, closingParenPosition: .sameLine)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -368,7 +375,7 @@ class TrailingCommasTests: XCTestCase {
             bar _: Int,
         ) {}
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -383,7 +390,7 @@ class TrailingCommasTests: XCTestCase {
             bar _: Int
         ) {}
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -402,7 +409,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -421,7 +428,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -436,7 +443,7 @@ class TrailingCommasTests: XCTestCase {
             1,
         )
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -451,7 +458,7 @@ class TrailingCommasTests: XCTestCase {
             1
         )
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -478,7 +485,7 @@ class TrailingCommasTests: XCTestCase {
             baz: 2,
         )
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -513,7 +520,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options, exclude: [.redundantReturn])
     }
 
@@ -537,7 +544,7 @@ class TrailingCommasTests: XCTestCase {
             ),
         )
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options, exclude: [.redundantReturn])
     }
 
@@ -552,7 +559,7 @@ class TrailingCommasTests: XCTestCase {
             0,
         )
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options, exclude: [.redundantParens])
     }
 
@@ -569,7 +576,7 @@ class TrailingCommasTests: XCTestCase {
             1,
         )
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -586,7 +593,7 @@ class TrailingCommasTests: XCTestCase {
             baz: 1
         )
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -600,7 +607,7 @@ class TrailingCommasTests: XCTestCase {
         )
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -619,7 +626,7 @@ class TrailingCommasTests: XCTestCase {
         )]]()
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options, exclude: [.propertyTypes])
     }
 
@@ -638,7 +645,7 @@ class TrailingCommasTests: XCTestCase {
         )>()
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options, exclude: [.typeSugar, .propertyTypes])
     }
 
@@ -654,7 +661,7 @@ class TrailingCommasTests: XCTestCase {
         ) {}
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -700,7 +707,7 @@ class TrailingCommasTests: XCTestCase {
         ) -> Void) {}
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -715,7 +722,7 @@ class TrailingCommasTests: XCTestCase {
         )?) {}
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -743,7 +750,7 @@ class TrailingCommasTests: XCTestCase {
         )?
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -770,7 +777,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -797,7 +804,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -824,7 +831,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -851,7 +858,7 @@ class TrailingCommasTests: XCTestCase {
             )
         }
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -888,7 +895,7 @@ class TrailingCommasTests: XCTestCase {
         default: break
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -899,7 +906,7 @@ class TrailingCommasTests: XCTestCase {
             baz: Int
         )
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -922,7 +929,7 @@ class TrailingCommasTests: XCTestCase {
         ): break
         }
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -939,7 +946,7 @@ class TrailingCommasTests: XCTestCase {
             bar
         ) = (0, 1)
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -949,7 +956,7 @@ class TrailingCommasTests: XCTestCase {
 
         )
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, rule: .trailingCommas,
                        options: options, exclude: [
                            .blankLinesAtEndOfScope,
@@ -974,7 +981,7 @@ class TrailingCommasTests: XCTestCase {
         )
         \"""
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -993,7 +1000,7 @@ class TrailingCommasTests: XCTestCase {
         )
         struct Qux {}
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1038,7 +1045,7 @@ class TrailingCommasTests: XCTestCase {
         extension CoreFoundation.CGFloat: Swift.SignedNumeric {}
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -1057,7 +1064,7 @@ class TrailingCommasTests: XCTestCase {
         )
         struct Qux {}
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1074,7 +1081,7 @@ class TrailingCommasTests: XCTestCase {
             "baz",
         )
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1091,7 +1098,7 @@ class TrailingCommasTests: XCTestCase {
             "baz"
         )
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1130,7 +1137,7 @@ class TrailingCommasTests: XCTestCase {
             T2,
         >() -> (T1, T2) {}
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1170,7 +1177,7 @@ class TrailingCommasTests: XCTestCase {
         > {}
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, rule: .trailingCommas, options: options, exclude: [.emptyExtensions, .typeSugar])
     }
 
@@ -1189,7 +1196,7 @@ class TrailingCommasTests: XCTestCase {
             T3
         > {}
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1200,7 +1207,7 @@ class TrailingCommasTests: XCTestCase {
         let output = """
         struct S<T1, T2, T3> {}
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1219,7 +1226,7 @@ class TrailingCommasTests: XCTestCase {
         ] in
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1238,7 +1245,7 @@ class TrailingCommasTests: XCTestCase {
         ] in
         }
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1253,7 +1260,7 @@ class TrailingCommasTests: XCTestCase {
             print(capturedValue1, capturedValue2)
         }
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1270,7 +1277,24 @@ class TrailingCommasTests: XCTestCase {
             y,
         ]
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
+        testFormatting(for: input, output, rule: .trailingCommas, options: options)
+    }
+
+    func testTrailingCommasRemoveFromSubscriptWhenCollectionsOnly() {
+        let input = """
+        let value = m[
+            x,
+            y,
+        ]
+        """
+        let output = """
+        let value = m[
+            x,
+            y
+        ]
+        """
+        let options = FormatOptions(trailingCommas: .collectionsOnly, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1287,7 +1311,7 @@ class TrailingCommasTests: XCTestCase {
             y
         ]
         """
-        let options = FormatOptions(trailingCommas: false)
+        let options = FormatOptions(trailingCommas: .never)
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1298,7 +1322,7 @@ class TrailingCommasTests: XCTestCase {
         let output = """
         let value = m[x, y]
         """
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
@@ -1325,10 +1349,22 @@ class TrailingCommasTests: XCTestCase {
         }
         """
 
-        let options = FormatOptions(trailingCommas: true, swiftVersion: "6.1")
+        let options = FormatOptions(trailingCommas: .always, swiftVersion: "6.1")
         testFormatting(for: input, output, rule: .trailingCommas, options: options)
     }
 
+    func testSingleLineArrayWithMultipleElements() {
+        let input = """
+        for file in files where
+            file != "build" && !file.hasPrefix(".") && ![
+                ".build", ".app", ".framework", ".xcodeproj", ".xcassets",
+            ].contains(where: { file.hasSuffix($0) }) {}
+        """
+
+        let options = FormatOptions(trailingCommas: .always)
+        testFormatting(for: input, rule: .trailingCommas, options: options)
+    }
+
     func testSingleLineArrayWithMultipleElementsFollowingNotOperator() {
         let input = """
         for file in files where
@@ -1337,7 +1373,7 @@ class TrailingCommasTests: XCTestCase {
             ].contains(where: { file.hasSuffix($0) }) {}
         """
 
-        let options = FormatOptions(trailingCommas: true)
+        let options = FormatOptions(trailingCommas: .always)
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
 
@@ -1352,7 +1388,38 @@ class TrailingCommasTests: XCTestCase {
         ].throwingOperation()
         """
 
-        let options = FormatOptions(trailingCommas: true)
+        let options = FormatOptions(trailingCommas: .always)
         testFormatting(for: input, rule: .trailingCommas, options: options)
     }
+
+    func testCollectionsOnlyAddsCollectionCommasAndRemovesNonCollectionCommas() {
+        let input = """
+        let array = [
+            1,
+            2
+        ]
+
+        func foo(
+            a: Int,
+            b: Int,
+        ) {
+            print(a, b)
+        }
+        """
+        let output = """
+        let array = [
+            1,
+            2,
+        ]
+
+        func foo(
+            a: Int,
+            b: Int
+        ) {
+            print(a, b)
+        }
+        """
+        let options = FormatOptions(trailingCommas: .collectionsOnly, swiftVersion: "6.1")
+        testFormatting(for: input, output, rule: .trailingCommas, options: options)
+    }
 }
diff --git a/Tests/Rules/WrapArgumentsTests.swift b/Tests/Rules/WrapArgumentsTests.swift
index 77700203..98bf02b9 100644
--- a/Tests/Rules/WrapArgumentsTests.swift
+++ b/Tests/Rules/WrapArgumentsTests.swift
@@ -1209,7 +1209,7 @@ class WrapArgumentsTests: XCTestCase {
     func testNoDoubleSpaceAddedToWrappedArray() {
         let input = "[ foo,\n    bar ]"
         let output = "[\n    foo,\n    bar\n]"
-        let options = FormatOptions(trailingCommas: false, wrapCollections: .beforeFirst)
+        let options = FormatOptions(trailingCommas: .never, wrapCollections: .beforeFirst)
         testFormatting(for: input, [output], rules: [.wrapArguments, .spaceInsideBrackets],
                        options: options)
     }
@@ -1217,7 +1217,7 @@ class WrapArgumentsTests: XCTestCase {
     func testTrailingCommasAddedToWrappedArray() {
         let input = "[foo,\n    bar]"
         let output = "[\n    foo,\n    bar,\n]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .beforeFirst)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .beforeFirst)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }
@@ -1225,7 +1225,7 @@ class WrapArgumentsTests: XCTestCase {
     func testTrailingCommasAddedToWrappedNestedDictionary() {
         let input = "[foo: [bar: baz,\n    bar2: baz2]]"
         let output = "[foo: [\n    bar: baz,\n    bar2: baz2,\n]]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .beforeFirst)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .beforeFirst)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }
@@ -1233,7 +1233,7 @@ class WrapArgumentsTests: XCTestCase {
     func testTrailingCommasAddedToSingleLineNestedDictionary() {
         let input = "[\n    foo: [bar: baz, bar2: baz2]]"
         let output = "[\n    foo: [bar: baz, bar2: baz2],\n]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .beforeFirst)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .beforeFirst)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }
@@ -1241,7 +1241,7 @@ class WrapArgumentsTests: XCTestCase {
     func testTrailingCommasAddedToWrappedNestedDictionaries() {
         let input = "[foo: [bar: baz,\n    bar2: baz2],\n    foo2: [bar: baz,\n    bar2: baz2]]"
         let output = "[\n    foo: [\n        bar: baz,\n        bar2: baz2,\n    ],\n    foo2: [\n        bar: baz,\n        bar2: baz2,\n    ],\n]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .beforeFirst)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .beforeFirst)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }
@@ -1311,7 +1311,7 @@ class WrapArgumentsTests: XCTestCase {
     func testNoBeforeFirstPreservedAndTrailingCommaIgnoredInMultilineNestedDictionary() {
         let input = "[foo: [bar: baz,\n    bar2: baz2]]"
         let output = "[foo: [bar: baz,\n       bar2: baz2]]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .preserve)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .preserve)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }
@@ -1319,7 +1319,7 @@ class WrapArgumentsTests: XCTestCase {
     func testBeforeFirstPreservedAndTrailingCommaAddedInSingleLineNestedDictionary() {
         let input = "[\n    foo: [bar: baz, bar2: baz2]]"
         let output = "[\n    foo: [bar: baz, bar2: baz2],\n]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .preserve)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .preserve)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }
@@ -1327,7 +1327,7 @@ class WrapArgumentsTests: XCTestCase {
     func testBeforeFirstPreservedAndTrailingCommaAddedInSingleLineNestedDictionaryWithOneNestedItem() {
         let input = "[\n    foo: [bar: baz]]"
         let output = "[\n    foo: [bar: baz],\n]"
-        let options = FormatOptions(trailingCommas: true, wrapCollections: .preserve)
+        let options = FormatOptions(trailingCommas: .always, wrapCollections: .preserve)
         testFormatting(for: input, [output], rules: [.wrapArguments, .trailingCommas],
                        options: options)
     }