From 06c4517c4e3b90bf638bbab0f290c93c690db8df Mon Sep 17 00:00:00 2001
From: Owen Voorhees <owen@squibner.com>
Date: Sat, 29 Aug 2020 21:12:08 -0700
Subject: [PATCH] Preserve relative ordering in ParsedOptions.arguments(for
 options:)

This is significant in at least one case (-F/-Fsystem ordering needs to be preserved),
and isn't that expensive, so always preserve the ordering to ensure more predictable behavior
---
 Sources/SwiftOptions/ParsedOptions.swift      | 10 ++++++----
 Tests/SwiftDriverTests/SwiftDriverTests.swift | 13 +++++++++++++
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/Sources/SwiftOptions/ParsedOptions.swift b/Sources/SwiftOptions/ParsedOptions.swift
index 12ccc532b..de00727dc 100644
--- a/Sources/SwiftOptions/ParsedOptions.swift
+++ b/Sources/SwiftOptions/ParsedOptions.swift
@@ -191,11 +191,13 @@ extension ParsedOptions {
   }
 
   public mutating func arguments(for options: Option...) -> [ParsedOption] {
-    return options.flatMap { lookup($0) }
+    return arguments(for: options)
   }
 
   public mutating func arguments(for options: [Option]) -> [ParsedOption] {
-    return options.flatMap { lookup($0) }
+    // The relative ordering of different options is sometimes significant, so
+    // sort the results by their position in the command line.
+    return options.flatMap { lookup($0) }.sorted { $0.index < $1.index }
   }
 
   public mutating func arguments(in group: Option.Group) -> [ParsedOption] {
@@ -203,11 +205,11 @@ extension ParsedOptions {
   }
 
   public mutating func last(for options: Option...) -> ParsedOption? {
-    return arguments(for: options).max { $0.index < $1.index }
+    return last(for: options)
   }
 
   public mutating func last(for options: [Option]) -> ParsedOption? {
-    return arguments(for: options).max { $0.index < $1.index }
+    return arguments(for: options).last
   }
 
   /// Return the last parsed options that matches the given predicate.
diff --git a/Tests/SwiftDriverTests/SwiftDriverTests.swift b/Tests/SwiftDriverTests/SwiftDriverTests.swift
index 53411a661..57e3e6140 100644
--- a/Tests/SwiftDriverTests/SwiftDriverTests.swift
+++ b/Tests/SwiftDriverTests/SwiftDriverTests.swift
@@ -124,6 +124,19 @@ final class SwiftDriverTests: XCTestCase {
     XCTAssertTrue(jobs[0].commandLine.contains(.joinedOptionAndPath("-F=", .relative(.init("other/relative/dir")))))
   }
 
+  func testRelativeOptionOrdering() throws {
+    var driver = try Driver(args: ["swiftc", "foo.swift",
+                                   "-F", "/path/to/frameworks",
+                                   "-Fsystem", "/path/to/systemframeworks",
+                                   "-F", "/path/to/more/frameworks"])
+    let jobs = try driver.planBuild()
+    XCTAssertEqual(jobs[0].kind, .compile)
+    // The relative ordering of -F and -Fsystem options should be preserved.
+    XCTAssertTrue(jobs[0].commandLine.contains(subsequence: [.flag("-F"), .path(.absolute(.init("/path/to/frameworks"))),
+                                                             .flag("-Fsystem"), .path(.absolute(.init("/path/to/systemframeworks"))),
+                                                             .flag("-F"), .path(.absolute(.init("/path/to/more/frameworks")))]))
+  }
+
   func testBatchModeDiagnostics() throws {
       try assertNoDriverDiagnostics(args: "swiftc", "-enable-batch-mode") { driver in
         switch driver.compilerMode {