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

Author: owenv

Sources/SwiftOptions/ParsedOptions.swift

@@ -191,23 +191,25 @@ 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] {
     return groupIndex[group, default: []]
   }
 
   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.

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 {