Stop depending on swift-collections-benchmark (apple#86)

Instead, move the benchmark suite into its own private nested package, under `Benchmarks/`.

The recommended way to build & run benchmarks is via the `Utils/run-benchmarks.sh` script, which continues to work as before with this change.

# Conflicts:
#	.swiftpm/xcode/xcshareddata/xcschemes/swift-collections-benchmark.xcscheme
#	Package.swift

.gitignore

@@ -4,3 +4,5 @@
 /*.xcodeproj
 xcuserdata/
 .*.sw?
+/Benchmarks/.swiftpm
+/Benchmarks/.build

Benchmarks/Package.resolved

@@ -0,0 +1,34 @@
+{
+  "object": {
+    "pins": [
+      {
+        "package": "swift-argument-parser",
+        "repositoryURL": "https://github.com/apple/swift-argument-parser",
+        "state": {
+          "branch": null,
+          "revision": "83b23d940471b313427da226196661856f6ba3e0",
+          "version": "0.4.4"
+        }
+      },
+      {
+        "package": "swift-collections-benchmark",
+        "repositoryURL": "https://github.com/apple/swift-collections-benchmark",
+        "state": {
+          "branch": null,
+          "revision": "665cbb154a55f45bcedd2ab4faf17b1b7ac06de3",
+          "version": "0.0.2"
+        }
+      },
+      {
+        "package": "swift-system",
+        "repositoryURL": "https://github.com/apple/swift-system",
+        "state": {
+          "branch": null,
+          "revision": "2bc160bfe34d843ae5ff47168080add24dfd7eac",
+          "version": "0.0.2"
+        }
+      }
+    ]
+  },
+  "version": 1
+}

Benchmarks/Package.swift

@@ -0,0 +1,47 @@
+// swift-tools-version:5.3
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Collections open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import PackageDescription
+
+let package = Package(
+  name: "swift-collections.Benchmarks",
+  dependencies: [
+    .package(name: "swift-collections", path: ".."),
+    .package(url: "https://github.com/apple/swift-collections-benchmark", from: "0.0.1"),
+  ],
+  targets: [
+    .target(
+      name: "Benchmarks",
+      dependencies: [
+        .product(name: "Collections", package: "swift-collections"),
+        .product(name: "CollectionsBenchmark", package: "swift-collections-benchmark"),
+        "CppBenchmarks",
+      ],
+      path: "Benchmarks",
+      resources: [
+        .copy("Library.json"),
+      ]
+    ),
+    .target(
+      name: "CppBenchmarks",
+      path: "CppBenchmarks"
+    ),
+    .target(
+      name: "benchmark",
+      dependencies: [
+        "Benchmarks",
+      ],
+      path: "benchmark-tool"
+    ),
+  ],
+  cxxLanguageStandard: .cxx1z
+)

Package.swift

@@ -55,10 +55,6 @@ let package = Package(
     .library(name: "DequeModule", targets: ["DequeModule"]),
     .library(name: "OrderedCollections", targets: ["OrderedCollections"]),
   ],
-  dependencies: [
-    // This is only used in the benchmark executable target.
-    .package(url: "https://github.com/apple/swift-collections-benchmark", from: "0.0.1"),
-  ],
   targets: [
     .target(
       name: "Collections",
@@ -86,31 +82,6 @@ let package = Package(
       dependencies: ["CollectionsTestSupport"],
       swiftSettings: settings),
 
-    // Benchmarking
-    .target(
-      name: "Benchmarks",
-      dependencies: [
-        .product(name: "CollectionsBenchmark", package: "swift-collections-benchmark"),
-        "CppBenchmarks",
-        "Collections",
-      ],
-      path: "Benchmarks/Benchmarks",
-      resources: [
-        .copy("Library.json"),
-      ]
-    ),
-    .target(
-      name: "CppBenchmarks",
-      path: "Benchmarks/CppBenchmarks"
-    ),
-    .target(
-      name: "swift-collections-benchmark",
-      dependencies: [
-        "Benchmarks",
-      ],
-      path: "Benchmarks/swift-collections-benchmark"
-    ),
-
     // Deque<Element>
     .target(
       name: "DequeModule",
@@ -130,6 +101,5 @@ let package = Package(
       name: "OrderedCollectionsTests",
       dependencies: ["OrderedCollections", "CollectionsTestSupport"],
       swiftSettings: settings),
-  ],
-  cxxLanguageStandard: .cxx1z
+  ]
 )

Utils/run-benchmarks.sh

@@ -2,7 +2,7 @@
 
 set -eu
 
-srcroot="$(dirname "$0")/.."
+srcroot="$(dirname "$0")/../Benchmarks"
 results="batch.results"
 
 command="${1:-help}"
@@ -12,7 +12,7 @@ run() {
   local flags
   flags="-c release"
   flags="$flags -Xswiftc -Xllvm -Xswiftc -align-module-to-page-size"
-  swift run --package-path "$srcroot" $flags swift-collections-benchmark "$@"
+  swift run --package-path "$srcroot" $flags benchmark "$@"
 }
 
 case "$command" in