From 694bf42cecb624e81776e7e65e857a1987a91ce3 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Thu, 23 Nov 2023 17:34:17 -0800
Subject: [PATCH 1/2] build: simplify the build rules with newer CMake (NFC)

Swift now requires CMake 3.19.6 as a minimum version.  Assume that we
can use CMake newer than 3.16 and simplify the build rules.
---
 CMakeLists.txt | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e2c28b25..b5c7fb1f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,24 +1,12 @@
-cmake_minimum_required(VERSION 3.15.1)
+cmake_minimum_required(VERSION 3.19)
 
 project(SwiftTSC LANGUAGES C Swift)
 
-set(SWIFT_VERSION 5)
-set(CMAKE_Swift_LANGUAGE_VERSION ${SWIFT_VERSION})
-if(CMAKE_VERSION VERSION_LESS 3.16)
-    add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-swift-version$<SEMICOLON>${SWIFT_VERSION}>)
-    # Workaround for CMake 3.15 which doesn't link libraries properly on Windows
-    set(CMAKE_LINK_LIBRARY_FLAG "-l")
-endif()
-
+set(CMAKE_Swift_LANGUAGE_VERSION 5)
 set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/swift)
 
-if(CMAKE_VERSION VERSION_LESS 3.16 AND CMAKE_SYSTEM_NAME STREQUAL Windows)
-  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-else()
-  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
-  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
-endif()
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 
 set(CMAKE_DISABLE_IN_SOURCE_BUILD YES)

From 0b7d13f26cb3c23c261de9ff495452ce4d534d23 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Thu, 23 Nov 2023 17:45:10 -0800
Subject: [PATCH 2/2] build: auto-Vendor SwiftSystem when not provided

When SwiftSystem is not provided to be built against explicitly (i.e.
`-D SwiftSystem_DIR=...`), vendor a copy of SwiftSystem to allow the
library to be built by including and building its dependencies.  This
behaviour is similar to how SPM based builds function.
---
 CMakeLists.txt                  | 19 ++++++++++++++++++-
 Sources/TSCBasic/CMakeLists.txt |  4 ++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b5c7fb1f..0ce75443 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,3 +1,7 @@
+if(POLICY CMP0028)
+  cmake_policy(SET CMP0028 NEW)
+endif()
+
 cmake_minimum_required(VERSION 3.19)
 
 project(SwiftTSC LANGUAGES C Swift)
@@ -13,10 +17,23 @@ set(CMAKE_DISABLE_IN_SOURCE_BUILD YES)
 
 option(BUILD_SHARED_LIBS "Build shared libraries by default" YES)
 
+# Toolchain bundled libraries
 find_package(dispatch QUIET)
 find_package(Foundation QUIET)
+
+# System Packages
 find_package(Threads QUIET)
-find_package(SwiftSystem CONFIG REQUIRED)
+
+# Package Dependencies
+find_package(SwiftSystem CONFIG)
+if(NOT SwiftSystem_FOUND)
+  include(FetchContent)
+  message("-- Vendoring SwiftSystem")
+  FetchContent_Declare(SwiftSystem
+    GIT_REPOSITORY https://github.com/apple/swift-system
+    GIT_TAG 1.1.1)
+  FetchContent_MakeAvailable(SwiftSystem)
+endif()
 
 add_subdirectory(Sources)
 add_subdirectory(cmake/modules)
diff --git a/Sources/TSCBasic/CMakeLists.txt b/Sources/TSCBasic/CMakeLists.txt
index 1217bdfc..97d70b51 100644
--- a/Sources/TSCBasic/CMakeLists.txt
+++ b/Sources/TSCBasic/CMakeLists.txt
@@ -6,6 +6,10 @@
 # See http://swift.org/LICENSE.txt for license information
 # See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 
+if(NOT SwiftSystem_FOUND)
+  add_library(SwiftSystem::SystemPackage ALIAS SystemPackage)
+endif()
+
 add_library(TSCBasic
   Await.swift
   ByteString.swift