Pin Swift 6.4 in peer connectivity CI

Author: 1amageek

.github/workflows/ci.yml

@@ -17,12 +17,15 @@ concurrency:
 jobs:
   test:
     name: macOS tests
-    runs-on: macos-26
+    runs-on: xcode-27
     timeout-minutes: 30
     steps:
       - name: Checkout
         uses: actions/checkout@v6
 
+      - name: Install pinned Swift toolchain
+        run: scripts/install-swift-ci.sh
+
       - name: Swift version
         run: swift --version
 

scripts/install-swift-ci.sh

@@ -0,0 +1,87 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+snapshot="swift-6.4.x-DEVELOPMENT-SNAPSHOT-2026-07-23-a"
+expected_commit="ef761e567dc94ee"
+toolchain_identifier="org.swift.64202607231a"
+download_root="https://download.swift.org/swift-6.4.x-branch"
+temporary_parent="${RUNNER_TEMP:-${TMPDIR:-/tmp}}"
+temporary_directory="$(mktemp -d "$temporary_parent/swift-toolchain.XXXXXX")"
+
+cleanup() {
+  rm -rf "$temporary_directory"
+}
+trap cleanup EXIT
+
+verify_compiler() {
+  local swift_binary="$1"
+  local version
+  version="$("$swift_binary" --version)"
+  if [[ "$version" != *"Swift $expected_commit"* ]]; then
+    echo "Unexpected Swift compiler. Required commit: $expected_commit" >&2
+    echo "$version" >&2
+    exit 1
+  fi
+  echo "$version"
+}
+
+append_github_path() {
+  local directory="$1"
+  if [[ -n "${GITHUB_PATH:-}" ]]; then
+    printf '%s\n' "$directory" >> "$GITHUB_PATH"
+  fi
+}
+
+install_macos_toolchain() {
+  local toolchain_root="$HOME/Library/Developer/Toolchains/$snapshot.xctoolchain"
+  if [[ ! -x "$toolchain_root/usr/bin/swift" ]]; then
+    local package_path="$temporary_directory/$snapshot-osx.pkg"
+    local package_url="$download_root/xcode/$snapshot/$snapshot-osx.pkg"
+    curl --fail --location --show-error "$package_url" --output "$package_path"
+
+    local signature
+    signature="$(pkgutil --check-signature "$package_path")"
+    if [[ "$signature" != *"Developer ID Installer: Swift Open Source (V9AUD2URP3)"* ]]; then
+      echo "Swift toolchain package signature verification failed." >&2
+      echo "$signature" >&2
+      exit 1
+    fi
+
+    installer -pkg "$package_path" -target CurrentUserHomeDirectory
+  fi
+
+  local toolchain_linker="$toolchain_root/usr/bin/ld"
+  if [[ ! -x "$toolchain_linker" ]]; then
+    local xcode_linker
+    xcode_linker="$(xcrun --toolchain XcodeDefault --find ld)"
+    if [[ ! -x "$xcode_linker" ]]; then
+      echo "The active Xcode toolchain does not provide an executable linker: $xcode_linker" >&2
+      exit 1
+    fi
+    if [[ -L "$toolchain_linker" ]]; then
+      unlink "$toolchain_linker"
+    elif [[ -e "$toolchain_linker" ]]; then
+      echo "The Swift toolchain linker path exists but is not executable: $toolchain_linker" >&2
+      exit 1
+    fi
+    ln -s "$xcode_linker" "$toolchain_linker"
+  fi
+
+  local swift_binary
+  swift_binary="$(xcrun --toolchain "$toolchain_identifier" --find swift)"
+  verify_compiler "$swift_binary"
+  append_github_path "${swift_binary%/swift}"
+  if [[ -n "${GITHUB_ENV:-}" ]]; then
+    printf 'TOOLCHAINS=%s\n' "$toolchain_identifier" >> "$GITHUB_ENV"
+  fi
+}
+
+case "$(uname -s)" in
+  Darwin)
+    install_macos_toolchain
+    ;;
+  *)
+    echo "Unsupported operating system: $(uname -s)" >&2
+    exit 1
+    ;;
+esac