Order package manifest to start with the package declaration

Instead of starting with environment variable parsing, start with the actual package manifest, which is most likely the most interesting to most users.

rdar://121441220

Author: ahoppen

Package.swift

@@ -3,40 +3,6 @@
 import Foundation
 import PackageDescription
 
-// MARK: - Parse build arguments
-
-func hasEnvironmentVariable(_ name: String) -> Bool {
-  return ProcessInfo.processInfo.environment[name] != nil
-}
-
-/// Use the `NonDarwinLogger` even if `os_log` can be imported.
-///
-/// This is useful when running tests using `swift test` because xctest will not display the output from `os_log` on the
-/// command line.
-let forceNonDarwinLogger = hasEnvironmentVariable("SOURCEKITLSP_FORCE_NON_DARWIN_LOGGER")
-
-// When building the toolchain on the CI, don't add the CI's runpath for the
-// final build before installing.
-let installAction = hasEnvironmentVariable("SOURCEKIT_LSP_CI_INSTALL")
-
-/// Assume that all the package dependencies are checked out next to sourcekit-lsp and use that instead of fetching a
-/// remote dependency.
-let useLocalDependencies = hasEnvironmentVariable("SWIFTCI_USE_LOCAL_DEPS")
-
-// MARK: - Compute custom build settings
-
-var sourcekitLSPLinkSettings: [LinkerSetting] = []
-if installAction {
-  sourcekitLSPLinkSettings += [.unsafeFlags(["-no-toolchain-stdlib-rpath"], .when(platforms: [.linux, .android]))]
-}
-
-var lspLoggingSwiftSettings: [SwiftSetting] = []
-if forceNonDarwinLogger {
-  lspLoggingSwiftSettings += [.define("SOURCEKITLSP_FORCE_NON_DARWIN_LOGGER")]
-}
-
-// MARK: - Build the package
-
 let package = Package(
   name: "SourceKitLSP",
   platforms: [.macOS("12.0")],
@@ -45,9 +11,7 @@ let package = Package(
     .library(name: "_SourceKitLSP", targets: ["SourceKitLSP"]),
     .library(name: "LSPBindings", targets: ["LanguageServerProtocol", "LanguageServerProtocolJSONRPC"]),
   ],
-  dependencies: [
-    // See 'Dependencies' below.
-  ],
+  dependencies: dependencies,
   targets: [
     // Formatting style:
     //  - One section for each target and its test target
@@ -311,31 +275,70 @@ let package = Package(
   ]
 )
 
-// MARK: Dependencies
+// MARK: - Parse build arguments
+
+func hasEnvironmentVariable(_ name: String) -> Bool {
+  return ProcessInfo.processInfo.environment[name] != nil
+}
+
+/// Use the `NonDarwinLogger` even if `os_log` can be imported.
+///
+/// This is useful when running tests using `swift test` because xctest will not display the output from `os_log` on the
+/// command line.
+var forceNonDarwinLogger: Bool { hasEnvironmentVariable("SOURCEKITLSP_FORCE_NON_DARWIN_LOGGER") }
+
+// When building the toolchain on the CI, don't add the CI's runpath for the
+// final build before installing.
+var installAction: Bool { hasEnvironmentVariable("SOURCEKIT_LSP_CI_INSTALL") }
+
+/// Assume that all the package dependencies are checked out next to sourcekit-lsp and use that instead of fetching a
+/// remote dependency.
+var useLocalDependencies: Bool { hasEnvironmentVariable("SWIFTCI_USE_LOCAL_DEPS") }
+
+// MARK: - Dependencies
 
 // When building with the swift build-script, use local dependencies whose contents are controlled
 // by the external environment. This allows sourcekit-lsp to take advantage of the automation used
 // for building the swift toolchain, such as `update-checkout`, or cross-repo PR tests.
 
-if useLocalDependencies {
-  package.dependencies += [
-    .package(path: "../indexstore-db"),
-    .package(name: "swift-package-manager", path: "../swiftpm"),
-    .package(path: "../swift-tools-support-core"),
-    .package(path: "../swift-argument-parser"),
-    .package(path: "../swift-syntax"),
-    .package(path: "../swift-crypto"),
-  ]
-} else {
-  let relatedDependenciesBranch = "main"
-
-  // Building standalone.
-  package.dependencies += [
-    .package(url: "https://github.com/apple/indexstore-db.git", branch: relatedDependenciesBranch),
-    .package(url: "https://github.com/apple/swift-package-manager.git", branch: relatedDependenciesBranch),
-    .package(url: "https://github.com/apple/swift-tools-support-core.git", branch: relatedDependenciesBranch),
-    .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2"),
-    .package(url: "https://github.com/apple/swift-syntax.git", branch: relatedDependenciesBranch),
-    .package(url: "https://github.com/apple/swift-crypto.git", from: "3.0.0"),
-  ]
+var dependencies: [Package.Dependency] {
+  if useLocalDependencies {
+    return [
+      .package(path: "../indexstore-db"),
+      .package(name: "swift-package-manager", path: "../swiftpm"),
+      .package(path: "../swift-tools-support-core"),
+      .package(path: "../swift-argument-parser"),
+      .package(path: "../swift-syntax"),
+      .package(path: "../swift-crypto"),
+    ]
+  } else {
+    let relatedDependenciesBranch = "main"
+
+    return [
+      .package(url: "https://github.com/apple/indexstore-db.git", branch: relatedDependenciesBranch),
+      .package(url: "https://github.com/apple/swift-package-manager.git", branch: relatedDependenciesBranch),
+      .package(url: "https://github.com/apple/swift-tools-support-core.git", branch: relatedDependenciesBranch),
+      .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2"),
+      .package(url: "https://github.com/apple/swift-syntax.git", branch: relatedDependenciesBranch),
+      .package(url: "https://github.com/apple/swift-crypto.git", from: "3.0.0"),
+    ]
+  }
+}
+
+// MARK: - Compute custom build settings
+
+var sourcekitLSPLinkSettings: [LinkerSetting] {
+  if installAction {
+    return [.unsafeFlags(["-no-toolchain-stdlib-rpath"], .when(platforms: [.linux, .android]))]
+  } else {
+    return []
+  }
+}
+
+var lspLoggingSwiftSettings: [SwiftSetting] {
+  if forceNonDarwinLogger {
+    return [.define("SOURCEKITLSP_FORCE_NON_DARWIN_LOGGER")]
+  } else {
+    return []
+  }
 }