build: remove the PreviewServer on Windows

This is the critical change to enable Windows support in DocC.  The
dependency on NIO is restricted to the PreviewServer and as NIO is
incapable of supporting non-POSIX models (or emulation of POSIX models),
we cannot use this dependency on Windows.  As a temporary solution,
remove the NIO dependency on Windows by removing the PreviewServer.

Author: compnerd

Package.swift

@@ -63,29 +63,6 @@ let package = Package(
             swiftSettings: swiftSettings
         ),
 
-        // Command-line tool library
-        .target(
-            name: "SwiftDocCUtilities",
-            dependencies: [
-                .target(name: "SwiftDocC"),
-                .product(name: "NIOHTTP1", package: "swift-nio"),
-                .product(name: "ArgumentParser", package: "swift-argument-parser")
-            ],
-            swiftSettings: swiftSettings
-        ),
-        .testTarget(
-            name: "SwiftDocCUtilitiesTests",
-            dependencies: [
-                .target(name: "SwiftDocCUtilities"),
-                .target(name: "SwiftDocC"),
-                .target(name: "SwiftDocCTestUtilities"),
-            ],
-            resources: [
-                .copy("Test Resources"),
-                .copy("Test Bundles"),
-            ],
-            swiftSettings: swiftSettings
-        ),
         // Test utility library
         .target(
             name: "SwiftDocCTestUtilities",
@@ -126,20 +103,74 @@ let package = Package(
     ]
 )
 
+// Command-line tool library
+#if os(Windows)
+package.targets.append(
+    .target(
+        name: "SwiftDocCUtilities",
+        dependencies: [
+            .target(name: "SwiftDocC"),
+            .product(name: "ArgumentParser", package: "swift-argument-parser")
+        ],
+        exclude: [
+            // PreviewServer requires NIO which cannot support non-POSIX platforms.
+            "PreviewServer",
+            "Action/Actions/PreviewAction.swift",
+            "ArgumentParsing/ActionExtensions/PreviewAction+CommandInitialization.swift",
+            "ArgumentParsing/Subcommands/Preview.swift",
+        ],
+        swiftSettings: swiftSettings
+    )
+)
+#else
+package.targets.append(
+    .target(
+        name: "SwiftDocCUtilities",
+        dependencies: [
+            .target(name: "SwiftDocC"),
+            .product(name: "NIOHTTP1", package: "swift-nio"),
+            .product(name: "ArgumentParser", package: "swift-argument-parser")
+        ],
+        swiftSettings: swiftSettings
+    )
+)
+#endif
+
+package.targets.append(
+    .testTarget(
+        name: "SwiftDocCUtilitiesTests",
+        dependencies: [
+            .target(name: "SwiftDocCUtilities"),
+            .target(name: "SwiftDocC"),
+            .target(name: "SwiftDocCTestUtilities"),
+        ],
+        resources: [
+            .copy("Test Resources"),
+            .copy("Test Bundles"),
+        ],
+        swiftSettings: swiftSettings
+    )
+)
+
 // If the `SWIFTCI_USE_LOCAL_DEPS` environment variable is set,
 // we're building in the Swift.org CI system alongside other projects in the Swift toolchain and
 // we can depend on local versions of our dependencies instead of fetching them remotely.
 if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
     // Building standalone, so fetch all dependencies remotely.
     package.dependencies += [
-        .package(url: "https://github.com/apple/swift-nio.git", from: "2.53.0"),
         .package(url: "https://github.com/apple/swift-markdown.git", branch: "main"),
         .package(url: "https://github.com/apple/swift-lmdb.git", branch: "main"),
         .package(url: "https://github.com/apple/swift-argument-parser", from: "1.2.2"),
         .package(url: "https://github.com/apple/swift-docc-symbolkit", branch: "main"),
         .package(url: "https://github.com/apple/swift-crypto.git", from: "2.5.0"),
         .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"),
     ]
+
+#if !os(Windows)
+    package.dependencies += [
+        .package(url: "https://github.com/apple/swift-nio.git", from: "2.53.0"),
+    ]
+#endif
 } else {
     // Building in the Swift.org CI system, so rely on local versions of dependencies.
     package.dependencies += [

Sources/SwiftDocCUtilities/Docc.swift

@@ -12,10 +12,15 @@ import ArgumentParser
 
 /// The default, command-line interface you use to compile and preview documentation.
 public struct Docc: ParsableCommand {
+    #if canImport(NIOHTTP)
+    let subcommands: [ParsableCommand.Type] = [Convert.self, Index.self, Preview.self, ProcessArchive.self]
+    #else
+    let subcommands: [ParsableCommand.Type] = [Convert.self, Index.self, ProcessArchive.self]
+    #endif
 
     public static var configuration = CommandConfiguration(
         abstract: "Documentation Compiler: compile, analyze, and preview documentation.",
-        subcommands: [Convert.self, Index.self, Preview.self, ProcessArchive.self])
+        subcommands: subcommands)
 
     public init() {}
 }