WASI support: build SQLKit without SwiftNIO

Package.swift

@@ -1,6 +1,11 @@
 // swift-tools-version:6.1
 import PackageDescription
 
+/// This list matches the [supported platforms on the Swift 6.1 release of SPM](https://github.com/swiftlang/swift-package-manager/blob/release/6.1/Sources/PackageDescription/SupportedPlatforms.swift).
+/// Don't add new platforms here unless raising the swift-tools-version of this manifest.
+let allPlatforms: [Platform] = [.macOS, .macCatalyst, .iOS, .tvOS, .watchOS, .visionOS, .driverKit, .linux, .windows, .android, .wasi, .openbsd]
+let nonWASIPlatforms: [Platform] = allPlatforms.filter { $0 != .wasi }
+
 let package = Package(
     name: "sql-kit",
     platforms: [
@@ -24,7 +29,11 @@ let package = Package(
             dependencies: [
                 .product(name: "Collections", package: "swift-collections"),
                 .product(name: "Logging", package: "swift-log"),
-                .product(name: "NIOCore", package: "swift-nio"),
+                // SwiftNIO does not support wasm32-unknown-wasip1. Target dependency conditions
+                // are evaluated per platform, so on WASI NIOCore is simply not linked and the
+                // `EventLoopFuture` surface drops out via `#if canImport(NIOCore)`; the async
+                // surface is unaffected.
+                .product(name: "NIOCore", package: "swift-nio", condition: .when(platforms: nonWASIPlatforms)),
             ],
             swiftSettings: swiftSettings
         ),
@@ -38,8 +47,9 @@ let package = Package(
         .testTarget(
             name: "SQLKitTests",
             dependencies: [
-                .product(name: "NIOCore", package: "swift-nio"),
-                .product(name: "NIOEmbedded", package: "swift-nio"),
+                // The test suite exercises the SwiftNIO surface, so it is not built for WASI.
+                .product(name: "NIOCore", package: "swift-nio", condition: .when(platforms: nonWASIPlatforms)),
+                .product(name: "NIOEmbedded", package: "swift-nio", condition: .when(platforms: nonWASIPlatforms)),
                 .target(name: "SQLKit"),
                 .target(name: "SQLKitBenchmark"),
             ],

Sources/SQLKit/Builders/Prototypes/SQLQueryBuilder.swift

@@ -1,4 +1,7 @@
+// EventLoopFuture is elided on builds without SwiftNIO.
+#if canImport(NIOCore)
 import class NIOCore.EventLoopFuture
+#endif
 
 /// Base definitions for builders which set up queries and execute them against a given database.
 ///
@@ -10,25 +13,31 @@ public protocol SQLQueryBuilder: AnyObject {
     /// Connection to execute query on.
     var database: any SQLDatabase { get }
 
+    // N.B.: The `#if` encloses the doc comment; placed between the comment and the declaration it
+    // would detach the doc from the symbol graph.
+    #if canImport(NIOCore)
     /// Execute the query on the connection, ignoring any results.
     ///
     /// Although it is a protocol requirement for historical reasons, this is considered a legacy interface
     /// thanks to its reliance on `EventLoopFuture`. Users should call ``run()-3tldd`` whenever possible.
     func run() -> EventLoopFuture<Void>
-
+    #endif
+
     /// Execute the query on the connection, ignoring any results.
     func run() async throws
 
 }
 
 extension SQLQueryBuilder {
+    #if canImport(NIOCore)
     /// Execute the query associated with the builder on the builder's database, ignoring any results.
     ///
     /// See ``SQLQueryFetcher`` for methods which retrieve results from a query.
     @inlinable
     public func run() -> EventLoopFuture<Void> {
         self.database.execute(sql: self.query) { _ in }
     }
+    #endif
 
     /// Execute the query associated with the builder on the builder's database, ignoring any results.
     ///

Sources/SQLKit/Builders/Prototypes/SQLQueryFetcher.swift

@@ -1,10 +1,15 @@
+// `EventLoopFuture` is unavailable where SwiftNIO is not linked. The `async` `first()`/`all()`/
+// `run(_:)` families further down are unconditional and carry the whole surface there.
+#if canImport(NIOCore)
 import class NIOCore.EventLoopFuture
+#endif
 
 /// Common definitions for ``SQLQueryBuilder``s which support retrieving result rows.
 public protocol SQLQueryFetcher: SQLQueryBuilder {}
 
 // MARK: - First (EventLoopFuture)
 
+#if canImport(NIOCore)
 extension SQLQueryFetcher {
     /// Returns the named column from the first output row, if any, decoded as a given type.
     ///
@@ -70,6 +75,8 @@ extension SQLQueryFetcher {
     }
 }
 
+#endif  // canImport(NIOCore)
+
 // MARK: - First (async)
 
 extension SQLQueryFetcher {
@@ -144,6 +151,7 @@ extension SQLQueryFetcher {
 
 // MARK: - All (EventLoopFuture)
 
+#if canImport(NIOCore)
 extension SQLQueryFetcher {
     /// Returns the named column from each output row, if any, decoded as a given type.
     ///
@@ -205,6 +213,8 @@ extension SQLQueryFetcher {
     }
 }
 
+#endif  // canImport(NIOCore)
+
 // MARK: - All (async)
 
 extension SQLQueryFetcher {
@@ -271,6 +281,7 @@ extension SQLQueryFetcher {
 
 // MARK: - Run (EventLoopFuture)
 
+#if canImport(NIOCore)
 extension SQLQueryFetcher {
     /// Using a default-configured ``SQLRowDecoder``, call the provided handler closure with the result of decoding
     /// each output row, if any, as a given type.
@@ -337,6 +348,8 @@ extension SQLQueryFetcher {
     }
 }
 
+#endif  // canImport(NIOCore)
+
 // MARK: - Run (async)
 
 extension SQLQueryFetcher {

Sources/SQLKit/Database/SQLDatabase.swift

@@ -1,5 +1,9 @@
+// SwiftNIO is not available on every platform SQLKit supports (see Package.swift); the
+// EventLoopFuture surface below is elided where it is absent.
+#if canImport(NIOCore)
 import protocol NIOCore.EventLoop
 import class NIOCore.EventLoopFuture
+#endif
 import struct Logging.Logger
 
 /// The common interface to SQLKit for both drivers and client code.
@@ -56,14 +60,18 @@ public protocol SQLDatabase: Sendable {
     /// The `Logger` used for logging all operations relating to a given database.
     var logger: Logger { get }
 
+    // N.B.: Every `#if` in this file encloses the doc comment of the declaration it gates; placed
+    // between the two it would silently detach the doc from the symbol graph.
+    #if canImport(NIOCore)
     /// The `EventLoop` used for asynchronous operations on a given database.
     ///
     /// If there is no specific `EventLoop` which handles the database (such as because it is a connection pool which
     /// assigns loops to connections at point of use, or because the underlying implementation is based on Swift
     /// Concurrency or some other asynchronous execution technology), a single consistent `EventLoop` must be chosen
     /// for the database and returned for this property nonetheless.
     var eventLoop: any EventLoop { get }
-
+    #endif
+
     /// The version number the database reports for itself.
     ///
     /// The version must be provided via a type conforming to the ``SQLDatabaseReportedVersion`` protocol. If the
@@ -102,6 +110,7 @@ public protocol SQLDatabase: Sendable {
     /// > it's unavoidable, as there are no direct entry points to SQLKit without a driver.
     var queryLogLevel: Logger.Level? { get }
 
+    #if canImport(NIOCore)
     /// Requests that the given generic SQL query be serialized and executed on the database, and that
     /// the `onRow` closure be invoked once for each result row the query returns (if any).
     ///
@@ -118,6 +127,7 @@ public protocol SQLDatabase: Sendable {
         sql query: any SQLExpression,
         _ onRow: @escaping @Sendable (any SQLRow) -> ()
     ) -> EventLoopFuture<Void>
+    #endif
 
     /// Requests that the given generic SQL query be serialized and executed on the database, and that
     /// the `onRow` closure be invoked once for each result row the query returns (if any).
@@ -200,6 +210,10 @@ extension SQLDatabase {
 }
 
 extension SQLDatabase {
+    // This default bridges the `async` requirement to the legacy `EventLoopFuture` one, so it can
+    // only exist where the latter does. Without SwiftNIO there is no future overload to forward to
+    // and conformers implement the `async` `execute` directly.
+    #if canImport(NIOCore)
     /// The default implementation for ``execute(sql:_:)-4eg19``.
     @inlinable
     public func execute(
@@ -208,7 +222,8 @@ extension SQLDatabase {
     ) async throws {
         try await self.execute(sql: query, onRow).get()
     }
-
+    #endif
+
     /// The default implementation for ``withSession(_:)-9b68j``.
     @inlinable
     public func withSession<R>(
@@ -227,10 +242,12 @@ private struct CustomLoggerSQLDatabase<D: SQLDatabase>: SQLDatabase {
     // See `SQLDatabase.logger`.
     let logger: Logger
 
+    #if canImport(NIOCore)
     // See `SQLDatabase.eventLoop`.
     var eventLoop: any EventLoop {
         self.database.eventLoop
     }
+    #endif
 
     // See `SQLDatabase.version`.
     var version: (any SQLDatabaseReportedVersion)? {
@@ -247,13 +264,15 @@ private struct CustomLoggerSQLDatabase<D: SQLDatabase>: SQLDatabase {
         self.database.queryLogLevel
     }
 
+    #if canImport(NIOCore)
     // See `SQLDatabase.execute(sql:_:)`.
     func execute(
         sql query: any SQLExpression,
         _ onRow: @escaping @Sendable (any SQLRow) -> ()
     ) -> EventLoopFuture<Void> {
         self.database.execute(sql: query, onRow)
     }
+    #endif
 
     // See `SQLDatabase.execute(sql:_:)`.
     func execute(

Sources/SQLKit/Exports.swift

@@ -1,3 +1,6 @@
+// EventLoop/EventLoopFuture are SwiftNIO types, elided where SwiftNIO is unavailable.
+#if canImport(NIOCore)
 @_documentation(visibility: internal) @_exported import protocol NIOCore.EventLoop
 @_documentation(visibility: internal) @_exported import class NIOCore.EventLoopFuture
+#endif
 @_documentation(visibility: internal) @_exported import struct Logging.Logger

Sources/SQLKitBenchmark/SQLBenchmarker.swift

@@ -1,5 +1,7 @@
 import Logging
+#if canImport(NIOCore)
 import NIOCore
+#endif
 public import SQLKit
 import XCTest
 
@@ -21,6 +23,8 @@ public final class SQLBenchmarker: Sendable {
         }
     }
 
+    // The deprecated EventLoopFuture bridges are elided where SwiftNIO is unavailable.
+    #if canImport(NIOCore)
     @available(*, deprecated, renamed: "runAllTests()", message: "Use `runAllTests()` instead.")
     public func testAll() throws {
         try database.eventLoop.makeFutureWithTask { try await self.runAllTests() }.wait()
@@ -30,6 +34,7 @@ public final class SQLBenchmarker: Sendable {
     public func run() throws {
         try self.testAll()
     }
+    #endif
 
     func runTest(
         _ name: String = #function,