Attempt to diagnose arguments to -sdk that point to unsupported SDKs

Sources/SwiftDriver/Driver/Driver.swift

@@ -2005,8 +2005,11 @@ extension Driver {
 
       if !fileSystem.exists(path) {
         diagnosticsEngine.emit(.warning_no_such_sdk(sdkPath))
+      } else if isSDKTooOld(sdkPath: path, fileSystem: fileSystem,
+                            diagnosticsEngine: diagnosticsEngine) {
+        diagnosticsEngine.emit(.error_sdk_too_old(sdkPath))
+        return nil
       }
-      // .. else check if SDK is too old (we need target triple to diagnose that).
 
       return .absolute(path)
     }
@@ -2015,6 +2018,32 @@ extension Driver {
   }
 }
 
+// SDK checking: attempt to diagnose if the SDK we are pointed at is too old.
+extension Driver {
+  static func isSDKTooOld(sdkPath: AbsolutePath, fileSystem: FileSystem,
+                          diagnosticsEngine: DiagnosticsEngine) -> Bool {
+    let sdkInfo = DarwinToolchain.readSDKInfo(fileSystem, VirtualPath.absolute(sdkPath).intern())
+    guard let sdkInfo = sdkInfo else {
+      diagnosticsEngine.emit(.warning_no_sdksettings_json(sdkPath.pathString))
+      return false
+    }
+    guard let sdkVersion = Version(potentiallyIncompleteVersionString: sdkInfo.versionString) else {
+      diagnosticsEngine.emit(.warning_fail_parse_sdk_ver(sdkInfo.versionString, sdkPath.pathString))
+      return false
+    }
+    if sdkInfo.canonicalName.hasPrefix("macos") {
+      return sdkVersion < Version(10, 15, 0)
+    } else if sdkInfo.canonicalName.hasPrefix("iphoneos") ||
+                sdkInfo.canonicalName.hasPrefix("appletvos") {
+      return sdkVersion < Version(13, 0, 0)
+    } else if sdkInfo.canonicalName.hasPrefix("watchos") {
+      return sdkVersion < Version(6, 0, 0)
+    } else {
+      return false
+    }
+  }
+}
+
 // Imported Objective-C header.
 extension Driver {
   /// Compute the path of the imported Objective-C header.

Sources/SwiftDriver/Jobs/PrebuiltModulesJob.swift

@@ -117,8 +117,11 @@ public struct SDKPrebuiltModuleInputsCollector {
     let canonicalName = sdkInfo.canonicalName
     func extractVersion(_ platform: String) -> Substring? {
       if canonicalName.starts(with: platform) {
-        return canonicalName.suffix(from: canonicalName.index(canonicalName.startIndex,
-                                                              offsetBy: platform.count))
+        let versionStartIndex = canonicalName.index(canonicalName.startIndex,
+                                                    offsetBy: platform.count)
+        let delimiterRange = canonicalName.range(of: "internal", options: .backwards)
+        let versionEndIndex = delimiterRange == nil ? canonicalName.endIndex : delimiterRange!.lowerBound
+        return canonicalName[versionStartIndex..<versionEndIndex]
       }
       return nil
     }

Sources/SwiftDriver/Utilities/Diagnostics.swift

@@ -93,6 +93,18 @@ extension Diagnostic.Message {
     .warning("no such SDK: \(path)")
   }
 
+  static func warning_no_sdksettings_json(_ path: String) -> Diagnostic.Message {
+      .warning("Could not read SDKSettings.json for SDK at: \(path)")
+  }
+
+  static func warning_fail_parse_sdk_ver(_ version: String, _ path: String) -> Diagnostic.Message {
+      .warning("Could not parse SDK version '\(version)' at: \(path)")
+  }
+
+  static func error_sdk_too_old(_ path: String) -> Diagnostic.Message {
+      .error("Swift does not support the SDK \(path)")
+  }
+
   static func error_unknown_target(_ target: String) -> Diagnostic.Message {
     .error("unknown target '\(target)'")
   }

Sources/SwiftDriver/Utilities/Triple+Platforms.swift

@@ -171,7 +171,7 @@ extension Triple {
   {
     switch compatibilityPlatform ?? darwinPlatform! {
     case .macOS:
-      return _macOSVersion!
+      return _macOSVersion ?? osVersion
     case .iOS, .tvOS:
       return _iOSVersion
     case .watchOS:

TestInputs/SDKChecks/MacOSX10.10.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.10",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.10"
+}

TestInputs/SDKChecks/MacOSX10.11.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.11",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.11"
+}

TestInputs/SDKChecks/MacOSX10.14.Internal.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.14",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.14internal"
+}

TestInputs/SDKChecks/MacOSX10.15.4.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.15.4",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.15.4"
+}

TestInputs/SDKChecks/MacOSX10.15.Internal.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.15",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.15internal"
+}

TestInputs/SDKChecks/MacOSX10.15.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.15",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.15"
+}

TestInputs/SDKChecks/MacOSX10.8.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.8",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.8"
+}

TestInputs/SDKChecks/MacOSX10.9.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "10.9",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx10.9"
+}

TestInputs/SDKChecks/MacOSX7.17.sdk/SDKSettings.json

@@ -0,0 +1,8 @@
+{
+	"Version": "7.17",
+	"VersionMap": {
+		"macOS_iOSMac": {},
+		"iOSMac_macOS": {}
+	},
+	"CanonicalName": "macosx7.17"
+}

TestInputs/SDKChecks/iPhoneOS.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "13.00",
+	"CanonicalName": "iphoneos13.0"
+}

TestInputs/SDKChecks/iPhoneOS12.99.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "12.99",
+	"CanonicalName": "iphoneos12.99"
+}

TestInputs/SDKChecks/iPhoneOS13.0.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "13.0",
+	"CanonicalName": "iphoneos13.0"
+}

TestInputs/SDKChecks/iPhoneOS7.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "7.0",
+	"CanonicalName": "iphoneos7.0"
+}

TestInputs/SDKChecks/tvOS.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "13.0",
+	"CanonicalName": "appletvos13.0"
+}

TestInputs/SDKChecks/tvOS13.0.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "13.0",
+	"CanonicalName": "appletvos13.0"
+}

TestInputs/SDKChecks/tvOS8.0.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "8.0",
+	"CanonicalName": "appletvos8.0"
+}

TestInputs/SDKChecks/watchOS.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "7.0",
+	"CanonicalName": "watchos7.0"
+}

TestInputs/SDKChecks/watchOS2.0.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "2.0",
+	"CanonicalName": "watchos2.0"
+}

TestInputs/SDKChecks/watchOS3.0.Internal.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "3.0",
+	"CanonicalName": "watchos3.0internal"
+}

TestInputs/SDKChecks/watchOS3.0.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "3.0",
+	"CanonicalName": "watchos3.0"
+}

TestInputs/SDKChecks/watchOS6.0.sdk/SDKSettings.json

@@ -0,0 +1,4 @@
+{
+	"Version": "6.0",
+	"CanonicalName": "watchos6.0"
+}

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -2581,7 +2581,7 @@ final class SwiftDriverTests: XCTestCase {
   // Test cases ported from Driver/macabi-environment.swift
   func testDarwinSDKVersioning() throws {
     try withTemporaryDirectory { tmpDir in
-      let sdk1 = tmpDir.appending(component: "MacOSX10.15.versioned.sdk")
+      let sdk1 = tmpDir.appending(component: "MacOSX10.15.sdk")
       try localFileSystem.writeFileContents(sdk1.appending(component: "SDKSettings.json")) {
         $0 <<< """
         {
@@ -2601,7 +2601,7 @@ final class SwiftDriverTests: XCTestCase {
         """
       }
 
-      let sdk2 = tmpDir.appending(component: "MacOSX10.15.4.versioned.sdk")
+      let sdk2 = tmpDir.appending(component: "MacOSX10.15.4.sdk")
       try localFileSystem.writeFileContents(sdk2.appending(component: "SDKSettings.json")) {
         $0 <<< """
         {
@@ -2738,6 +2738,60 @@ final class SwiftDriverTests: XCTestCase {
     }
   }
 
+  func testDarwinSDKTooOld() throws {
+    func getSDKPath(sdkDirName: String) -> AbsolutePath {
+      let packageRootPath = AbsolutePath(String(URL(fileURLWithPath: #file).pathComponents
+          .prefix(while: { $0 != "Tests" }).joined(separator: "/").dropFirst()))
+      let testInputsPath = packageRootPath.appending(component: "TestInputs")
+                                          .appending(component: "SDKChecks")
+      return testInputsPath.appending(component: sdkDirName)
+    }
+    // Ensure an error is emitted for an unsupported SDK
+    func checkSDKUnsupported(sdkDirName: String)
+    throws {
+      let sdkPath = getSDKPath(sdkDirName: sdkDirName)
+      // Get around the check for SDK's existence
+      try localFileSystem.createDirectory(sdkPath)
+      let args = [ "swiftc", "foo.swift", "-sdk", sdkPath.pathString ]
+      try assertDriverDiagnostics(args: args) { driver, verifier in
+        verifier.expect(.error("Swift does not support the SDK \(sdkPath.pathString)"))
+      }
+    }
+
+    // Ensure no error is emitted for a supported SDK
+    func checkSDKOkay(sdkDirName: String) throws {
+      let sdkPath = getSDKPath(sdkDirName: sdkDirName)
+      try localFileSystem.createDirectory(sdkPath)
+      let args = [ "swiftc", "foo.swift", "-sdk", sdkPath.pathString ]
+      try assertNoDiagnostics { de in let _ = try Driver(args: args, diagnosticsEngine: de) }
+    }
+
+    // Ensure old/bogus SDK versions are caught
+    try checkSDKUnsupported(sdkDirName: "tvOS8.0.sdk")
+    try checkSDKUnsupported(sdkDirName: "MacOSX10.8.sdk")
+    try checkSDKUnsupported(sdkDirName: "MacOSX10.9.sdk")
+    try checkSDKUnsupported(sdkDirName: "MacOSX10.10.sdk")
+    try checkSDKUnsupported(sdkDirName: "MacOSX10.11.sdk")
+    try checkSDKUnsupported(sdkDirName: "MacOSX7.17.sdk")
+    try checkSDKUnsupported(sdkDirName: "MacOSX10.14.Internal.sdk")
+    try checkSDKUnsupported(sdkDirName: "iPhoneOS7.sdk")
+    try checkSDKUnsupported(sdkDirName: "iPhoneOS12.99.sdk")
+    try checkSDKUnsupported(sdkDirName: "watchOS2.0.sdk")
+    try checkSDKUnsupported(sdkDirName: "watchOS3.0.sdk")
+    try checkSDKUnsupported(sdkDirName: "watchOS3.0.Internal.sdk")
+
+    // Verify a selection of okay SDKs
+    try checkSDKOkay(sdkDirName: "MacOSX10.15.sdk")
+    try checkSDKOkay(sdkDirName: "MacOSX10.15.4.sdk")
+    try checkSDKOkay(sdkDirName: "MacOSX10.15.Internal.sdk")
+    try checkSDKOkay(sdkDirName: "iPhoneOS13.0.sdk")
+    try checkSDKOkay(sdkDirName: "tvOS13.0.sdk")
+    try checkSDKOkay(sdkDirName: "watchOS6.0.sdk")
+    try checkSDKOkay(sdkDirName: "iPhoneOS.sdk")
+    try checkSDKOkay(sdkDirName: "tvOS.sdk")
+    try checkSDKOkay(sdkDirName: "watchOS.sdk")
+  }
+
   func testDarwinLinkerPlatformVersion() throws {
     do {
       var driver = try Driver(args: ["swiftc",