Merge pull request #89 from DougGregor/macos-deployment-10.10

Set macOS minimum deployment target to 10.10.

Author: DougGregor

Package.swift

@@ -5,7 +5,7 @@ import class Foundation.ProcessInfo
 let package = Package(
   name: "swift-driver",
   platforms: [
-    .macOS(.v10_13),
+    .macOS(.v10_10),
   ],
   products: [
     .executable(

Sources/SwiftDriver/Execution/ParsableOutput.swift

@@ -30,7 +30,11 @@ public struct ParsableMessage {
 
   public func toJSON() throws -> Data {
     let encoder = JSONEncoder()
-    encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
+    if #available(macOS 10.13, *) {
+      encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
+    } else {
+      encoder.outputFormatting = [.prettyPrinted]
+    }
     return try encoder.encode(self)
   }
 }

Tests/SwiftDriverTests/AssertDiagnosticsTests.swift

@@ -185,10 +185,14 @@ class FailableTestCase: XCTestCase {
       return
     }
 
-    super.recordFailure(
-      withDescription: description,
-      inFile: filePath, atLine: lineNumber,
-      expected: expected
-    )
+    if #available(macOS 10.13, *) {
+      super.recordFailure(
+        withDescription: description,
+        inFile: filePath, atLine: lineNumber,
+        expected: expected
+      )
+    } else {
+      fatalError(description, line: UInt(lineNumber))
+    }
   }
 }

Tests/SwiftDriverTests/Helpers/AssertDiagnostics.swift

@@ -111,10 +111,18 @@ final class DiagnosticVerifier {
   // Access to `actual` and `expected` must be synchronized on `queue`. (Even
   // reads should be, although we only enforce writes.)
   fileprivate var actual: [Diagnostic] = [] {
-    didSet { dispatchPrecondition(condition: .onQueue(queue!)) }
+    didSet {
+      if #available(macOS 10.12, *) {
+        dispatchPrecondition(condition: .onQueue(queue!))
+      }
+    }
   }
   fileprivate var expected: [Expectation] = [] {
-     didSet { dispatchPrecondition(condition: .onQueue(queue!)) }
+    didSet {
+      if #available(macOS 10.12, *) {
+        dispatchPrecondition(condition: .onQueue(queue!))
+      }
+    }
   }
 
   // Access to `permitted` is not synchronized because it is only used from the