Fixes SR-822, support tests directly under Tests directory

Author: bhargavg

Fixtures/ValidLayouts/SingleModule/DirectTests/Package.swift

@@ -0,0 +1,3 @@
+class Foo {
+    var bar: Int = 0
+}

Fixtures/ValidLayouts/SingleModule/DirectTests/Sources/Foo.swift

@@ -0,0 +1,6 @@
+import XCTest
+
+class FooTests: XCTestCase {
+    func testSuccess() {
+    }
+}

Fixtures/ValidLayouts/SingleModule/DirectTests/Tests/FooTests.swift

@@ -0,0 +1,8 @@
+import XCTest
+
+@testable import DirectTests
+
+XCTMain([
+    FooTests(),
+])
+

Fixtures/ValidLayouts/SingleModule/DirectTests/Tests/LinuxMain.swift

@@ -13,8 +13,24 @@ import Utility
 
 extension Package {
     func testModules() throws -> [TestModule] {
-        return try walk(path, "Tests", recursively: false).filter{ $0.isDirectory }.map { dir in
-            return TestModule(basename: dir.basename, sources: try self.sourcify(dir))
+        let (directories, files) = walk(path, "Tests", recursively: false).partition{ $0.isDirectory }
+        
+        if (directories.count > 0) {
+            return try directories
+                .filter { !excludes.contains($0) }
+                .map { TestModule(basename: $0.basename, sources: try self.sourcify($0)) }
+            
+        } else {
+            let rootTestFiles = files.filter { 
+                !$0.hasSuffix("LinuxMain.swift") && isValidSource($0)
+            }
+            
+            if (rootTestFiles.count > 0) {
+                let rootTestSource = Sources(paths: rootTestFiles, root: path)
+                return [TestModule(basename: name, sources: rootTestSource)]
+            }
         }
+        
+        return []
     }
 }

Sources/Transmute/Package+testModules.swift

@@ -0,0 +1,28 @@
+/*
+This source file is part of the Swift.org open source project
+
+Copyright 2015 - 2016 Apple Inc. and the Swift project authors
+Licensed under Apache License v2.0 with Runtime Library Exception
+
+See http://swift.org/LICENSE.txt for license information
+See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+extension SequenceType {
+    @warn_unused_result
+    public func partition(@noescape include:(Generator.Element)->Bool) -> ([Generator.Element], [Generator.Element]) {
+        var left = Array<Generator.Element>()
+        var right = Array<Generator.Element>()
+        
+        for element in self {
+            if include(element) {
+                left.append(element)
+            } else {
+                right.append(element)
+            }
+        }
+        
+        return (left, right)
+    }
+}
+

Sources/Utility/SequenceTypeExtensions.swift

@@ -50,6 +50,13 @@ class ValidLayoutsTestCase: XCTestCase {
         }
     }
 
+    func testEmptyPackageWithDirectTests() {
+        fixture(name: "ValidLayouts/SingleModule/DirectTests", file: #file, line: #line) { prefix in
+            XCTAssertBuilds(prefix)
+            XCTAssertFileExists(prefix, ".build", "debug", "DirectTests.swiftmodule")
+        }
+    }
+
     func testMultipleModulesLibraries() {
         runLayoutFixture(name: "MultipleModules/Libraries") { prefix in
             XCTAssertBuilds(prefix)