StdlibUnittest: don't pass the name of the executable on the command line

Also, add a test for the command line of the child process.

Author: gribozavr

stdlib/private/StdlibUnittest/StdlibUnittest.swift.gyb

@@ -786,6 +786,7 @@ public func runAllTests() {
     var filter: String? = nil
     var args = [String]()
     var i = 0
+    i += 1 // Skip the name of the executable.
     while i < Process.arguments.count {
       let arg = Process.arguments[i]
       if arg == "--stdlib-unittest-in-process" {
@@ -810,8 +811,8 @@ public func runAllTests() {
         print(message)
         return
       }
-      
-      // pass through arguments to the child process
+
+      // Pass through unparsed arguments to the child process.
       args.append(Process.arguments[i])
 
       i += 1

test/1_stdlib/PrintFloat.swift

@@ -2,7 +2,7 @@
 // RUN: %target-build-swift -c -force-single-frontend-invocation -parse-as-library -emit-module -emit-module-path %t/PrintTestTypes.swiftmodule -o %t/PrintTestTypes.o %S/Inputs/PrintTestTypes.swift
 // RUN: %target-build-swift %s -Xlinker %t/PrintTestTypes.o -I %t -L %t -o %t/main.out
 // RUN: %target-run %t/main.out
-// RUN: %target-run %t/main.out --env ru_RU.UTF-8
+// RUN: %target-run %t/main.out --locale ru_RU.UTF-8
 // REQUIRES: executable_test
 // XFAIL: linux
 
@@ -13,8 +13,8 @@ import PrintTestTypes
 let PrintTests = TestSuite("PrintFloat")
 
 PrintTests.setUp {
-  if Process.arguments.contains("--env") {
-    let locale = Process.arguments[4]
+  if let localeArgIndex = Process.arguments.indexOf("--locale") {
+    let locale = Process.arguments[localeArgIndex + 1]
     expectEqual("ru_RU.UTF-8", locale)
     setlocale(LC_ALL, locale)
   } else {

validation-test/stdlib/StdlibUnittestCommandLine.swift

@@ -0,0 +1,28 @@
+// RUN: rm -rf %t && mkdir %t
+// RUN: %target-build-swift %s -o %t/main.out
+// RUN: %target-run %t/main.out | FileCheck -check-prefix=CHECK-EMPTY %s
+// RUN: %target-run %t/main.out --abc | FileCheck -check-prefix=CHECK-1 %s
+// RUN: %target-run %t/main.out --abc def | FileCheck -check-prefix=CHECK-2 %s
+// RUN: %target-run %t/main.out a --bcd efghijk | FileCheck -check-prefix=CHECK-3 %s
+// REQUIRES: executable_test
+
+import StdlibUnittest
+
+// Also import modules which are used by StdlibUnittest internally. This
+// workaround is needed to link all required libraries in case we compile
+// StdlibUnittest with -sil-serialize-all.
+#if _runtime(_ObjC)
+import ObjectiveC
+#endif
+
+var CommandLineArguments = TestSuite("CommandLineArguments")
+CommandLineArguments.test("printCommandLineArguments") {
+  debugPrint(Process.arguments)
+}
+// CHECK-EMPTY: {{^}}out>>> ["{{[^"]+}}", "--stdlib-unittest-run-child"]{{$}}
+// CHECK-1: {{^}}out>>> ["{{[^"]+}}", "--stdlib-unittest-run-child", "--abc"]{{$}}
+// CHECK-2: {{^}}out>>> ["{{[^"]+}}", "--stdlib-unittest-run-child", "--abc", "def"]{{$}}
+// CHECK-3: {{^}}out>>> ["{{[^"]+}}", "--stdlib-unittest-run-child", "a", "--bcd", "efghijk"]{{$}}
+
+runAllTests()
+