[Caching] Mark -emit-module-source-info-path as CacheInvariant

include/swift/Option/Options.td

@@ -730,12 +730,12 @@ def avoid_emit_module_source_info :
 def emit_module_source_info_path :
   Separate<["-"], "emit-module-source-info-path">,
   Flags<[FrontendOption, NoInteractiveOption, ArgumentIsPath,
-         SupplementaryOutput]>,
+         SupplementaryOutput, CacheInvariant]>,
   MetaVarName<"<path>">, HelpText<"Output module source info file to <path>">;
 def emit_variant_module_source_info_path :
   Separate<["-"], "emit-variant-module-source-info-path">,
   Flags<[FrontendOption, NoInteractiveOption, ArgumentIsPath,
-         SupplementaryOutput, NewDriverOnlyOption]>,
+         SupplementaryOutput, NewDriverOnlyOption, CacheInvariant]>,
   MetaVarName<"<path>">, HelpText<"Output module source info file for the target variant to <path>">;
 
 def emit_parseable_module_interface :

unittests/Basic/CMakeLists.txt

@@ -24,6 +24,7 @@ add_swift_unittest(SwiftBasicTests
   ImmutablePointerSetTest.cpp
   JSONSerialization.cpp
   OptionSetTest.cpp
+  Options.cpp
   OwnedStringTest.cpp
   MultiMapCacheTest.cpp
   PointerIntEnumTest.cpp
@@ -48,8 +49,10 @@ add_dependencies(SwiftBasicTests "${gyb_dependency_targets}")
 target_link_libraries(SwiftBasicTests
   PRIVATE
   swiftBasic
+  swiftOption
   swiftThreading
   clangBasic
+  LLVMOption
   LLVMTestingSupport
   )
 

unittests/Basic/Options.cpp

@@ -0,0 +1,40 @@
+//===--- Options.cpp ------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/Option/Options.h"
+#include "llvm/Option/Option.h"
+#include "gtest/gtest.h"
+
+using namespace swift;
+using namespace swift::options;
+
+TEST(Options, outputPathCacheInvariant) {
+  auto optTable = createSwiftOptTable();
+  // 0 is OP_INVALD
+  for (auto id = 1; id < LastOption; ++id) {
+    auto opt = optTable->getOption(id);
+    // Only check the flag accepted by swift-frontend.
+    if (!opt.hasFlag(SwiftFlags::FrontendOption))
+      continue;
+
+    // The following two options are only accepted by migrator.
+    if (id == OPT_emit_migrated_file_path || id == OPT_emit_remap_file_path)
+      continue;
+
+    auto name = opt.getName();
+    // Check that if a flag matches the convention `-emit-*-path{=}`, it should
+    // be a path to an output file and should be marked as cache invariant.
+    if (name.starts_with("emit") &&
+        (name.ends_with("-path") || name.ends_with("-path=")))
+      ASSERT_TRUE(opt.hasFlag(SwiftFlags::CacheInvariant));
+  }
+}