Add ClangImporterOptions::getRemappedExtraArgs

This commit adds a function to remap the clang arguments passed
during compilation. This is intented to be shared across the
Swift compiler and LLDB to apply path remapping for debug info
paths.

include/swift/Basic/LangOptions.h

@@ -771,6 +771,9 @@ namespace swift {
                           DisableOverlayModules,
                           EnableClangSPI);
     }
+
+    std::vector<std::string> getRemappedExtraArgs(
+        std::function<std::string(StringRef)> pathRemapCallback) const;
   };
 
 } // end namespace swift

lib/Basic/LangOptions.cpp

@@ -408,3 +408,56 @@ DiagnosticBehavior LangOptions::getAccessNoteFailureLimit() const {
   }
   llvm_unreachable("covered switch");
 }
+
+std::vector<std::string> ClangImporterOptions::getRemappedExtraArgs(
+    std::function<std::string(StringRef)> pathRemapCallback) const {
+  auto consumeIncludeOption = [](StringRef &arg, StringRef &prefix) {
+    static StringRef options[] = {"-I",
+                                  "-F",
+                                  "-fmodule-map-file=",
+                                  "-iquote",
+                                  "-idirafter",
+                                  "-iframeworkwithsysroot",
+                                  "-iframework",
+                                  "-iprefix",
+                                  "-iwithprefixbefore",
+                                  "-iwithprefix",
+                                  "-isystemafter",
+                                  "-isystem",
+                                  "-isysroot",
+                                  "-ivfsoverlay",
+                                  "-working-directory=",
+                                  "-working-directory"};
+    for (StringRef &option : options)
+      if (arg.consume_front(option)) {
+        prefix = option;
+        return true;
+      }
+    return false;
+  };
+
+  // true if the previous argument was the dash-option of an option pair
+  bool remap_next = false;
+  std::vector<std::string> args;
+  for (auto A : ExtraArgs) {
+    StringRef prefix;
+    StringRef arg(A);
+
+    if (remap_next) {
+      remap_next = false;
+      args.push_back(pathRemapCallback(arg));
+    } else if (consumeIncludeOption(arg, prefix)) {
+      if (arg.empty()) {
+        // Option pair
+        remap_next = true;
+        args.push_back(prefix.str());
+      } else {
+        // Combine prefix with remapped path value
+        args.push_back(prefix.str() + pathRemapCallback(arg));
+      }
+    } else {
+      args.push_back(A);
+    }
+  }
+  return args;
+}

unittests/Basic/CMakeLists.txt

@@ -8,6 +8,7 @@ handle_gyb_sources(
 add_swift_unittest(SwiftBasicTests
   BlotMapVectorTest.cpp
   CacheTest.cpp
+  ClangImporterOptionsTest.cpp
   ClusteredBitVectorTest.cpp
   DemangleTest.cpp
   DiverseStackTest.cpp

unittests/Basic/ClangImporterOptionsTest.cpp

@@ -0,0 +1,50 @@
+//===--- ClangImporterOptionsTest.cpp -------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2021 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/Basic/LangOptions.h"
+#include "llvm/ADT/StringRef.h"
+#include "gtest/gtest.h"
+
+static std::string remap(llvm::StringRef path) { return "remapped"; }
+
+TEST(ClangImporterOptions, nonPathsSkipped) {
+  std::vector<std::string> args = {"-unmapped", "-another=unmapped"};
+  swift::ClangImporterOptions options;
+  options.ExtraArgs = args;
+
+  EXPECT_EQ(options.getRemappedExtraArgs(remap), args);
+}
+
+TEST(ClangImporterOptions, optionPairs) {
+  std::vector<std::string> args = {"-unmapped",    "-another=unmapped",
+                                   "-I",           "some/path",
+                                   "-ivfsoverlay", "another/path"};
+  swift::ClangImporterOptions options;
+  options.ExtraArgs = args;
+
+  std::vector<std::string> expected = {"-unmapped",    "-another=unmapped",
+                                       "-I",           "remapped",
+                                       "-ivfsoverlay", "remapped"};
+  EXPECT_EQ(options.getRemappedExtraArgs(remap), expected);
+}
+
+TEST(ClangImporterOptions, joinedPaths) {
+  std::vector<std::string> args = {"-unmapped", "-another=unmapped",
+                                   "-Isome/path",
+                                   "-working-directory=another/path"};
+  swift::ClangImporterOptions options;
+  options.ExtraArgs = args;
+
+  std::vector<std::string> expected = {"-unmapped", "-another=unmapped",
+                                       "-Iremapped",
+                                       "-working-directory=remapped"};
+  EXPECT_EQ(options.getRemappedExtraArgs(remap), expected);
+}