[tooling] Add a new argument adjuster for deleting plugin related command line args

[kadircet]

Summary

Currently both clangd and clang-tidy makes use of this mechanism so
putting it into tooling so that all tools can make use of it.

[ilya-biryukov]

include/clang/Tooling/ArgumentsAdjusters.h

73

Maybe put the function before combineAdjusters?
The latter is a function that works on two adjusters, therefore a bit different from the rest, which are adjusters themselves.

75

Maybe drop "clang" from the name? `getStripPluginsAdjuster()?

lib/Tooling/ArgumentsAdjusters.cpp

111

remove the comment? we already have one in the header

[ilya-biryukov]

Just a few NITs from my side, LG when fixed.

[ilya-biryukov]

LGTM after the nits are fixed

[kadircet]

• Address comments

include/clang/Tooling/ArgumentsAdjusters.h

ArgumentsAdjuster getInsertArgumentAdjuster(const CommandLineArguments &Extra,
                                             ArgumentInsertPosition Pos);
 
 /// Gets an argument adjuster which inserts an \p Extra argument in the
 /// specified position.
 ArgumentsAdjuster getInsertArgumentAdjuster(
     const char *Extra,
     ArgumentInsertPosition Pos = ArgumentInsertPosition::END);
 
+/// Gets an argument adjuster which strips plugin related command line
+/// arguments.
+ArgumentsAdjuster getStripPluginsAdjuster();
+
 /// Gets an argument adjuster which adjusts the arguments in sequence
 /// with the \p First adjuster and then with the \p Second one.
 ArgumentsAdjuster combineAdjusters(ArgumentsAdjuster First,
                                    ArgumentsAdjuster Second);
 
 } // namespace tooling
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLING_ARGUMENTSADJUSTERS_H

lib/Tooling/ArgumentsAdjusters.cpp

if (!First)
     return Second;
   if (!Second)
     return First;
   return [First, Second](const CommandLineArguments &Args, StringRef File) {
     return Second(First(Args, File), File);
   };
 }
 
+ArgumentsAdjuster getStripPluginsAdjuster() {
+  return [](const CommandLineArguments &Args, StringRef /*unused*/) {
+    CommandLineArguments AdjustedArgs;
+    for (size_t I = 0, E = Args.size(); I != E; I++) {
+      // According to https://clang.llvm.org/docs/ClangPlugins.html
+      // plugin arguments are in the form:
+      // -Xclang {-load, -plugin, -plugin-arg-<plugin-name>, -add-plugin}
+      // -Xclang <arbitrary-argument>
+      if (I + 4 < E && Args[I] == "-Xclang" &&
+          (Args[I + 1] == "-load" || Args[I + 1] == "-plugin" ||
+           llvm::StringRef(Args[I + 1]).startswith("-plugin-arg-") ||
+           Args[I + 1] == "-add-plugin") &&
+          Args[I + 2] == "-Xclang") {
+        I += 3;
+        continue;
+      }
+      AdjustedArgs.push_back(Args[I]);
+    }
+    return AdjustedArgs;
+  };
+}
+
 } // end namespace tooling
 } // end namespace clang

unittests/Tooling/ToolingTest.cpp

return std::find(FinalArgs.begin(), FinalArgs.end(), Flag) !=
            FinalArgs.end();
   };
   EXPECT_FALSE(HasFlag("-MD"));
   EXPECT_FALSE(HasFlag("-MMD"));
   EXPECT_TRUE(HasFlag("-c"));
   EXPECT_TRUE(HasFlag("-w"));
 }
 
+// Check getClangStripPluginsAdjuster strips plugin related args.
+TEST(ClangToolTest, StripPluginsAdjuster) {
+  FixedCompilationDatabase Compilations(
+      "/", {"-Xclang", "-add-plugin", "-Xclang", "random-plugin"});
+
+  ClangTool Tool(Compilations, std::vector<std::string>(1, "/a.cc"));
+  Tool.mapVirtualFile("/a.cc", "void a() {}");
+
+  std::unique_ptr<FrontendActionFactory> Action(
+      newFrontendActionFactory<SyntaxOnlyAction>());
+
+  CommandLineArguments FinalArgs;
+  ArgumentsAdjuster CheckFlagsAdjuster =
+      [&FinalArgs](const CommandLineArguments &Args, StringRef /*unused*/) {
+        FinalArgs = Args;
+        return Args;
+      };
+  Tool.clearArgumentsAdjusters();
+  Tool.appendArgumentsAdjuster(getStripPluginsAdjuster());
+  Tool.appendArgumentsAdjuster(CheckFlagsAdjuster);
+  Tool.run(Action.get());
+
+  auto HasFlag = [&FinalArgs](const std::string &Flag) {
+    return std::find(FinalArgs.begin(), FinalArgs.end(), Flag) !=
+           FinalArgs.end();
+  };
+  EXPECT_FALSE(HasFlag("-Xclang"));
+  EXPECT_FALSE(HasFlag("-add-plugin"));
+  EXPECT_FALSE(HasFlag("-random-plugin"));
+}
+
 namespace {
 /// Find a target name such that looking for it in TargetRegistry by that name
 /// returns the same target. We expect that there is at least one target
 /// configured with this property.
 std::string getAnyTarget() {
   llvm::InitializeAllTargets();
   for (const auto &Target : llvm::TargetRegistry::targets()) {
     std::string Error;