[clang][Tooling] Filter flags that generate output in SyntaxOnlyAdjuster

Summary:
Flags that generate output could result in failures when creating
syntax only actions. This patch introduces initial logic for filtering out
those. The first such flag is "save-temps", which saves intermediate
files(bitcode, assembly, etc.) into a specified directory.

Fixes clangd/clangd#191

Reviewers: hokein

Subscribers: ilya-biryukov, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70173

Author: kadircet

clang/lib/Tooling/ArgumentsAdjusters.cpp

@@ -13,20 +13,32 @@
 
 #include "clang/Tooling/ArgumentsAdjusters.h"
 #include "clang/Basic/LLVM.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include <cstddef>
+#include <vector>
 
 namespace clang {
 namespace tooling {
 
-/// Add -fsyntax-only option to the command line arguments.
+/// Add -fsyntax-only option and drop options that triggers output generation.
 ArgumentsAdjuster getClangSyntaxOnlyAdjuster() {
   return [](const CommandLineArguments &Args, StringRef /*unused*/) {
     CommandLineArguments AdjustedArgs;
     bool HasSyntaxOnly = false;
+    const std::vector<llvm::StringRef> OutputCommands = {
+        // FIXME: Add other options that generate output.
+        "-save-temps",
+        "--save-temps",
+    };
     for (size_t i = 0, e = Args.size(); i < e; ++i) {
       StringRef Arg = Args[i];
-      // FIXME: Remove options that generate output.
+      // Skip output commands.
+      if (llvm::any_of(OutputCommands, [&Arg](llvm::StringRef OutputCommand) {
+            return Arg.startswith(OutputCommand);
+          }))
+        continue;
+
       if (!Arg.startswith("-fcolor-diagnostics") &&
           !Arg.startswith("-fdiagnostics-color"))
         AdjustedArgs.push_back(Args[i]);

clang/unittests/Tooling/ToolingTest.cpp

@@ -13,15 +13,18 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendAction.h"
 #include "clang/Frontend/FrontendActions.h"
+#include "clang/Tooling/ArgumentsAdjusters.h"
 #include "clang/Tooling/CompilationDatabase.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "gtest/gtest.h"
 #include <algorithm>
 #include <string>
+#include <vector>
 
 namespace clang {
 namespace tooling {
@@ -429,6 +432,37 @@ TEST(ClangToolTest, NoDoubleSyntaxOnly) {
   EXPECT_EQ(SyntaxOnlyCount, 1U);
 }
 
+TEST(ClangToolTest, NoOutputCommands) {
+  FixedCompilationDatabase Compilations("/", {"-save-temps", "-save-temps=cwd",
+                                              "--save-temps",
+                                              "--save-temps=somedir"});
+
+  ClangTool Tool(Compilations, std::vector<std::string>(1, "/a.cc"));
+  Tool.mapVirtualFile("/a.cc", "void a() {}");
+
+  std::unique_ptr<FrontendActionFactory> Action(
+      newFrontendActionFactory<SyntaxOnlyAction>());
+
+  const std::vector<llvm::StringRef> OutputCommands = {"-save-temps"};
+  bool Ran = false;
+  ArgumentsAdjuster CheckSyntaxOnlyAdjuster =
+      [&OutputCommands, &Ran](const CommandLineArguments &Args,
+                              StringRef /*unused*/) {
+        for (llvm::StringRef Arg : Args) {
+          for (llvm::StringRef OutputCommand : OutputCommands)
+            EXPECT_FALSE(Arg.contains(OutputCommand));
+        }
+        Ran = true;
+        return Args;
+      };
+
+  Tool.clearArgumentsAdjusters();
+  Tool.appendArgumentsAdjuster(getClangSyntaxOnlyAdjuster());
+  Tool.appendArgumentsAdjuster(CheckSyntaxOnlyAdjuster);
+  Tool.run(Action.get());
+  EXPECT_TRUE(Ran);
+}
+
 TEST(ClangToolTest, BaseVirtualFileSystemUsage) {
   FixedCompilationDatabase Compilations("/", std::vector<std::string>());
   llvm::IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> OverlayFileSystem(