[clangd] Fix sysroot flag handling in CommandMangler to prevent duplicates

[kon72]

CommandMangler should guess the sysroot path of the host system and add that through -isysroot flag only when there is no --sysroot or -isysroot flag in the original compile command to avoid duplicate sysroot.

Previously, CommandMangler appropriately avoided adding a guessed sysroot flag if the original command had an argument in the form of --sysroot=<sysroot>, --sysroot <sysroot>, or -isysroot <sysroot>.
However, when presented as -isysroot<sysroot> (without spaces after -isysroot), CommandMangler mistakenly appended the guessed sysroot flag, resulting in duplicated sysroot in the final command.

This commit fixes it, ensuring the final command has no duplicate sysroot flags.
Also adds unit tests for this fix.

[llvmbot]

@llvm/pr-subscribers-clangd

Author: Kon (kon72)

Changes

In CommandMangler, it guesses sysroot path of the host system and adds that through -isysroot flag only when there is no --sysroot or -isysroot flag beforehand.
Previously, it could not find -isysroot<sysroot> flag in the original compile command, resulting in duplicate -isysroot flags.
This commit fixes it and ensures the explicitly specified sysroot is respected. Also adds unit tests for this fix.

---

Full diff: https://github.com/llvm/llvm-project/pull/75694.diff

2 Files Affected:

• (modified) clang-tools-extra/clangd/CompileCommands.cpp (+13-10)
• (modified) clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp (+78-3)

diff --git a/clang-tools-extra/clangd/CompileCommands.cpp b/clang-tools-extra/clangd/CompileCommands.cpp
index f43ce928463b90..a3c6f3f41118e4 100644
--- a/clang-tools-extra/clangd/CompileCommands.cpp
+++ b/clang-tools-extra/clangd/CompileCommands.cpp
@@ -328,13 +328,15 @@ void CommandMangler::operator()(tooling::CompileCommand &Command,
 
   tooling::addTargetAndModeForProgramName(Cmd, Cmd.front());
 
-  // Check whether the flag exists, either as -flag or -flag=*
-  auto Has = [&](llvm::StringRef Flag) {
-    for (llvm::StringRef Arg : Cmd) {
-      if (Arg.consume_front(Flag) && (Arg.empty() || Arg[0] == '='))
-        return true;
-    }
-    return false;
+  // Check whether the flag exists in the command.
+  auto HasExact = [&](llvm::StringRef Flag) {
+    return llvm::any_of(Cmd, [&](llvm::StringRef Arg) { return Arg == Flag; });
+  };
+
+  // Check whether the flag appears in the command as a prefix.
+  auto HasPrefix = [&](llvm::StringRef Flag) {
+    return llvm::any_of(
+        Cmd, [&](llvm::StringRef Arg) { return Arg.startswith(Flag); });
   };
 
   llvm::erase_if(Cmd, [](llvm::StringRef Elem) {
@@ -342,12 +344,13 @@ void CommandMangler::operator()(tooling::CompileCommand &Command,
   });
 
   std::vector<std::string> ToAppend;
-  if (ResourceDir && !Has("-resource-dir"))
+  if (ResourceDir && !HasExact("-resource-dir") && !HasPrefix("-resource-dir="))
     ToAppend.push_back(("-resource-dir=" + *ResourceDir));
 
   // Don't set `-isysroot` if it is already set or if `--sysroot` is set.
   // `--sysroot` is a superset of the `-isysroot` argument.
-  if (Sysroot && !Has("-isysroot") && !Has("--sysroot")) {
+  if (Sysroot && !HasPrefix("-isysroot") && !HasExact("--sysroot") &&
+      !HasPrefix("--sysroot=")) {
     ToAppend.push_back("-isysroot");
     ToAppend.push_back(*Sysroot);
   }
@@ -358,7 +361,7 @@ void CommandMangler::operator()(tooling::CompileCommand &Command,
   }
 
   if (!Cmd.empty()) {
-    bool FollowSymlink = !Has("-no-canonical-prefixes");
+    bool FollowSymlink = !HasExact("-no-canonical-prefixes");
     Cmd.front() =
         (FollowSymlink ? ResolvedDrivers : ResolvedDriversNoFollow)
             .get(Cmd.front(), [&, this] {
diff --git a/clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp b/clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp
index 28f0d85d332caa..cad135923f71c1 100644
--- a/clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp
@@ -385,9 +385,8 @@ TEST(ArgStripperTest, OrderDependent) {
 }
 
 TEST(PrintArgvTest, All) {
-  std::vector<llvm::StringRef> Args = {
-      "one", "two", "thr ee", "f\"o\"ur", "fi\\ve", "$"
-  };
+  std::vector<llvm::StringRef> Args = {"one",      "two",    "thr ee",
+                                       "f\"o\"ur", "fi\\ve", "$"};
   const char *Expected = R"(one two "thr ee" "f\"o\"ur" "fi\\ve" $)";
   EXPECT_EQ(Expected, printArgv(Args));
 }
@@ -465,6 +464,82 @@ TEST(CommandMangler, PathsAsPositional) {
   Mangler(Cmd, "a.cc");
   EXPECT_THAT(Cmd.CommandLine, Contains("foo"));
 }
+
+TEST(CommandMangler, RespectsOriginalResourceDir) {
+  auto Mangler = CommandMangler::forTests();
+  Mangler.ResourceDir = testPath("fake/resources");
+
+  {
+    tooling::CompileCommand Cmd;
+    Cmd.CommandLine = {"clang++", "-resource-dir", testPath("true/resources"),
+                       "foo.cc"};
+    Mangler(Cmd, "foo.cc");
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                HasSubstr("-resource-dir " + testPath("true/resources")));
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                Not(HasSubstr(testPath("fake/resources"))));
+  }
+
+  {
+    tooling::CompileCommand Cmd;
+    Cmd.CommandLine = {"clang++", "-resource-dir=" + testPath("true/resources"),
+                       "foo.cc"};
+    Mangler(Cmd, "foo.cc");
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                HasSubstr("-resource-dir=" + testPath("true/resources")));
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                Not(HasSubstr(testPath("fake/resources"))));
+  }
+}
+
+TEST(CommandMangler, RespectsOriginalSysroot) {
+  auto Mangler = CommandMangler::forTests();
+  Mangler.Sysroot = testPath("fake/sysroot");
+
+  {
+    tooling::CompileCommand Cmd;
+    Cmd.CommandLine = {"clang++", "-isysroot", testPath("true/sysroot"),
+                       "foo.cc"};
+    Mangler(Cmd, "foo.cc");
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                HasSubstr("-isysroot " + testPath("true/sysroot")));
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                Not(HasSubstr(testPath("fake/sysroot"))));
+  }
+
+  {
+    tooling::CompileCommand Cmd;
+    Cmd.CommandLine = {"clang++", "-isysroot" + testPath("true/sysroot"),
+                       "foo.cc"};
+    Mangler(Cmd, "foo.cc");
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                HasSubstr("-isysroot" + testPath("true/sysroot")));
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                Not(HasSubstr(testPath("fake/sysroot"))));
+  }
+
+  {
+    tooling::CompileCommand Cmd;
+    Cmd.CommandLine = {"clang++", "--sysroot", testPath("true/sysroot"),
+                       "foo.cc"};
+    Mangler(Cmd, "foo.cc");
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                HasSubstr("--sysroot " + testPath("true/sysroot")));
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                Not(HasSubstr(testPath("fake/sysroot"))));
+  }
+
+  {
+    tooling::CompileCommand Cmd;
+    Cmd.CommandLine = {"clang++", "--sysroot=" + testPath("true/sysroot"),
+                       "foo.cc"};
+    Mangler(Cmd, "foo.cc");
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                HasSubstr("--sysroot=" + testPath("true/sysroot")));
+    EXPECT_THAT(llvm::join(Cmd.CommandLine, " "),
+                Not(HasSubstr(testPath("fake/sysroot"))));
+  }
+}
 } // namespace
 } // namespace clangd
 } // namespace clang

[kon72]

Hello @HighCommander4 ,

Could you take a look at this change? Thanks!

[HighCommander4]

Thanks, LGTM!

[kon72]

Hello @HighCommander4,

Thank you for the review.
Since I don't have permission to commit the change, could you merge this on my behalf?

[HighCommander4]

Thank you for the review. Since I don't have permission to commit the change, could you merge this on my behalf?

Sure, done.