[clangd] Allow diagnostics to be suppressed with configuration

This has been specifically requested:
  clangd/vscode-clangd#114
and various issues can be addressed with this as a workaround, e.g.:
  clangd/clangd#662

Differential Revision: https://reviews.llvm.org/D95349

clang-tools-extra/clangd/Config.h

@@ -28,6 +28,7 @@
 #include "llvm/ADT/FunctionExtras.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringSet.h"
 #include <string>
 #include <vector>
 
@@ -77,6 +78,12 @@ struct Config {
     llvm::Optional<ExternalIndexSpec> External;
   } Index;
 
+  /// Controls warnings and errors when parsing code.
+  struct {
+    bool SuppressAll = false;
+    llvm::StringSet<> Suppress;
+  } Diagnostics;
+
   /// Style of the codebase.
   struct {
     // Namespaces that should always be fully qualified, meaning no "using"

clang-tools-extra/clangd/ConfigCompile.cpp

@@ -27,6 +27,7 @@
 #include "Config.h"
 #include "ConfigFragment.h"
 #include "ConfigProvider.h"
+#include "Diagnostics.h"
 #include "Features.inc"
 #include "TidyProvider.h"
 #include "support/Logger.h"
@@ -187,6 +188,7 @@ struct FragmentCompiler {
     compile(std::move(F.If));
     compile(std::move(F.CompileFlags));
     compile(std::move(F.Index));
+    compile(std::move(F.Diagnostics));
     compile(std::move(F.ClangTidy));
   }
 
@@ -328,6 +330,27 @@ struct FragmentCompiler {
     });
   }
 
+  void compile(Fragment::DiagnosticsBlock &&F) {
+    std::vector<llvm::StringRef> Normalized;
+    for (const auto &Suppressed : F.Suppress) {
+      if (*Suppressed == "*") {
+        Out.Apply.push_back([&](const Params &, Config &C) {
+          C.Diagnostics.SuppressAll = true;
+          C.Diagnostics.Suppress.clear();
+        });
+        return;
+      }
+      Normalized.push_back(normalizeSuppressedCode(*Suppressed));
+    }
+    if (!Normalized.empty())
+      Out.Apply.push_back([Normalized](const Params &, Config &C) {
+        if (C.Diagnostics.SuppressAll)
+          return;
+        for (llvm::StringRef N : Normalized)
+          C.Diagnostics.Suppress.insert(N);
+      });
+  }
+
   void compile(Fragment::StyleBlock &&F) {
     if (!F.FullyQualifiedNamespaces.empty()) {
       std::vector<std::string> FullyQualifiedNamespaces;

clang-tools-extra/clangd/ConfigFragment.h

@@ -181,6 +181,24 @@ struct Fragment {
   };
   IndexBlock Index;
 
+  /// Controls behavior of diagnostics (errors and warnings).
+  struct DiagnosticsBlock {
+    /// Diagnostic codes that should be suppressed.
+    ///
+    /// Valid values are:
+    /// - *, to disable all diagnostics
+    /// - diagnostic codes exposed by clangd (e.g unknown_type, -Wunused-result)
+    /// - clang internal diagnostic codes (e.g. err_unknown_type)
+    /// - warning categories (e.g. unused-result)
+    /// - clang-tidy check names (e.g. bugprone-narrowing-conversions)
+    ///
+    /// This is a simple filter. Diagnostics can be controlled in other ways
+    /// (e.g. by disabling a clang-tidy check, or the -Wunused compile flag).
+    /// This often has other advantages, such as skipping some analysis.
+    std::vector<Located<std::string>> Suppress;
+  };
+  DiagnosticsBlock Diagnostics;
+
   // Describes the style of the codebase, beyond formatting.
   struct StyleBlock {
     // Namespaces that should always be fully qualified, meaning no "using"
@@ -195,6 +213,7 @@ struct Fragment {
   ///
   /// The settings are merged with any settings found in .clang-tidy
   /// configiration files with these ones taking precedence.
+  // FIXME: move this to Diagnostics.Tidy.
   struct ClangTidyBlock {
     std::vector<Located<std::string>> Add;
     /// List of checks to disable.

clang-tools-extra/clangd/Diagnostics.cpp

@@ -801,5 +801,23 @@ void StoreDiags::flushLastDiag() {
   Output.push_back(std::move(*LastDiag));
 }
 
+bool isBuiltinDiagnosticSuppressed(unsigned ID,
+                                   const llvm::StringSet<> &Suppress) {
+  if (const char *CodePtr = getDiagnosticCode(ID)) {
+    if (Suppress.contains(normalizeSuppressedCode(CodePtr)))
+      return true;
+  }
+  StringRef Warning = DiagnosticIDs::getWarningOptionForDiag(ID);
+  if (!Warning.empty() && Suppress.contains(Warning))
+    return true;
+  return false;
+}
+
+llvm::StringRef normalizeSuppressedCode(llvm::StringRef Code) {
+  Code.consume_front("err_");
+  Code.consume_front("-W");
+  return Code;
+}
+
 } // namespace clangd
 } // namespace clang

clang-tools-extra/clangd/Diagnostics.h

@@ -159,6 +159,15 @@ class StoreDiags : public DiagnosticConsumer {
   bool LastPrimaryDiagnosticWasSuppressed = false;
 };
 
+/// Determine whether a (non-clang-tidy) diagnostic is suppressed by config.
+bool isBuiltinDiagnosticSuppressed(unsigned ID,
+                                   const llvm::StringSet<> &Suppressed);
+/// Take a user-specified diagnostic code, and convert it to a normalized form
+/// stored in the config and consumed by isBuiltinDiagnosticsSuppressed.
+///
+/// (This strips err_ and -W prefix so we can match with or without them.)
+llvm::StringRef normalizeSuppressedCode(llvm::StringRef);
+
 } // namespace clangd
 } // namespace clang
 

clang-tools-extra/clangd/ParsedAST.cpp

@@ -12,6 +12,7 @@
 #include "../clang-tidy/ClangTidyModuleRegistry.h"
 #include "AST.h"
 #include "Compiler.h"
+#include "Config.h"
 #include "Diagnostics.h"
 #include "Headers.h"
 #include "IncludeFixer.h"
@@ -315,12 +316,18 @@ ParsedAST::build(llvm::StringRef Filename, const ParseInputs &Inputs,
       Check->registerMatchers(&CTFinder);
     }
 
-    if (!CTChecks.empty()) {
-      ASTDiags.setLevelAdjuster([&CTContext](DiagnosticsEngine::Level DiagLevel,
-                                             const clang::Diagnostic &Info) {
+    ASTDiags.setLevelAdjuster([&, &Cfg(Config::current())](
+                                  DiagnosticsEngine::Level DiagLevel,
+                                  const clang::Diagnostic &Info) {
+      if (Cfg.Diagnostics.SuppressAll ||
+          isBuiltinDiagnosticSuppressed(Info.getID(), Cfg.Diagnostics.Suppress))
+        return DiagnosticsEngine::Ignored;
+      if (!CTChecks.empty()) {
         std::string CheckName = CTContext->getCheckName(Info.getID());
         bool IsClangTidyDiag = !CheckName.empty();
         if (IsClangTidyDiag) {
+          if (Cfg.Diagnostics.Suppress.contains(CheckName))
+            return DiagnosticsEngine::Ignored;
           // Check for suppression comment. Skip the check for diagnostics not
           // in the main file, because we don't want that function to query the
           // source buffer for preamble files. For the same reason, we ask
@@ -342,9 +349,9 @@ ParsedAST::build(llvm::StringRef Filename, const ParseInputs &Inputs,
             return DiagnosticsEngine::Error;
           }
         }
-        return DiagLevel;
-      });
-    }
+      }
+      return DiagLevel;
+    });
   }
 
   // Add IncludeFixer which can recover diagnostics caused by missing includes

clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp

@@ -11,6 +11,7 @@
 #include "ConfigTesting.h"
 #include "Features.inc"
 #include "TestFS.h"
+#include "clang/Basic/DiagnosticSema.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
@@ -30,6 +31,7 @@ using ::testing::ElementsAre;
 using ::testing::IsEmpty;
 using ::testing::SizeIs;
 using ::testing::StartsWith;
+using ::testing::UnorderedElementsAre;
 
 class ConfigCompileTests : public ::testing::Test {
 protected:
@@ -183,6 +185,39 @@ TEST_F(ConfigCompileTests, PathSpecMatch) {
   }
 }
 
+TEST_F(ConfigCompileTests, DiagnosticSuppression) {
+  Frag.Diagnostics.Suppress.emplace_back("bugprone-use-after-move");
+  Frag.Diagnostics.Suppress.emplace_back("unreachable-code");
+  Frag.Diagnostics.Suppress.emplace_back("-Wunused-variable");
+  Frag.Diagnostics.Suppress.emplace_back("typecheck_bool_condition");
+  Frag.Diagnostics.Suppress.emplace_back("err_unexpected_friend");
+  Frag.Diagnostics.Suppress.emplace_back("warn_alloca");
+  EXPECT_TRUE(compileAndApply());
+  EXPECT_THAT(Conf.Diagnostics.Suppress.keys(),
+              UnorderedElementsAre("bugprone-use-after-move",
+                                   "unreachable-code", "unused-variable",
+                                   "typecheck_bool_condition",
+                                   "unexpected_friend", "warn_alloca"));
+  EXPECT_TRUE(isBuiltinDiagnosticSuppressed(diag::warn_unreachable,
+                                            Conf.Diagnostics.Suppress));
+  // Subcategory not respected/suppressed.
+  EXPECT_FALSE(isBuiltinDiagnosticSuppressed(diag::warn_unreachable_break,
+                                             Conf.Diagnostics.Suppress));
+  EXPECT_TRUE(isBuiltinDiagnosticSuppressed(diag::warn_unused_variable,
+                                            Conf.Diagnostics.Suppress));
+  EXPECT_TRUE(isBuiltinDiagnosticSuppressed(diag::err_typecheck_bool_condition,
+                                            Conf.Diagnostics.Suppress));
+  EXPECT_TRUE(isBuiltinDiagnosticSuppressed(diag::err_unexpected_friend,
+                                            Conf.Diagnostics.Suppress));
+  EXPECT_TRUE(isBuiltinDiagnosticSuppressed(diag::warn_alloca,
+                                            Conf.Diagnostics.Suppress));
+
+  Frag.Diagnostics.Suppress.emplace_back("*");
+  EXPECT_TRUE(compileAndApply());
+  EXPECT_TRUE(Conf.Diagnostics.SuppressAll);
+  EXPECT_THAT(Conf.Diagnostics.Suppress, IsEmpty());
+}
+
 TEST_F(ConfigCompileTests, Tidy) {
   Frag.ClangTidy.Add.emplace_back("bugprone-use-after-move");
   Frag.ClangTidy.Add.emplace_back("llvm-*");

clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp

@@ -98,7 +98,7 @@ TEST(ParseYAML, Locations) {
             YAML.range());
 }
 
-TEST(ParseYAML, Diagnostics) {
+TEST(ParseYAML, ConfigDiagnostics) {
   CapturedDiags Diags;
   Annotations YAML(R"yaml(
 If:

clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "Annotations.h"
+#include "Config.h"
 #include "Diagnostics.h"
 #include "ParsedAST.h"
 #include "Protocol.h"
@@ -16,6 +17,7 @@
 #include "TestTU.h"
 #include "TidyProvider.h"
 #include "index/MemIndex.h"
+#include "support/Context.h"
 #include "support/Path.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticSema.h"
@@ -371,6 +373,28 @@ TEST(DiagnosticTest, NoMultipleDiagnosticInFlight) {
           DiagSource(Diag::ClangTidy), DiagName("modernize-loop-convert"))));
 }
 
+TEST(DiagnosticTest, RespectsDiagnosticConfig) {
+  Annotations Main(R"cpp(
+    // error-ok
+    void x() {
+      [[unknown]]();
+      $ret[[return]] 42;
+    }
+  )cpp");
+  auto TU = TestTU::withCode(Main.code());
+  EXPECT_THAT(
+      TU.build().getDiagnostics(),
+      ElementsAre(Diag(Main.range(), "use of undeclared identifier 'unknown'"),
+                  Diag(Main.range("ret"),
+                       "void function 'x' should not return a value")));
+  Config Cfg;
+  Cfg.Diagnostics.Suppress.insert("return-type");
+  WithContextValue WithCfg(Config::Key, std::move(Cfg));
+  EXPECT_THAT(TU.build().getDiagnostics(),
+              ElementsAre(Diag(Main.range(),
+                               "use of undeclared identifier 'unknown'")));
+}
+
 TEST(DiagnosticTest, ClangTidySuppressionComment) {
   Annotations Main(R"cpp(
     int main() {