[clangd] Add a hidden tweak to dump symbol under the cursor.

[hokein]

Summary

This provides a convenient way to see the SymbolID/USR of the symbol, mainly
for debugging purpose.

[merge_guards_bot]

Build result: fail - 59659 tests passed, 2 failed and 805 were skipped.

failed: libc++.libcxx/thread/thread_threads/thread_thread_this/sleep_for.pass.cpp
failed: LLVM.tools/llvm-ar/mri-utf8.test

Log files: cmake-log.txt, ninja_check_all-log.txt, CMakeCache.txt

[ilya-biryukov]

LGTM

[ilya-biryukov]

NIT: a typo in the title: s/curosr/cursor

clang-tools-extra/clangd/refactor/tweaks/DumpAST.cpp

 //===--- DumpAST.cpp ---------------------------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 // Defines a few tweaks that expose AST and related information.
 // Some of these are fairly clang-specific and hidden (e.g. textual AST dumps).
 // Others are more generally useful (class layout) and are exposed by default.
 //===----------------------------------------------------------------------===//
+#include "XRefs.h"
 #include "refactor/Tweak.h"
 #include "clang/AST/ASTTypeTraits.h"
 #include "clang/AST/Type.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace clang {
Expected<Effect> apply(const Selection &Inputs) override {
     return Effect::showMessage(llvm::to_string(Inputs.ASTSelection));
   }
   std::string title() const override { return "Show selection tree"; }
   Intent intent() const override { return Info; }
   bool hidden() const override { return true; }
 };
 REGISTER_TWEAK(ShowSelectionTree)
 
+/// Dumps the symbol under the cursor.
+/// Inputs:
+/// void foo();
+///      ^^^
+/// Message:
+///  foo -
+///  {"containerName":null,"id":"CA2EBE44A1D76D2A","name":"foo","usr":"c:@F@foo#"}
+class DumpSymbol : public Tweak {
+  const char *id() const override final;
+  bool prepare(const Selection &Inputs) override { return true; }
+  Expected<Effect> apply(const Selection &Inputs) override {
+    std::string Storage;
+    llvm::raw_string_ostream Out(Storage);
+
+    for (auto &Sym : getSymbolInfo(
+             Inputs.AST,
+             sourceLocToPosition(Inputs.AST.getSourceManager(), Inputs.Cursor)))
+      Out << Sym;
+    return Effect::showMessage(Out.str());
+  }
+  std::string title() const override { return "Dump symbol under the cursor"; }
+  Intent intent() const override { return Info; }
+  bool hidden() const override { return true; }
+};
+REGISTER_TWEAK(DumpSymbol)
+
 /// Shows the layout of the RecordDecl under the cursor.
 /// Input:
 /// struct X { int foo; };
 /// ^^^^^^^^
 /// Message:
 ///        0 | struct S
 ///        0 |   int foo
 ///          | [sizeof=4, dsize=4, align=4,

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

TEST_F(DumpASTTest, Test) {
   EXPECT_UNAVAILABLE("/*c^omment*/ int foo() return 2 ^ + 2; }");
   EXPECT_THAT(apply("int x = 2 ^+ 2;"),
               AllOf(StartsWith("message:"), HasSubstr("BinaryOperator"),
                     HasSubstr("'+'"), HasSubstr("|-IntegerLiteral"),
                     HasSubstr("<col:9> 'int' 2\n`-IntegerLiteral"),
                     HasSubstr("<col:13> 'int' 2")));
 }
 
+TWEAK_TEST(DumpSymbol);
+TEST_F(DumpSymbolTest, Test) {
+  std::string ID = R"("id":"CA2EBE44A1D76D2A")";
+  std::string USR = R"("usr":"c:@F@foo#")";
+  EXPECT_THAT(apply("void f^oo();"),
+              AllOf(StartsWith("message:"), testing::HasSubstr(ID),
+                    testing::HasSubstr(USR)));
+}
+
 TWEAK_TEST(ShowSelectionTree);
 TEST_F(ShowSelectionTreeTest, Test) {
   EXPECT_AVAILABLE("^int f^oo() { re^turn 2 ^+ 2; }");
   EXPECT_AVAILABLE("/*c^omment*/ int foo() return 2 ^ + 2; }");
 
   const char *Output = R"(message:
  TranslationUnitDecl 
    VarDecl int x = fcall(2 + 2)