[clangd] Pull CodeCompletionString handling logic into its own file and add unit test.

[sammccall]

clangd/CompletionString.cpp

51

if you actually care about performance, escapeSnippet should take the string to append to as a parameter

67

these comments are just copies of the enum documentation, mind removing them while here?

118

you've grouped these into a default case above - do the same here?

clangd/CompletionString.h

1

nit: CodeCompletionStrings?

plural because it doesn't define the type, but operations on it.
Full name because we have too many ways to spell things already...

25

This IsSnippet signature is clever, and matches the existing behavior (even if snippets are supported, we send plaintext if possible).

However that doesn't seem important to preserve - either snippets are supported or they're not, and the logic is simpler if we just tell getLabelAndInsertText what style we want.

28

nit: std::pair is always hard to remember - can we take two out-params so code-completion can help us?

34

I'm skeptical that CodeCompletionString is actually where we want to be generating documentation in the long run, vs something like Decl which will give us more flexibility. But this matches what we currently do and seems fine for now.

37

nit: result -> return type

unittests/clangd/CompletionStringTests.cpp

89

I like the fine-grained tests of the features, but I'd also like to be able to see how these strings compare for more typical examples, like the one in this test.

Could you have a test (maybe this one or maybe a new one) where you build a typical function CCS, and then assert all the strings: label, insert text, filter text, with and without snippets...

clangd/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Support
   )
 
 add_clang_library(clangDaemon
   ClangdLSPServer.cpp
   ClangdServer.cpp
   ClangdUnit.cpp
   ClangdUnitStore.cpp
   CodeComplete.cpp
   Context.cpp
+  CompletionString.cpp
   Compiler.cpp
   DraftStore.cpp
   FuzzyMatch.cpp
   GlobalCompilationDatabase.cpp
   JSONExpr.cpp
   JSONRPCDispatcher.cpp
   Logger.cpp
   Protocol.cpp

clangd/CodeComplete.cpp

 //
 // Signature help works in a similar way as code completion, but it is simpler
 // as there are typically fewer candidates.
 //
 //===---------------------------------------------------------------------===//
 
 #include "CodeComplete.h"
 #include "Compiler.h"
+#include "CompletionString.h"
 #include "Logger.h"
 #include "index/Index.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/Sema/CodeCompleteConsumer.h"
 #include "clang/Sema/Sema.h"
 #include <queue>
 
CompletionItemKind toCompletionItemKind(index::SymbolKind Kind) {
   case SK::StaticProperty:
     return CompletionItemKind::Property;
   case SK::Constructor:
     return CompletionItemKind::Constructor;
   }
   llvm_unreachable("Unhandled clang::index::SymbolKind.");
 }
 
-std::string escapeSnippet(const llvm::StringRef Text) {
-  std::string Result;
-  Result.reserve(Text.size()); // Assume '$', '}' and '\\' are rare.
-  for (const auto Character : Text) {
-    if (Character == '$' || Character == '}' || Character == '\\')
-      Result.push_back('\\');
-    Result.push_back(Character);
-  }
-  return Result;
-}
-
-std::string getDocumentation(const CodeCompletionString &CCS) {
-  // Things like __attribute__((nonnull(1,3))) and [[noreturn]]. Present this
-  // information in the documentation field.
-  std::string Result;
-  const unsigned AnnotationCount = CCS.getAnnotationCount();
-  if (AnnotationCount > 0) {
-    Result += "Annotation";
-    if (AnnotationCount == 1) {
-      Result += ": ";
-    } else /* AnnotationCount > 1 */ {
-      Result += "s: ";
-    }
-    for (unsigned I = 0; I < AnnotationCount; ++I) {
-      Result += CCS.getAnnotation(I);
-      Result.push_back(I == AnnotationCount - 1 ? '\n' : ' ');
-    }
-  }
-  // Add brief documentation (if there is any).
-  if (CCS.getBriefComment() != nullptr) {
-    if (!Result.empty()) {
-      // This means we previously added annotations. Add an extra newline
-      // character to make the annotations stand out.
-      Result.push_back('\n');
-    }
-    Result += CCS.getBriefComment();
-  }
-  return Result;
-}
-
 /// Get the optional chunk as a string. This function is possibly recursive.
 ///
 /// The parameter info for each parameter is appended to the Parameters.
 std::string
 getOptionalParameters(const CodeCompletionString &CCS,
                       std::vector<ParameterInformation> &Parameters) {
   std::string Result;
   for (const auto &Chunk : CCS) {

 class CompletionItemsCollector : public CodeCompleteConsumer {
 public:
   CompletionItemsCollector(const CodeCompleteOptions &CodeCompleteOpts,
                            CompletionList &Items, NameToComplete &CompletedName)
       : CodeCompleteConsumer(CodeCompleteOpts.getClangCompleteOpts(),
                              /*OutputIsBinary=*/false),
         ClangdOpts(CodeCompleteOpts), Items(Items),
         Allocator(std::make_shared<clang::GlobalCodeCompletionAllocator>()),
-        CCTUInfo(Allocator), CompletedName(CompletedName) {}
+        CCTUInfo(Allocator), CompletedName(CompletedName),
+        EnableSnippets(CodeCompleteOpts.EnableSnippets) {}
 
   void ProcessCodeCompleteResults(Sema &S, CodeCompletionContext Context,
                                   CodeCompletionResult *Results,
                                   unsigned NumResults) override final {
     if (auto SS = Context.getCXXScopeSpecifier())
       CompletedName.SSInfo = extraCompletionScope(S, **SS);
 
     CompletedName.Filter = S.getPreprocessor().getCodeCompletionFilter();
private:
 
   CompletionItem
   ProcessCodeCompleteResult(const CompletionCandidate &Candidate,
                             const CodeCompletionString &CCS) const {
 
     // Adjust this to InsertTextFormat::Snippet iff we encounter a
     // CK_Placeholder chunk in SnippetCompletionItemsCollector.
     CompletionItem Item;
-    Item.insertTextFormat = InsertTextFormat::PlainText;
 
     Item.documentation = getDocumentation(CCS);
     Item.sortText = Candidate.sortText();
 
-    // Fill in the label, detail, insertText and filterText fields of the
-    // CompletionItem.
-    ProcessChunks(CCS, Item);
+    Item.detail = getDetail(CCS);
+    Item.filterText = getFilterText(CCS);
+    bool IsSnippet = false;
+    auto LabelAndInsertText =
+        getLabelAndInsertText(CCS, EnableSnippets ? &IsSnippet : nullptr);
+    Item.label = LabelAndInsertText.first;
+    Item.insertText = LabelAndInsertText.second;
+
+    Item.insertTextFormat =
+        IsSnippet ? InsertTextFormat::Snippet : InsertTextFormat::PlainText;
 
     // Fill in the kind field of the CompletionItem.
     Item.kind = toCompletionItemKind(Candidate.Result->Kind,
                                      Candidate.Result->CursorKind);
 
     return Item;
   }
 
-  virtual void ProcessChunks(const CodeCompletionString &CCS,
-                             CompletionItem &Item) const = 0;
-
   CodeCompleteOptions ClangdOpts;
   CompletionList &Items;
   std::shared_ptr<clang::GlobalCodeCompletionAllocator> Allocator;
   CodeCompletionTUInfo CCTUInfo;
   NameToComplete &CompletedName;
+  bool EnableSnippets;
 }; // CompletionItemsCollector
 
-bool isInformativeQualifierChunk(CodeCompletionString::Chunk const &Chunk) {
-  return Chunk.Kind == CodeCompletionString::CK_Informative &&
-         StringRef(Chunk.Text).endswith("::");
-}
-
-class PlainTextCompletionItemsCollector final
-    : public CompletionItemsCollector {
-
-public:
-  PlainTextCompletionItemsCollector(const CodeCompleteOptions &CodeCompleteOpts,
-                                    CompletionList &Items,
-                                    NameToComplete &CompletedName)
-      : CompletionItemsCollector(CodeCompleteOpts, Items, CompletedName) {}
-
-private:
-  void ProcessChunks(const CodeCompletionString &CCS,
-                     CompletionItem &Item) const override {
-    for (const auto &Chunk : CCS) {
-      // Informative qualifier chunks only clutter completion results, skip
-      // them.
-      if (isInformativeQualifierChunk(Chunk))
-        continue;
-
-      switch (Chunk.Kind) {
-      case CodeCompletionString::CK_TypedText:
-        // There's always exactly one CK_TypedText chunk.
-        Item.insertText = Item.filterText = Chunk.Text;
-        Item.label += Chunk.Text;
-        break;
-      case CodeCompletionString::CK_ResultType:
-        assert(Item.detail.empty() && "Unexpected extraneous CK_ResultType");
-        Item.detail = Chunk.Text;
-        break;
-      case CodeCompletionString::CK_Optional:
-        break;
-      default:
-        Item.label += Chunk.Text;
-        break;
-      }
-    }
-  }
-}; // PlainTextCompletionItemsCollector
-
-class SnippetCompletionItemsCollector final : public CompletionItemsCollector {
-
-public:
-  SnippetCompletionItemsCollector(const CodeCompleteOptions &CodeCompleteOpts,
-                                  CompletionList &Items,
-                                  NameToComplete &CompletedName)
-      : CompletionItemsCollector(CodeCompleteOpts, Items, CompletedName) {}
-
-private:
-  void ProcessChunks(const CodeCompletionString &CCS,
-                     CompletionItem &Item) const override {
-    unsigned ArgCount = 0;
-    for (const auto &Chunk : CCS) {
-      // Informative qualifier chunks only clutter completion results, skip
-      // them.
-      if (isInformativeQualifierChunk(Chunk))
-        continue;
-
-      switch (Chunk.Kind) {
-      case CodeCompletionString::CK_TypedText:
-        // The piece of text that the user is expected to type to match
-        // the code-completion string, typically a keyword or the name of
-        // a declarator or macro.
-        Item.filterText = Chunk.Text;
-        LLVM_FALLTHROUGH;
-      case CodeCompletionString::CK_Text:
-        // A piece of text that should be placed in the buffer,
-        // e.g., parentheses or a comma in a function call.
-        Item.label += Chunk.Text;
-        Item.insertText += Chunk.Text;
-        break;
-      case CodeCompletionString::CK_Optional:
-        // A code completion string that is entirely optional.
-        // For example, an optional code completion string that
-        // describes the default arguments in a function call.
-
-        // FIXME: Maybe add an option to allow presenting the optional chunks?
-        break;
-      case CodeCompletionString::CK_Placeholder:
-        // A string that acts as a placeholder for, e.g., a function call
-        // argument.
-        ++ArgCount;
-        Item.insertText += "${" + std::to_string(ArgCount) + ':' +
-                           escapeSnippet(Chunk.Text) + '}';
-        Item.label += Chunk.Text;
-        Item.insertTextFormat = InsertTextFormat::Snippet;
-        break;
-      case CodeCompletionString::CK_Informative:
-        // A piece of text that describes something about the result
-        // but should not be inserted into the buffer.
-        // For example, the word "const" for a const method, or the name of
-        // the base class for methods that are part of the base class.
-        Item.label += Chunk.Text;
-        // Don't put the informative chunks in the insertText.
-        break;
-      case CodeCompletionString::CK_ResultType:
-        // A piece of text that describes the type of an entity or,
-        // for functions and methods, the return type.
-        assert(Item.detail.empty() && "Unexpected extraneous CK_ResultType");
-        Item.detail = Chunk.Text;
-        break;
-      case CodeCompletionString::CK_CurrentParameter:
-        // A piece of text that describes the parameter that corresponds to
-        // the code-completion location within a function call, message send,
-        // macro invocation, etc.
-        //
-        // This should never be present while collecting completion items,
-        // only while collecting overload candidates.
-        llvm_unreachable("Unexpected CK_CurrentParameter while collecting "
-                         "CompletionItems");
-        break;
-      case CodeCompletionString::CK_LeftParen:
-        // A left parenthesis ('(').
-      case CodeCompletionString::CK_RightParen:
-        // A right parenthesis (')').
-      case CodeCompletionString::CK_LeftBracket:
-        // A left bracket ('[').
-      case CodeCompletionString::CK_RightBracket:
-        // A right bracket (']').
-      case CodeCompletionString::CK_LeftBrace:
-        // A left brace ('{').
-      case CodeCompletionString::CK_RightBrace:
-        // A right brace ('}').
-      case CodeCompletionString::CK_LeftAngle:
-        // A left angle bracket ('<').
-      case CodeCompletionString::CK_RightAngle:
-        // A right angle bracket ('>').
-      case CodeCompletionString::CK_Comma:
-        // A comma separator (',').
-      case CodeCompletionString::CK_Colon:
-        // A colon (':').
-      case CodeCompletionString::CK_SemiColon:
-        // A semicolon (';').
-      case CodeCompletionString::CK_Equal:
-        // An '=' sign.
-      case CodeCompletionString::CK_HorizontalSpace:
-        // Horizontal whitespace (' ').
-        Item.insertText += Chunk.Text;
-        Item.label += Chunk.Text;
-        break;
-      case CodeCompletionString::CK_VerticalSpace:
-        // Vertical whitespace ('\n' or '\r\n', depending on the
-        // platform).
-        Item.insertText += Chunk.Text;
-        // Don't even add a space to the label.
-        break;
-      }
-    }
-  }
-}; // SnippetCompletionItemsCollector
-
 class SignatureHelpCollector final : public CodeCompleteConsumer {
 
 public:
   SignatureHelpCollector(const clang::CodeCompleteOptions &CodeCompleteOpts,
                          SignatureHelp &SigHelp)
       : CodeCompleteConsumer(CodeCompleteOpts, /*OutputIsBinary=*/false),
         SigHelp(SigHelp),
         Allocator(std::make_shared<clang::GlobalCodeCompletionAllocator>()),
void ProcessOverloadCandidates(Sema &S, unsigned CurrentArg,
     }
   }
 
   GlobalCodeCompletionAllocator &getAllocator() override { return *Allocator; }
 
   CodeCompletionTUInfo &getCodeCompletionTUInfo() override { return CCTUInfo; }
 
 private:
+  // FIXME(ioeric): consider moving CodeCompletionString logic here to
+  // CompletionString.h.
   SignatureInformation
   ProcessOverloadCandidate(const OverloadCandidate &Candidate,
                            const CodeCompletionString &CCS) const {
     SignatureInformation Result;
     const char *ReturnType = nullptr;
 
     Result.documentation = getDocumentation(CCS);
 

 CompletionList codeComplete(const Context &Ctx, PathRef FileName,
                             const tooling::CompileCommand &Command,
                             PrecompiledPreamble const *Preamble,
                             StringRef Contents, Position Pos,
                             IntrusiveRefCntPtr<vfs::FileSystem> VFS,
                             std::shared_ptr<PCHContainerOperations> PCHs,
                             CodeCompleteOptions Opts) {
   CompletionList Results;
-  std::unique_ptr<CodeCompleteConsumer> Consumer;
   NameToComplete CompletedName;
-  if (Opts.EnableSnippets) {
-    Consumer = llvm::make_unique<SnippetCompletionItemsCollector>(
-        Opts, Results, CompletedName);
-  } else {
-    Consumer = llvm::make_unique<PlainTextCompletionItemsCollector>(
-        Opts, Results, CompletedName);
-  }
+  auto Consumer =
+      llvm::make_unique<CompletionItemsCollector>(Opts, Results, CompletedName);
   invokeCodeComplete(Ctx, std::move(Consumer), Opts.getClangCompleteOpts(),
                      FileName, Command, Preamble, Contents, Pos, std::move(VFS),
                      std::move(PCHs));
   if (Opts.Index && CompletedName.SSInfo) {
     if (!Results.items.empty())
       log(Ctx, "WARNING: Got completion results from sema for completion on "
                "qualified ID while symbol index is provided.");
     Results.items.clear();

clangd/CompletionString.h

+//===--- CompletionString.h --------------------------------------*- C++-*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+//
+// Functions for retrieving code completion information from
+// `CodeCompletionString`.
+//
+//===---------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_COMPLETIONSTRING_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_COMPLETIONSTRING_H
+
+#include "clang/Sema/CodeCompleteConsumer.h"
+
+namespace clang {
+namespace clangd {
+
+/// Gets label and insert text for a completion item. For example, for function
+/// `Foo`, this returns <"Foo(int x, int y)", "Foo"> without snippts enabled.
+///
+/// If \p IsSnippet is not nullptr, this will try to use snippet for the insert
+/// text and sets `IsSnippet` to true when a snippet is created. Otherwise, the
+/// insert text will always be plain text.
+std::pair<std::string, std::string>
+getLabelAndInsertText(const CodeCompletionString &CCS,
+                      bool *IsSnippet = nullptr);
+
+/// Gets the documentation for a completion item. For example, comment for the
+/// a class declaration.
+std::string getDocumentation(const CodeCompletionString &CCS);
+
+/// Gets detail to be used as the detail field in an LSP completion item. This
+/// is usually the result of a function.
+std::string getDetail(const CodeCompletionString &CCS);
+
+/// Gets the piece of text that the user is expected to type to match the
+/// code-completion string, typically a keyword or the name of a declarator or
+/// macro.
+std::string getFilterText(const CodeCompletionString &CCS);
+
+} // namespace clangd
+} // namespace clang
+
+#endif

clangd/CompletionString.cpp

+//===--- CompletionString.cpp ------------------------------------*- C++-*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+
+#include "CompletionString.h"
+#include <utility>
+
+namespace clang {
+namespace clangd {
+
+namespace {
+
+bool isInformativeQualifierChunk(CodeCompletionString::Chunk const &Chunk) {
+  return Chunk.Kind == CodeCompletionString::CK_Informative &&
+         StringRef(Chunk.Text).endswith("::");
+}
+
+std::pair<std::string, std::string>
+processPlainTextChunks(const CodeCompletionString &CCS) {
+  std::string Label;
+  std::string InsertText;
+  for (const auto &Chunk : CCS) {
+    // Informative qualifier chunks only clutter completion results, skip
+    // them.
+    if (isInformativeQualifierChunk(Chunk))
+      continue;
+
+    switch (Chunk.Kind) {
+    case CodeCompletionString::CK_ResultType:
+    case CodeCompletionString::CK_Optional:
+      break;
+    case CodeCompletionString::CK_TypedText:
+      InsertText += Chunk.Text;
+      Label += Chunk.Text;
+      break;
+    default:
+      Label += Chunk.Text;
+      break;
+    }
+  }
+  return {Label, InsertText};
+}
+
+std::string escapeSnippet(const llvm::StringRef Text) {
+  std::string Result;
+  Result.reserve(Text.size()); // Assume '$', '}' and '\\' are rare.
+  for (const auto Character : Text) {
+    if (Character == '$' || Character == '}' || Character == '\\')
+      Result.push_back('\\');
+    Result.push_back(Character);
+  }
+  return Result;
+}
+
+std::pair<std::string, std::string>
+processSnippetChunks(const CodeCompletionString &CCS, bool *IsSnippet) {
+  std::string Label;
+  std::string InsertText;
+
+  unsigned ArgCount = 0;
+  for (const auto &Chunk : CCS) {
+    // Informative qualifier chunks only clutter completion results, skip
+    // them.
+    if (isInformativeQualifierChunk(Chunk))
+      continue;
+
+    switch (Chunk.Kind) {
+    case CodeCompletionString::CK_TypedText:
+      // The piece of text that the user is expected to type to match
+      // the code-completion string, typically a keyword or the name of
+      // a declarator or macro.
+    case CodeCompletionString::CK_Text:
+      Label += Chunk.Text;
+      InsertText += Chunk.Text;
+      break;
+    case CodeCompletionString::CK_Optional:
+      // A code completion string that is entirely optional.
+      // For example, an optional code completion string that
+      // describes the default arguments in a function call.
+
+      // FIXME: Maybe add an option to allow presenting the optional chunks?
+      break;
+    case CodeCompletionString::CK_Placeholder:
+      // A string that acts as a placeholder for, e.g., a function call
+      // argument.
+      ++ArgCount;
+      InsertText += "${" + std::to_string(ArgCount) + ':' +
+                    escapeSnippet(Chunk.Text) + '}';
+      Label += Chunk.Text;
+      *IsSnippet = true;
+      break;
+    case CodeCompletionString::CK_Informative:
+      // A piece of text that describes something about the result
+      // but should not be inserted into the buffer.
+      // For example, the word "const" for a const method, or the name of
+      // the base class for methods that are part of the base class.
+      Label += Chunk.Text;
+      // Don't put the informative chunks in the insertText.
+      break;
+    case CodeCompletionString::CK_ResultType:
+      // This is retrieved as detail.
+      break;
+    case CodeCompletionString::CK_CurrentParameter:
+      // A piece of text that describes the parameter that corresponds to
+      // the code-completion location within a function call, message send,
+      // macro invocation, etc.
+      //
+      // This should never be present while collecting completion items,
+      // only while collecting overload candidates.
+      llvm_unreachable("Unexpected CK_CurrentParameter while collecting "
+                       "CompletionItems");
+      break;
+    case CodeCompletionString::CK_LeftParen:
+      // A left parenthesis ('(').
+    case CodeCompletionString::CK_RightParen:
+      // A right parenthesis (')').
+    case CodeCompletionString::CK_LeftBracket:
+      // A left bracket ('[').
+    case CodeCompletionString::CK_RightBracket:
+      // A right bracket (']').
+    case CodeCompletionString::CK_LeftBrace:
+      // A left brace ('{').
+    case CodeCompletionString::CK_RightBrace:
+      // A right brace ('}').
+    case CodeCompletionString::CK_LeftAngle:
+      // A left angle bracket ('<').
+    case CodeCompletionString::CK_RightAngle:
+      // A right angle bracket ('>').
+    case CodeCompletionString::CK_Comma:
+      // A comma separator (',').
+    case CodeCompletionString::CK_Colon:
+      // A colon (':').
+    case CodeCompletionString::CK_SemiColon:
+      // A semicolon (';').
+    case CodeCompletionString::CK_Equal:
+      // An '=' sign.
+    case CodeCompletionString::CK_HorizontalSpace:
+      // Horizontal whitespace (' ').
+      InsertText += Chunk.Text;
+      Label += Chunk.Text;
+      break;
+    case CodeCompletionString::CK_VerticalSpace:
+      // Vertical whitespace ('\n' or '\r\n', depending on the
+      // platform).
+      InsertText += Chunk.Text;
+      // Don't even add a space to the label.
+      break;
+    }
+  }
+  return {std::move(Label), std::move(InsertText)};
+}
+
+} // namespace
+
+std::pair<std::string, std::string>
+getLabelAndInsertText(const CodeCompletionString &CCS, bool *IsSnippet) {
+  return IsSnippet ? processSnippetChunks(CCS, IsSnippet)
+                   : processPlainTextChunks(CCS);
+}
+
+std::string getDocumentation(const CodeCompletionString &CCS) {
+  // Things like __attribute__((nonnull(1,3))) and [[noreturn]]. Present this
+  // information in the documentation field.
+  std::string Result;
+  const unsigned AnnotationCount = CCS.getAnnotationCount();
+  if (AnnotationCount > 0) {
+    Result += "Annotation";
+    if (AnnotationCount == 1) {
+      Result += ": ";
+    } else /* AnnotationCount > 1 */ {
+      Result += "s: ";
+    }
+    for (unsigned I = 0; I < AnnotationCount; ++I) {
+      Result += CCS.getAnnotation(I);
+      Result.push_back(I == AnnotationCount - 1 ? '\n' : ' ');
+    }
+  }
+  // Add brief documentation (if there is any).
+  if (CCS.getBriefComment() != nullptr) {
+    if (!Result.empty()) {
+      // This means we previously added annotations. Add an extra newline
+      // character to make the annotations stand out.
+      Result.push_back('\n');
+    }
+    Result += CCS.getBriefComment();
+  }
+  return Result;
+}
+
+std::string getDetail(const CodeCompletionString &CCS) {
+  for (const auto &Chunk : CCS) {
+    // Informative qualifier chunks only clutter completion results, skip
+    // them.
+    switch (Chunk.Kind) {
+    case CodeCompletionString::CK_ResultType:
+      return Chunk.Text;
+    default:
+      break;
+    }
+  }
+  return "";
+}
+
+std::string getFilterText(const CodeCompletionString &CCS) {
+  for (const auto &Chunk : CCS) {
+    switch (Chunk.Kind) {
+    case CodeCompletionString::CK_TypedText:
+      // There's always exactly one CK_TypedText chunk.
+      return Chunk.Text;
+    default:
+      break;
+    }
+  }
+  return "";
+}
+
+} // namespace clangd
+} // namespace clang

unittests/clangd/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   support
   )
 
 get_filename_component(CLANGD_SOURCE_DIR
   ${CMAKE_CURRENT_SOURCE_DIR}/../../clangd REALPATH)
 include_directories(
   ${CLANGD_SOURCE_DIR}
   )
 
 add_extra_unittest(ClangdTests
   ClangdTests.cpp
   CodeCompleteTests.cpp
+  CompletionStringTests.cpp
   ContextTests.cpp
   FileIndexTests.cpp
   FuzzyMatchTests.cpp
   IndexTests.cpp
   JSONExprTests.cpp
   TestFS.cpp
   TraceTests.cpp
   SourceCodeTests.cpp

unittests/clangd/CompletionStringTests.cpp

+//===-- CompletionStringTests.cpp -------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CompletionString.h"
+#include "clang/Sema/CodeCompleteConsumer.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace clang {
+namespace clangd {
+namespace {
+
+class CompletionStringTest : public ::testing::Test {
+public:
+  CompletionStringTest()
+      : Allocator(std::make_shared<clang::GlobalCodeCompletionAllocator>()),
+        CCTUInfo(Allocator), Builder(*Allocator, CCTUInfo) {}
+
+protected:
+  std::shared_ptr<clang::GlobalCodeCompletionAllocator> Allocator;
+  CodeCompletionTUInfo CCTUInfo;
+  CodeCompletionBuilder Builder;
+};
+
+TEST_F(CompletionStringTest, Detail) {
+  Builder.AddResultTypeChunk("result");
+  Builder.AddResultTypeChunk("redundant result no no");
+  EXPECT_EQ(getDetail(*Builder.TakeString()), "result");
+}
+
+TEST_F(CompletionStringTest, FilterText) {
+  Builder.AddTypedTextChunk("typed");
+  Builder.AddTypedTextChunk("redundant typed no no");
+  auto *S = Builder.TakeString();
+  EXPECT_EQ(getFilterText(*S), "typed");
+}
+
+TEST_F(CompletionStringTest, Documentation) {
+  Builder.addBriefComment("Is this brief?");
+  EXPECT_EQ(getDocumentation(*Builder.TakeString()), "Is this brief?");
+}
+
+TEST_F(CompletionStringTest, DocumentationWithAnnotation) {
+  Builder.addBriefComment("Is this brief?");
+  Builder.AddAnnotation("Ano");
+  EXPECT_EQ(getDocumentation(*Builder.TakeString()),
+            "Annotation: Ano\n\nIs this brief?");
+}
+
+TEST_F(CompletionStringTest, MultipleAnnotations) {
+  Builder.AddAnnotation("Ano1");
+  Builder.AddAnnotation("Ano2");
+  Builder.AddAnnotation("Ano3");
+
+  EXPECT_EQ(getDocumentation(*Builder.TakeString()),
+            "Annotations: Ano1 Ano2 Ano3\n");
+}
+
+TEST_F(CompletionStringTest, SimpleLabelAndInsert) {
+  Builder.AddTypedTextChunk("X");
+  Builder.AddResultTypeChunk("result no no");
+  auto Pair = getLabelAndInsertText(*Builder.TakeString());
+  EXPECT_EQ(Pair.first, "X");
+  EXPECT_EQ(Pair.second, "X");
+}
+
+TEST_F(CompletionStringTest, FunctionPlainText) {
+  Builder.AddResultTypeChunk("result no no");
+  Builder.AddTypedTextChunk("Foo");
+  Builder.AddChunk(CodeCompletionString::CK_LeftParen);
+  Builder.AddPlaceholderChunk("p1");
+  Builder.AddChunk(CodeCompletionString::CK_Comma);
+  Builder.AddPlaceholderChunk("p2");
+  Builder.AddChunk(CodeCompletionString::CK_RightParen);
+  Builder.AddChunk(CodeCompletionString::CK_HorizontalSpace);
+  Builder.AddInformativeChunk("const");
+
+  auto Pair = getLabelAndInsertText(*Builder.TakeString());
+  EXPECT_EQ(Pair.first, "Foo(p1, p2) const");
+  EXPECT_EQ(Pair.second, "Foo");
+}
+
+TEST_F(CompletionStringTest, FunctionSnippet) {
+  Builder.AddResultTypeChunk("result no no");
+  Builder.AddTypedTextChunk("Foo");
+  Builder.AddTextChunk("d");
+  Builder.AddChunk(CodeCompletionString::CK_LeftParen);
+  Builder.AddPlaceholderChunk("p1");
+  Builder.AddChunk(CodeCompletionString::CK_Comma);
+  Builder.AddPlaceholderChunk("p2");
+  Builder.AddChunk(CodeCompletionString::CK_RightParen);
+
+  bool IsSnippet = false;
+  auto Pair = getLabelAndInsertText(*Builder.TakeString(), &IsSnippet);
+  EXPECT_TRUE(IsSnippet);
+  EXPECT_EQ(Pair.first, "Food(p1, p2)");
+  EXPECT_EQ(Pair.second, "Food(${1:p1}, ${2:p2})");
+}
+
+TEST_F(CompletionStringTest, EscapeSnippet) {
+  Builder.AddTypedTextChunk("Foo");
+  Builder.AddChunk(CodeCompletionString::CK_LeftParen);
+  Builder.AddPlaceholderChunk("$p}1\\");
+  Builder.AddChunk(CodeCompletionString::CK_RightParen);
+
+  bool IsSnippet = false;
+  auto Pair = getLabelAndInsertText(*Builder.TakeString(), &IsSnippet);
+  EXPECT_TRUE(IsSnippet);
+  EXPECT_EQ(Pair.first, "Foo($p}1\\)");
+  EXPECT_EQ(Pair.second, "Foo(${1:\\$p\\}1\\\\})");
+}
+
+TEST_F(CompletionStringTest, IgnoreInformativeQualifier) {
+  Builder.AddTypedTextChunk("X");
+  Builder.AddInformativeChunk("info ok");
+  Builder.AddInformativeChunk("info no no::");
+  auto Pair = getLabelAndInsertText(*Builder.TakeString());
+  EXPECT_EQ(Pair.first, "Xinfo ok");
+  EXPECT_EQ(Pair.second, "X");
+}
+
+} // namespace
+} // namespace clangd
+} // namespace clang