[clangd] Add CodePatterns config option under Completion (#137613)

Allows enabling/disabling code pattern & snippet suggestions
during code completion.

Resolves https://github.com/clangd/clangd/discussions/1867

clang-tools-extra/clangd/ClangdServer.cpp

@@ -457,6 +457,7 @@ void ClangdServer::codeComplete(PathRef File, Position Pos,
     CodeCompleteOpts.ArgumentLists = Config::current().Completion.ArgumentLists;
     CodeCompleteOpts.InsertIncludes =
         Config::current().Completion.HeaderInsertion;
+    CodeCompleteOpts.CodePatterns = Config::current().Completion.CodePatterns;
     // FIXME(ibiryukov): even if Preamble is non-null, we may want to check
     // both the old and the new version in case only one of them matches.
     CodeCompleteResult Result = clangd::codeComplete(

clang-tools-extra/clangd/CodeComplete.cpp

@@ -926,7 +926,8 @@ struct CompletionRecorder : public CodeCompleteConsumer {
     // FIXME: in case there is no future sema completion callback after the
     // recovery mode, we might still want to provide some results (e.g. trivial
     // identifier-based completion).
-    if (Context.getKind() == CodeCompletionContext::CCC_Recovery) {
+    CodeCompletionContext::Kind ContextKind = Context.getKind();
+    if (ContextKind == CodeCompletionContext::CCC_Recovery) {
       log("Code complete: Ignoring sema code complete callback with Recovery "
           "context.");
       return;
@@ -950,6 +951,12 @@ struct CompletionRecorder : public CodeCompleteConsumer {
     // Retain the results we might want.
     for (unsigned I = 0; I < NumResults; ++I) {
       auto &Result = InResults[I];
+      if (Config::current().Completion.CodePatterns ==
+              Config::CodePatternsPolicy::None &&
+          Result.Kind == CodeCompletionResult::RK_Pattern &&
+          // keep allowing the include files autocomplete suggestions
+          ContextKind != CodeCompletionContext::CCC_IncludedFile)
+        continue;
       // Class members that are shadowed by subclasses are usually noise.
       if (Result.Hidden && Result.Declaration &&
           Result.Declaration->isCXXClassMember())
@@ -2153,7 +2160,8 @@ private:
 
 clang::CodeCompleteOptions CodeCompleteOptions::getClangCompleteOpts() const {
   clang::CodeCompleteOptions Result;
-  Result.IncludeCodePatterns = EnableSnippets;
+  Result.IncludeCodePatterns =
+      EnableSnippets && (CodePatterns != Config::CodePatternsPolicy::None);
   Result.IncludeMacros = true;
   Result.IncludeGlobals = true;
   // We choose to include full comments and not do doxygen parsing in

clang-tools-extra/clangd/CodeComplete.h

@@ -111,6 +111,9 @@ struct CodeCompleteOptions {
   Config::ArgumentListsPolicy ArgumentLists =
       Config::ArgumentListsPolicy::FullPlaceholders;
 
+  /// Whether to suggest code patterns & snippets or not in completion
+  Config::CodePatternsPolicy CodePatterns = Config::CodePatternsPolicy::All;
+
   /// Whether to use the clang parser, or fallback to text-based completion
   /// (using identifiers in the current file and symbol indexes).
   enum CodeCompletionParse {

clang-tools-extra/clangd/Config.h

@@ -152,6 +152,11 @@ struct Config {
     NeverInsert // Never insert headers as part of code completion
   };
 
+  enum class CodePatternsPolicy {
+    All, // Suggest all code patterns and snippets
+    None // Suggest none of the code patterns and snippets
+  };
+
   /// Configures code completion feature.
   struct {
     /// Whether code completion includes results that are not visible in current
@@ -161,6 +166,8 @@ struct Config {
     ArgumentListsPolicy ArgumentLists = ArgumentListsPolicy::FullPlaceholders;
     /// Controls if headers should be inserted when completions are accepted
     HeaderInsertionPolicy HeaderInsertion = HeaderInsertionPolicy::IWYU;
+    /// Enables code patterns & snippets suggestions
+    CodePatternsPolicy CodePatterns = CodePatternsPolicy::All;
   } Completion;
 
   /// Configures hover feature.

clang-tools-extra/clangd/ConfigCompile.cpp

@@ -707,6 +707,17 @@ struct FragmentCompiler {
           C.Completion.HeaderInsertion = *Val;
         });
     }
+
+    if (F.CodePatterns) {
+      if (auto Val = compileEnum<Config::CodePatternsPolicy>("CodePatterns",
+                                                             *F.CodePatterns)
+                         .map("All", Config::CodePatternsPolicy::All)
+                         .map("None", Config::CodePatternsPolicy::None)
+                         .value())
+        Out.Apply.push_back([Val](const Params &, Config &C) {
+          C.Completion.CodePatterns = *Val;
+        });
+    }
   }
 
   void compile(Fragment::HoverBlock &&F) {

clang-tools-extra/clangd/ConfigFragment.h

@@ -349,6 +349,11 @@ struct Fragment {
     ///     symbol is forward-declared
     ///   "Never": Never insert headers
     std::optional<Located<std::string>> HeaderInsertion;
+    /// Will suggest code patterns & snippets.
+    /// Values are Config::CodePatternsPolicy:
+    ///   All  => enable all code patterns and snippets suggestion
+    ///   None => disable all code patterns and snippets suggestion
+    std::optional<Located<std::string>> CodePatterns;
   };
   CompletionBlock Completion;
 

clang-tools-extra/clangd/ConfigYAML.cpp

@@ -249,6 +249,10 @@ private:
       if (auto HeaderInsertion = scalarValue(N, "HeaderInsertion"))
         F.HeaderInsertion = *HeaderInsertion;
     });
+    Dict.handle("CodePatterns", [&](Node &N) {
+      if (auto CodePatterns = scalarValue(N, "CodePatterns"))
+        F.CodePatterns = *CodePatterns;
+    });
     Dict.parse(N);
   }
 

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

@@ -3326,6 +3326,40 @@ TEST(CompletionTest, AllScopesCompletion) {
                                  kind(CompletionItemKind::EnumMember))));
 }
 
+TEST(CompletionTest, NoCodePatternsIfDisabled) {
+  clangd::CodeCompleteOptions Opts = {};
+  Opts.EnableSnippets = true;
+  Opts.CodePatterns = Config::CodePatternsPolicy::None;
+
+  auto Results = completions(R"cpp(
+    void function() {
+      /// Trying to trigger "for (init-statement; condition; inc-expression)
+      /// {statements}~" code pattern
+      for^
+    }
+  )cpp",
+                             {}, Opts);
+
+  EXPECT_THAT(Results.Completions,
+              Not(Contains(kind(CompletionItemKind::Snippet))));
+}
+
+TEST(CompletionTest, CompleteIncludeIfCodePatternsNone) {
+  clangd::CodeCompleteOptions Opts = {};
+  Opts.EnableSnippets = true;
+  Opts.CodePatterns = Config::CodePatternsPolicy::None;
+
+  Annotations Test(R"cpp(#include "^)cpp");
+  auto TU = TestTU::withCode(Test.code());
+  TU.AdditionalFiles["foo/bar.h"] = "";
+  TU.ExtraArgs.push_back("-I" + testPath("foo"));
+
+  auto Results = completions(TU, Test.point(), {}, Opts);
+  EXPECT_THAT(Results.Completions,
+              AllOf(has("foo/", CompletionItemKind::Folder),
+                    has("bar.h\"", CompletionItemKind::File)));
+}
+
 TEST(CompletionTest, NoQualifierIfShadowed) {
   clangd::CodeCompleteOptions Opts = {};
   Opts.AllScopes = true;

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

@@ -217,6 +217,19 @@ Completion:
   EXPECT_THAT(Results[0].Completion.AllScopes, testing::Eq(std::nullopt));
 }
 
+TEST(ParseYAML, CodePatterns) {
+  CapturedDiags Diags;
+  Annotations YAML(R"yaml(
+    Completion:
+      CodePatterns: None
+  )yaml");
+  auto Results =
+      Fragment::parseYAML(YAML.code(), "config.yaml", Diags.callback());
+  ASSERT_THAT(Diags.Diagnostics, IsEmpty());
+  ASSERT_EQ(Results.size(), 1u);
+  EXPECT_THAT(Results[0].Completion.CodePatterns, llvm::ValueIs(val("None")));
+}
+
 TEST(ParseYAML, ShowAKA) {
   CapturedDiags Diags;
   Annotations YAML(R"yaml(