[clangd] Support configuration of inlay hints.maain

The idea is that the feature will always be advertised at the LSP level, but
depending on config we'll return partial or no responses.

We try to avoid doing the analysis for hints we're not going to return.

Examples of syntax:
```
InlayHints:
  Enabled: No
---
InlayHints:
  ParameterNames: No
---
InlayHints:
  ParameterNames: Yes
  DeducedTypes: Yes
```

Differential Revision: https://reviews.llvm.org/D116713

1 files changed, 30 insertions, 6 deletions

diff --git a/clang-tools-extra/clangd/InlayHints.cpp b/clang-tools-extra/clangd/InlayHints.cpp
index 60d20a38ecd2..e534faa80c4b 100644
--- a/clang-tools-extra/clangd/InlayHints.cpp
+++ b/clang-tools-extra/clangd/InlayHints.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 #include "InlayHints.h"
+#include "Config.h"
 #include "HeuristicResolver.h"
 #include "ParsedAST.h"
 #include "clang/AST/DeclarationName.h"
@@ -23,8 +24,8 @@ enum class HintSide { Left, Right };
 class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
 public:
   InlayHintVisitor(std::vector<InlayHint> &Results, ParsedAST &AST,
-                   llvm::Optional<Range> RestrictRange)
-      : Results(Results), AST(AST.getASTContext()),
+                   const Config &Cfg, llvm::Optional<Range> RestrictRange)
+      : Results(Results), AST(AST.getASTContext()), Cfg(Cfg),
         RestrictRange(std::move(RestrictRange)),
         MainFileID(AST.getSourceManager().getMainFileID()),
         Resolver(AST.getHeuristicResolver()),
@@ -65,6 +66,9 @@ public:
   }
 
   bool VisitCallExpr(CallExpr *E) {
+    if (!Cfg.InlayHints.Parameters)
+      return true;
+
     // Do not show parameter hints for operator calls written using operator
     // syntax or user-defined literals. (Among other reasons, the resulting
     // hints can look awkard, e.g. the expression can itself be a function
@@ -135,7 +139,7 @@ private:
   // the entire argument list likely appears in the main file and can be hinted.
   void processCall(SourceLocation Anchor, const FunctionDecl *Callee,
                    llvm::ArrayRef<const Expr *const> Args) {
-    if (Args.size() == 0 || !Callee)
+    if (!Cfg.InlayHints.Parameters || Args.size() == 0 || !Callee)
       return;
 
     // If the anchor location comes from a macro defintion, there's nowhere to
@@ -323,6 +327,23 @@ private:
   void addInlayHint(SourceRange R, HintSide Side, InlayHintKind Kind,
                     llvm::StringRef Prefix, llvm::StringRef Label,
                     llvm::StringRef Suffix) {
+    // We shouldn't get as far as adding a hint if the category is disabled.
+    // We'd like to disable as much of the analysis as possible above instead.
+    // Assert in debug mode but add a dynamic check in production.
+    assert(Cfg.InlayHints.Enabled && "Shouldn't get here if disabled!");
+    switch (Kind) {
+#define CHECK_KIND(Enumerator, ConfigProperty)                                 \
+  case InlayHintKind::Enumerator:                                              \
+    assert(Cfg.InlayHints.ConfigProperty &&                                    \
+           "Shouldn't get here if kind is disabled!");                         \
+    if (!Cfg.InlayHints.ConfigProperty)                                        \
+      return;                                                                  \
+    break
+      CHECK_KIND(ParameterHint, Parameters);
+      CHECK_KIND(TypeHint, DeducedTypes);
+#undef CHECK_KIND
+    }
+
     auto FileRange =
         toHalfOpenFileRange(AST.getSourceManager(), AST.getLangOpts(), R);
     if (!FileRange)
@@ -348,8 +369,7 @@ private:
 
   void addTypeHint(SourceRange R, QualType T, llvm::StringRef Prefix,
                    const PrintingPolicy &Policy) {
-    // Do not print useless "NULL TYPE" hint.
-    if (!T.getTypePtrOrNull())
+    if (!Cfg.InlayHints.DeducedTypes || T.isNull())
       return;
 
     std::string TypeName = T.getAsString(Policy);
@@ -360,6 +380,7 @@ private:
 
   std::vector<InlayHint> &Results;
   ASTContext &AST;
+  const Config &Cfg;
   llvm::Optional<Range> RestrictRange;
   FileID MainFileID;
   StringRef MainFileBuf;
@@ -381,7 +402,10 @@ private:
 std::vector<InlayHint> inlayHints(ParsedAST &AST,
                                   llvm::Optional<Range> RestrictRange) {
   std::vector<InlayHint> Results;
-  InlayHintVisitor Visitor(Results, AST, std::move(RestrictRange));
+  const auto &Cfg = Config::current();
+  if (!Cfg.InlayHints.Enabled)
+    return Results;
+  InlayHintVisitor Visitor(Results, AST, Cfg, std::move(RestrictRange));
   Visitor.TraverseAST(AST.getASTContext());
 
   // De-duplicate hints. Duplicates can sometimes occur due to e.g. explicit