[Clangd] Make the type hint length limit configurable

This commit is about clangd's type name hint length limit. The past behavior was 32 characters fixed limit. It is now configurable.

Projects can now add the following config fragment to their .clangd:

```
InlayHints:
  TypeNameLimit: 34
```

Ref: [[ clangd/clangd#1357  | Make the type hint length limit configurable ]]

Reviewed By: hokein

Differential Revision: https://reviews.llvm.org/D147395

Author: zhangyi1357

Diff for: clang-tools-extra/clangd/Config.h

@@ -147,6 +147,8 @@ struct Config {
     bool Parameters = true;
     bool DeducedTypes = true;
     bool Designators = true;
+    // Limit the length of type names in inlay hints. (0 means no limit)
+    uint32_t TypeNameLimit = 32;
   } InlayHints;
 };
 

Diff for: clang-tools-extra/clangd/ConfigCompile.cpp

@@ -611,6 +611,11 @@ struct FragmentCompiler {
       Out.Apply.push_back([Value(**F.Designators)](const Params &, Config &C) {
         C.InlayHints.Designators = Value;
       });
+    if (F.TypeNameLimit)
+      Out.Apply.push_back(
+          [Value(**F.TypeNameLimit)](const Params &, Config &C) {
+            C.InlayHints.TypeNameLimit = Value;
+          });
   }
 
   constexpr static llvm::SourceMgr::DiagKind Error = llvm::SourceMgr::DK_Error;

Diff for: clang-tools-extra/clangd/ConfigFragment.h

@@ -322,6 +322,8 @@ struct Fragment {
     std::optional<Located<bool>> DeducedTypes;
     /// Show designators in aggregate initialization.
     std::optional<Located<bool>> Designators;
+    /// Limit the length of type name hints. (0 means no limit)
+    std::optional<Located<uint32_t>> TypeNameLimit;
   };
   InlayHintsBlock InlayHints;
 };

Diff for: clang-tools-extra/clangd/ConfigYAML.cpp

@@ -254,6 +254,10 @@ class Parser {
       if (auto Value = boolValue(N, "Designators"))
         F.Designators = *Value;
     });
+    Dict.handle("TypeNameLimit", [&](Node &N) {
+      if (auto Value = uint32Value(N, "TypeNameLimit"))
+        F.TypeNameLimit = *Value;
+    });
     Dict.parse(N);
   }
 
@@ -375,6 +379,17 @@ class Parser {
     return std::nullopt;
   }
 
+  std::optional<Located<uint32_t>> uint32Value(Node &N, llvm::StringRef Desc) {
+    if (auto Scalar = scalarValue(N, Desc)) {
+      unsigned long long Num;
+      if (!llvm::getAsUnsignedInteger(**Scalar, 0, Num)) {
+        return Located<uint32_t>(Num, Scalar->Range);
+      }
+    }
+    warning(Desc + " invalid number", N);
+    return std::nullopt;
+  }
+
   // Try to parse a list of single scalar values, or just a single value.
   std::optional<std::vector<Located<std::string>>> scalarValues(Node &N) {
     std::vector<Located<std::string>> Result;

Diff for: clang-tools-extra/clangd/InlayHints.cpp

@@ -688,7 +688,8 @@ class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
       return;
 
     std::string TypeName = T.getAsString(Policy);
-    if (TypeName.length() < TypeNameLimit)
+    if (Cfg.InlayHints.TypeNameLimit == 0 ||
+        TypeName.length() < Cfg.InlayHints.TypeNameLimit)
       addInlayHint(R, HintSide::Right, InlayHintKind::Type, Prefix, TypeName,
                    /*Suffix=*/"");
   }
@@ -714,8 +715,6 @@ class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
   // the policies are initialized for more details.)
   PrintingPolicy TypeHintPolicy;
   PrintingPolicy StructuredBindingPolicy;
-
-  static const size_t TypeNameLimit = 32;
 };
 
 } // namespace

Diff for: clang-tools-extra/clangd/unittests/InlayHintTests.cpp

@@ -1324,6 +1324,21 @@ TEST(TypeHints, LongTypeName) {
     // Omit type hint past a certain length (currently 32)
     auto var = foo();
   )cpp");
+
+  Config Cfg;
+  Cfg.InlayHints.TypeNameLimit = 0;
+  WithContextValue WithCfg(Config::Key, std::move(Cfg));
+
+  assertTypeHints(
+      R"cpp(
+    template <typename, typename, typename>
+    struct A {};
+    struct MultipleWords {};
+    A<MultipleWords, MultipleWords, MultipleWords> foo();
+    // Should have type hint with TypeNameLimit = 0
+    auto $var[[var]] = foo();
+  )cpp",
+      ExpectedHint{": A<MultipleWords, MultipleWords, MultipleWords>", "var"});
 }
 
 TEST(TypeHints, DefaultTemplateArgs) {