[clang-tools-extra] [llvm] [llvm] add support for mustache templating language (PR #105893)

[Nicolas van Kempen via cfe-commits]

================
@@ -0,0 +1,724 @@
+//===-- Mustache.cpp ------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Mustache.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/raw_ostream.h"
+#include <sstream>
+
+using namespace llvm;
+using namespace llvm::json;
+
+namespace llvm {
+namespace mustache {
+
+class Token {
+public:
+  enum class Type {
+    Text,
+    Variable,
+    Partial,
+    SectionOpen,
+    SectionClose,
+    InvertSectionOpen,
+    UnescapeVariable,
+    Comment,
+  };
+
+  Token(StringRef Str);
+
+  Token(StringRef RawBody, StringRef Str, char Identifier);
+
+  StringRef getTokenBody() const { return TokenBody; };
+
+  StringRef getRawBody() const { return RawBody; };
+
+  void setTokenBody(StringRef NewBody) { TokenBody = NewBody.str(); };
+
+  Accessor getAccessor() const { return Accessor; };
+
+  Type getType() const { return TokenType; };
+
+  void setIndentation(size_t NewIndentation) { Indentation = NewIndentation; };
+
+  size_t getIndentation() const { return Indentation; };
+
+  static Type getTokenType(char Identifier);
+
+private:
+  size_t Indentation;
+  Type TokenType;
+  // RawBody is the original string that was tokenized
+  std::string RawBody;
+  Accessor Accessor;
+  // TokenBody is the original string with the identifier removed
+  std::string TokenBody;
+};
+
+class ASTNode {
+public:
+  enum Type {
+    Root,
+    Text,
+    Partial,
+    Variable,
+    UnescapeVariable,
+    Section,
+    InvertSection,
+  };
+
+  ASTNode() : T(Type::Root), ParentContext(nullptr) {};
+
+  ASTNode(StringRef Body, ASTNode *Parent)
+      : T(Type::Text), Body(Body), Parent(Parent), ParentContext(nullptr) {};
+
+  // Constructor for Section/InvertSection/Variable/UnescapeVariable
+  ASTNode(Type T, Accessor Accessor, ASTNode *Parent)
+      : T(T), Parent(Parent), Children({}), Accessor(Accessor),
+        ParentContext(nullptr) {};
+
+  void addChild(ASTNode *Child) { Children.emplace_back(Child); };
+
+  void setBody(StringRef NewBody) { Body = NewBody; };
----------------
nicovank wrote:

```suggestion
  void setBody(std::string NewBody) { Body = std::move(NewBody); };
```

https://github.com/llvm/llvm-project/pull/105893