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

[Paul Kirth via llvm-commits]

================
@@ -0,0 +1,446 @@
+//===-- 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"
+
+using namespace llvm;
+using namespace llvm::json;
+using namespace llvm::mustache;
+
+SmallString<128> escapeString(StringRef Input,
+                              DenseMap<char, StringRef> &Escape) {
+  SmallString<128> EscapedString("");
+  for (char C : Input) {
+    if (Escape.find(C) != Escape.end())
+      EscapedString += Escape[C];
+    else
+      EscapedString += C;
+  }
+  return EscapedString;
+}
+
+std::vector<SmallString<128>> split(StringRef Str, char Delimiter) {
+  std::vector<SmallString<128>> Tokens;
+  if (Str == ".") {
+    Tokens.push_back(Str);
+    return Tokens;
+  }
+  StringRef Ref(Str);
+  while (!Ref.empty()) {
+    llvm::StringRef Part;
+    std::tie(Part, Ref) = Ref.split(Delimiter);
+    Tokens.push_back(Part.trim());
+  }
+  return Tokens;
+}
+
+Token::Token(StringRef RawBody, StringRef InnerBody, char Identifier)
+    : RawBody(RawBody), TokenBody(InnerBody) {
+
+  TokenType = getTokenType(Identifier);
+  if (TokenType == Type::Comment)
+    return;
+
+  StringRef AccessorStr = InnerBody;
+  if (TokenType != Type::Variable)
+    AccessorStr = InnerBody.substr(1);
+
+  Accessor = split(AccessorStr.trim(), '.');
+}
+
+Token::Token(StringRef Str)
+    : RawBody(Str), TokenType(Type::Text), TokenBody(Str), Accessor({}) {}
+
+Token::Type Token::getTokenType(char Identifier) {
+  switch (Identifier) {
+  case '#':
+    return Type::SectionOpen;
+  case '/':
+    return Type::SectionClose;
+  case '^':
+    return Type::InvertSectionOpen;
+  case '!':
+    return Type::Comment;
+  case '>':
+    return Type::Partial;
+  case '&':
+    return Type::UnescapeVariable;
+  default:
+    return Type::Variable;
+  }
+}
+
+std::vector<Token> tokenize(StringRef Template) {
+  // Simple tokenizer that splits the template into tokens
+  // the mustache spec allows {{{ }}} to unescape variables
+  // but we don't support that here unescape variable
+  // is represented only by {{& variable}}
+  std::vector<Token> Tokens;
+  SmallString<128> Open("{{");
+  SmallString<128> Close("}}");
+  std::size_t Start = 0;
+  std::size_t DelimiterStart = Template.find(Open);
+  if (DelimiterStart == StringRef::npos) {
+    Tokens.push_back(Token(Template));
+    return Tokens;
+  }
+  while (DelimiterStart != StringRef::npos) {
+    if (DelimiterStart != Start) {
+      Token TextToken = Token(Template.substr(Start, DelimiterStart - Start));
+      Tokens.push_back(TextToken);
+    }
+
+    std::size_t DelimiterEnd = Template.find(Close, DelimiterStart);
+    if (DelimiterEnd == StringRef::npos) {
+      break;
+    }
+
+    SmallString<128> Interpolated =
+        Template.substr(DelimiterStart + Open.size(),
+                        DelimiterEnd - DelimiterStart - Close.size());
+    SmallString<128> RawBody;
+    RawBody += Open;
+    RawBody += Interpolated;
+    RawBody += Close;
+
+    Tokens.push_back(Token(RawBody, Interpolated, Interpolated[0]));
+    Start = DelimiterEnd + Close.size();
+    DelimiterStart = Template.find(Open, Start);
+  }
+
+  if (Start < Template.size())
+    Tokens.push_back(Token(Template.substr(Start)));
+
+  // fix up white spaces for
+  // open sections/inverted sections/close section/comment
+  for (std::size_t I = 0; I < Tokens.size(); I++) {
----------------
ilovepi wrote:

```suggestion
  for (size_t Idx = 0, End = Tokens.size(); Idx < end; ++I) {
```
prefer pre-increment over post-increment. Avoid calling `size()` in the loop header, unless you're mutating `Tokens`. Avoid `I` as a variable name, unless its an `Instruction`. Loop indexes are one of the few place we allow lowercase variable names, like `i`. 

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