Does <llvm/Support/Json.h> support parsing comments? Why not?

LLVM Project
1

I wrote a small program to parse a json file with comment:

#include <llvm/Support/JSON.h>
#include <llvm/Support/MemoryBuffer.h>

int
main(int argc, char* argv[])
{
  auto path = argv[1];
  auto fOrErr = llvm::MemoryBuffer::getFile(path);
  auto f = std::move(fOrErr.get());
  auto jval = llvm::json::parse(f->getBuffer());
  if (!jval) {
    llvm::errs() << jval.takeError();
    return 1;
  }
  llvm::outs() << *jval << '\n';
}

Here’s my JSON file:

{
  // 123
  "dadaf": 123
}

And it fails to parse:

[2:3, byte=5]: Expected object key

I thought <llvm/Support/Json.h> may not support handling comments, but it suprised me that llvm::json::OStream has a void comment(llvm::StringRef); method to emit comments. To me, it seems weird that <llvm/Support/Json.h> can dump comments but cannot parse them back.

Am I wrong? If not, why doesn’t <llvm/Support/Json.h> support parsing comments? Does LLVM support any other data formats in substitution of JSON comments?

2

Comments are not part of the JSON specification, so that’s probably why. Any JSON parser that supports comments is a non-standard extension.

From your observation though, as they seem to be intended, maybe adding it upstream would be accepted.

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