ignore_comment=true fails on multiple consecutive lines starting with comments

[mattbement]

I know comments are not supported in json, but I'm trying to migrate a project that used YAJL, which has an option for allowing comments, specifically multiple consecutive lines of comments:

// description
// more description
{
...
}

I'm using the parse(...,ignore_comments=true) option, but it's failing on the second comment line. I

What is the issue you have?

Please describe the steps to reproduce the issue.

std::string ss = "//\n//\n{\n}\n";
json j = json::parse(ss,nullptr,true,true);

Can you provide a small but working code example?

std::string ss = "//\n//\n{\n}\n";
json j = json::parse(ss,nullptr,true,true);

What is the expected behavior?

should ignore both lines

And what is the actual behavior instead?

terminate called after throwing an instance of 'nlohmann::detail::parse_error'
what(): [json.exception.parse_error.101] parse error at line 2, column 1: syntax error while parsing value - invalid literal; last read: '//<U+000A>/'
Aborted (core dumped)

Which compiler and operating system are you using?

• Compiler: gcc 9.2
• Operating system: Ubuntu 20.04

Which version of the library did you use?

• latest release version 3.9.0
• other release - please state the version: ___
• [x ] the develop branch (35daa5c)

If you experience a compilation error: can you compile and run the unit tests?

• [x ] yes
• no - please copy/paste the error message below

[nlohmann]

The library does not skip comments inside strings, but only "between" JSON values, like around commas, colons, etc.

[mattbement]

Understood, but this isn't within strings. This is multiple lines of comments at the very beginning of a file, before the first {

[nlohmann]

Oh, I see. Will check tonight.

[nlohmann]

Thanks for reporting! This is indeed a bug. I had code to skip a comment, but did not check for situations with two or more consecutive comments. Replacing an if with a while does the job. I will open a PR.