[RFC] Introduce a new macro function: JSON_INTERNAL_CATCH

[simnalamburt]

Description

Patch devsisters@d0e60de4 introduces a new macro function; JSON_INTERNAL_CATCH.

With this patch, users will be able to separately handle exceptions raised by nlohmann/json itself and exceptions raised by the STL.

Devsisters Corp. is already using this patch internally. We're sending this PR for the users which might be able to meet similar cases.

The name "JSON_INTERNAL_CATCH" can be changed if you think it is inappropriate. Feedbacks are welcomed.

This patch is completely backward compatible.

Example

https://github.com/simnalamburt/snippets/blob/master/cpp/exception-with-stacktrace.cpp

Pull request checklist

• Changes are described in the pull request, or an existing issue is referenced.
• The test suite compiles and runs without error.
• Code coverage is 100%. Test cases can be added by editing the test suite.
• The source code is amalgamated; that is, after making changes to the sources in the include/nlohmann directory, run make amalgamate to create the single-header file single_include/nlohmann/json.hpp. The whole process is described here.

[coveralls]

Coverage remained the same at 100.0% when pulling d0e60de on devsisters:json-internal-catch into 3ce4325 on nlohmann:develop.

[nlohmann]

Looks good to me.