it should be possible to load native extensions from an object file at runtime

[mikedanese]

Similart to --jpath, we need an --npath that is search for symbols that match a convention, then dlopen and register them as native extensions. Lua supports a similar feature.

https://www.lua.org/pil/8.2.html

[mikedanese]

Use casese:

• I want to maintain a yaml import function out of tree
• I want to maintain a regexp library out of tree

[sparkprime]

So you're suggesting that the commandline executable would do this so you don't have to write a frontend yourself (in the style of jsonnet_test_snippet)?

[sparkprime]

Is there any way to do this portably? What if the user had to give the dynamic library using a commandline param and then it was assumed to implement a particular ABI?

[mikedanese]

Is there any way to do this portably?

There are various degrees of support. We should be able to rig something up on linux and mac. Here's where luajit does it for unixy systems:

https://github.com/LuaJIT/LuaJIT/blob/db1b399af134e715b8ba9a0e4ad9cbafbe06ecb1/src/lib_package.c#L58-L66

That function is only defined three times in that file :)

So you're suggesting that the commandline executable would do this so you don't have to write a frontend yourself (in the style of jsonnet_test_snippet)?

Yes, this would be a feature of the jsonnet cli tool that would allow for some basic not-compiled-in extensions. It would server the "import" functionality for native functions.

[sparkprime]

dlopen and dlsym are standard but they don't let you search for files or search through files. However if the user gave the filename and we assumed a particular function name (that set up all the callbacks) then it could work.