example of using the API within another go program

[ghostsquad]

Wondering if someone could create an example of how to use the API within another go program.

[sbarzowski]

Yeah, it probably should be included in the README.

In the simplest case, it goes something like this (I haven't tested this snippet yet):

vm := jsonnet.MakeVM()
vm.EvaluateSnippet(
     "filename-to-be-used-in-stacktraces.jsonnet",
     "local foo(x) = x * 2; foo(17)"  // any Jsonnet code you want
)

You can set up parameters using the VM object. There are options are roughly equivalent to the commandline ones. It is also possible to do some things which wouldn't be practical when using commandline, i.e. to use custom importer (to for example load libraries from the memory rather than from the disk) and to define native functions (user provided builtins for pure functions). If you have a particular feature that you could use an example of, let me know. You can also take a look at this file https://github.com/google/go-jsonnet/blob/master/vm.go which contains the whole API.

BTW depending on your use case I would seriously consider running Jsonnet as a separate process and just executing Jsonnet binary. It makes it easier to provide your users with the exact command to run if they need to debug something. It also allows setting resource limits (e.g. a time limit) for the computation.

[ghostsquad]

@sbarzowski thank you for the quick reply! Regarding your advice to run as a separate process, it seems it would be useful to submit a PR to allow EvaluateSnippet to take a context so that cancellations can be handled.