can pants install binary build dependencies when running , building or packaging a target. For example, download and install golang when building go targets?

It depends on the language or tool.

Not particularly to any specific dependency but as general. Like in Bazel we can download packages using "http_archive" and write custom functions in starlark to achieve custom functionality. How can we do it in pants? For example, a python project requires tika parser jar server to run to parse pdf documents to extract text out of it. Java environment is required to run jar server. So one need to install jar, run the server and then init the package functionality. How can this be automated in Pants?

There are two issues there. (1) Can Pants rules download tools to run? (2) Can Pants be configured in BUILD files to download tools?

i need both... but please explain the 2nd too

The

adhoc_tool

target type available v2.16.x allows you to run any "runnable" target. https://www.pantsbuild.org/v2.16/docs/reference-adhoc_tool

thank you @fast-nail-55400 i will look into it

kind of

You can use

adhoc_tool

to invoke Python code via any of the target types:

pex_binary

,

python_requirement

,

python_source

, and

pyoxidizer_binary

do we have a demo example?

https://github.com/pantsbuild/example-adhoc is an example repo.

Not sure if this is relevant, but you can also run Python code at BUILD file parsing time via macros: https://www.pantsbuild.org/docs/macros