[bitcoin] Allow bitcoin to be compiled with optional zmq dependency

[mecampbellsoup]

Since the 0.12 release of bitcoin, it has been possible to utilize ZMQ for pub-sub messaging to allow bitcoind to communicate with other processes.

The UNIX installation docs list it as an optional dependency: https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md#dependencies

Here are detailed docs in the bitcoin GH repo discussing how to make use of ZMQ.

In particular, ZMQ is needed to facilitate message passing from bitcoind to-and-from lnd. Here are docs from the Lightning team discussing how to wire up bitcoind to communicate with lnd.

[ilovezfs]

Let's require it. No need for an option.

[mecampbellsoup]

@ilovezfs SGTM. So remove the => :optional flag?

Once that change is made, the compilation process should report yes when checking for ZMQ, correct?

Strange that ZMQ isn't found during the build... perhaps not strange at all since I haven't made it a required dependency.

[ilovezfs]

yup

Options used to compile and link:
  with wallet   = yes
  with gui / qt = no
  with zmq      = yes
  with test     = yes
  with bench    = yes
  with upnp     = yes
  debug enabled = no
  werror        = no

just remove the => :optional

[ilovezfs]

also we should bump the revision here

[mecampbellsoup]

@ilovezfs where is the revision set, is that the sha256 macro?

[ilovezfs]

here's an example 656e549

[mecampbellsoup]

Cool, it looks like there's no revision yet in the bitcoin.rb recipe, so just set it to revision 1? Or is it zero-index, i.e. revision 0?

[ilovezfs]

Counting starts from 0 but revision 0 is always left implicit.

[mecampbellsoup]

@ilovezfs cool I pushed a commit adding revision 1.

[mecampbellsoup]

@ilovezfs hm, build still failing - does this look familiar to you at all?

[ilovezfs]

@mecampbellsoup it's this: bitcoin/bitcoin#12009

[ilovezfs]

if you rebase this, it should build now

[mecampbellsoup]

@ilovezfs revision inside this patch block, or outside?

[ilovezfs]

should go under homepage in this case

[fxcoudert]

Thanks @mecampbellsoup for the pull request and congrats on your first contribution to Homebrew!