[LINT] Add rule explicit-begin

[suzizecat]

Add rule to check if the begin keyword always follows a if/else/for.
Related to #1321

[suzizecat]

This should be OK (clang-format was ran and tests were performed on a testcase).
I have not run the integrated tests because I didn't found a way to only run my test (I'm a noob with bazel).

[hzeller]

You can run your test with

bazel test //verilog/analysis/checkers:explicit_begin_rule_test

[suzizecat]

Thanks, I understood the "reject" pattern thing.
This should be ok. however I need to add tests for "for" constructions

[hzeller]

What is the status of this PR @suzizecat ? Looks like we were almost there, just needed to make all the tests work.
Can you re-base and make the tests work, so that we're ready for review ?

[suzizecat]

Hi @hzeller , I don't have access to the computer used for developing this before next week, but I'll have a look again at this time.
IIRC I have some issues with cases I hadn't accounted for at first glance.

I'll let you know if I run in any issues.

[sconwayaus]

Hi @suzizecat. I was interested in this feature as a user and came across this PR. Are you wanting to finish this one off? Otherwise I'm happy to pick this up.

FWIW: I copied your code into a branch here: https://github.com/sconwayaus/verible/tree/begin_end_rule. Wasn't a lot of work to make this build at the head, (couple of BUILD files was about it), and I added some for loop tests too.

[suzizecat]

Hi @sconwayaus, I had issues with building (probably the BUILD files you fixed) but had no time to work on this.
If I remember correctly, there was also quite a few edge cases that weren't taken into account by this PR, but if you are willing to pick this up, please feel free to do so.