Automate code formatting using Maven (2019 rules)

[walles]

Same as #2494 but with HBase rules from 2019 (the other PR uses the existing 2014 ruleset).

Before this change

CONTRIBUTING.md encouraged reformatting sources using make format.

make format would reformat lots of files, not just the ones you changed.

With this change in place

Any mvn operation will implicitly format sources.

CI will validate code formatting.

This implicitly means that people have to at least mvn compile their sources locally before making PRs to make sure they don't get refused by CI.

This enforces good practice, regardless of the actual formatting.

Notes

Files to be reviewed (the rest have been auto formatted):

• pom.xml
• Makefile
• .github/CONTRIBUTING.md

Also, checking the commits list might be easier than looking at files changed, all reformatting is confined to the last change.

The code formatting Maven plugin being used didn't have any validate goal so I replaced with another one.

Still running the Eclipse formatter though, so hbase-formatter.xml still works.

hbase-formatter.xml has been updated to a newer one from 2019.

[walles]

The formatter considered by hash that my files were already formatted since #2494 and ignored them after I upgraded the formatting rules, had to make some attempts to get around that.

Should be good now.

[walles]

Formatter caching problem reported here: revelc/formatter-maven-plugin#453

[walles]

Closing.

If somebody wants to revive this, any Java conflicts could probably be fixed by:

1. Dropping the last commit (Run "mvn compile" to get sources formatted)
2. Rebase on latest master
3. mvn compile to reformat the code
4. Commit and push reformatting changes as a new Run "mvn compile" to get sources formatted change
5. Force push since you just replaced a commit

[walles]

@sazzad16, just out of curiosity, what kind of discussion do you think would be needed?

Are the instructions in CONTRIBUTING.md still valid?

[sazzad16]

@walles

what kind of discussion do you think would be needed?

It's mostly "when" would we want to merge the change as it's likely to invalidate all the existing PRs.

Are the instructions in CONTRIBUTING.md still valid?

Yes. (We should improve it. But current one doesn't seem wrong.)

[walles]

Are the instructions in CONTRIBUTING.md still valid?

Yes. (We should improve it. But current one doesn't seem wrong.)

The instructions say:

• You can run make format anytime to reformat without IDEs

Which will change tons of code, invalidating all other PRs.

So CONTRIBUTING.md actually does contain instructions that don't work.

[sazzad16]

• You can run make format anytime to reformat without IDEs

@walles Thanks. Striking it for the time being.