Refactoring hints

Random hints on refactoring.

Refactorings differ, but some findings remain useful. Recently I was busy with a massive change of a common functionality, such as logging interface across a multi-module project.

Some project stats:

For scala and java files:

sloc . --exclude '\.(html|xml|yaml|py|svg|css|js)'

---------- Result ------------

            Physical :  133286
              Source :  109278
             Comment :  7745
 Single-line comment :  4205
       Block comment :  3540
               Mixed :  1271
 Empty block comment :  6
               Empty :  17540
               To Do :  160

Number of files read :  1238

----------------------------

It takes 10.5 min to run mvn test on MacBook Pro (16-inch, 2019) with 2,3 GHz 8-Core i9 and 32 GB 2667 MHz DDR4.

Hints

Good test coverage

Don’t ever start refactoring without having tests at start.

Test reruns

When your refactored code is already compiling but some tests have now outdated expectations, you find them when doing Run > All Tests in project. Then, you iterate over failed test cases while fixing them. And then you Rerun Failed Tests – it is a good thing to have. If it is broken (aparently in current project Run > All Tests is broken), then you run all tests with mvn test -fn which will not fail and run really all tests (later you’ll need to fish for *** FAILED *** in the output).

Separate commits

It’s good to commit changes separately. You can work with git history later. Imagine, while you were doing all that refactoring, how many unrelated (to the story) fixes/ideas you’ve made. All such unrelated fixes and ideas are better to discuss and review in a separate PR.

If each such change has its own commit, then:

git checkout -b introduce-new-feature origin/master
git cherry-pick -x $COMMIT_WITH_NEW_FEATURE
git push

Later, when that separate PR is merged to master, just rebase your big branch, and cherry-picked commits will disappear.

Soft resets

Sometimes you’re in the middle of a change but the day is over. There is a thing you can do to still have a “backup”: commit all, push it to origin and do a soft reset with git reset --soft head~. That way your WIP changes are on your branch on remote repo and you still see all the changes uncommitted locally.