I don't have any specific preference on the style. But I am glad you are bringing it up. Every other project I worked on had a specific import style, and the random import changes in PRs are pretty annoying.
On Wed, Oct 14, 2020 at 10:36 PM Dongjin Lee <dong...@apache.org> wrote: > > Hello. I hope to open a discussion about the import order in Java code. > > As Nikolay stated recently[^1], Kafka uses a relatively strict code style > for Java code. However, it misses any rule on import order. For this > reason, the code formatting settings of every local dev environment are > different from person to person, resulting in the countless meaningless > import order changes in the PR. > > For example, in `NamedCache.java` in the streams module, the `java.*` > imports are split into two chunks, embracing the other imports between > them. So, I propose to define an import order to prevent these kinds of > cases in the future. > > To define the import order, we have to regard the following three > orthogonal issues beforehand: > > a. How to group the type imports? > b. Whether to sort the imports alphabetically? > c. Where to place static imports: above the type imports, or below them. > > Since b and c seem relatively straightforward (sort the imports > alphabetically and place the static imports below the type imports), I hope > to focus the available alternatives on the problem a. > > I evaluated the following alternatives and checked how many files are get > effected for each case. (based on commit 1457cc652) And here are the > results: > > *1. kafka, org.apache.kafka, *, javax, java (5 groups): 1222 files.* > > ``` > <module name="ImportOrder"> > <property name="groups" > value="kafka,/^org\.apache\.kafka.*$/,*,javax,java"/> > <property name="ordered" value="true"/> > <property name="separated" value="true"/> > <property name="option" value="bottom"/> > <property name="sortStaticImportsAlphabetically" value="true"/> > </module> > ``` > > *2. (kafka|org.apache.kafka), *, javax? (3 groups): 968 files.* > > ``` > <module name="ImportOrder"> > <property name="groups" value="(kafka|org\.apache\.kafka),*,javax?"/> > <property name="ordered" value="true"/> > <property name="separated" value="true"/> > <property name="option" value="bottom"/> > <property name="sortStaticImportsAlphabetically" value="true"/> > </module> > ``` > > *3. (kafka|org.apache.kafka), *, javax, java (4 groups): 533 files.* > > ``` > <module name="ImportOrder"> > <property name="groups" > value="(kafka|org\.apache\.kafka),*,javax,java"/> > <property name="ordered" value="true"/> > <property name="separated" value="true"/> > <property name="option" value="bottom"/> > <property name="sortStaticImportsAlphabetically" value="true"/> > </module> > ``` > > *4. *, javax? (2 groups): 707 files.* > > ``` > <module name="ImportOrder"> > <property name="groups" value="*,javax?"/> > <property name="ordered" value="true"/> > <property name="separated" value="true"/> > <property name="option" value="bottom"/> > <property name="sortStaticImportsAlphabetically" value="true"/> > </module> > ``` > > *5. javax?, * (2 groups): 1822 files.* > > ``` > <module name="ImportOrder"> > <property name="groups" value="javax?,*"/> > <property name="ordered" value="true"/> > <property name="separated" value="true"/> > <property name="option" value="bottom"/> > <property name="sortStaticImportsAlphabetically" value="true"/> > </module> > ``` > > *6. java, javax, * (3 groups): 1809 files.* > > ``` > <module name="ImportOrder"> > <property name="groups" value="java,javax,*"/> > <property name="ordered" value="true"/> > <property name="separated" value="true"/> > <property name="option" value="bottom"/> > <property name="sortStaticImportsAlphabetically" value="true"/> > </module> > ``` > > I hope to get some feedback on this issue here. > > For the WIP PR, please refer here: https://github.com/apache/kafka/pull/8404 > > Best, > Dongjin > > [^1]: > https://lists.apache.org/thread.html/r2bbee24b8a459842a0fc840c6e40958e7158d29f3f2d6c0d223be80b%40%3Cdev.kafka.apache.org%3E > [^2]: > https://github.com/apache/kafka/blob/trunk/streams/src/main/java/org/apache/kafka/streams/state/internals/NamedCache.java > > -- > *Dongjin Lee* > > *A hitchhiker in the mathematical world.* > > > > > *github: <http://goog_969573159/>github.com/dongjinleekr > <https://github.com/dongjinleekr>keybase: https://keybase.io/dongjinleekr > <https://keybase.io/dongjinleekr>linkedin: kr.linkedin.com/in/dongjinleekr > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck: speakerdeck.com/dongjin > <https://speakerdeck.com/dongjin>* -- Gwen Shapira Engineering Manager | Confluent 650.450.2760 | @gwenshap Follow us: Twitter | blog
