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# Contributing to Lucene Guide
## Working with Code
### Getting the source code
First of all, you need the Lucene source code.
Get the source code using: `git clone https://github.com/apache/lucene`
### Notes for required Java version
Be sure that you are using an appropriate version of the JDK. Please check [README](./README.md) for the required JDK version for current main branch.
### Building with Gradle
Lucene uses [Gradle](https://gradle.org/) for build control. Gradle is itself Java-based and may be incompatible with newer Java versions; you can still build and test Lucene with these Java releases, see [jvms.txt](./help/jvms.txt) for more information.
Run "./gradlew help", this will show the main tasks that can be executed to show help sub-topics.
If you want to build Lucene, type:
```
./gradlew assemble
```
NOTE: DO NOT use the `gradle` command that is perhaps installed on your machine. This may result in using a different gradle version than the project requires and this is known to lead to very cryptic errors. The "gradle wrapper" (gradlew script) does everything required to build the project from scratch: it downloads the correct version of gradle, sets up sane local configurations and is tested on multiple environments.
The first time you run gradlew, it will create a file "gradle.properties" that contains machine-specific settings. Normally you can use this file as-is, but it can be modified if necessary.
`./gradlew check` will assemble Lucene and run all validation
tasks (including tests).
`./gradlew help` will print a list of help guides that introduce and explain
various parts of the build system, including typical workflow tasks.
If you want to just build the documentation, type:
Please make sure that all unit tests and validations succeed before constructing your patch: `./gradlew check`. If you've modified any sources, run `./gradlew tidy` to apply code formatting conventions automatically (see [help/formatting.txt](https://github.com/apache/lucene/blob/main/help/formatting.txt)).
To run a single test case from the lucene/core directory in your working copy: `./gradlew -p lucene/core test --tests NameOfYourUnitTest`. Run `./gradlew helpTests` to get more information about running tests.
In case your contribution fixes a bug, please create a new test case that fails before your fix, to show the presence of the bug and ensure it never re-occurs. A test case showing the presence of a bug is also a good contribution by itself.
### IDE support
- *IntelliJ* - IntelliJ idea can import and build gradle-based projects out of the box.
- *Eclipse* - Basic support ([help/IDEs.txt](https://github.com/apache/lucene/blob/main/help/IDEs.txt#L7)).
- *Netbeans* - Not tested.
## Contributing your work
You have two options to contribute your work: you can either create a patch and attach it to an issue on [Jira](https://issues.apache.org/jira/browse/LUCENE), or open a pull request at https://github.com/apache/lucene - whichever works best for you.
Please be patient. Committers are busy people too. If no one responds to your patch after a few days, please make friendly reminders. Please incorporate others' suggestions into into your patch if you think they're reasonable. Finally, remember that even a patch that is not committed is useful to the community.
You may want to open a Jira issue before opening a pull request or creating a patch. This is especially required when adding a [CHANGES](./lucene/CHANGES.txt) entry. If your contribution is a small one (such as fixing typo in documentation) this can be optional.
Please refer to [GitHub's documentation](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests) for an explanation of how to create a pull request. The pull request title should start with the Jira issue number that your work is related to, this way your pull request will get automatically linked from the Jira issue.
### Creating a patch
Note that you do not need to create a patch if you already opened a pull request on GitHub.
Before creating your patch, you may want to get 'main' up to date with the latest from upstream. This will help avoid the possibility of others finding merge conflicts when applying your patch. This can be done with git pull if main is the current branch.
If your changes are in your git working tree (i.e. not committed to a branch), then do this:
1. Check to see what files you have modified with: `git status`
2. Add any new files with: `git add src/.../MyNewClass.java`
3. In order to create a patch, just type `git diff HEAD > LUCENE-NNNN.patch`
If your changes are all committed to the current (feature) branch: `git diff main... > LUCENE-NNNN.patch`
If some of your changes are committed to the current (feature) branch but you have working-copy changes too: `git diff {{git merge-base main head > LUCENE-NNNN.patch}}`. This will save a diff into the LUCENE-NNNN.patch file. Read the patch file. Make sure it includes ONLY the modifications required to fix a single issue.
Patches should be attached to an issue in Jira.
To enable automatic validation of Jira patches, switch the issue's status to "Patch Available" by clicking on the "Enable Patch Review" button near the top of the page. This will enqueue an ASF Jenkins job PreCommit-LUCENE-Build to run various quality checks on the patch and post a validation report as a comment (by "Lucene/Solr QA") on the issue. Expect a delay of 12 hours or so before the patch validation job actually runs. Note that in order for a patch file to trigger validation, its name must conform to the naming rules outlined here: https://yetus.apache.org/documentation/in-progress/precommit-patchnames/
## Stay involved
Contributors should join the [Lucene mailing lists](https://lucene.apache.org/core/discussion.html). In particular, the commit list (to see changes as they are made), the dev list (to join discussions of changes) and the user list (to help others).
Please keep discussions about Lucene on list so that everyone benefits. Emailing individual committers with questions about specific Lucene issues is discouraged. See http://people.apache.org/~hossman/#private_q.
## Getting your feet wet: where to begin?
New to Lucene? Want to find JIRA issues that you can work on without taking on the whole world?
The Lucene/Solr developers use the "newdev" label to mark issues that developers new to Lucene might be interested in working on. The rough criteria used to make this selection are:
- Nobody has done any work on the issue yet.
- The issue is likely not controversial.
- The issue is likely self-contained with limited scope.
To see a list of open Lucene issues with the newdev label, look at this link [http://s.apache.org/newdevlucenesolr](https://issues.apache.org/jira/browse/SOLR-15591?jql=(project%3DLUCENE)%20AND%20resolution%3DUnresolved%20AND%20labels%3Dnewdev).
## Developer tips
For more contribution guidelines and tips, see [DeveloperTips](https://cwiki.apache.org/confluence/display/LUCENE/DeveloperTips).
