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Contributing to Ballerina

Ballerina is a cloud native programming language and runtime, including a message broker and API gateway, which makes it easy to create resilient services that integrate and orchestrate transactions across distributed endpoints.

We are an open-source project under Apache license and the work of hundreds of contributors.

We appreciate your help!

Getting Started

  • Download Ballerina at https://ballerina.io and go through the getting started tutorials at https://ballerina.io/learn
  • Read our Code of Conduct
  • Join the conversations at:
    • StackOverflow: to get help with Ballerina; use Ballerina tag for any your questions there,
    • Slack: for real-time discussions with the team and community,
    • Ballerina-Dev Google Group: developer team mailing list to discuss Ballerina roadmap, features and issues on the works, and so on,
    • GitHub: file issues, comment on other issues, send your pull requests.
  • Submit issues:
    • Found a security flaw? Please email security@ballerina.io
    • Submitting a bug is just as important as contributing code. Go to the Issues tab of the GitHub repo and click the New Issue button to file a bug report.
  • Start with easy fix issues:
    • Browse issues labeled easyfix,
    • Use comments on the issue itself to indicate that you will be working on it and get guidance and help.

Communicating with the team

Ballerina-Dev Google Group is the main Ballerina project discussion forum.

StackOverflow is used for support, Slack for real-time communications, and GitHub for issues and code repositories.

Filing issues

If you are unsure whether you have found a bug, please consider searching existing issues in github and asking in Ballerina-Dev Google Group.

IMPORTANT: Sensitive security-related issues should be reported to security@ballerina.io. See the security policy for details.

To file non-security issues:

  1. Click the Issues tab in the github repository,

  2. Click the New Issue button,

  3. Fill out all sections in the issue template and submit.

Contributing site changes, docs, and examples

Contributing code

Accepting Contributor License Agreement (CLA)

Before you submit your first contribution please accept our Contributor License Agreement (CLA) here. When you send your first Pull Request (PR), GitHub will ask you to accept the CLA.

There is no need to do this before you send your first PR.

Subsequent PRs will not require CLA acceptance.

If for some (unlikely) reason at any time CLA changes, you will get presented with the new CLA text on your first PR after the change.

Obtaining the Source Code and Building the Project

Build Prerequisites

Prerequisite 1 - Install a Java Development Kit (JDK) version 8

Building Ballerina requires a Java SE Development Kit (JDK) version 8 to be installed. You can download one from one of the following locations:

NOTE: Set an environment variable JAVA_HOME to the path name of the directory into which you installed the JDK release.

Prerequisite 2 - Install Maven 3.5.0 or later

Install Apache Maven 3.5.0 or a later version: https://maven.apache.org/install.html

Set the MAVEN_OPTS environment variable to avoid the Maven OutOfMemoryError.

MAVEN_OPTS="-Xmx2048M -XX:MaxPermSize=1024m"

Make sure you have an active Internet connection to download dependencies while building.

Prerequisite 3 - Node (v8.9.x or latest LTS release) + npm (v5.6.0 or later)

Prerequisite 4 - Docker

Building from the source

Clone this repository using the following command.

git clone --recursive https://github.com/ballerinalang/ballerina

If you download the sources, you need to update the git submodules using the following command.

git submodule update --init

Run the Maven command mvn clean install from the Ballerina root directory:

Command Description
mvn clean install Build and install the artifacts into the local repository.
mvn clean install -Dmaven.test.skip=true Build and install the artifacts into the local repository, without running any of the unit tests.
mvn clean install -P ballerina The ballerina profile is used to build only the modules necessary for the runtime distribution (i.e., excluding the tools, etc.)

Extract the Ballerina distribution created at distribution/zip/ballerina/target/ballerina-<version>-SNAPSHOT.zip. The zip/ballerina directory contains the runtime only. zip/ballerina-tools/ contains the runtime and tools (e.g., Ballerina Composer).

Setting up your development environment

Setup IntelliJ IDEA

Importing a Ballerina Project

Import any Ballerina project to IntelliJ IDEA similar to any other maven project.

  • Navigate to Import Project
  • Browse the filesystem and Select Ballerina Project's root pom.xml
  • In "Import Project from Maven" Wizard, set followings.
    • Set "Import Maven Projects Automatically" .
    • Set Project SDK as Java 1.8

Optionally, you can use the following Maven command to build an IDEA project.

mvn idea:idea

See http://maven.apache.org/plugins/maven-idea-plugin/ for more information.

Useful IDEA Plugins

Setup Eclipse

Importing a Ballerina Project

All Ballerina repositories are developed as maven projects. So you can import any Ballerina project to Eclipse similar to any maven project.

  • Navigate to File → Import..
  • Select Existing Maven Projects under Maven
  • Next, browse the file system, and open the Maven module.
Installing ANTLR4 plugin

If you are working with the grammar, it would be useful to have ANTLR 4 IDE plugin installed for Eclipse. To install this using Eclipse marketplace:

  1. Navigate to Help → Eclipse Marketplace

  2. Search for antlr4

  3. Install ANTLR 4 IDE plugin (which supports antlr 4.x version).

To open the plugin views:

  1. Navigate to Window → Show View → Other.

  2. Under ANTLR4 section, select and enable Parse Tree view and Syntax Diagram views.

Working With Ballerina Grammar

Ballerina grammar has been implemented using ANTLR4. It is recommended to have some basic understanding on anltr4 grammar syntax and concepts, before working with the Ballerina grammar. “Parr, Terence (January 15, 2013), The Definitive ANTLR 4 Reference” is a good reference to get started with.

Ballerina grammar can be found under docs/grammar in the Ballerina repository. It consists of two files:

  • BallerinaLexer.g4 - Contains the lexer rules for Ballerina grammar. Lexer is responsible for tokenizing an input Ballerina source code.
  • BallerinaParser.g4 - Contains the parser rules. Parser listens to the token stream generated by the lexer. High level grammar productions/abstractions are defined in the parser using those tokens.

TIP: If you want to check and validate a grammar rule you just wrote, you can use the antlr4 plugin of your IDE. See Setting up your development environment section for more details.

Generating Parsers

Once a change is done to the any of the grammar files, it is needed to re-generate the parsers. To generate parsers, we first need to download antlr-complete-4.5.3.jar file. Then navigate to <ballerina>/docs/grammar, and generate the lexer followed by the parser (order is important) using the following command:

java -jar /<path-to-antlr-jar>/antlr-4.5.3-complete.jar *.g4 -package org.wso2.ballerinalang.compiler.parser.antlr4 -o ../../compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/parser/antlr4/.

The above command will autogenerate some Java classes. Out of the autogenerated classes, BallerinaParserBaseListener.java in particular is important, as the Ballerina AST builder is written on top of it. Thus, if any new rules are added to the BallerinaParser.g4, above command will generate new methods in the BallerinaParserBaseListener.java, and you need to override those newly added methods inside BLangParserListener.java accordingly.

Ballerina Compiler

https://medium.com/@sameera.jayasoma/ballerina-compiler-design-3406acc2476c

Ballerina VM

https://medium.com/@sameera.jayasoma/ballerina-runtime-evolution-f82305e4ab8e

Creating a Patch for Review

Fork the Repo

Make Your Changes

Add Unit Tests

Build process automatically runs all the tests.

Commit to Your Fork

We follow these commit message requirements:

  • Separate subject from body with a blank line
  • Limit the subject line to 50 characters
  • Capitalize the subject line
  • Do not end the subject line with a period
  • Use the imperative mood in the subject line
  • Wrap the body at 72 characters
  • Use the body to explain what and why vs. how

Please find details at: https://chris.beams.io/posts/git-commit/

Proposing Changes To Ballerina

Start with the discussion in the Ballerina-Dev Google Group.

Once there is enough consensus around the proposal, you will likely be asked to file an Issue in GitHub and label it as Proposal, to continue the discussion on details there.