enso/CONTRIBUTING.md

Contributing to Enso

Thank you for your interest in contributing to Enso! We believe that only through community involvement can Enso be the best it can be! There are a whole host of ways to contribute, and every single one is appreciated. The major sections of this document are linked below:

• Issues
• Feature Enhancements
• Bug Reports
• Hacking on Enso
• Pull Requests
• Documentation
• Issue Triage
• Out-of-Tree Contributions
• Helpful Documentation and Links

All contributions to Luna should be in keeping with our Code of Conduct.

Issues

If you are looking for somewhere to start, check out the Help Wanted tag in the following repositories:

• Enso
• Luna Studio
• Luna Manager
• Luna Dataframes

Feature Enhancements

If you feel like you have a suggestion for a change to the way that Enso works as a language, please open an issue in our RFCs Repository, rather than in this one! New features and other significant language changes must go through the RFC process so they can be properly discussed.

Bug Reports

While it's never great to find a bug, they are a reality of software and software development! We can't fix or improve on the things that we don't know about, so report as many bugs as you can! If you're not sure whether something is a bug, file it anyway!

If you are concerned that your bug publicly presents a security risk to the users of Enso, please contact security@luna-lang.org.

Even though GitHub search can be a bit hard to use sometimes, we'd appreciate if you could search for your issue before filing a bug as it's possible that someone else has already reported the issue. We know the search isn't the best, and it can be hard to know what to search for, so we really don't mind if you do submit a duplicate!

Opening an issue is as easy as following this link and filling out the fields. The template is intended to collect all the information we need to best diagnose the issue, so please take the time to fill it out accurately.

The reproduction steps are particularly important, as the more easily we can reproduce it, the faster we can fix the bug! It's also helpful to have the output of enso --version, as that will let us know if the bug is Operating System or Architecture specific.

Hacking on Enso

This will get you up and running for Enso development, with only a minimal amount of setup required. Enso's build system is fairly simple, allowing you to bootstrap the compiler as long as you have...

Design Documentation

If you're going to start contributing to Enso, it is often a good idea to take a look at the design documentation for the language. These files explain provide both a rigorous specification of Enso's design, but also insight into the why behind the decisions that have been made.

These can be found in doc/design/, and are organised by the part of the compiler that they relate to.

System Requirements

In order to build and run Enso you will need the following tools:

• sbt with version at least 1.3.0.
• GraalVM with version at least 19.2.0 and configured as your default JVM. Jenv is a useful tool for managing multiple JVMs.

Getting the Sources

Given you've probably been reading this document on GitHub, you might have an inkling where to look!. You can clone Luna using two methods:

• Via HTTPS: We recommend you only use HTTPS if checking out the sources as read-only.

git clone https://github.com/luna/enso.git

• Via SSH: For those who plan on regularly making direct commits, cloning over SSH may provide a better user experience (but requires setting up your SSH Keys with GitHub).

git clone git@github.com:luna/enso.git

Building Enso

There are multiple projects in this repository, but all can be built, run and tested using sbt. As long as your configuration is correct, with the correct versions of SBT and GraalVM, the same steps can be followed on all of our supported platforms (Linux, MacOS and Windows).

SBT will handle downloading and building library dependencies as needed, meaning that you don't need to handle any of this manually.

Please note that at the current time, the Windows build of GraalVM is in an experimental state. This means that while it may function, we are not intending to provide work-arounds for building on that platform while it is still in an unstable state.

Building Enso Components

In order to build a specific component (e.g. interpreter), please follow the following steps.

1. Enter the sbt shell in the repository root directory by typing sbt.
2. Change to the project you are concerned with (in our case interpreter) by executing project interpreter.
3. Execute compile in order to compile the project in question. This will compile the project and all its dependencies as necessary.

You can substitute both bench and test for compile in step 3, and the sbt shell will execute the appropriate thing. Furthermore we have testOnly and benchOnly that accept a glob pattern that delineates some subset of the tests or benchmarks to run (e.g. testOnly *FunctionArguments*).

Building the Interpreter CLI Fat Jar

In order to build a fat jar with the CLI component, run the assembly task inside the interpreter subproject:

sbt "interpreter/assembly"

This will produce an executable enso.jar fat jar in the repository root. It's self contained, with its only dependencies being available inside a vanilla GraalVM distribution. To run it, use:

JAVA_HOME=<PATH_TO_GRAAL_HOME> ./enso.jar <CLI_ARGS>

If you decide not to use the default launcher script, make sure to pass the -XX:-UseJVMCIClassLoader option to the java command.

Passing Debug Options

GraalVM provides some useful debugging options, including the ability to output the compilation graph during JIT optimisation, and the ASM generated by the JIT.

However, as we don't want these things polluting our standard builds, we provide a helper SBT command withDebug to allow for passing these options. It supports the following flags:

• --dumpGraphs: This dumps the IGV (a Graal tool) graphs for the program to allow for manual analysis and discovery of optimisation failures.
• --showCompilations: Prints the truffle compilation trace information.
• --printAssembly: Prints the assembly output from the HotSpot JIT tier.

For more information on this sbt command, please see WithDebugCommand.scala.

It is used as an addendum to the basic sbt command you want to run (e.g. test from above). The format is withDebug COMMAND [OPTIONS...], and if you need to pass any additional options to COMMAND you must do so following a --. For example:

withDebug run --dumpGraphs --printAssembly -- --run MyFile.enso
withDebug benchOnly --showCompilations -- RecursionBenchmark

Native Image

Native image is a capability provided alongside GraalVM that allows the generation of native executables from JVM language programs (such as the Enso interpreter itself). However, it results in significantly degraded peak performance, so it is not part of our roadmap currently.

If you would like to experiment with it, you can execute the buildNativeImage command in the sbt shell while inside the interpreter project. Please note that while the command is available at the moment, and you are welcome to report an issue with the functionality, any bugs you report will not be considered high priority.

WE CURRENTLY DO NOT SUPPORT THE NATIVE IMAGE BUILD.

Using IntelliJ

Internally, most of the developers working on the Enso project use IntelliJ as their primary IDE. To that end, what follows is a basic set of instructions for getting the project into a working state in IntelliJ.

1. Clone the project sources.
2. Open IntelliJ
3. File -> New -> Project From Existing Sources.
4. Navigate to the directory into which you cloned the project sources. By default this will be called enso. Select the directory, and not the build.sbt file it contains.
5. In the 'Import Project' dialogue, select 'Import project from external model' and choose 'sbt'.
6. Where it says 'Download:', ensure you check both 'Library Sources' and 'sbt sources'.
7. In addition, check the boxes next to 'Use sbt shell:' such that it is used both 'for imports' and 'for builds'.
8. Disallow the overriding of the sbt version.
9. Under the 'Project JDK' setting, please ensure that it is set up to use a GraalVM version as described in Requirements. You may need to add it using the 'New' button if it isn't already set up.
10. Click 'Finish'. This will prompt you as to whether you want to overwrite the project folder. Select 'Yes' to continue. The Enso project will load up with an open SBT shell, which can be interacted with as described above. You will want to use scalafmt for formatting of Scala code, and install Google Java Format for formatting Java code. For more information see the relevant Style Guides.

However, as mentioned in the Troubleshooting section below, the forked nature of execution in the SBT shell means that we can't trivially make use of the IntelliJ debugger. In order to get debugging working, you will need to follow these steps:

1. Go to Run -> Edit Configurations.
2. Click the + button in the header of the 'Run/Debug Configurations' dialogue that pops up.
3. Select 'Remote' and name the new configuration appropriately.
4. In the options for that configuration select 'Listen to remote JVM' under 'Debugger mode:'
5. Where it provides the command-line arguments for the remote JVM, copy these and add them to truffleRunOptions in build.sbt.
6. Now, when you want to debug something, you can place a breakpoint as usual in IntelliJ, and then execute your remote debugging configuration. Now, in the SBT shell, run a command to execute the code you want to debug (e.g. testOnly *CurryingTest*). This will open the standard debugger interface and will allow you to step through your code.

Please be careful to ensure that you don't commit these changes to the sbt configuration as they are specific to your machine.

Troubleshooting

If you are having issues building Enso, please check the list below before filing an issue with us.

• StackOverflowError During Compilation: Please ensure that your version of sbt is respecting the project's .jvmopts settings. We make significant use of recursion when expanding macros for the parser, and these require use of additional stack. Alternatively, you can explicitly pass -Xss8M to the sbt invocation.
• Debugging Not Working: The sbt tasks run the invoked programs in a forked JVM. This means that to attach a debugger to it you need to use the JVM remote debugging support. We cannot support all possible configurations for this, but if you use IntelliJ please see the Using IntelliJ section above for instructions.

If your problem was not listed above, please file a bug report in our issue tracker and we will get back to you as soon as possible.

Running Enso

The only component in this repository with a proper executable is the Enso interpreter. It can be run using the sbt run command in the project interpreter and provides a rudimentary command-line interface to the basic capabilities of the interpreter.

Detailed information on the flags it supports can be obtained by executing run --help, but the primary functionality is as follows:

• --new PATH: Creates a new Enso project at the location spcified by PATH.
• --run PATH: Executes the interpreter on the Enso source specified by PATH. In this case, PATH must point to either a standalone Enso file or an Enso project.

Language Server Mode

Though operating the Enso binary as a language server is functionality planned for the 2.0 release, it is not currently implemented. For more information on the planned functionality and its progress, please see the Issue Tracker.

Pull Requests

Pull Requests are the primary method for making changes to Enso. GitHub has fantastic documentation on using the pull request feature. Luna uses the 'fork-and-pull' model of development. It is as described here and involves people pushing changes to their own fork and creating pull requests to bring those changes into the main Luna repository.

Please make all pull requests against the master branch.

Before making your PR, please make sure that the commit passes the Enso test suite. You can run all the tests by ... TBC. In addition, please ensure that your code conforms to the Enso Scala Style Guide and Haskell Style Guide as relevant.

Make sure you perform these checks before every pull request. You can even add git hooks before every push to make sure that you can't forget.

Every pull request for Enso is reviewed by another person! You'll get a reviewer from the core team assigned at random, but feel free to ask for a specific person if you've dealt with them in a certain area before!

Once the reviewer approves your pull request it will be tested by our continuous integration provider before being merged!

Documentation

Documentation improvements are very welcome! The source for the Enso, Book can be found in luna/luna-book, but most of the API documentation is generated directly from the code!

Documentation pull requests are reviewed in exactly the same way as normal pull requests.

To find documentation-related issues, sort by the Category: Documentation label.

Issue Triage

Sometimes issues can be left open long after the bug has been fixed. Other times, a bug might go stale because something has changed in the meantime.

It can be helpful to go through older bug reports and make sure that they are still valid. Load up an older issue, double check that it's still true, and leave a comment letting us know if it is or is not. The least recently updated sort is good for finding issues like this.

Contributors with sufficient permissions can help by adding labels to help with issue triage.

If you're looking for somewhere to start, take a look at the Difficulty: Beginner issue label, as well as the Status: Help Wanted label.

Out-of-Tree Contributions

As helpful as contributing to Enso directly is, it can also be just as helpful to contribute in other ways outside this repository:

• Answer questions in the Discord or on StackOverflow.
• Participate in the RFC Process.

Helpful Documentation and Links

For people new to Luna, and just starting to contribute, or even for more seasoned developers, some useful places to look for information are:

• The Enso Book
• The community! Don't be afraid to ask questions.