Contributing Code

Kasey Uhlenhuth edited this page Dec 5, 2016 · 19 revisions
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Contributing Code

Before submitting a feature or substantial code contribution please discuss it with the team and ensure it follows the product roadmap. The team rigorously reviews and tests all code submissions. The submissions must meet an extremely high bar for quality, design, and roadmap appropriateness.

The Roslyn project is a member of the .NET Foundation and follow the same developer guide. The team enforces this by regularly running the .NET code formatter tool on the code base. Contributors should ensure they follow these guidelines when making submissions.

For now, the team has set the following limits on pull requests:

  • Contributions beyond the level of a bug fix must be discussed with the team first, or they will likely be declined. As our process matures and our experience grows, the team expects to take larger contributions.
  • Only contributions against the master branch will be accepted. Authors submitting pull requests that target experimental feature branches or release branches will likely be asked target their pull request at the master branch.
  • Pull requests that do not merge easily with the tip of the master branch will be declined. The author will be asked to merge with tip and update the pull request.
  • Submissions must meet functional and performance expectations, including scenarios for which the team doesn’t yet have open source tests. This means you may be asked to fix and resubmit your pull request against a new open test case if it fails one of these tests.
  • Submissions must follow the .editorconfig settings for each directory. For the most part, these follow the rules stated in the .NET Foundation Coding Guidelines with the exception that most Roslyn projects prefer to use 'var' everywhere.
  • Contributors must sign the .NET CLA

When you are ready to proceed with making a change, get set up to build the code and familiarize yourself with our workflow and our coding conventions. These two blogs posts on contributing code to open source projects are good too: Open Source Contribution Etiquette by Miguel de Icaza and Don’t “Push” Your Pull Requests by Ilya Grigorik.

You must sign a Contributor License Agreement (CLA) before submitting your pull request. To complete the CLA, submit a request via the form and electronically sign the CLA when you receive the email containing the link to the document. You need to complete the CLA only once to cover all .NET Foundation projects.

Developer Workflow

  1. Work item is assigned to a developer during the triage process
  2. Both Roslyn and external contributors are expected to do their work in a local fork and submit code for consideration via a pull request.
  3. When the pull request process deems the change ready it will be merged directly into the tree.

Getting started coding in Visual Studio

  1. After you've cloned the roslyn repro, run Restore.cmd. This restores all required NuGet packages. (Normally VS does this as part of a build, but the auto-restore feature has been disabled for Roslyn).
  2. Load the Roslyn.sln solution into VS and build. (Other solutions can be used, but depend upon this main solution having been built).
  3. To run individual tests, install Test Driven .NET. You can right-click on a file, or a test within a file, to run that test.
  4. To test your changes live within the VS IDE itself, use Roslyn.sln and the project VisualStudio\VisualStudioSetup: when you do F5 on this project, it launches an isolated instance ("hive") of VS which runs upon your modified version of Roslyn for IDE. (Or, you can install Binaries\Debug\Roslyn.VisualStudio.Setup.vsix on its own, no other files required). (TODO: explain how to get it to work for Ctrl+Shift+B as well...)
  5. To run all tests, run cibuild.cmd. This restores, builds, and runs all tests. (It won't tell you which ones failed until after it's completely finished, though).

Creating New Issues

Please follow these guidelines when creating new issues in the issue tracker:

  • Use a descriptive title that identifies the issue to be addressed or the requested feature. For example when describing an issue where the compiler is not behaving as expected, write your bug title in terms of what the compiler should do rather than what it is doing – “C# compiler should report CS1234 when Xyz is used in Abcd.”
  • Do not set any bug fields other than Impact.
  • Specify a detailed description of the issue or requested feature.
  • For bug reports, please also:
    • Describe the expected behavior and the actual behavior. If it is not self-evident such as in the case of a crash, provide an explanation for why the expected behavior is expected.
    • Provide example code that reproduces the issue.
    • Specify any relevant exception messages and stack traces.
  • Subscribe to notifications for the created issue in case there are any follow up questions.

Coding Conventions

  • Use the coding style outlined in the .NET Foundation Coding Guidelines
  • Use plain code to validate parameters at public boundaries. Do not use Contracts or magic helpers.
if (argument == null)
{
    throw new ArgumentNullException("argument");
}
  • Use Debug.Assert() for checks not needed in retail builds. Always include a “message” string in your assert to identify failure conditions. Add assertions to document assumptions on non-local program state or parameter values, e.g. “At this point in parsing the scanner should have been advanced to a ‘.’ token by the caller”.
  • Avoid allocations in compiler hot paths:
    • Avoid LINQ.
    • Avoid using foreach over collections that do not have a struct enumerator.
    • Consider using an object pool. There are many usages of object pools in the compiler to see an example.

Code Formatter

The Roslyn team regularly uses the .NET code formatter tool to ensure the code base maintains a consistent style over time. The specific options we pass to this tool are the following:

  • /nounicode: In general we follow this rule of not having unicode characters embedded in string literals. However there are a few cases where this is needed to verify compiler behavior hence this option is disabled for now.
  • /copyright: The default copyright is MIT. Roslyn is released under Apache2 hence we need to override this option.

Visual Basic Conventions

For all of the C# guidelines which have analogs in Visual Basic, the team applies the spirit of the guideline to Visual Basic. Guidelines surrounding spacing, indentation, parameter names, and the use of named parameters are all generally applicable to Visual Basic. ‘Dim’ statements should also follow the guidelines for the use of ‘var’ in C#. Specific to Visual Basic, field names should begin with ‘m_’ or ‘_’. And the team prefers that all field declarations be placed at the beginning of a type definition. The Visual Studio members dropdown does not show fields in VB. Having them at the beginning of the type aids in navigation.

Tips 'n' Tricks

Our team finds using this enhanced source view of Roslyn helpful when developing.