The Open Source Journey of the .NET Compiler Platform, a Year Later

Kasey Uhlenhuth of the Managed Languages Team opens up about lessons learned in Microsoft's efforts to develop the upcoming "Roslyn" compiler with help from the open source community.

It all started with the .NET Compiler Platform -- or, "Roslyn" -- a year ago, and from there, Microsoft has opened up the whole of the project's development to the open source community. On Monday, Kasey Uhlenhuth, a program manager on the Managed Languages Team at Microsoft, chronicled the past year's worth of open source work on the Roslyn compiler on on the .NET Framework blog.

"The decision to make Roslyn open source did not come out of the blue," Uhlenhuth posted, "in our original architecture discussions in 2009, we dreamt of open sourcing our language compilers." What convinced the Roslyn developers to finally take that route a year ago, he said, is the success of other units working on F#, ASP.NET and TypeScript.

The project was managed on the Microsoft CodePlex open source project site at first, but was eventually fully migrated over to the popular GitHub open source source code control repository in January this year. Uhlenhuth said that the group had also been using a "'source open with limited contributions' model" before committing to the transparency of fully developing in the open. He notes that with the more transparent approach, his team has seen contributions increase at a faster pace, and has seen a doubling of community engagements in a third of the time. He said he has also seen exponential growth in the number of users contributing code and steady growth in users contributing issues.

"We file bugs and design notes in GitHub's issue tracking system and submit all of our code changes as pull-requests," blogged Uhlenhuth. "We use GitHub's code review system as our own and use Markdown to link issues or communicate about code. We also established a crisper idea of what we accept for pull-requests, what sign-offs we require for pull-requests to be merged, what style guide we recommend, and what an acceptable time frame for closing a pull-request is (roughly 1o [sic] days, if you were wondering)."

But there are issues that still need to be worked out, according to Uhlenhuth, of which the following three are just a start:

  • Migrating historical issues over to GitHub
  • Issue labels on GitHub
  • Mapping commits to product releases

Roslyn is expected at the same time as Visual Studio 2015.

On a related note, the .NET Foundation has appointed a new executive director. Jay Schmelzer, president of the .NET Foundation, said in a blog that Martin Woodward was hired in the new role to "[ensure] the rapid growth and continued innovation of the .NET open source ecosystem." The .NET Foundation was organized as an independent entity to "foster open development and collaboration around the growing collection of open source technologies for .NET." Woodward will head an advisory council formed in February for ushering more projects into the open source community.

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