Microsoft has released a Community Technology preview code-named Roslyn, that opens up its C# and Visual Basic compilers as APIs so developers can take advantage of the compiler's inner workings.
Microsoft has
released a Community Technology Preview of its new compiler-as-a-service
offering, code-named Roslyn.
Microsoft said
the reasoning behind a compiler as a service is to open up the inner workings
of a complier so developers can take advantage of them. The
Roslyn
project enables Microsoft's C# and Visual Basic compilers to be used
as a service. In essence, Roslyn opens up the Visual Basic and C# compilers as
APIs. These APIs allow tools and end users to share in the wealth of
information the compilers have about code, Microsoft said on the
MSDN
page on the project.
In a
blog post on Roslyn, S. Somasegar, corporate vice
president of Microsoft's Developer Division, explained that historically, the
managed compilers Microsoft has shipped in Visual Studio "have been opaque
boxes: you provide source files, and they churn those files into output
assemblies. Developers haven't been privy to the intermediate knowledge
that the compiler itself generates as part of the compilation process, and yet
such rich data is incredibly valuable for building the kinds of higher-level
services and tools we've come to expect in modern-day development environments
like Visual Studio."
A Roslyn
overview document available as a link off the MSDN page, further describes the
scenario this way:
Traditionally,
compilers are black boxes-source code goes in one end, magic happens in the
middle, and object files or assemblies come out the other end. As compilers
perform their magic, they build up deep understanding of the code they are
processing, but that knowledge is unavailable to anyone but the compiler
implementation wizards, and it is promptly forgotten after the translated
output is produced.
For decades,
this world view has served us well, but it is no longer sufficient.
Increasingly, we rely on integrated development environment (IDE) features such
as IntelliSense, refactoring, intelligent rename, "Find all references," and "Go to definition" to increase our productivity. We rely on code-analysis tools
to improve our code quality and code generators to aid in application
construction. As these tools get smarter, they need access to more and more of
the deep code knowledge that only compilers possess. This is the core mission
of the Roslyn project: opening up the black boxes and allowing tools and end
users to share in the wealth of information compilers have about our code.
Instead of being opaque source-code-in and object-code-out translators, through
the Roslyn project, compilers become services-APIs that you can use for code-related
tasks in your tools and applications.
Thus, the
Roslyn compilers become services exposed for general consumption, with all of
that internal compiler-discovered knowledge made available for developers and
their tools to harness, Somasegar said. "The stages of the compiler for
parsing, for doing semantic analysis, for binding, and for IL emitting are all
exposed to developers via rich managed APIs," he said.
In a
separate blog post, Kevin Pilch-Bisson, a
development lead at Microsoft responsible for the C# and Visual Basic language
services in Roslyn, called it a forward-looking "effort to make the wealth of
language understanding that the compiler generates available to developers in
other scenarios. ...The foundation of this work is a new C# compiler, written in
C# (and a new VB compiler written in VB too, see the VB Team blog for details).
This compiler is written as a library that exposes a rich public API. Next up
is a new language service written purely using that public API and exposing its
own extensibility points to allow 3rd parties to do amazing things inside
Visual Studio with that language understanding."
Somasegar said
Microsoft's tools team has been busy working on C# 5 and Visual Basic 11. Yet,
via Roslyn, they also have been working concurrently on a complete rewrite of
the C# and Visual Basic compilers, he said. "Whereas today's compilers are
implemented in native C++, in Roslyn we've rewritten the compilers from the
ground up, implementing the C# compiler in C# and the Visual Basic compiler in
Visual Basic. That in and of itself isn't entirely noteworthy, as it's long
been a tradition for a language compiler to be implemented in its target
language, something that's been true of both our F# and Visual C++
compilers. What's quite noteworthy are the scenarios and services this
work enables."
What it
enables is the next generation of language object models for code generation,
analysis and refactoring, and the upcoming support for scripting and
interactive use of VB and C#, Microsoft said.
Microsoft
began talking about its compiler-as-a-service
technology at least as far back as the Microsoft Professional Developers
Conference (PDC) in 2009.
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