How to make VS2008 auto insert indent for F#?

Question

Just as my title . I want my VS to auto indent for me like in VBNET . Please help.

Answer 1

Sadly, the indentation-sensitive syntax that F# inherited from languages like Haskell makes it impossible to auto-indent. This is actually my only major gripe with the F# language because, in addition to making it impossible to implement professional tools like auto-indenters, it renders programs fragile in the absence of correct indentation which means an accidental change in whitespace can silently corrupt a program and cut-and-paste (e.g. from blogs) is prone to breaking or corrupting programs. F# almost always screws up if you feed it OCaml code, partly because it cannot handle tabs.

The damn crying shame is that OCaml already got this right by providing a concise unambiguous syntax and powerful tools. For example, you can autoindent any definition by pressing ALT+Q in Emacs. This makes it much easier to manipulate OCaml code and can be an enormous time saver. I often find myself trawling through F# code trying to reindent it by hand, having to read the code in detail and understand the algorithm just to indent it is seriously frustrating. Having done this many times, I can also state quite confidently that the verbosity savings of the #light syntax are insignificant. In fact, F# is almost always more verbose than OCaml in practice.

Answer 2

I prefer to pour cold water all over this question. In principle, it's impossible to provide an auto-formatter for a whitespace-significant language.

(Pragmatically, you could add a few small niceties to the editor, e.g. if you type a line of code that starts with if and ends with the matching then and press enter, the editor could get smart and also insert the next indent so you don't also have to press tab. But this is a far cry from auto-formatting, which I think would be wrong-headed to even attempt.)

Answer 3

As far as I know, the F# language integration doesn't support this feature.

Also, automatic formatting is not as useful in F# as it is in Visual Basic. In VB, the formatting is not really important (so you can write code with crazy indentation and the formatter can fix it). In F#, the indenation (partly) determines what code means, so you need to write correctly indented code (although I agree that the automatic formatting could make the code more consistent).

In principle it should be possible to implement this feature as a Visual Studio plugin using the open source release of F#. There is a similar plugin that adds colors for nested expressions by Brian, so that could be used as an inspiration, but it's definitely not something I could write in the answer box :-).