Compile time filesystem access?

[Timon Gehr]

On 01/30/2012 04:18 PM, Adam D. Ruppe wrote:
> On Monday, 30 January 2012 at 14:24:32 UTC, Manu wrote:
>> I want to know if a library is present, and automatically disable
>> non-vital features if it isn't.
>
> I'd like it too... here's what I tried. It doesn't
> work, though.
>
> ===
> void libraryTest(string lib)() { mixin("import " ~ lib ~ ";"); }
>
> template libraryExists(string lib) {
> enum libraryExists = __traits(compiles, libraryTest!lib());
> }
>
> void main() {
> static if(libraryExists!"arsd.cgi") {
> import arsd.cgi;
> auto cgi = new Cgi();
> cgi.write("hello w/ cgi");
> } else {
> import std.stdio;
> writeln("hello w/ stdio");
> }
> }
> ===
>
>
> That's the idea, but I couldn't get it to actually work.
> Imports are apparently done by the compiler before
> anything else (which makes sense, really) and that breaks
> the if compiles thing; it fails before it gets there. If
> you move the libraryTest inline to the compiles thing, it
> never uses the lib, so that's no good either.
>
>
> Alas.

The fact that this does not work is a compiler bug:

static if(is(typeof({import asdf;}))){}

it fails with exit code 1 without spitting out an error message.
Once that is fixed, it could be used to detect presence or absence of a 
library.

http://d.puremagic.com/issues/show_bug.cgi?id=7399