src/libsyntax_ext/env.rs

   1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 /*
  12  * The compiler code necessary to support the env! extension.  Eventually this
  13  * should all get sucked into either the compiler syntax extension plugin
  14  * interface.
  15  */
  16
  17 use syntax::ast;
  18 use syntax::codemap::Span;
  19 use syntax::ext::base::*;
  20 use syntax::ext::base;
  21 use syntax::ext::build::AstBuilder;
  22 use syntax::parse::token;
  23
  24 use std::env;
  25
  26 pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
  27                               -> Box<base::MacResult+'cx> {
  28     let var = match get_single_str_from_tts(cx, sp, tts, "option_env!") {
  29         None => return DummyResult::expr(sp),
  30         Some(v) => v
  31     };
  32
  33     let e = match env::var(&var[..]) {
  34       Err(..) => {
  35           cx.expr_path(cx.path_all(sp,
  36                                    true,
  37                                    cx.std_path(&["option", "Option", "None"]),
  38                                    Vec::new(),
  39                                    vec!(cx.ty_rptr(sp,
  40                                                    cx.ty_ident(sp,
  41                                                         cx.ident_of("str")),
  42                                                    Some(cx.lifetime(sp,
  43                                                         cx.ident_of(
  44                                                             "'static").name)),
  45                                                    ast::MutImmutable)),
  46                                    Vec::new()))
  47       }
  48       Ok(s) => {
  49           cx.expr_call_global(sp,
  50                               cx.std_path(&["option", "Option", "Some"]),
  51                               vec!(cx.expr_str(sp,
  52                                                token::intern_and_get_ident(
  53                                           &s[..]))))
  54       }
  55     };
  56     MacEager::expr(e)
  57 }
  58
  59 pub fn expand_env<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
  60                        -> Box<base::MacResult+'cx> {
  61     let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
  62         Some(ref exprs) if exprs.is_empty() => {
  63             cx.span_err(sp, "env! takes 1 or 2 arguments");
  64             return DummyResult::expr(sp);
  65         }
  66         None => return DummyResult::expr(sp),
  67         Some(exprs) => exprs.into_iter()
  68     };
  69
  70     let var = match expr_to_string(cx,
  71                                 exprs.next().unwrap(),
  72                                 "expected string literal") {
  73         None => return DummyResult::expr(sp),
  74         Some((v, _style)) => v
  75     };
  76     let msg = match exprs.next() {
  77         None => {
  78             token::intern_and_get_ident(&format!("environment variable `{}` \
  79                                                  not defined",
  80                                                 var))
  81         }
  82         Some(second) => {
  83             match expr_to_string(cx, second, "expected string literal") {
  84                 None => return DummyResult::expr(sp),
  85                 Some((s, _style)) => s
  86             }
  87         }
  88     };
  89
  90     match exprs.next() {
  91         None => {}
  92         Some(_) => {
  93             cx.span_err(sp, "env! takes 1 or 2 arguments");
  94             return DummyResult::expr(sp);
  95         }
  96     }
  97
  98     let e = match env::var(&var[..]) {
  99         Err(_) => {
 100             cx.span_err(sp, &msg);
 101             cx.expr_usize(sp, 0)
 102         }
 103         Ok(s) => cx.expr_str(sp, token::intern_and_get_ident(&s))
 104     };
 105     MacEager::expr(e)
 106 }