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 ast;
  18 use codemap::Span;
  19 use ext::base::*;
  20 use ext::base;
  21 use ext::build::AstBuilder;
  22 use 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                                    vec!(cx.ident_of_std("core"),
  38                                         cx.ident_of("option"),
  39                                         cx.ident_of("Option"),
  40                                         cx.ident_of("None")),
  41                                    Vec::new(),
  42                                    vec!(cx.ty_rptr(sp,
  43                                                    cx.ty_ident(sp,
  44                                                         cx.ident_of("str")),
  45                                                    Some(cx.lifetime(sp,
  46                                                         cx.ident_of(
  47                                                             "'static").name)),
  48                                                    ast::MutImmutable)),
  49                                    Vec::new()))
  50       }
  51       Ok(s) => {
  52           cx.expr_call_global(sp,
  53                               vec!(cx.ident_of_std("core"),
  54                                    cx.ident_of("option"),
  55                                    cx.ident_of("Option"),
  56                                    cx.ident_of("Some")),
  57                               vec!(cx.expr_str(sp,
  58                                                token::intern_and_get_ident(
  59                                           &s[]))))
  60       }
  61     };
  62     MacExpr::new(e)
  63 }
  64
  65 pub fn expand_env<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
  66                        -> Box<base::MacResult+'cx> {
  67     let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
  68         Some(ref exprs) if exprs.len() == 0 => {
  69             cx.span_err(sp, "env! takes 1 or 2 arguments");
  70             return DummyResult::expr(sp);
  71         }
  72         None => return DummyResult::expr(sp),
  73         Some(exprs) => exprs.into_iter()
  74     };
  75
  76     let var = match expr_to_string(cx,
  77                                 exprs.next().unwrap(),
  78                                 "expected string literal") {
  79         None => return DummyResult::expr(sp),
  80         Some((v, _style)) => v
  81     };
  82     let msg = match exprs.next() {
  83         None => {
  84             token::intern_and_get_ident(&format!("environment variable `{}` \
  85                                                  not defined",
  86                                                 var)[])
  87         }
  88         Some(second) => {
  89             match expr_to_string(cx, second, "expected string literal") {
  90                 None => return DummyResult::expr(sp),
  91                 Some((s, _style)) => s
  92             }
  93         }
  94     };
  95
  96     match exprs.next() {
  97         None => {}
  98         Some(_) => {
  99             cx.span_err(sp, "env! takes 1 or 2 arguments");
 100             return DummyResult::expr(sp);
 101         }
 102     }
 103
 104     let e = match env::var(&var[]) {
 105         Err(_) => {
 106             cx.span_err(sp, &msg);
 107             cx.expr_usize(sp, 0)
 108         }
 109         Ok(s) => cx.expr_str(sp, token::intern_and_get_ident(&s))
 110     };
 111     MacExpr::new(e)
 112 }