rustc_builtin_macros/
env.rs

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1// The compiler code necessary to support the env! extension. Eventually this
2// should all get sucked into either the compiler syntax extension plugin
3// interface.
4//
5
6use std::env;
7use std::env::VarError;
8
9use rustc_ast::token::{self, LitKind};
10use rustc_ast::tokenstream::TokenStream;
11use rustc_ast::{AstDeref, ExprKind, GenericArg, Mutability};
12use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
13use rustc_span::{Ident, Span, Symbol, kw, sym};
14use thin_vec::thin_vec;
15
16use crate::errors;
17use crate::util::{expr_to_string, get_exprs_from_tts, get_single_expr_from_tts};
18
19fn lookup_env<'cx>(cx: &'cx ExtCtxt<'_>, var: Symbol) -> Result<Symbol, VarError> {
20    let var = var.as_str();
21    if let Some(value) = cx.sess.opts.logical_env.get(var) {
22        return Ok(Symbol::intern(value));
23    }
24    // If the environment variable was not defined with the `--env-set` option, we try to retrieve it
25    // from rustc's environment.
26    Ok(Symbol::intern(&env::var(var)?))
27}
28
29pub(crate) fn expand_option_env<'cx>(
30    cx: &'cx mut ExtCtxt<'_>,
31    sp: Span,
32    tts: TokenStream,
33) -> MacroExpanderResult<'cx> {
34    let ExpandResult::Ready(mac_expr) = get_single_expr_from_tts(cx, sp, tts, "option_env!") else {
35        return ExpandResult::Retry(());
36    };
37    let var_expr = match mac_expr {
38        Ok(var_expr) => var_expr,
39        Err(guar) => return ExpandResult::Ready(DummyResult::any(sp, guar)),
40    };
41    let ExpandResult::Ready(mac) =
42        expr_to_string(cx, var_expr.clone(), "argument must be a string literal")
43    else {
44        return ExpandResult::Retry(());
45    };
46    let var = match mac {
47        Ok((var, _)) => var,
48        Err(guar) => return ExpandResult::Ready(DummyResult::any(sp, guar)),
49    };
50
51    let sp = cx.with_def_site_ctxt(sp);
52    let value = lookup_env(cx, var);
53    cx.sess.psess.env_depinfo.borrow_mut().insert((var, value.as_ref().ok().copied()));
54    let e = match value {
55        Err(VarError::NotPresent) => {
56            let lt = cx.lifetime(sp, Ident::new(kw::StaticLifetime, sp));
57            cx.expr_path(cx.path_all(
58                sp,
59                true,
60                cx.std_path(&[sym::option, sym::Option, sym::None]),
61                vec![GenericArg::Type(cx.ty_ref(
62                    sp,
63                    cx.ty_ident(sp, Ident::new(sym::str, sp)),
64                    Some(lt),
65                    Mutability::Not,
66                ))],
67            ))
68        }
69        Err(VarError::NotUnicode(_)) => {
70            let ExprKind::Lit(token::Lit {
71                kind: LitKind::Str | LitKind::StrRaw(..), symbol, ..
72            }) = &var_expr.kind
73            else {
74                unreachable!("`expr_to_string` ensures this is a string lit")
75            };
76
77            let guar = cx.dcx().emit_err(errors::EnvNotUnicode { span: sp, var: *symbol });
78            return ExpandResult::Ready(DummyResult::any(sp, guar));
79        }
80        Ok(value) => cx.expr_call_global(
81            sp,
82            cx.std_path(&[sym::option, sym::Option, sym::Some]),
83            thin_vec![cx.expr_str(sp, value)],
84        ),
85    };
86    ExpandResult::Ready(MacEager::expr(e))
87}
88
89pub(crate) fn expand_env<'cx>(
90    cx: &'cx mut ExtCtxt<'_>,
91    sp: Span,
92    tts: TokenStream,
93) -> MacroExpanderResult<'cx> {
94    let ExpandResult::Ready(mac) = get_exprs_from_tts(cx, tts) else {
95        return ExpandResult::Retry(());
96    };
97    let mut exprs = match mac {
98        Ok(exprs) if exprs.is_empty() || exprs.len() > 2 => {
99            let guar = cx.dcx().emit_err(errors::EnvTakesArgs { span: sp });
100            return ExpandResult::Ready(DummyResult::any(sp, guar));
101        }
102        Err(guar) => return ExpandResult::Ready(DummyResult::any(sp, guar)),
103        Ok(exprs) => exprs.into_iter(),
104    };
105
106    let var_expr = exprs.next().unwrap();
107    let ExpandResult::Ready(mac) = expr_to_string(cx, var_expr.clone(), "expected string literal")
108    else {
109        return ExpandResult::Retry(());
110    };
111    let var = match mac {
112        Ok((var, _)) => var,
113        Err(guar) => return ExpandResult::Ready(DummyResult::any(sp, guar)),
114    };
115
116    let custom_msg = match exprs.next() {
117        None => None,
118        Some(second) => {
119            let ExpandResult::Ready(mac) = expr_to_string(cx, second, "expected string literal")
120            else {
121                return ExpandResult::Retry(());
122            };
123            match mac {
124                Ok((s, _)) => Some(s),
125                Err(guar) => return ExpandResult::Ready(DummyResult::any(sp, guar)),
126            }
127        }
128    };
129
130    let span = cx.with_def_site_ctxt(sp);
131    let value = lookup_env(cx, var);
132    cx.sess.psess.env_depinfo.borrow_mut().insert((var, value.as_ref().ok().copied()));
133    let e = match value {
134        Err(err) => {
135            let ExprKind::Lit(token::Lit {
136                kind: LitKind::Str | LitKind::StrRaw(..), symbol, ..
137            }) = &var_expr.kind
138            else {
139                unreachable!("`expr_to_string` ensures this is a string lit")
140            };
141
142            let guar = match err {
143                VarError::NotPresent => {
144                    if let Some(msg_from_user) = custom_msg {
145                        cx.dcx()
146                            .emit_err(errors::EnvNotDefinedWithUserMessage { span, msg_from_user })
147                    } else if is_cargo_env_var(var.as_str()) {
148                        cx.dcx().emit_err(errors::EnvNotDefined::CargoEnvVar {
149                            span,
150                            var: *symbol,
151                            var_expr: var_expr.ast_deref(),
152                        })
153                    } else {
154                        cx.dcx().emit_err(errors::EnvNotDefined::CustomEnvVar {
155                            span,
156                            var: *symbol,
157                            var_expr: var_expr.ast_deref(),
158                        })
159                    }
160                }
161                VarError::NotUnicode(_) => {
162                    cx.dcx().emit_err(errors::EnvNotUnicode { span, var: *symbol })
163                }
164            };
165
166            return ExpandResult::Ready(DummyResult::any(sp, guar));
167        }
168        Ok(value) => cx.expr_str(span, value),
169    };
170    ExpandResult::Ready(MacEager::expr(e))
171}
172
173/// Returns `true` if an environment variable from `env!` is one used by Cargo.
174fn is_cargo_env_var(var: &str) -> bool {
175    var.starts_with("CARGO_")
176        || var.starts_with("DEP_")
177        || matches!(var, "OUT_DIR" | "OPT_LEVEL" | "PROFILE" | "HOST" | "TARGET")
178}
rustc_builtin_macros/env.rs

rustc_builtin_macros/
env.rs
