rust/clippy_lints/src/option_env_unwrap.rs

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use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::is_direct_expn_of;
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use if_chain::if_chain;
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use rustc_ast::ast::{Expr, ExprKind};
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use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// **What it does:** Checks for usage of `option_env!(...).unwrap()` and
/// suggests usage of the `env!` macro.
///
/// **Why is this bad?** Unwrapping the result of `option_env!` will panic
/// at run-time if the environment variable doesn't exist, whereas `env!`
/// catches it at compile-time.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust,no_run
/// let _ = option_env!("HOME").unwrap();
/// ```
///
/// Is better expressed as:
///
/// ```rust,no_run
/// let _ = env!("HOME");
/// ```
pub OPTION_ENV_UNWRAP,
correctness,
"using `option_env!(...).unwrap()` to get environment variable"
}
declare_lint_pass!(OptionEnvUnwrap => [OPTION_ENV_UNWRAP]);
impl EarlyLintPass for OptionEnvUnwrap {
fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
if_chain! {
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if let ExprKind::MethodCall(path_segment, args, _) = &expr.kind;
let method_name = path_segment.ident.as_str();
if method_name == "expect" || method_name == "unwrap";
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if let ExprKind::Call(caller, _) = &args[0].kind;
if is_direct_expn_of(caller.span, "option_env").is_some();
then {
span_lint_and_help(
cx,
OPTION_ENV_UNWRAP,
expr.span,
"this will panic at run-time if the environment variable doesn't exist at compile-time",
None,
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"consider using the `env!` macro instead"
);
}
}
}
}