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use crate::utils::{is_expn_of, match_function_call, paths, span_lint, span_lint_and_sugg};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::*;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use syntax::ast::LitKind;
declare_clippy_lint! {
/// **What it does:** Checks for usage of `write!()` / `writeln()!` which can be
/// replaced with `(e)print!()` / `(e)println!()`
///
/// **Why is this bad?** Using `(e)println! is clearer and more concise
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # use std::io::Write;
/// # let bar = "furchtbar";
/// // this would be clearer as `eprintln!("foo: {:?}", bar);`
/// writeln!(&mut std::io::stderr(), "foo: {:?}", bar).unwrap();
/// ```
pub EXPLICIT_WRITE,
complexity,
"using the `write!()` family of functions instead of the `print!()` family of functions, when using the latter would work"
}
declare_lint_pass!(ExplicitWrite => [EXPLICIT_WRITE]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitWrite {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
if_chain! {
// match call to unwrap
if let ExprKind::MethodCall(ref unwrap_fun, _, ref unwrap_args) = expr.kind;
if unwrap_fun.ident.name == sym!(unwrap);
// match call to write_fmt
if !unwrap_args.is_empty();
if let ExprKind::MethodCall(ref write_fun, _, write_args) =
unwrap_args[0].kind;
if write_fun.ident.name == sym!(write_fmt);
// match calls to std::io::stdout() / std::io::stderr ()
if !write_args.is_empty();
if let Some(dest_name) = if match_function_call(cx, &write_args[0], &paths::STDOUT).is_some() {
Some("stdout")
} else if match_function_call(cx, &write_args[0], &paths::STDERR).is_some() {
Some("stderr")
} else {
None
};
then {
let write_span = unwrap_args[0].span;
let calling_macro =
// ordering is important here, since `writeln!` uses `write!` internally
if is_expn_of(write_span, "writeln").is_some() {
Some("writeln")
} else if is_expn_of(write_span, "write").is_some() {
Some("write")
} else {
None
};
let prefix = if dest_name == "stderr" {
"e"
} else {
""
};
// We need to remove the last trailing newline from the string because the
// underlying `fmt::write` function doesn't know whether `println!` or `print!` was
// used.
if let Some(mut write_output) = write_output_string(write_args) {
if write_output.ends_with('\n') {
write_output.pop();
}
if let Some(macro_name) = calling_macro {
span_lint_and_sugg(
cx,
EXPLICIT_WRITE,
expr.span,
&format!(
"use of `{}!({}(), ...).unwrap()`",
macro_name,
dest_name
),
"try this",
format!("{}{}!(\"{}\")", prefix, macro_name.replace("write", "print"), write_output.escape_default()),
Applicability::MachineApplicable
);
} else {
span_lint_and_sugg(
cx,
EXPLICIT_WRITE,
expr.span,
&format!("use of `{}().write_fmt(...).unwrap()`", dest_name),
"try this",
format!("{}print!(\"{}\")", prefix, write_output.escape_default()),
Applicability::MachineApplicable
);
}
} else {
// We don't have a proper suggestion
if let Some(macro_name) = calling_macro {
span_lint(
cx,
EXPLICIT_WRITE,
expr.span,
&format!(
"use of `{}!({}(), ...).unwrap()`. Consider using `{}{}!` instead",
macro_name,
dest_name,
prefix,
macro_name.replace("write", "print")
)
);
} else {
span_lint(
cx,
EXPLICIT_WRITE,
expr.span,
&format!("use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead", dest_name, prefix),
);
}
}
}
}
}
}
// Extract the output string from the given `write_args`.
fn write_output_string(write_args: &[Expr<'_>]) -> Option<String> {
if_chain! {
// Obtain the string that should be printed
if write_args.len() > 1;
if let ExprKind::Call(_, ref output_args) = write_args[1].kind;
if !output_args.is_empty();
if let ExprKind::AddrOf(BorrowKind::Ref, _, ref output_string_expr) = output_args[0].kind;
if let ExprKind::Array(ref string_exprs) = output_string_expr.kind;
// we only want to provide an automatic suggestion for simple (non-format) strings
if string_exprs.len() == 1;
if let ExprKind::Lit(ref lit) = string_exprs[0].kind;
if let LitKind::Str(ref write_output, _) = lit.node;
then {
return Some(write_output.to_string())
}
}
None
}
|
