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Add suggestion for explicit_write lint #3450

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merged 7 commits into from Dec 12, 2018
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@@ -10,8 +10,9 @@
use crate::rustc::hir::*;
use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
use crate::utils::opt_def_id;
use crate::utils::{is_expn_of, match_def_path, resolve_node, span_lint};
use crate::rustc_errors::Applicability;
use crate::syntax::ast::LitKind;
use crate::utils::{is_expn_of, match_def_path, opt_def_id, resolve_node, span_lint, span_lint_and_sugg};
use if_chain::if_chain;

/// **What it does:** Checks for usage of `write!()` / `writeln()!` which can be
@@ -81,32 +82,85 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
} else {
""
};
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")
)
);

// 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 {
span_lint(
cx,
EXPLICIT_WRITE,
expr.span,
&format!(
"use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead",
dest_name,
prefix,
)
);
// 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: &HirVec<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].node;
if output_args.len() > 0;
if let ExprKind::AddrOf(_, ref output_string_expr) = output_args[0].node;
if let ExprKind::Array(ref string_exprs) = output_string_expr.node;
if string_exprs.len() > 0;
if let ExprKind::Lit(ref lit) = string_exprs[0].node;
if let LitKind::Str(ref write_output, _) = lit.node;
then {
return Some(write_output.to_string())
}
}
None
}
Copy path View file
@@ -14,6 +14,7 @@
#![feature(slice_patterns)]
#![feature(stmt_expr_attributes)]
#![feature(range_contains)]
#![feature(str_escape)]
#![allow(clippy::missing_docs_in_private_items)]
#![recursion_limit = "256"]
#![warn(rust_2018_idioms, trivial_casts, trivial_numeric_casts)]
Copy path View file
@@ -27,6 +27,10 @@ fn main() {
writeln!(std::io::stderr(), "test").unwrap();
std::io::stdout().write_fmt(format_args!("test")).unwrap();
std::io::stderr().write_fmt(format_args!("test")).unwrap();

// including newlines
writeln!(std::io::stdout(), "test\ntest").unwrap();
writeln!(std::io::stderr(), "test\ntest").unwrap();
}
// these should not warn, different destination
{
Copy path View file
@@ -1,40 +1,52 @@
error: use of `write!(stdout(), ...).unwrap()`. Consider using `print!` instead
error: use of `write!(stdout(), ...).unwrap()`
--> $DIR/explicit_write.rs:24:9
|
24 | write!(std::io::stdout(), "test").unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `print!("test")`
|
= note: `-D clippy::explicit-write` implied by `-D warnings`

error: use of `write!(stderr(), ...).unwrap()`. Consider using `eprint!` instead
error: use of `write!(stderr(), ...).unwrap()`
--> $DIR/explicit_write.rs:25:9
|
25 | write!(std::io::stderr(), "test").unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `eprint!("test")`

error: use of `writeln!(stdout(), ...).unwrap()`. Consider using `println!` instead
error: use of `writeln!(stdout(), ...).unwrap()`
--> $DIR/explicit_write.rs:26:9
|
26 | writeln!(std::io::stdout(), "test").unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `println!("test")`

error: use of `writeln!(stderr(), ...).unwrap()`. Consider using `eprintln!` instead
error: use of `writeln!(stderr(), ...).unwrap()`
--> $DIR/explicit_write.rs:27:9
|
27 | writeln!(std::io::stderr(), "test").unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `eprintln!("test")`

error: use of `stdout().write_fmt(...).unwrap()`. Consider using `print!` instead
error: use of `stdout().write_fmt(...).unwrap()`
--> $DIR/explicit_write.rs:28:9
|
28 | std::io::stdout().write_fmt(format_args!("test")).unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `print!("test")`

error: use of `stderr().write_fmt(...).unwrap()`. Consider using `eprint!` instead
error: use of `stderr().write_fmt(...).unwrap()`
--> $DIR/explicit_write.rs:29:9
|
29 | std::io::stderr().write_fmt(format_args!("test")).unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `eprint!("test")`

error: aborting due to 6 previous errors
error: use of `writeln!(stdout(), ...).unwrap()`
--> $DIR/explicit_write.rs:32:9
|
32 | writeln!(std::io::stdout(), "test/ntest").unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `println!("test/ntest")`

error: use of `writeln!(stderr(), ...).unwrap()`
--> $DIR/explicit_write.rs:33:9
|
33 | writeln!(std::io::stderr(), "test/ntest").unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `eprintln!("test/ntest")`

error: aborting due to 8 previous errors

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