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rust-clippy/clippy_lints/src/write.rs

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use rustc::lint::*;
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use rustc::{declare_lint, lint_array};
use syntax::ast::*;
use syntax::tokenstream::{ThinTokenStream, TokenStream};
use syntax::parse::{token, parser};
use crate::utils::{span_lint, span_lint_and_sugg};
/// **What it does:** This lint warns when you use `println!("")` to
/// print a newline.
///
/// **Why is this bad?** You should use `println!()`, which is simpler.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// println!("");
/// ```
declare_clippy_lint! {
pub PRINTLN_EMPTY_STRING,
style,
"using `println!(\"\")` with an empty string"
}
/// **What it does:** This lint warns when you use `print!()` with a format
/// string that
/// ends in a newline.
///
/// **Why is this bad?** You should use `println!()` instead, which appends the
/// newline.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// print!("Hello {}!\n", name);
/// ```
declare_clippy_lint! {
pub PRINT_WITH_NEWLINE,
style,
"using `print!()` with a format string that ends in a newline"
}
/// **What it does:** Checks for printing on *stdout*. The purpose of this lint
/// is to catch debugging remnants.
///
/// **Why is this bad?** People often print on *stdout* while debugging an
/// application and might forget to remove those prints afterward.
///
/// **Known problems:** Only catches `print!` and `println!` calls.
///
/// **Example:**
/// ```rust
/// println!("Hello world!");
/// ```
declare_clippy_lint! {
pub PRINT_STDOUT,
restriction,
"printing on stdout"
}
/// **What it does:** Checks for use of `Debug` formatting. The purpose of this
/// lint is to catch debugging remnants.
///
/// **Why is this bad?** The purpose of the `Debug` trait is to facilitate
/// debugging Rust code. It should not be used in in user-facing output.
///
/// **Example:**
/// ```rust
/// println!("{:?}", foo);
/// ```
declare_clippy_lint! {
pub USE_DEBUG,
restriction,
"use of `Debug`-based formatting"
}
/// **What it does:** This lint warns about the use of literals as `print!`/`println!` args.
///
/// **Why is this bad?** Using literals as `println!` args is inefficient
/// (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
/// (i.e., just put the literal in the format string)
///
/// **Known problems:** Will also warn with macro calls as arguments that expand to literals
/// -- e.g., `println!("{}", env!("FOO"))`.
///
/// **Example:**
/// ```rust
/// println!("{}", "foo");
/// ```
declare_clippy_lint! {
pub PRINT_LITERAL,
style,
"printing a literal with a format string"
}
/// **What it does:** This lint warns when you use `writeln!(buf, "")` to
/// print a newline.
///
/// **Why is this bad?** You should use `writeln!(buf)`, which is simpler.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// writeln!("");
/// ```
declare_clippy_lint! {
pub WRITELN_EMPTY_STRING,
style,
"using `writeln!(\"\")` with an empty string"
}
/// **What it does:** This lint warns when you use `write!()` with a format
/// string that
/// ends in a newline.
///
/// **Why is this bad?** You should use `writeln!()` instead, which appends the
/// newline.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// write!(buf, "Hello {}!\n", name);
/// ```
declare_clippy_lint! {
pub WRITE_WITH_NEWLINE,
style,
"using `write!()` with a format string that ends in a newline"
}
/// **What it does:** This lint warns about the use of literals as `write!`/`writeln!` args.
///
/// **Why is this bad?** Using literals as `writeln!` args is inefficient
/// (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
/// (i.e., just put the literal in the format string)
///
/// **Known problems:** Will also warn with macro calls as arguments that expand to literals
/// -- e.g., `writeln!(buf, "{}", env!("FOO"))`.
///
/// **Example:**
/// ```rust
/// writeln!(buf, "{}", "foo");
/// ```
declare_clippy_lint! {
pub WRITE_LITERAL,
style,
"writing a literal with a format string"
}
#[derive(Copy, Clone, Debug)]
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(
PRINT_WITH_NEWLINE,
PRINTLN_EMPTY_STRING,
PRINT_STDOUT,
USE_DEBUG,
PRINT_LITERAL,
WRITE_WITH_NEWLINE,
WRITELN_EMPTY_STRING,
WRITE_LITERAL
)
}
}
impl EarlyLintPass for Pass {
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fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &Mac) {
if mac.node.path == "println" {
span_lint(cx, PRINT_STDOUT, mac.span, "use of `println!`");
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, false) {
if fmtstr == "" {
span_lint_and_sugg(
cx,
PRINTLN_EMPTY_STRING,
mac.span,
"using `println!(\"\")`",
"replace it with",
"println!()".to_string(),
);
}
}
} else if mac.node.path == "print" {
span_lint(cx, PRINT_STDOUT, mac.span, "use of `print!`");
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, false) {
if fmtstr.ends_with("\\n") {
span_lint(cx, PRINT_WITH_NEWLINE, mac.span,
"using `print!()` with a format string that ends in a \
newline, consider using `println!()` instead");
}
}
} else if mac.node.path == "write" {
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, true) {
if fmtstr.ends_with("\\n") {
span_lint(cx, WRITE_WITH_NEWLINE, mac.span,
"using `write!()` with a format string that ends in a \
newline, consider using `writeln!()` instead");
}
}
} else if mac.node.path == "writeln" {
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, true) {
if fmtstr == "" {
span_lint_and_sugg(
cx,
WRITELN_EMPTY_STRING,
mac.span,
"using `writeln!(v, \"\")`",
"replace it with",
"writeln!(v)".to_string(),
);
}
}
}
}
}
fn check_tts(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -> Option<String> {
let tts = TokenStream::from(tts.clone());
let mut parser = parser::Parser::new(
&cx.sess.parse_sess,
tts,
None,
false,
false,
);
if is_write {
// skip the initial write target
parser.parse_expr().map_err(|mut err| err.cancel()).ok()?;
// might be `writeln!(foo)`
parser.expect(&token::Comma).map_err(|mut err| err.cancel()).ok()?;
}
let fmtstr = parser.parse_str().map_err(|mut err| err.cancel()).ok()?.0.to_string();
use fmt_macros::*;
let tmp = fmtstr.clone();
let mut args = vec![];
let mut fmt_parser = Parser::new(&tmp, None);
while let Some(piece) = fmt_parser.next() {
if !fmt_parser.errors.is_empty() {
return None;
}
if let Piece::NextArgument(arg) = piece {
if arg.format.ty == "?" {
// FIXME: modify rustc's fmt string parser to give us the current span
span_lint(cx, USE_DEBUG, parser.prev_span, "use of `Debug`-based formatting");
}
args.push(arg);
}
}
let lint = if is_write {
WRITE_LITERAL
} else {
PRINT_LITERAL
};
let mut idx = 0;
loop {
if !parser.eat(&token::Comma) {
assert!(parser.eat(&token::Eof));
return Some(fmtstr);
}
let expr = parser.parse_expr().map_err(|mut err| err.cancel()).ok()?;
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const SIMPLE: FormatSpec<'_> = FormatSpec {
fill: None,
align: AlignUnknown,
flags: 0,
precision: CountImplied,
width: CountImplied,
ty: "",
};
match &expr.node {
ExprKind::Lit(_) => {
let mut all_simple = true;
let mut seen = false;
for arg in &args {
match arg.position {
| ArgumentImplicitlyIs(n)
| ArgumentIs(n)
=> if n == idx {
all_simple &= arg.format == SIMPLE;
seen = true;
},
ArgumentNamed(_) => {},
}
}
if all_simple && seen {
span_lint(cx, lint, expr.span, "literal with an empty format string");
}
idx += 1;
},
ExprKind::Assign(lhs, rhs) => {
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if let ExprKind::Lit(_) = rhs.node {
if let ExprKind::Path(_, p) = &lhs.node {
let mut all_simple = true;
let mut seen = false;
for arg in &args {
match arg.position {
| ArgumentImplicitlyIs(_)
| ArgumentIs(_)
=> {},
ArgumentNamed(name) => if *p == name {
seen = true;
all_simple &= arg.format == SIMPLE;
},
}
}
if all_simple && seen {
span_lint(cx, lint, rhs.span, "literal with an empty format string");
}
}
}
},
_ => idx += 1,
}
}
}