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rust-clippy/clippy_lints/src/write.rs

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use crate::utils::{snippet, span_lint, span_lint_and_sugg};
use crate::rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
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use std::borrow::Cow;
use crate::syntax::ast::*;
use crate::syntax::parse::{parser, token};
use crate::syntax::tokenstream::{ThinTokenStream, TokenStream};
/// **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);
/// ```
/// use println!() instead
/// ```rust
/// println!("Hello {}!", name);
/// ```
declare_clippy_lint! {
pub PRINT_WITH_NEWLINE,
style,
"using `print!()` with a format string that ends in a single 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");
/// ```
/// use the literal without formatting:
/// ```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 single 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).0 {
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).0 {
if fmtstr.ends_with("\\n") &&
// don't warn about strings with several `\n`s (#3126)
fmtstr.matches("\\n").count() == 1
{
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span_lint(
cx,
PRINT_WITH_NEWLINE,
mac.span,
"using `print!()` with a format string that ends in a \
single newline, consider using `println!()` instead",
);
}
}
} else if mac.node.path == "write" {
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, true).0 {
if fmtstr.ends_with("\\n") &&
// don't warn about strings with several `\n`s (#3126)
fmtstr.matches("\\n").count() == 1
{
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span_lint(
cx,
WRITE_WITH_NEWLINE,
mac.span,
"using `write!()` with a format string that ends in a \
single newline, consider using `writeln!()` instead",
);
}
}
} else if mac.node.path == "writeln" {
let check_tts = check_tts(cx, &mac.node.tts, true);
if let Some(fmtstr) = check_tts.0 {
if fmtstr == "" {
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let suggestion = check_tts
.1
.map_or(Cow::Borrowed("v"), |expr| snippet(cx, expr.span, "v"));
span_lint_and_sugg(
cx,
WRITELN_EMPTY_STRING,
mac.span,
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format!("using `writeln!({}, \"\")`", suggestion).as_str(),
"replace it with",
format!("writeln!({})", suggestion),
);
}
}
}
}
}
fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -> (Option<String>, Option<Expr>) {
use crate::fmt_macros::*;
let tts = TokenStream::from(tts.clone());
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let mut parser = parser::Parser::new(&cx.sess.parse_sess, tts, None, false, false);
let mut expr: Option<Expr> = None;
if is_write {
expr = match parser.parse_expr().map_err(|mut err| err.cancel()) {
Ok(p) => Some(p.into_inner()),
Err(_) => return (None, None),
};
// might be `writeln!(foo)`
if parser.expect(&token::Comma).map_err(|mut err| err.cancel()).is_err() {
return (None, expr);
}
}
let fmtstr = match parser.parse_str().map_err(|mut err| err.cancel()) {
Ok(token) => token.0.to_string(),
Err(_) => return (None, expr),
};
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, expr);
}
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);
}
}
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let lint = if is_write { WRITE_LITERAL } else { PRINT_LITERAL };
let mut idx = 0;
loop {
if !parser.eat(&token::Comma) {
return (Some(fmtstr), expr);
}
let token_expr = match parser.parse_expr().map_err(|mut err| err.cancel()) {
Ok(expr) => expr,
Err(_) => return (Some(fmtstr), None),
};
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const SIMPLE: FormatSpec<'_> = FormatSpec {
fill: None,
align: AlignUnknown,
flags: 0,
precision: CountImplied,
width: CountImplied,
ty: "",
};
match &token_expr.node {
ExprKind::Lit(_) => {
let mut all_simple = true;
let mut seen = false;
for arg in &args {
match arg.position {
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ArgumentImplicitlyIs(n) | ArgumentIs(n) => if n == idx {
all_simple &= arg.format == SIMPLE;
seen = true;
},
ArgumentNamed(_) => {},
}
}
if all_simple && seen {
span_lint(cx, lint, token_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 {
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ArgumentImplicitlyIs(_) | ArgumentIs(_) => {},
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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,
}
}
}