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Merge pull request #3059 from elpiel/writeln_empty_string_harcoded-suggestion

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#3016 writeln_empty_string Hardcoded suggestion
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Philipp Krones 2018-08-24 18:28:50 +02:00 committed by GitHub
commit 562c576ed3
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3 changed files with 46 additions and 21 deletions
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50
clippy_lints/src/write.rs
View file

@ -3,7 +3,8 @@ 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};
use std::borrow::Cow;
use crate::utils::{span_lint, span_lint_and_sugg, snippet};
/// **What it does:** This lint warns when you use `println!("")` to
/// print a newline.
@ -179,7 +180,7 @@ impl EarlyLintPass for Pass {
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 let Some(fmtstr) = check_tts(cx, &mac.node.tts, false).0 {
if fmtstr == "" {
span_lint_and_sugg(
cx,
@ -193,7 +194,7 @@ impl EarlyLintPass for Pass {
}
} 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 let Some(fmtstr) = check_tts(cx, &mac.node.tts, false).0 {
if fmtstr.ends_with("\\n") && !fmtstr.ends_with("\\n\\n") {
span_lint(cx, PRINT_WITH_NEWLINE, mac.span,
"using `print!()` with a format string that ends in a \
@ -201,7 +202,7 @@ impl EarlyLintPass for Pass {
}
}
} else if mac.node.path == "write" {
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, true) {
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, true).0 {
if fmtstr.ends_with("\\n") && !fmtstr.ends_with("\\n\\n") {
span_lint(cx, WRITE_WITH_NEWLINE, mac.span,
"using `write!()` with a format string that ends in a \
@ -209,15 +210,18 @@ impl EarlyLintPass for Pass {
}
}
} else if mac.node.path == "writeln" {
if let Some(fmtstr) = check_tts(cx, &mac.node.tts, true) {
let check_tts = check_tts(cx, &mac.node.tts, true);
if let Some(fmtstr) = check_tts.0 {
if fmtstr == "" {
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,
"using `writeln!(v, \"\")`",
format!("using `writeln!({}, \"\")`", suggestion).as_str(),
"replace it with",
"writeln!(v)".to_string(),
format!("writeln!({})", suggestion),
);
}
}
@ -225,7 +229,7 @@ impl EarlyLintPass for Pass {
}
}
fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -> Option<String> {
fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -> (Option<String>, Option<Expr>) {
let tts = TokenStream::from(tts.clone());
let mut parser = parser::Parser::new(
&cx.sess.parse_sess,
@ -234,20 +238,29 @@ fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -
false,
false,
);
let mut expr: Option<Expr> = None;
if is_write {
// skip the initial write target
parser.parse_expr().map_err(|mut err| err.cancel()).ok()?;
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)`
parser.expect(&token::Comma).map_err(|mut err| err.cancel()).ok()?;
if parser.expect(&token::Comma).map_err(|mut err| err.cancel()).is_err() {
return (None, expr);
}
}
let fmtstr = parser.parse_str().map_err(|mut err| err.cancel()).ok()?.0.to_string();
let fmtstr = match parser.parse_str().map_err(|mut err| err.cancel()) {
Ok(token) => token.0.to_string(),
Err(_) => return (None, expr),
};
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;
return (None, expr);
}
if let Piece::NextArgument(arg) = piece {
if arg.format.ty == "?" {
@ -266,9 +279,12 @@ fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -
loop {
if !parser.eat(&token::Comma) {
assert!(parser.eat(&token::Eof));
return Some(fmtstr);
return (Some(fmtstr), expr);
}
let expr = parser.parse_expr().map_err(|mut err| err.cancel()).ok()?;
let token_expr = match parser.parse_expr().map_err(|mut err| err.cancel()) {
Ok(expr) => expr,
Err(_) => return (Some(fmtstr), None),
};
const SIMPLE: FormatSpec<'_> = FormatSpec {
fill: None,
align: AlignUnknown,
@ -277,7 +293,7 @@ fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -
width: CountImplied,
ty: "",
};
match &expr.node {
match &token_expr.node {
ExprKind::Lit(_) => {
let mut all_simple = true;
let mut seen = false;
@ -293,7 +309,7 @@ fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &ThinTokenStream, is_write: bool) -
}
}
if all_simple && seen {
span_lint(cx, lint, expr.span, "literal with an empty format string");
span_lint(cx, lint, token_expr.span, "literal with an empty format string");
}
idx += 1;
},

5
tests/ui/writeln_empty_string.rs
View file

@ -5,9 +5,12 @@ use std::io::Write;
fn main() {
let mut v = Vec::new();
// This should fail
// These should fail
writeln!(&mut v, "");
let mut suggestion = Vec::new();
writeln!(&mut suggestion, "");
// These should be fine
writeln!(&mut v);
writeln!(&mut v, " ");

12
tests/ui/writeln_empty_string.stderr
View file

@ -1,10 +1,16 @@
error: using `writeln!(v, "")`
error: using `writeln!(&mut v, "")`
--> $DIR/writeln_empty_string.rs:9:5
|
9 | writeln!(&mut v, "");
| ^^^^^^^^^^^^^^^^^^^^ help: replace it with: `writeln!(v)`
| ^^^^^^^^^^^^^^^^^^^^ help: replace it with: `writeln!(&mut v)`
|
= note: `-D writeln-empty-string` implied by `-D warnings`
error: aborting due to previous error
error: using `writeln!(&mut suggestion, "")`
--> $DIR/writeln_empty_string.rs:12:5
|
12 | writeln!(&mut suggestion, "");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `writeln!(&mut suggestion)`
error: aborting due to 2 previous errors