1 use crate::utils::{snippet_with_applicability, span_lint, span_lint_and_sugg};
2 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
3 use rustc::{declare_tool_lint, lint_array};
4 use rustc_errors::Applicability;
7 use syntax::parse::{parser, token};
8 use syntax::tokenstream::{TokenStream, TokenTree};
10 declare_clippy_lint! {
11 /// **What it does:** This lint warns when you use `println!("")` to
14 /// **Why is this bad?** You should use `println!()`, which is simpler.
16 /// **Known problems:** None.
22 pub PRINTLN_EMPTY_STRING,
24 "using `println!(\"\")` with an empty string"
27 declare_clippy_lint! {
28 /// **What it does:** This lint warns when you use `print!()` with a format
30 /// ends in a newline.
32 /// **Why is this bad?** You should use `println!()` instead, which appends the
35 /// **Known problems:** None.
39 /// print!("Hello {}!\n", name);
41 /// use println!() instead
43 /// println!("Hello {}!", name);
45 pub PRINT_WITH_NEWLINE,
47 "using `print!()` with a format string that ends in a single newline"
50 declare_clippy_lint! {
51 /// **What it does:** Checks for printing on *stdout*. The purpose of this lint
52 /// is to catch debugging remnants.
54 /// **Why is this bad?** People often print on *stdout* while debugging an
55 /// application and might forget to remove those prints afterward.
57 /// **Known problems:** Only catches `print!` and `println!` calls.
61 /// println!("Hello world!");
68 declare_clippy_lint! {
69 /// **What it does:** Checks for use of `Debug` formatting. The purpose of this
70 /// lint is to catch debugging remnants.
72 /// **Why is this bad?** The purpose of the `Debug` trait is to facilitate
73 /// debugging Rust code. It should not be used in in user-facing output.
77 /// println!("{:?}", foo);
81 "use of `Debug`-based formatting"
84 declare_clippy_lint! {
85 /// **What it does:** This lint warns about the use of literals as `print!`/`println!` args.
87 /// **Why is this bad?** Using literals as `println!` args is inefficient
88 /// (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
89 /// (i.e., just put the literal in the format string)
91 /// **Known problems:** Will also warn with macro calls as arguments that expand to literals
92 /// -- e.g., `println!("{}", env!("FOO"))`.
96 /// println!("{}", "foo");
98 /// use the literal without formatting:
104 "printing a literal with a format string"
107 declare_clippy_lint! {
108 /// **What it does:** This lint warns when you use `writeln!(buf, "")` to
111 /// **Why is this bad?** You should use `writeln!(buf)`, which is simpler.
113 /// **Known problems:** None.
117 /// writeln!(buf, "");
119 pub WRITELN_EMPTY_STRING,
121 "using `writeln!(buf, \"\")` with an empty string"
124 declare_clippy_lint! {
125 /// **What it does:** This lint warns when you use `write!()` with a format
127 /// ends in a newline.
129 /// **Why is this bad?** You should use `writeln!()` instead, which appends the
132 /// **Known problems:** None.
136 /// write!(buf, "Hello {}!\n", name);
138 pub WRITE_WITH_NEWLINE,
140 "using `write!()` with a format string that ends in a single newline"
143 declare_clippy_lint! {
144 /// **What it does:** This lint warns about the use of literals as `write!`/`writeln!` args.
146 /// **Why is this bad?** Using literals as `writeln!` args is inefficient
147 /// (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
148 /// (i.e., just put the literal in the format string)
150 /// **Known problems:** Will also warn with macro calls as arguments that expand to literals
151 /// -- e.g., `writeln!(buf, "{}", env!("FOO"))`.
155 /// writeln!(buf, "{}", "foo");
159 "writing a literal with a format string"
162 #[derive(Copy, Clone, Debug)]
165 impl LintPass for Pass {
166 fn get_lints(&self) -> LintArray {
169 PRINTLN_EMPTY_STRING,
174 WRITELN_EMPTY_STRING,
179 fn name(&self) -> &'static str {
184 impl EarlyLintPass for Pass {
185 fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &Mac) {
186 if mac.node.path == "println" {
187 span_lint(cx, PRINT_STDOUT, mac.span, "use of `println!`");
188 if let Some(fmtstr) = check_tts(cx, &mac.node.tts, false).0 {
192 PRINTLN_EMPTY_STRING,
194 "using `println!(\"\")`",
196 "println!()".to_string(),
197 Applicability::MachineApplicable,
201 } else if mac.node.path == "print" {
202 span_lint(cx, PRINT_STDOUT, mac.span, "use of `print!`");
203 if let (Some(fmtstr), _, is_raw) = check_tts(cx, &mac.node.tts, false) {
204 if check_newlines(&fmtstr, is_raw) {
209 "using `print!()` with a format string that ends in a \
210 single newline, consider using `println!()` instead",
214 } else if mac.node.path == "write" {
215 if let (Some(fmtstr), _, is_raw) = check_tts(cx, &mac.node.tts, true) {
216 if check_newlines(&fmtstr, is_raw) {
221 "using `write!()` with a format string that ends in a \
222 single newline, consider using `writeln!()` instead",
226 } else if mac.node.path == "writeln" {
227 let check_tts = check_tts(cx, &mac.node.tts, true);
228 if let Some(fmtstr) = check_tts.0 {
230 let mut applicability = Applicability::MachineApplicable;
231 let suggestion = check_tts.1.map_or_else(
233 applicability = Applicability::HasPlaceholders;
236 move |expr| snippet_with_applicability(cx, expr.span, "v", &mut applicability),
241 WRITELN_EMPTY_STRING,
243 format!("using `writeln!({}, \"\")`", suggestion).as_str(),
245 format!("writeln!({})", suggestion),
254 /// Checks the arguments of `print[ln]!` and `write[ln]!` calls. It will return a tuple of two
255 /// options and a bool. The first part of the tuple is `format_str` of the macros. The second part
256 /// of the tuple is in the `write[ln]!` case the expression the `format_str` should be written to.
257 /// The final part is a boolean flag indicating if the string is a raw string.
261 /// Calling this function on
263 /// writeln!(buf, "string to write: {}", something)
267 /// (Some("string to write: {}"), Some(buf), false)
269 fn check_tts<'a>(cx: &EarlyContext<'a>, tts: &TokenStream, is_write: bool) -> (Option<String>, Option<Expr>, bool) {
271 let tts = tts.clone();
272 let mut is_raw = false;
273 if let TokenStream(Some(tokens)) = &tts {
274 for token in tokens.iter() {
275 if let (TokenTree::Token(_, token::Token::Literal(lit, _)), _) = token {
277 token::Lit::Str_(_) => break,
278 token::Lit::StrRaw(_, _) => {
287 let mut parser = parser::Parser::new(&cx.sess.parse_sess, tts, None, false, false);
288 let mut expr: Option<Expr> = None;
290 expr = match parser.parse_expr().map_err(|mut err| err.cancel()) {
291 Ok(p) => Some(p.into_inner()),
292 Err(_) => return (None, None, is_raw),
294 // might be `writeln!(foo)`
295 if parser.expect(&token::Comma).map_err(|mut err| err.cancel()).is_err() {
296 return (None, expr, is_raw);
300 let fmtstr = match parser.parse_str().map_err(|mut err| err.cancel()) {
301 Ok(token) => token.0.to_string(),
302 Err(_) => return (None, expr, is_raw),
304 let tmp = fmtstr.clone();
305 let mut args = vec![];
306 let mut fmt_parser = Parser::new(&tmp, None, Vec::new(), false);
307 while let Some(piece) = fmt_parser.next() {
308 if !fmt_parser.errors.is_empty() {
309 return (None, expr, is_raw);
311 if let Piece::NextArgument(arg) = piece {
312 if arg.format.ty == "?" {
313 // FIXME: modify rustc's fmt string parser to give us the current span
314 span_lint(cx, USE_DEBUG, parser.prev_span, "use of `Debug`-based formatting");
319 let lint = if is_write { WRITE_LITERAL } else { PRINT_LITERAL };
322 const SIMPLE: FormatSpec<'_> = FormatSpec {
326 precision: CountImplied,
330 if !parser.eat(&token::Comma) {
331 return (Some(fmtstr), expr, is_raw);
333 let token_expr = match parser.parse_expr().map_err(|mut err| err.cancel()) {
335 Err(_) => return (Some(fmtstr), None, is_raw),
337 match &token_expr.node {
338 ExprKind::Lit(_) => {
339 let mut all_simple = true;
340 let mut seen = false;
343 ArgumentImplicitlyIs(n) | ArgumentIs(n) => {
345 all_simple &= arg.format == SIMPLE;
349 ArgumentNamed(_) => {},
352 if all_simple && seen {
353 span_lint(cx, lint, token_expr.span, "literal with an empty format string");
357 ExprKind::Assign(lhs, rhs) => {
358 if let ExprKind::Lit(_) = rhs.node {
359 if let ExprKind::Path(_, p) = &lhs.node {
360 let mut all_simple = true;
361 let mut seen = false;
364 ArgumentImplicitlyIs(_) | ArgumentIs(_) => {},
365 ArgumentNamed(name) => {
368 all_simple &= arg.format == SIMPLE;
373 if all_simple && seen {
374 span_lint(cx, lint, rhs.span, "literal with an empty format string");
384 // Checks if `s` constains a single newline that terminates it
385 // Literal and escaped newlines are both checked (only literal for raw strings)
386 fn check_newlines(s: &str, is_raw: bool) -> bool {
387 if s.ends_with('\n') {
397 let bytes = s.as_bytes();
398 if bytes[bytes.len() - 2] != b'\\' || bytes[bytes.len() - 1] != b'n' {
402 let mut escaping = false;
403 for (index, &byte) in bytes.iter().enumerate() {
406 return index == bytes.len() - 1;
409 } else if byte == b'\\' {