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Write literal suggestion #6821

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merged 4 commits into from
Mar 17, 2021
Merged

Write literal suggestion #6821

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4450c21
Keep track of spans in format strings
Jarcho Mar 1, 2021
4c10471
More specific spans for `use_debug` lint
Jarcho Mar 1, 2021
a7fa2a6
Add suggestion to `write_literal` and `print_literal`
Jarcho Mar 1, 2021
d45873b
Remove SmallVec
Jarcho Mar 16, 2021
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284 changes: 191 additions & 93 deletions clippy_lints/src/write.rs
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Original file line number Diff line number Diff line change
@@ -1,19 +1,19 @@
use std::borrow::Cow;
use std::ops::Range;
use std::iter;
use std::ops::{Deref, Range};

use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
use clippy_utils::source::snippet_with_applicability;
use if_chain::if_chain;
use rustc_ast::ast::{Expr, ExprKind, ImplKind, Item, ItemKind, LitKind, MacCall, StrLit, StrStyle};
use rustc_ast::token;
use clippy_utils::source::{snippet_opt, snippet_with_applicability};
use rustc_ast::ast::{Expr, ExprKind, ImplKind, Item, ItemKind, MacCall, Path, StrLit, StrStyle};
use rustc_ast::token::{self, LitKind};
use rustc_ast::tokenstream::TokenStream;
use rustc_errors::Applicability;
use rustc_lexer::unescape::{self, EscapeError};
use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_parse::parser;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::symbol::kw;
use rustc_span::{sym, BytePos, Span};
use rustc_span::symbol::{kw, Symbol};
use rustc_span::{sym, BytePos, Span, DUMMY_SP};

declare_clippy_lint! {
/// **What it does:** This lint warns when you use `println!("")` to
Expand Down Expand Up @@ -354,7 +354,120 @@ fn newline_span(fmtstr: &StrLit) -> Span {
sp.with_lo(newline_sp_hi - newline_sp_len).with_hi(newline_sp_hi)
}

/// Stores a list of replacement spans for each argument, but only if all the replacements used an
/// empty format string.
#[derive(Default)]
struct SimpleFormatArgs {
unnamed: Vec<Vec<Span>>,
named: Vec<(Symbol, Vec<Span>)>,
}
impl SimpleFormatArgs {
fn get_unnamed(&self) -> impl Iterator<Item = &[Span]> {
self.unnamed.iter().map(|x| match x.as_slice() {
// Ignore the dummy span added from out of order format arguments.
[DUMMY_SP] => &[],
x => x,
})
}

fn get_named(&self, n: &Path) -> &[Span] {
self.named.iter().find(|x| *n == x.0).map_or(&[], |x| x.1.as_slice())
}

fn push(&mut self, arg: rustc_parse_format::Argument<'_>, span: Span) {
use rustc_parse_format::{
AlignUnknown, ArgumentImplicitlyIs, ArgumentIs, ArgumentNamed, CountImplied, FormatSpec,
};

const SIMPLE: FormatSpec<'_> = FormatSpec {
fill: None,
align: AlignUnknown,
flags: 0,
precision: CountImplied,
precision_span: None,
width: CountImplied,
width_span: None,
ty: "",
ty_span: None,
};

match arg.position {
ArgumentIs(n) | ArgumentImplicitlyIs(n) => {
if self.unnamed.len() <= n {
// Use a dummy span to mark all unseen arguments.
self.unnamed.resize_with(n, || vec![DUMMY_SP]);
if arg.format == SIMPLE {
self.unnamed.push(vec![span]);
} else {
self.unnamed.push(Vec::new());
}
} else {
let args = &mut self.unnamed[n];
match (args.as_mut_slice(), arg.format == SIMPLE) {
// A non-empty format string has been seen already.
([], _) => (),
// Replace the dummy span, if it exists.
([dummy @ DUMMY_SP], true) => *dummy = span,
([_, ..], true) => args.push(span),
([_, ..], false) => *args = Vec::new(),
}
}
},
ArgumentNamed(n) => {
if let Some(x) = self.named.iter_mut().find(|x| x.0 == n) {
match x.1.as_slice() {
// A non-empty format string has been seen already.
[] => (),
[_, ..] if arg.format == SIMPLE => x.1.push(span),
[_, ..] => x.1 = Vec::new(),
}
} else if arg.format == SIMPLE {
self.named.push((n, vec![span]));
} else {
self.named.push((n, Vec::new()));
}
},
};
}
}

impl Write {
/// Parses a format string into a collection of spans for each argument. This only keeps track
/// of empty format arguments. Will also lint usages of debug format strings outside of debug
/// impls.
fn parse_fmt_string(&self, cx: &EarlyContext<'_>, str_lit: &StrLit) -> Option<SimpleFormatArgs> {
use rustc_parse_format::{ParseMode, Parser, Piece};

let str_sym = str_lit.symbol_unescaped.as_str();
let style = match str_lit.style {
StrStyle::Cooked => None,
StrStyle::Raw(n) => Some(n as usize),
};

let mut parser = Parser::new(&str_sym, style, snippet_opt(cx, str_lit.span), false, ParseMode::Format);
let mut args = SimpleFormatArgs::default();

while let Some(arg) = parser.next() {
let arg = match arg {
Piece::String(_) => continue,
Piece::NextArgument(arg) => arg,
};
let span = parser
.arg_places
.last()
.map_or(DUMMY_SP, |&x| str_lit.span.from_inner(x));

if !self.in_debug_impl && arg.format.ty == "?" {
// FIXME: modify rustc's fmt string parser to give us the current span
span_lint(cx, USE_DEBUG, span, "use of `Debug`-based formatting");
}

args.push(arg, span);
}

parser.errors.is_empty().then(move || args)
}

/// Checks the arguments of `print[ln]!` and `write[ln]!` calls. It will return a tuple of two
/// `Option`s. The first `Option` of the tuple is the macro's format string. It includes
/// the contents of the string, whether it's a raw string, and the span of the literal in the
Expand All @@ -376,111 +489,96 @@ impl Write {
/// ```
#[allow(clippy::too_many_lines)]
fn check_tts<'a>(&self, cx: &EarlyContext<'a>, tts: TokenStream, is_write: bool) -> (Option<StrLit>, Option<Expr>) {
use rustc_parse_format::{
AlignUnknown, ArgumentImplicitlyIs, ArgumentIs, ArgumentNamed, CountImplied, FormatSpec, ParseMode, Parser,
Piece,
};

let mut parser = parser::Parser::new(&cx.sess.parse_sess, tts, false, None);
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 expr = if is_write {
match parser
.parse_expr()
.map(rustc_ast::ptr::P::into_inner)
.map_err(|mut e| e.cancel())
{
// write!(e, ...)
Ok(p) if parser.eat(&token::Comma) => Some(p),
// write!(e) or error
e => return (None, e.ok()),
}
}
} else {
None
};

let fmtstr = match parser.parse_str_lit() {
Ok(fmtstr) => fmtstr,
Err(_) => return (None, expr),
};
let tmp = fmtstr.symbol.as_str();
let mut args = vec![];
let mut fmt_parser = Parser::new(&tmp, None, None, false, ParseMode::Format);
while let Some(piece) = fmt_parser.next() {
if !fmt_parser.errors.is_empty() {
return (None, expr);
}
if let Piece::NextArgument(arg) = piece {
if !self.in_debug_impl && arg.format.ty == "?" {
// FIXME: modify rustc's fmt string parser to give us the current span
span_lint(cx, USE_DEBUG, parser.prev_token.span, "use of `Debug`-based formatting");
}
args.push(arg);
}
}

let args = match self.parse_fmt_string(cx, &fmtstr) {
Some(args) => args,
None => return (Some(fmtstr), expr),
};

let lint = if is_write { WRITE_LITERAL } else { PRINT_LITERAL };
let mut idx = 0;
let mut unnamed_args = args.get_unnamed();
loop {
const SIMPLE: FormatSpec<'_> = FormatSpec {
fill: None,
align: AlignUnknown,
flags: 0,
precision: CountImplied,
precision_span: None,
width: CountImplied,
width_span: None,
ty: "",
ty_span: None,
};
if !parser.eat(&token::Comma) {
return (Some(fmtstr), expr);
}

let comma_span = parser.prev_token.span;
let token_expr = if let Ok(expr) = parser.parse_expr().map_err(|mut err| err.cancel()) {
expr
} else {
return (Some(fmtstr), None);
};
match &token_expr.kind {
ExprKind::Lit(lit) if !matches!(lit.kind, LitKind::Int(..) | LitKind::Float(..)) => {
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, token_expr.span, "literal with an empty format string");
}
idx += 1;
let (fmt_spans, lit) = match &token_expr.kind {
ExprKind::Lit(lit) => (unnamed_args.next().unwrap_or(&[]), lit),
ExprKind::Assign(lhs, rhs, _) => match (&lhs.kind, &rhs.kind) {
(ExprKind::Path(_, p), ExprKind::Lit(lit)) => (args.get_named(p), lit),
_ => continue,
},
ExprKind::Assign(lhs, rhs, _) => {
if_chain! {
if let ExprKind::Lit(ref lit) = rhs.kind;
if !matches!(lit.kind, LitKind::Int(..) | LitKind::Float(..));
if let ExprKind::Path(_, p) = &lhs.kind;
then {
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");
}
}
}
_ => {
unnamed_args.next();
continue;
},
};

let replacement: String = match lit.token.kind {
LitKind::Integer | LitKind::Float | LitKind::Err => continue,
LitKind::StrRaw(_) | LitKind::ByteStrRaw(_) if matches!(fmtstr.style, StrStyle::Raw(_)) => {
lit.token.symbol.as_str().replace("{", "{{").replace("}", "}}")
},
_ => idx += 1,
LitKind::Str | LitKind::ByteStr if matches!(fmtstr.style, StrStyle::Cooked) => {
lit.token.symbol.as_str().replace("{", "{{").replace("}", "}}")
},
LitKind::StrRaw(_) | LitKind::Str | LitKind::ByteStrRaw(_) | LitKind::ByteStr => continue,
LitKind::Byte | LitKind::Char => match &*lit.token.symbol.as_str() {
"\"" if matches!(fmtstr.style, StrStyle::Cooked) => "\\\"",
"\"" if matches!(fmtstr.style, StrStyle::Raw(0)) => continue,
"\\\\" if matches!(fmtstr.style, StrStyle::Raw(_)) => "\\",
"\\'" => "'",
"{" => "{{",
"}" => "}}",
x if matches!(fmtstr.style, StrStyle::Raw(_)) && x.starts_with('\\') => continue,
x => x,
}
.into(),
LitKind::Bool => lit.token.symbol.as_str().deref().into(),
};

if !fmt_spans.is_empty() {
span_lint_and_then(
cx,
lint,
token_expr.span,
"literal with an empty format string",
|diag| {
diag.multipart_suggestion(
"try this",
iter::once((comma_span.to(token_expr.span), String::new()))
.chain(fmt_spans.iter().cloned().zip(iter::repeat(replacement)))
.collect(),
Applicability::MachineApplicable,
);
},
);
}
}
}
Expand Down
12 changes: 6 additions & 6 deletions tests/ui/print.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
error: use of `Debug`-based formatting
--> $DIR/print.rs:11:19
--> $DIR/print.rs:11:20
|
LL | write!(f, "{:?}", 43.1415)
| ^^^^^^
| ^^^^
|
= note: `-D clippy::use-debug` implied by `-D warnings`

Expand Down Expand Up @@ -33,10 +33,10 @@ LL | print!("Hello {:?}", "World");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: use of `Debug`-based formatting
--> $DIR/print.rs:28:12
--> $DIR/print.rs:28:19
|
LL | print!("Hello {:?}", "World");
| ^^^^^^^^^^^^
| ^^^^

error: use of `print!`
--> $DIR/print.rs:30:5
Expand All @@ -45,10 +45,10 @@ LL | print!("Hello {:#?}", "#orld");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: use of `Debug`-based formatting
--> $DIR/print.rs:30:12
--> $DIR/print.rs:30:19
|
LL | print!("Hello {:#?}", "#orld");
| ^^^^^^^^^^^^^
| ^^^^^

error: aborting due to 8 previous errors

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