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Fix false negative in TRIVIAL_REGEX #631

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Merged
merged 1 commit into from
Feb 6, 2016
Merged

Fix false negative in TRIVIAL_REGEX #631

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96 changes: 55 additions & 41 deletions src/regex.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,32 +55,40 @@ impl LateLintPass for RegexPass {
], {
if let ExprLit(ref lit) = args[0].node {
if let LitStr(ref r, _) = lit.node {
if let Err(e) = regex_syntax::Expr::parse(r) {
match regex_syntax::Expr::parse(r) {
Ok(r) => {
if let Some(repl) = is_trivial_regex(&r) {
span_help_and_lint(cx, TRIVIAL_REGEX, args[0].span,
&"trivial regex",
&format!("consider using {}", repl));
}
}
Err(e) => {
span_lint(cx,
INVALID_REGEX,
str_span(args[0].span, &r, e.position()),
&format!("regex syntax error: {}",
e.description()));
}
}
}
} else if let Some(r) = const_str(cx, &*args[0]) {
match regex_syntax::Expr::parse(&r) {
Ok(r) => {
if let Some(repl) = is_trivial_regex(&r) {
span_help_and_lint(cx, TRIVIAL_REGEX, args[0].span,
&"trivial regex",
&format!("consider using {}", repl));
}
}
Err(e) => {
span_lint(cx,
INVALID_REGEX,
str_span(args[0].span, &r, e.position()),
&format!("regex syntax error: {}",
args[0].span,
&format!("regex syntax error on position {}: {}",
e.position(),
e.description()));
}
else if let Some(repl) = is_trivial_regex(r) {
span_help_and_lint(cx, TRIVIAL_REGEX, args[0].span,
&"trivial regex",
&format!("consider using {}", repl));
}
}
} else if let Some(r) = const_str(cx, &*args[0]) {
if let Err(e) = regex_syntax::Expr::parse(&r) {
span_lint(cx,
INVALID_REGEX,
args[0].span,
&format!("regex syntax error on position {}: {}",
e.position(),
e.description()));
}
else if let Some(repl) = is_trivial_regex(&r) {
span_help_and_lint(cx, TRIVIAL_REGEX, args[0].span,
&"trivial regex",
&format!("{}", repl));
}
}
}}
Expand All @@ -103,25 +111,31 @@ fn const_str(cx: &LateContext, e: &Expr) -> Option<InternedString> {
}
}

fn is_trivial_regex(s: &str) -> Option<&'static str> {
// some unlikely but valid corner cases
match s {
"" | "^" | "$" => return Some("the regex is unlikely to be useful as it is"),
"^$" => return Some("consider using `str::is_empty`"),
_ => (),
}

let (start, end, repl) = match (s.starts_with('^'), s.ends_with('$')) {
(true, true) => (1, s.len()-1, "consider using `==` on `str`s"),
(false, true) => (0, s.len()-1, "consider using `str::ends_with`"),
(true, false) => (1, s.len(), "consider using `str::starts_with`"),
(false, false) => (0, s.len(), "consider using `str::contains`"),
};
fn is_trivial_regex(s: &regex_syntax::Expr) -> Option<&'static str> {
use regex_syntax::Expr;

if !s.chars().take(end).skip(start).any(regex_syntax::is_punct) {
Some(repl)
}
else {
None
match *s {
Expr::Empty | Expr::StartText | Expr::EndText => Some("the regex is unlikely to be useful as it is"),
Expr::Literal {..} => Some("consider using `str::contains`"),
Expr::Concat(ref exprs) => {
match exprs.len() {
2 => match (&exprs[0], &exprs[1]) {
(&Expr::StartText, &Expr::EndText) => Some("consider using `str::is_empty`"),
(&Expr::StartText, &Expr::Literal {..}) => Some("consider using `str::starts_with`"),
(&Expr::Literal {..}, &Expr::EndText) => Some("consider using `str::ends_with`"),
_ => None,
},
3 => {
if let (&Expr::StartText, &Expr::Literal {..}, &Expr::EndText) = (&exprs[0], &exprs[1], &exprs[2]) {
Some("consider using `==` on `str`s")
}
else {
None
}
},
_ => None,
}
}
_ => None,
}
}
9 changes: 9 additions & 0 deletions tests/compile-fail/regex.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,16 +45,25 @@ fn trivial_regex() {
//~^ERROR: trivial regex
//~|HELP consider using `str::contains`

let trivial_backslash = Regex::new("a\\.b");
//~^ERROR: trivial regex
//~|HELP consider using `str::contains`

// unlikely corner cases
let trivial_empty = Regex::new("");
//~^ERROR: trivial regex
//~|HELP the regex is unlikely to be useful

let trivial_empty = Regex::new("^");
//~^ERROR: trivial regex
//~|HELP the regex is unlikely to be useful

let trivial_empty = Regex::new("^$");
//~^ERROR: trivial regex
//~|HELP consider using `str::is_empty`

// non-trivial regexes
let non_trivial_dot = Regex::new("a.b");
let non_trivial_eq = Regex::new("^foo|bar$");
let non_trivial_starts_with = Regex::new("^foo|bar");
let non_trivial_ends_with = Regex::new("^foo|bar");
Expand Down