rust/clippy_lints/src/regex.rs

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use regex_syntax;
use rustc::hir::*;
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use rustc::lint::*;
use rustc::middle::const_val::ConstVal;
use rustc_const_eval::EvalHint::ExprTypeChecked;
use rustc_const_eval::eval_const_expr_partial;
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use std::collections::HashSet;
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use std::error::Error;
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use syntax::ast::{LitKind, NodeId};
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use syntax::codemap::{Span, BytePos};
use syntax::parse::token::InternedString;
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use utils::{is_expn_of, match_def_path, match_type, paths, span_lint, span_help_and_lint};
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/// **What it does:** This lint checks [regex] creation (with `Regex::new`, `RegexBuilder::new` or
/// `RegexSet::new`) for correct regex syntax.
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///
/// **Why is this bad?** This will lead to a runtime panic.
///
/// **Known problems:** None.
///
/// **Example:** `Regex::new("|")`
declare_lint! {
pub INVALID_REGEX,
Deny,
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"finds invalid regular expressions"
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}
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/// **What it does:** This lint checks for trivial [regex] creation (with `Regex::new`,
/// `RegexBuilder::new` or `RegexSet::new`).
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///
/// **Why is this bad?** This can likely be replaced by `==` or `str::starts_with`,
/// `str::ends_with` or `std::contains` or other `str` methods.
///
/// **Known problems:** None.
///
/// **Example:** `Regex::new("^foobar")`
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///
/// [regex]: https://crates.io/crates/regex
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declare_lint! {
pub TRIVIAL_REGEX,
Warn,
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"finds trivial regular expressions"
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}
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/// **What it does:** This lint checks for usage of `regex!(_)` which as of now is usually slower than `Regex::new(_)` unless called in a loop (which is a bad idea anyway).
///
/// **Why is this bad?** Performance, at least for now. The macro version is likely to catch up long-term, but for now the dynamic version is faster.
///
/// **Known problems:** None
///
/// **Example:** `regex!("foo|bar")`
declare_lint! {
pub REGEX_MACRO,
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Warn,
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"finds use of `regex!(_)`, suggests `Regex::new(_)` instead"
}
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#[derive(Clone, Default)]
pub struct RegexPass {
spans: HashSet<Span>,
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last: Option<NodeId>,
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}
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impl LintPass for RegexPass {
fn get_lints(&self) -> LintArray {
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lint_array!(INVALID_REGEX, REGEX_MACRO, TRIVIAL_REGEX)
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}
}
impl LateLintPass for RegexPass {
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fn check_crate(&mut self, _: &LateContext, _: &Crate) {
self.spans.clear();
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}
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fn check_block(&mut self, cx: &LateContext, block: &Block) {
if_let_chain!{[
self.last.is_none(),
let Some(ref expr) = block.expr,
match_type(cx, cx.tcx.expr_ty(expr), &paths::REGEX),
let Some(span) = is_expn_of(cx, expr.span, "regex"),
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], {
if !self.spans.contains(&span) {
span_lint(cx,
REGEX_MACRO,
span,
"`regex!(_)` found. \
Please use `Regex::new(_)`, which is faster for now.");
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self.spans.insert(span);
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}
self.last = Some(block.id);
}}
}
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fn check_block_post(&mut self, _: &LateContext, block: &Block) {
if self.last.map_or(false, |id| block.id == id) {
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self.last = None;
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}
}
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if_let_chain!{[
let ExprCall(ref fun, ref args) = expr.node,
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args.len() == 1,
let Some(def) = cx.tcx.def_map.borrow().get(&fun.id),
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], {
let def_id = def.full_def().def_id();
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if match_def_path(cx, def_id, &paths::REGEX_NEW) ||
match_def_path(cx, def_id, &paths::REGEX_BUILDER_NEW) {
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check_regex(cx, &args[0], true);
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} else if match_def_path(cx, def_id, &paths::REGEX_BYTES_NEW) ||
match_def_path(cx, def_id, &paths::REGEX_BYTES_BUILDER_NEW) {
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check_regex(cx, &args[0], false);
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} else if match_def_path(cx, def_id, &paths::REGEX_SET_NEW) {
check_set(cx, &args[0], true);
} else if match_def_path(cx, def_id, &paths::REGEX_BYTES_SET_NEW) {
check_set(cx, &args[0], false);
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}
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}}
}
}
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#[allow(cast_possible_truncation)]
fn str_span(base: Span, s: &str, c: usize) -> Span {
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let mut si = s.char_indices().skip(c);
match (si.next(), si.next()) {
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(Some((l, _)), Some((h, _))) => {
Span {
lo: base.lo + BytePos(l as u32),
hi: base.lo + BytePos(h as u32),
..base
}
}
_ => base,
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}
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}
fn const_str(cx: &LateContext, e: &Expr) -> Option<InternedString> {
match eval_const_expr_partial(cx.tcx, e, ExprTypeChecked, None) {
Ok(ConstVal::Str(r)) => Some(r),
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_ => None,
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}
}
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fn is_trivial_regex(s: &regex_syntax::Expr) -> Option<&'static str> {
use regex_syntax::Expr;
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match *s {
Expr::Empty | Expr::StartText | Expr::EndText => Some("the regex is unlikely to be useful as it is"),
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Expr::Literal { .. } => Some("consider using `str::contains`"),
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Expr::Concat(ref exprs) => {
match exprs.len() {
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2 => {
match (&exprs[0], &exprs[1]) {
(&Expr::StartText, &Expr::EndText) => Some("consider using `str::is_empty`"),
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(&Expr::StartText, &Expr::Literal { .. }) => Some("consider using `str::starts_with`"),
(&Expr::Literal { .. }, &Expr::EndText) => Some("consider using `str::ends_with`"),
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_ => None,
}
}
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3 => {
if let (&Expr::StartText, &Expr::Literal {..}, &Expr::EndText) = (&exprs[0], &exprs[1], &exprs[2]) {
Some("consider using `==` on `str`s")
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} else {
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None
}
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}
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_ => None,
}
}
_ => None,
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}
}
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fn check_set(cx: &LateContext, expr: &Expr, utf8: bool) {
if_let_chain! {[
let ExprAddrOf(_, ref expr) = expr.node,
let ExprVec(ref exprs) = expr.node,
], {
for expr in exprs {
check_regex(cx, expr, utf8);
}
}}
}
fn check_regex(cx: &LateContext, expr: &Expr, utf8: bool) {
let builder = regex_syntax::ExprBuilder::new().unicode(utf8);
if let ExprLit(ref lit) = expr.node {
if let LitKind::Str(ref r, _) = lit.node {
match builder.parse(r) {
Ok(r) => {
if let Some(repl) = is_trivial_regex(&r) {
span_help_and_lint(cx,
TRIVIAL_REGEX,
expr.span,
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"trivial regex",
&format!("consider using {}", repl));
}
}
Err(e) => {
span_lint(cx,
INVALID_REGEX,
str_span(expr.span, r, e.position()),
&format!("regex syntax error: {}",
e.description()));
}
}
}
} else if let Some(r) = const_str(cx, expr) {
match builder.parse(&r) {
Ok(r) => {
if let Some(repl) = is_trivial_regex(&r) {
span_help_and_lint(cx,
TRIVIAL_REGEX,
expr.span,
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"trivial regex",
&format!("consider using {}", repl));
}
}
Err(e) => {
span_lint(cx,
INVALID_REGEX,
expr.span,
&format!("regex syntax error on position {}: {}",
e.position(),
e.description()));
}
}
}
}