1 //! Utils for extracting, inspecting or transforming source code
3 #![allow(clippy::module_name_repetitions)]
5 use rustc_errors::Applicability;
6 use rustc_hir::{Expr, ExprKind};
7 use rustc_lint::{LateContext, LintContext};
8 use rustc_session::Session;
9 use rustc_span::hygiene;
10 use rustc_span::source_map::{original_sp, SourceMap};
11 use rustc_span::{BytePos, Pos, Span, SpanData, SyntaxContext, DUMMY_SP};
14 /// Like `snippet_block`, but add braces if the expr is not an `ExprKind::Block`.
15 /// Also takes an `Option<String>` which can be put inside the braces.
16 pub fn expr_block<'a, T: LintContext>(
19 option: Option<String>,
21 indent_relative_to: Option<Span>,
23 let code = snippet_block(cx, expr.span, default, indent_relative_to);
24 let string = option.unwrap_or_default();
25 if expr.span.from_expansion() {
26 Cow::Owned(format!("{{ {} }}", snippet_with_macro_callsite(cx, expr.span, default)))
27 } else if let ExprKind::Block(_, _) = expr.kind {
28 Cow::Owned(format!("{code}{string}"))
29 } else if string.is_empty() {
30 Cow::Owned(format!("{{ {code} }}"))
32 Cow::Owned(format!("{{\n{code};\n{string}\n}}"))
36 /// Returns a new Span that extends the original Span to the first non-whitespace char of the first
42 /// // will be converted to
46 pub fn first_line_of_span<T: LintContext>(cx: &T, span: Span) -> Span {
47 first_char_in_first_line(cx, span).map_or(span, |first_char_pos| span.with_lo(first_char_pos))
50 fn first_char_in_first_line<T: LintContext>(cx: &T, span: Span) -> Option<BytePos> {
51 let line_span = line_span(cx, span);
52 snippet_opt(cx, line_span).and_then(|snip| {
53 snip.find(|c: char| !c.is_whitespace())
54 .map(|pos| line_span.lo() + BytePos::from_usize(pos))
58 /// Extends the span to the beginning of the spans line, incl. whitespaces.
63 /// // will be converted to
67 fn line_span<T: LintContext>(cx: &T, span: Span) -> Span {
68 let span = original_sp(span, DUMMY_SP);
69 let source_map_and_line = cx.sess().source_map().lookup_line(span.lo()).unwrap();
70 let line_no = source_map_and_line.line;
71 let line_start = source_map_and_line.sf.lines(|lines| lines[line_no]);
72 span.with_lo(line_start)
75 /// Returns the indentation of the line of a span
79 /// // ^^ -- will return 0
81 /// // ^^ -- will return 4
83 pub fn indent_of<T: LintContext>(cx: &T, span: Span) -> Option<usize> {
84 snippet_opt(cx, line_span(cx, span)).and_then(|snip| snip.find(|c: char| !c.is_whitespace()))
87 /// Gets a snippet of the indentation of the line of a span
88 pub fn snippet_indent<T: LintContext>(cx: &T, span: Span) -> Option<String> {
89 snippet_opt(cx, line_span(cx, span)).map(|mut s| {
90 let len = s.len() - s.trim_start().len();
96 // If the snippet is empty, it's an attribute that was inserted during macro
97 // expansion and we want to ignore those, because they could come from external
98 // sources that the user has no control over.
99 // For some reason these attributes don't have any expansion info on them, so
100 // we have to check it this way until there is a better way.
101 pub fn is_present_in_source<T: LintContext>(cx: &T, span: Span) -> bool {
102 if let Some(snippet) = snippet_opt(cx, span) {
103 if snippet.is_empty() {
110 /// Returns the position just before rarrow
113 /// fn into(self) -> () {}
115 /// // in case of unformatted code
116 /// fn into2(self)-> () {}
118 /// fn into3(self) -> () {}
121 pub fn position_before_rarrow(s: &str) -> Option<usize> {
122 s.rfind("->").map(|rpos| {
124 let chars: Vec<char> = s.chars().collect();
126 if let Some(c) = chars.get(rpos - 1) {
127 if c.is_whitespace() {
138 /// Reindent a multiline string with possibility of ignoring the first line.
139 #[expect(clippy::needless_pass_by_value)]
140 pub fn reindent_multiline(s: Cow<'_, str>, ignore_first: bool, indent: Option<usize>) -> Cow<'_, str> {
141 let s_space = reindent_multiline_inner(&s, ignore_first, indent, ' ');
142 let s_tab = reindent_multiline_inner(&s_space, ignore_first, indent, '\t');
143 reindent_multiline_inner(&s_tab, ignore_first, indent, ' ').into()
146 fn reindent_multiline_inner(s: &str, ignore_first: bool, indent: Option<usize>, ch: char) -> String {
149 .skip(usize::from(ignore_first))
154 // ignore empty lines
155 Some(l.char_indices().find(|&(_, x)| x != ch).unwrap_or((l.len(), ch)).0)
160 let indent = indent.unwrap_or(0);
164 if (ignore_first && i == 0) || l.is_empty() {
166 } else if x > indent {
167 l.split_at(x - indent).1.to_owned()
169 " ".repeat(indent - x) + l
172 .collect::<Vec<String>>()
176 /// Converts a span to a code snippet if available, otherwise returns the default.
178 /// This is useful if you want to provide suggestions for your lint or more generally, if you want
179 /// to convert a given `Span` to a `str`. To create suggestions consider using
180 /// [`snippet_with_applicability`] to ensure that the applicability stays correct.
184 /// // Given two spans one for `value` and one for the `init` expression.
185 /// let value = Vec::new();
186 /// // ^^^^^ ^^^^^^^^^^
189 /// // The snipped call would return the corresponding code snippet
190 /// snippet(cx, span1, "..") // -> "value"
191 /// snippet(cx, span2, "..") // -> "Vec::new()"
193 pub fn snippet<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<'a, str> {
194 snippet_opt(cx, span).map_or_else(|| Cow::Borrowed(default), From::from)
197 /// Same as [`snippet`], but it adapts the applicability level by following rules:
199 /// - Applicability level `Unspecified` will never be changed.
200 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
201 /// - If the default value is used and the applicability level is `MachineApplicable`, change it to
202 /// `HasPlaceholders`
203 pub fn snippet_with_applicability<'a, T: LintContext>(
207 applicability: &mut Applicability,
209 snippet_with_applicability_sess(cx.sess(), span, default, applicability)
212 fn snippet_with_applicability_sess<'a>(
216 applicability: &mut Applicability,
218 if *applicability != Applicability::Unspecified && span.from_expansion() {
219 *applicability = Applicability::MaybeIncorrect;
221 snippet_opt_sess(sess, span).map_or_else(
223 if *applicability == Applicability::MachineApplicable {
224 *applicability = Applicability::HasPlaceholders;
226 Cow::Borrowed(default)
232 /// Same as `snippet`, but should only be used when it's clear that the input span is
233 /// not a macro argument.
234 pub fn snippet_with_macro_callsite<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<'a, str> {
235 snippet(cx, span.source_callsite(), default)
238 /// Converts a span to a code snippet. Returns `None` if not available.
239 pub fn snippet_opt(cx: &impl LintContext, span: Span) -> Option<String> {
240 snippet_opt_sess(cx.sess(), span)
243 fn snippet_opt_sess(sess: &Session, span: Span) -> Option<String> {
244 sess.source_map().span_to_snippet(span).ok()
247 /// Converts a span (from a block) to a code snippet if available, otherwise use default.
249 /// This trims the code of indentation, except for the first line. Use it for blocks or block-like
250 /// things which need to be printed as such.
252 /// The `indent_relative_to` arg can be used, to provide a span, where the indentation of the
253 /// resulting snippet of the given span.
258 /// snippet_block(cx, block.span, "..", None)
259 /// // where, `block` is the block of the if expr
263 /// // will return the snippet
270 /// snippet_block(cx, block.span, "..", Some(if_expr.span))
271 /// // where, `block` is the block of the if expr
275 /// // will return the snippet
278 /// } // aligned with `if`
280 /// Note that the first line of the snippet always has 0 indentation.
281 pub fn snippet_block<'a, T: LintContext>(
285 indent_relative_to: Option<Span>,
287 let snip = snippet(cx, span, default);
288 let indent = indent_relative_to.and_then(|s| indent_of(cx, s));
289 reindent_multiline(snip, true, indent)
292 /// Same as `snippet_block`, but adapts the applicability level by the rules of
293 /// `snippet_with_applicability`.
294 pub fn snippet_block_with_applicability<'a>(
295 cx: &impl LintContext,
298 indent_relative_to: Option<Span>,
299 applicability: &mut Applicability,
301 let snip = snippet_with_applicability(cx, span, default, applicability);
302 let indent = indent_relative_to.and_then(|s| indent_of(cx, s));
303 reindent_multiline(snip, true, indent)
306 /// Same as `snippet_with_applicability`, but first walks the span up to the given context. This
307 /// will result in the macro call, rather then the expansion, if the span is from a child context.
308 /// If the span is not from a child context, it will be used directly instead.
310 /// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR node
311 /// would result in `box []`. If given the context of the address of expression, this function will
312 /// correctly get a snippet of `vec![]`.
314 /// This will also return whether or not the snippet is a macro call.
315 pub fn snippet_with_context<'a>(
316 cx: &impl LintContext,
318 outer: SyntaxContext,
320 applicability: &mut Applicability,
321 ) -> (Cow<'a, str>, bool) {
322 snippet_with_context_sess(cx.sess(), span, outer, default, applicability)
325 fn snippet_with_context_sess<'a>(
328 outer: SyntaxContext,
330 applicability: &mut Applicability,
331 ) -> (Cow<'a, str>, bool) {
332 let (span, is_macro_call) = walk_span_to_context(span, outer).map_or_else(
334 // The span is from a macro argument, and the outer context is the macro using the argument
335 if *applicability != Applicability::Unspecified {
336 *applicability = Applicability::MaybeIncorrect;
338 // TODO: get the argument span.
341 |outer_span| (outer_span, span.ctxt() != outer),
345 snippet_with_applicability_sess(sess, span, default, applicability),
350 /// Walks the span up to the target context, thereby returning the macro call site if the span is
351 /// inside a macro expansion, or the original span if it is not. Note this will return `None` in the
352 /// case of the span being in a macro expansion, but the target context is from expanding a macro
355 /// Given the following
358 /// macro_rules! m { ($e:expr) => { f($e) }; }
362 /// If called with a span of the call to `f` and a context of the call to `g` this will return a
363 /// span containing `m!(0)`. However, if called with a span of the literal `0` this will give a span
364 /// containing `0` as the context is the same as the outer context.
366 /// This will traverse through multiple macro calls. Given the following:
369 /// macro_rules! m { ($e:expr) => { n!($e, 0) }; }
370 /// macro_rules! n { ($e:expr, $f:expr) => { f($e, $f) }; }
374 /// If called with a span of the call to `f` and a context of the call to `g` this will return a
375 /// span containing `m!(0)`.
376 pub fn walk_span_to_context(span: Span, outer: SyntaxContext) -> Option<Span> {
377 let outer_span = hygiene::walk_chain(span, outer);
378 (outer_span.ctxt() == outer).then_some(outer_span)
381 /// Removes block comments from the given `Vec` of lines.
386 /// without_block_comments(vec!["/*", "foo", "*/"]);
389 /// without_block_comments(vec!["bar", "/*", "foo", "*/"]);
390 /// // => vec!["bar"]
392 pub fn without_block_comments(lines: Vec<&str>) -> Vec<&str> {
393 let mut without = vec![];
395 let mut nest_level = 0;
398 if line.contains("/*") {
401 } else if line.contains("*/") {
414 /// Trims the whitespace from the start and the end of the span.
415 pub fn trim_span(sm: &SourceMap, span: Span) -> Span {
416 let data = span.data();
417 let sf: &_ = &sm.lookup_source_file(data.lo);
418 let Some(src) = sf.src.as_deref() else {
421 let Some(snip) = &src.get((data.lo - sf.start_pos).to_usize()..(data.hi - sf.start_pos).to_usize()) else {
424 let trim_start = snip.len() - snip.trim_start().len();
425 let trim_end = snip.len() - snip.trim_end().len();
427 lo: data.lo + BytePos::from_usize(trim_start),
428 hi: data.hi - BytePos::from_usize(trim_end),
435 /// Expand a span to include a preceding comma
437 /// writeln!(o, "") -> writeln!(o, "")
440 pub fn expand_past_previous_comma(cx: &LateContext<'_>, span: Span) -> Span {
441 let extended = cx.sess().source_map().span_extend_to_prev_char(span, ',', true);
442 extended.with_lo(extended.lo() - BytePos(1))
447 use super::{reindent_multiline, without_block_comments};
450 fn test_reindent_multiline_single_line() {
451 assert_eq!("", reindent_multiline("".into(), false, None));
452 assert_eq!("...", reindent_multiline("...".into(), false, None));
453 assert_eq!("...", reindent_multiline(" ...".into(), false, None));
454 assert_eq!("...", reindent_multiline("\t...".into(), false, None));
455 assert_eq!("...", reindent_multiline("\t\t...".into(), false, None));
460 fn test_reindent_multiline_block() {
466 }", reindent_multiline(" if x {
470 }".into(), false, None));
476 }", reindent_multiline(" if x {
480 }".into(), false, None));
485 fn test_reindent_multiline_empty_line() {
492 }", reindent_multiline(" if x {
497 }".into(), false, None));
502 fn test_reindent_multiline_lines_deeper() {
508 }", reindent_multiline("\
513 }".into(), true, Some(8)));
517 fn test_without_block_comments_lines_without_block_comments() {
518 let result = without_block_comments(vec!["/*", "", "*/"]);
519 println!("result: {result:?}");
520 assert!(result.is_empty());
522 let result = without_block_comments(vec!["", "/*", "", "*/", "#[crate_type = \"lib\"]", "/*", "", "*/", ""]);
523 assert_eq!(result, vec!["", "#[crate_type = \"lib\"]", ""]);
525 let result = without_block_comments(vec!["/* rust", "", "*/"]);
526 assert!(result.is_empty());
528 let result = without_block_comments(vec!["/* one-line comment */"]);
529 assert!(result.is_empty());
531 let result = without_block_comments(vec!["/* nested", "/* multi-line", "comment", "*/", "test", "*/"]);
532 assert!(result.is_empty());
534 let result = without_block_comments(vec!["/* nested /* inline /* comment */ test */ */"]);
535 assert!(result.is_empty());
537 let result = without_block_comments(vec!["foo", "bar", "baz"]);
538 assert_eq!(result, vec!["foo", "bar", "baz"]);