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_span::hygiene;
9 use rustc_span::source_map::{original_sp, SourceMap};
10 use rustc_span::{BytePos, Pos, Span, SpanData, SyntaxContext, DUMMY_SP};
13 /// Like `snippet_block`, but add braces if the expr is not an `ExprKind::Block`.
14 /// Also takes an `Option<String>` which can be put inside the braces.
15 pub fn expr_block<'a, T: LintContext>(
18 option: Option<String>,
20 indent_relative_to: Option<Span>,
22 let code = snippet_block(cx, expr.span, default, indent_relative_to);
23 let string = option.unwrap_or_default();
24 if expr.span.from_expansion() {
25 Cow::Owned(format!("{{ {} }}", snippet_with_macro_callsite(cx, expr.span, default)))
26 } else if let ExprKind::Block(_, _) = expr.kind {
27 Cow::Owned(format!("{code}{string}"))
28 } else if string.is_empty() {
29 Cow::Owned(format!("{{ {code} }}"))
31 Cow::Owned(format!("{{\n{code};\n{string}\n}}"))
35 /// Returns a new Span that extends the original Span to the first non-whitespace char of the first
41 /// // will be converted to
45 pub fn first_line_of_span<T: LintContext>(cx: &T, span: Span) -> Span {
46 first_char_in_first_line(cx, span).map_or(span, |first_char_pos| span.with_lo(first_char_pos))
49 fn first_char_in_first_line<T: LintContext>(cx: &T, span: Span) -> Option<BytePos> {
50 let line_span = line_span(cx, span);
51 snippet_opt(cx, line_span).and_then(|snip| {
52 snip.find(|c: char| !c.is_whitespace())
53 .map(|pos| line_span.lo() + BytePos::from_usize(pos))
57 /// Extends the span to the beginning of the spans line, incl. whitespaces.
62 /// // will be converted to
66 fn line_span<T: LintContext>(cx: &T, span: Span) -> Span {
67 let span = original_sp(span, DUMMY_SP);
68 let source_map_and_line = cx.sess().source_map().lookup_line(span.lo()).unwrap();
69 let line_no = source_map_and_line.line;
70 let line_start = source_map_and_line.sf.lines(|lines| lines[line_no]);
71 span.with_lo(line_start)
74 /// Returns the indentation of the line of a span
78 /// // ^^ -- will return 0
80 /// // ^^ -- will return 4
82 pub fn indent_of<T: LintContext>(cx: &T, span: Span) -> Option<usize> {
83 snippet_opt(cx, line_span(cx, span)).and_then(|snip| snip.find(|c: char| !c.is_whitespace()))
86 /// Gets a snippet of the indentation of the line of a span
87 pub fn snippet_indent<T: LintContext>(cx: &T, span: Span) -> Option<String> {
88 snippet_opt(cx, line_span(cx, span)).map(|mut s| {
89 let len = s.len() - s.trim_start().len();
95 // If the snippet is empty, it's an attribute that was inserted during macro
96 // expansion and we want to ignore those, because they could come from external
97 // sources that the user has no control over.
98 // For some reason these attributes don't have any expansion info on them, so
99 // we have to check it this way until there is a better way.
100 pub fn is_present_in_source<T: LintContext>(cx: &T, span: Span) -> bool {
101 if let Some(snippet) = snippet_opt(cx, span) {
102 if snippet.is_empty() {
109 /// Returns the position just before rarrow
112 /// fn into(self) -> () {}
114 /// // in case of unformatted code
115 /// fn into2(self)-> () {}
117 /// fn into3(self) -> () {}
120 pub fn position_before_rarrow(s: &str) -> Option<usize> {
121 s.rfind("->").map(|rpos| {
123 let chars: Vec<char> = s.chars().collect();
125 if let Some(c) = chars.get(rpos - 1) {
126 if c.is_whitespace() {
137 /// Reindent a multiline string with possibility of ignoring the first line.
138 #[expect(clippy::needless_pass_by_value)]
139 pub fn reindent_multiline(s: Cow<'_, str>, ignore_first: bool, indent: Option<usize>) -> Cow<'_, str> {
140 let s_space = reindent_multiline_inner(&s, ignore_first, indent, ' ');
141 let s_tab = reindent_multiline_inner(&s_space, ignore_first, indent, '\t');
142 reindent_multiline_inner(&s_tab, ignore_first, indent, ' ').into()
145 fn reindent_multiline_inner(s: &str, ignore_first: bool, indent: Option<usize>, ch: char) -> String {
148 .skip(usize::from(ignore_first))
153 // ignore empty lines
154 Some(l.char_indices().find(|&(_, x)| x != ch).unwrap_or((l.len(), ch)).0)
159 let indent = indent.unwrap_or(0);
163 if (ignore_first && i == 0) || l.is_empty() {
165 } else if x > indent {
166 l.split_at(x - indent).1.to_owned()
168 " ".repeat(indent - x) + l
171 .collect::<Vec<String>>()
175 /// Converts a span to a code snippet if available, otherwise returns the default.
177 /// This is useful if you want to provide suggestions for your lint or more generally, if you want
178 /// to convert a given `Span` to a `str`. To create suggestions consider using
179 /// [`snippet_with_applicability`] to ensure that the applicability stays correct.
183 /// // Given two spans one for `value` and one for the `init` expression.
184 /// let value = Vec::new();
185 /// // ^^^^^ ^^^^^^^^^^
188 /// // The snipped call would return the corresponding code snippet
189 /// snippet(cx, span1, "..") // -> "value"
190 /// snippet(cx, span2, "..") // -> "Vec::new()"
192 pub fn snippet<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<'a, str> {
193 snippet_opt(cx, span).map_or_else(|| Cow::Borrowed(default), From::from)
196 /// Same as [`snippet`], but it adapts the applicability level by following rules:
198 /// - Applicability level `Unspecified` will never be changed.
199 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
200 /// - If the default value is used and the applicability level is `MachineApplicable`, change it to
201 /// `HasPlaceholders`
202 pub fn snippet_with_applicability<'a, T: LintContext>(
206 applicability: &mut Applicability,
208 if *applicability != Applicability::Unspecified && span.from_expansion() {
209 *applicability = Applicability::MaybeIncorrect;
211 snippet_opt(cx, span).map_or_else(
213 if *applicability == Applicability::MachineApplicable {
214 *applicability = Applicability::HasPlaceholders;
216 Cow::Borrowed(default)
222 /// Same as `snippet`, but should only be used when it's clear that the input span is
223 /// not a macro argument.
224 pub fn snippet_with_macro_callsite<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<'a, str> {
225 snippet(cx, span.source_callsite(), default)
228 /// Converts a span to a code snippet. Returns `None` if not available.
229 pub fn snippet_opt<T: LintContext>(cx: &T, span: Span) -> Option<String> {
230 cx.sess().source_map().span_to_snippet(span).ok()
233 /// Converts a span (from a block) to a code snippet if available, otherwise use default.
235 /// This trims the code of indentation, except for the first line. Use it for blocks or block-like
236 /// things which need to be printed as such.
238 /// The `indent_relative_to` arg can be used, to provide a span, where the indentation of the
239 /// resulting snippet of the given span.
244 /// snippet_block(cx, block.span, "..", None)
245 /// // where, `block` is the block of the if expr
249 /// // will return the snippet
256 /// snippet_block(cx, block.span, "..", Some(if_expr.span))
257 /// // where, `block` is the block of the if expr
261 /// // will return the snippet
264 /// } // aligned with `if`
266 /// Note that the first line of the snippet always has 0 indentation.
267 pub fn snippet_block<'a, T: LintContext>(
271 indent_relative_to: Option<Span>,
273 let snip = snippet(cx, span, default);
274 let indent = indent_relative_to.and_then(|s| indent_of(cx, s));
275 reindent_multiline(snip, true, indent)
278 /// Same as `snippet_block`, but adapts the applicability level by the rules of
279 /// `snippet_with_applicability`.
280 pub fn snippet_block_with_applicability<'a, T: LintContext>(
284 indent_relative_to: Option<Span>,
285 applicability: &mut Applicability,
287 let snip = snippet_with_applicability(cx, span, default, applicability);
288 let indent = indent_relative_to.and_then(|s| indent_of(cx, s));
289 reindent_multiline(snip, true, indent)
292 /// Same as `snippet_with_applicability`, but first walks the span up to the given context. This
293 /// will result in the macro call, rather then the expansion, if the span is from a child context.
294 /// If the span is not from a child context, it will be used directly instead.
296 /// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR node
297 /// would result in `box []`. If given the context of the address of expression, this function will
298 /// correctly get a snippet of `vec![]`.
300 /// This will also return whether or not the snippet is a macro call.
301 pub fn snippet_with_context<'a>(
302 cx: &LateContext<'_>,
304 outer: SyntaxContext,
306 applicability: &mut Applicability,
307 ) -> (Cow<'a, str>, bool) {
308 let (span, is_macro_call) = walk_span_to_context(span, outer).map_or_else(
310 // The span is from a macro argument, and the outer context is the macro using the argument
311 if *applicability != Applicability::Unspecified {
312 *applicability = Applicability::MaybeIncorrect;
314 // TODO: get the argument span.
317 |outer_span| (outer_span, span.ctxt() != outer),
321 snippet_with_applicability(cx, span, default, applicability),
326 /// Walks the span up to the target context, thereby returning the macro call site if the span is
327 /// inside a macro expansion, or the original span if it is not. Note this will return `None` in the
328 /// case of the span being in a macro expansion, but the target context is from expanding a macro
331 /// Given the following
334 /// macro_rules! m { ($e:expr) => { f($e) }; }
338 /// If called with a span of the call to `f` and a context of the call to `g` this will return a
339 /// span containing `m!(0)`. However, if called with a span of the literal `0` this will give a span
340 /// containing `0` as the context is the same as the outer context.
342 /// This will traverse through multiple macro calls. Given the following:
345 /// macro_rules! m { ($e:expr) => { n!($e, 0) }; }
346 /// macro_rules! n { ($e:expr, $f:expr) => { f($e, $f) }; }
350 /// If called with a span of the call to `f` and a context of the call to `g` this will return a
351 /// span containing `m!(0)`.
352 pub fn walk_span_to_context(span: Span, outer: SyntaxContext) -> Option<Span> {
353 let outer_span = hygiene::walk_chain(span, outer);
354 (outer_span.ctxt() == outer).then_some(outer_span)
357 /// Removes block comments from the given `Vec` of lines.
362 /// without_block_comments(vec!["/*", "foo", "*/"]);
365 /// without_block_comments(vec!["bar", "/*", "foo", "*/"]);
366 /// // => vec!["bar"]
368 pub fn without_block_comments(lines: Vec<&str>) -> Vec<&str> {
369 let mut without = vec![];
371 let mut nest_level = 0;
374 if line.contains("/*") {
377 } else if line.contains("*/") {
390 /// Trims the whitespace from the start and the end of the span.
391 pub fn trim_span(sm: &SourceMap, span: Span) -> Span {
392 let data = span.data();
393 let sf: &_ = &sm.lookup_source_file(data.lo);
394 let Some(src) = sf.src.as_deref() else {
397 let Some(snip) = &src.get((data.lo - sf.start_pos).to_usize()..(data.hi - sf.start_pos).to_usize()) else {
400 let trim_start = snip.len() - snip.trim_start().len();
401 let trim_end = snip.len() - snip.trim_end().len();
403 lo: data.lo + BytePos::from_usize(trim_start),
404 hi: data.hi - BytePos::from_usize(trim_end),
411 /// Expand a span to include a preceding comma
413 /// writeln!(o, "") -> writeln!(o, "")
416 pub fn expand_past_previous_comma(cx: &LateContext<'_>, span: Span) -> Span {
417 let extended = cx.sess().source_map().span_extend_to_prev_char(span, ',', true);
418 extended.with_lo(extended.lo() - BytePos(1))
423 use super::{reindent_multiline, without_block_comments};
426 fn test_reindent_multiline_single_line() {
427 assert_eq!("", reindent_multiline("".into(), false, None));
428 assert_eq!("...", reindent_multiline("...".into(), false, None));
429 assert_eq!("...", reindent_multiline(" ...".into(), false, None));
430 assert_eq!("...", reindent_multiline("\t...".into(), false, None));
431 assert_eq!("...", reindent_multiline("\t\t...".into(), false, None));
436 fn test_reindent_multiline_block() {
442 }", reindent_multiline(" if x {
446 }".into(), false, None));
452 }", reindent_multiline(" if x {
456 }".into(), false, None));
461 fn test_reindent_multiline_empty_line() {
468 }", reindent_multiline(" if x {
473 }".into(), false, None));
478 fn test_reindent_multiline_lines_deeper() {
484 }", reindent_multiline("\
489 }".into(), true, Some(8)));
493 fn test_without_block_comments_lines_without_block_comments() {
494 let result = without_block_comments(vec!["/*", "", "*/"]);
495 println!("result: {result:?}");
496 assert!(result.is_empty());
498 let result = without_block_comments(vec!["", "/*", "", "*/", "#[crate_type = \"lib\"]", "/*", "", "*/", ""]);
499 assert_eq!(result, vec!["", "#[crate_type = \"lib\"]", ""]);
501 let result = without_block_comments(vec!["/* rust", "", "*/"]);
502 assert!(result.is_empty());
504 let result = without_block_comments(vec!["/* one-line comment */"]);
505 assert!(result.is_empty());
507 let result = without_block_comments(vec!["/* nested", "/* multi-line", "comment", "*/", "test", "*/"]);
508 assert!(result.is_empty());
510 let result = without_block_comments(vec!["/* nested /* inline /* comment */ test */ */"]);
511 assert!(result.is_empty());
513 let result = without_block_comments(vec!["foo", "bar", "baz"]);
514 assert_eq!(result, vec!["foo", "bar", "baz"]);