1 //! Utils for extracting, inspecting or transforming source code
3 #![allow(clippy::module_name_repetitions)]
6 use rustc_errors::Applicability;
7 use rustc_hir::{Expr, ExprKind};
8 use rustc_lint::{LateContext, LintContext};
9 use rustc_span::hygiene;
10 use rustc_span::source_map::SourceMap;
11 use rustc_span::{BytePos, Pos, Span, SyntaxContext};
14 /// Checks if the span starts with the given text. This will return false if the span crosses
15 /// multiple files or if source is not available.
17 /// This is used to check for proc macros giving unhelpful spans to things.
18 pub fn span_starts_with<T: LintContext>(cx: &T, span: Span, text: &str) -> bool {
19 fn helper(sm: &SourceMap, span: Span, text: &str) -> bool {
20 let pos = sm.lookup_byte_offset(span.lo());
21 let Some(ref src) = pos.sf.src else {
24 let end = span.hi() - pos.sf.start_pos;
25 src.get(pos.pos.0 as usize..end.0 as usize)
26 // Expression spans can include wrapping parenthesis. Remove them first.
27 .map_or(false, |s| s.trim_start_matches('(').starts_with(text))
29 helper(cx.sess().source_map(), span, text)
32 /// Like `snippet_block`, but add braces if the expr is not an `ExprKind::Block`.
33 /// Also takes an `Option<String>` which can be put inside the braces.
34 pub fn expr_block<'a, T: LintContext>(
37 option: Option<String>,
39 indent_relative_to: Option<Span>,
41 let code = snippet_block(cx, expr.span, default, indent_relative_to);
42 let string = option.unwrap_or_default();
43 if expr.span.from_expansion() {
44 Cow::Owned(format!("{{ {} }}", snippet_with_macro_callsite(cx, expr.span, default)))
45 } else if let ExprKind::Block(_, _) = expr.kind {
46 Cow::Owned(format!("{}{}", code, string))
47 } else if string.is_empty() {
48 Cow::Owned(format!("{{ {} }}", code))
50 Cow::Owned(format!("{{\n{};\n{}\n}}", code, string))
54 /// Returns a new Span that extends the original Span to the first non-whitespace char of the first
60 /// // will be converted to
64 pub fn first_line_of_span<T: LintContext>(cx: &T, span: Span) -> Span {
65 first_char_in_first_line(cx, span).map_or(span, |first_char_pos| span.with_lo(first_char_pos))
68 fn first_char_in_first_line<T: LintContext>(cx: &T, span: Span) -> Option<BytePos> {
69 let line_span = line_span(cx, span);
70 snippet_opt(cx, line_span).and_then(|snip| {
71 snip.find(|c: char| !c.is_whitespace())
72 .map(|pos| line_span.lo() + BytePos::from_usize(pos))
76 /// Returns the indentation of the line of a span
80 /// // ^^ -- will return 0
82 /// // ^^ -- will return 4
84 pub fn indent_of<T: LintContext>(cx: &T, span: Span) -> Option<usize> {
85 snippet_opt(cx, line_span(cx, span)).and_then(|snip| snip.find(|c: char| !c.is_whitespace()))
88 /// Gets a snippet of the indentation of the line of a span
89 pub fn snippet_indent<T: LintContext>(cx: &T, span: Span) -> Option<String> {
90 snippet_opt(cx, line_span(cx, span)).map(|mut s| {
91 let len = s.len() - s.trim_start().len();
97 // If the snippet is empty, it's an attribute that was inserted during macro
98 // expansion and we want to ignore those, because they could come from external
99 // sources that the user has no control over.
100 // For some reason these attributes don't have any expansion info on them, so
101 // we have to check it this way until there is a better way.
102 pub fn is_present_in_source<T: LintContext>(cx: &T, span: Span) -> bool {
103 if let Some(snippet) = snippet_opt(cx, span) {
104 if snippet.is_empty() {
111 /// Returns the position just before rarrow
114 /// fn into(self) -> () {}
116 /// // in case of unformatted code
117 /// fn into2(self)-> () {}
119 /// fn into3(self) -> () {}
122 pub fn position_before_rarrow(s: &str) -> Option<usize> {
123 s.rfind("->").map(|rpos| {
125 let chars: Vec<char> = s.chars().collect();
127 if let Some(c) = chars.get(rpos - 1) {
128 if c.is_whitespace() {
139 /// Reindent a multiline string with possibility of ignoring the first line.
140 #[expect(clippy::needless_pass_by_value)]
141 pub fn reindent_multiline(s: Cow<'_, str>, ignore_first: bool, indent: Option<usize>) -> Cow<'_, str> {
142 let s_space = reindent_multiline_inner(&s, ignore_first, indent, ' ');
143 let s_tab = reindent_multiline_inner(&s_space, ignore_first, indent, '\t');
144 reindent_multiline_inner(&s_tab, ignore_first, indent, ' ').into()
147 fn reindent_multiline_inner(s: &str, ignore_first: bool, indent: Option<usize>, ch: char) -> String {
150 .skip(usize::from(ignore_first))
155 // ignore empty lines
156 Some(l.char_indices().find(|&(_, x)| x != ch).unwrap_or((l.len(), ch)).0)
161 let indent = indent.unwrap_or(0);
165 if (ignore_first && i == 0) || l.is_empty() {
167 } else if x > indent {
168 l.split_at(x - indent).1.to_owned()
170 " ".repeat(indent - x) + l
173 .collect::<Vec<String>>()
177 /// Converts a span to a code snippet if available, otherwise returns the default.
179 /// This is useful if you want to provide suggestions for your lint or more generally, if you want
180 /// to convert a given `Span` to a `str`. To create suggestions consider using
181 /// [`snippet_with_applicability`] to ensure that the applicability stays correct.
185 /// // Given two spans one for `value` and one for the `init` expression.
186 /// let value = Vec::new();
187 /// // ^^^^^ ^^^^^^^^^^
190 /// // The snipped call would return the corresponding code snippet
191 /// snippet(cx, span1, "..") // -> "value"
192 /// snippet(cx, span2, "..") // -> "Vec::new()"
194 pub fn snippet<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<'a, str> {
195 snippet_opt(cx, span).map_or_else(|| Cow::Borrowed(default), From::from)
198 /// Same as [`snippet`], but it adapts the applicability level by following rules:
200 /// - Applicability level `Unspecified` will never be changed.
201 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
202 /// - If the default value is used and the applicability level is `MachineApplicable`, change it to
203 /// `HasPlaceholders`
204 pub fn snippet_with_applicability<'a, T: LintContext>(
208 applicability: &mut Applicability,
210 if *applicability != Applicability::Unspecified && span.from_expansion() {
211 *applicability = Applicability::MaybeIncorrect;
213 snippet_opt(cx, span).map_or_else(
215 if *applicability == Applicability::MachineApplicable {
216 *applicability = Applicability::HasPlaceholders;
218 Cow::Borrowed(default)
224 /// Same as `snippet`, but should only be used when it's clear that the input span is
225 /// not a macro argument.
226 pub fn snippet_with_macro_callsite<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<'a, str> {
227 snippet(cx, span.source_callsite(), default)
230 /// Converts a span to a code snippet. Returns `None` if not available.
231 pub fn snippet_opt<T: LintContext>(cx: &T, span: Span) -> Option<String> {
232 cx.sess().source_map().span_to_snippet(span).ok()
235 /// Converts a span (from a block) to a code snippet if available, otherwise use default.
237 /// This trims the code of indentation, except for the first line. Use it for blocks or block-like
238 /// things which need to be printed as such.
240 /// The `indent_relative_to` arg can be used, to provide a span, where the indentation of the
241 /// resulting snippet of the given span.
246 /// snippet_block(cx, block.span, "..", None)
247 /// // where, `block` is the block of the if expr
251 /// // will return the snippet
258 /// snippet_block(cx, block.span, "..", Some(if_expr.span))
259 /// // where, `block` is the block of the if expr
263 /// // will return the snippet
266 /// } // aligned with `if`
268 /// Note that the first line of the snippet always has 0 indentation.
269 pub fn snippet_block<'a, T: LintContext>(
273 indent_relative_to: Option<Span>,
275 let snip = snippet(cx, span, default);
276 let indent = indent_relative_to.and_then(|s| indent_of(cx, s));
277 reindent_multiline(snip, true, indent)
280 /// Same as `snippet_block`, but adapts the applicability level by the rules of
281 /// `snippet_with_applicability`.
282 pub fn snippet_block_with_applicability<'a, T: LintContext>(
286 indent_relative_to: Option<Span>,
287 applicability: &mut Applicability,
289 let snip = snippet_with_applicability(cx, span, default, applicability);
290 let indent = indent_relative_to.and_then(|s| indent_of(cx, s));
291 reindent_multiline(snip, true, indent)
294 /// Same as `snippet_with_applicability`, but first walks the span up to the given context. This
295 /// will result in the macro call, rather then the expansion, if the span is from a child context.
296 /// If the span is not from a child context, it will be used directly instead.
298 /// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR node
299 /// would result in `box []`. If given the context of the address of expression, this function will
300 /// correctly get a snippet of `vec![]`.
302 /// This will also return whether or not the snippet is a macro call.
303 pub fn snippet_with_context<'a>(
304 cx: &LateContext<'_>,
306 outer: SyntaxContext,
308 applicability: &mut Applicability,
309 ) -> (Cow<'a, str>, bool) {
310 let (span, is_macro_call) = walk_span_to_context(span, outer).map_or_else(
312 // The span is from a macro argument, and the outer context is the macro using the argument
313 if *applicability != Applicability::Unspecified {
314 *applicability = Applicability::MaybeIncorrect;
316 // TODO: get the argument span.
319 |outer_span| (outer_span, span.ctxt() != outer),
323 snippet_with_applicability(cx, span, default, applicability),
328 /// Walks the span up to the target context, thereby returning the macro call site if the span is
329 /// inside a macro expansion, or the original span if it is not. Note this will return `None` in the
330 /// case of the span being in a macro expansion, but the target context is from expanding a macro
333 /// Given the following
336 /// macro_rules! m { ($e:expr) => { f($e) }; }
340 /// If called with a span of the call to `f` and a context of the call to `g` this will return a
341 /// span containing `m!(0)`. However, if called with a span of the literal `0` this will give a span
342 /// containing `0` as the context is the same as the outer context.
344 /// This will traverse through multiple macro calls. Given the following:
347 /// macro_rules! m { ($e:expr) => { n!($e, 0) }; }
348 /// macro_rules! n { ($e:expr, $f:expr) => { f($e, $f) }; }
352 /// If called with a span of the call to `f` and a context of the call to `g` this will return a
353 /// span containing `m!(0)`.
354 pub fn walk_span_to_context(span: Span, outer: SyntaxContext) -> Option<Span> {
355 let outer_span = hygiene::walk_chain(span, outer);
356 (outer_span.ctxt() == outer).then(|| outer_span)
359 /// Removes block comments from the given `Vec` of lines.
364 /// without_block_comments(vec!["/*", "foo", "*/"]);
367 /// without_block_comments(vec!["bar", "/*", "foo", "*/"]);
368 /// // => vec!["bar"]
370 pub fn without_block_comments(lines: Vec<&str>) -> Vec<&str> {
371 let mut without = vec![];
373 let mut nest_level = 0;
376 if line.contains("/*") {
379 } else if line.contains("*/") {
394 use super::{reindent_multiline, without_block_comments};
397 fn test_reindent_multiline_single_line() {
398 assert_eq!("", reindent_multiline("".into(), false, None));
399 assert_eq!("...", reindent_multiline("...".into(), false, None));
400 assert_eq!("...", reindent_multiline(" ...".into(), false, None));
401 assert_eq!("...", reindent_multiline("\t...".into(), false, None));
402 assert_eq!("...", reindent_multiline("\t\t...".into(), false, None));
407 fn test_reindent_multiline_block() {
413 }", reindent_multiline(" if x {
417 }".into(), false, None));
423 }", reindent_multiline(" if x {
427 }".into(), false, None));
432 fn test_reindent_multiline_empty_line() {
439 }", reindent_multiline(" if x {
444 }".into(), false, None));
449 fn test_reindent_multiline_lines_deeper() {
455 }", reindent_multiline("\
460 }".into(), true, Some(8)));
464 fn test_without_block_comments_lines_without_block_comments() {
465 let result = without_block_comments(vec!["/*", "", "*/"]);
466 println!("result: {:?}", result);
467 assert!(result.is_empty());
469 let result = without_block_comments(vec!["", "/*", "", "*/", "#[crate_type = \"lib\"]", "/*", "", "*/", ""]);
470 assert_eq!(result, vec!["", "#[crate_type = \"lib\"]", ""]);
472 let result = without_block_comments(vec!["/* rust", "", "*/"]);
473 assert!(result.is_empty());
475 let result = without_block_comments(vec!["/* one-line comment */"]);
476 assert!(result.is_empty());
478 let result = without_block_comments(vec!["/* nested", "/* multi-line", "comment", "*/", "test", "*/"]);
479 assert!(result.is_empty());
481 let result = without_block_comments(vec!["/* nested /* inline /* comment */ test */ */"]);
482 assert!(result.is_empty());
484 let result = without_block_comments(vec!["foo", "bar", "baz"]);
485 assert_eq!(result, vec!["foo", "bar", "baz"]);