rust-clippy/clippy_lints/src/doc.rs
2021-03-29 17:20:04 +09:00

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use clippy_utils::diagnostics::{span_lint, span_lint_and_note};
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
use clippy_utils::{is_entrypoint_fn, is_expn_of, match_panic_def_id, method_chain_args, return_ty};
use if_chain::if_chain;
use itertools::Itertools;
use rustc_ast::ast::{Async, AttrKind, Attribute, FnKind, FnRetTy, ItemKind};
use rustc_ast::token::CommentKind;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::sync::Lrc;
use rustc_errors::emitter::EmitterWriter;
use rustc_errors::Handler;
use rustc_hir as hir;
use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_hir::{Expr, ExprKind, QPath};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::hir::map::Map;
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty;
use rustc_parse::maybe_new_parser_from_source_str;
use rustc_parse::parser::ForceCollect;
use rustc_session::parse::ParseSess;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::edition::Edition;
use rustc_span::source_map::{BytePos, FilePathMapping, MultiSpan, SourceMap, Span};
use rustc_span::{sym, FileName, Pos};
use std::io;
use std::ops::Range;
use url::Url;
declare_clippy_lint! {
/// **What it does:** Checks for the presence of `_`, `::` or camel-case words
/// outside ticks in documentation.
///
/// **Why is this bad?** *Rustdoc* supports markdown formatting, `_`, `::` and
/// camel-case probably indicates some code which should be included between
/// ticks. `_` can also be used for emphasis in markdown, this lint tries to
/// consider that.
///
/// **Known problems:** Lots of bad docs wont be fixed, what the lint checks
/// for is limited, and there are still false positives.
///
/// In addition, when writing documentation comments, including `[]` brackets
/// inside a link text would trip the parser. Therfore, documenting link with
/// `[`SmallVec<[T; INLINE_CAPACITY]>`]` and then [`SmallVec<[T; INLINE_CAPACITY]>`]: SmallVec
/// would fail.
///
/// **Examples:**
/// ```rust
/// /// Do something with the foo_bar parameter. See also
/// /// that::other::module::foo.
/// // ^ `foo_bar` and `that::other::module::foo` should be ticked.
/// fn doit(foo_bar: usize) {}
/// ```
///
/// ```rust
/// // Link text with `[]` brackets should be written as following:
/// /// Consume the array and return the inner
/// /// [`SmallVec<[T; INLINE_CAPACITY]>`][SmallVec].
/// /// [SmallVec]: SmallVec
/// fn main() {}
/// ```
pub DOC_MARKDOWN,
pedantic,
"presence of `_`, `::` or camel-case outside backticks in documentation"
}
declare_clippy_lint! {
/// **What it does:** Checks for the doc comments of publicly visible
/// unsafe functions and warns if there is no `# Safety` section.
///
/// **Why is this bad?** Unsafe functions should document their safety
/// preconditions, so that users can be sure they are using them safely.
///
/// **Known problems:** None.
///
/// **Examples:**
/// ```rust
///# type Universe = ();
/// /// This function should really be documented
/// pub unsafe fn start_apocalypse(u: &mut Universe) {
/// unimplemented!();
/// }
/// ```
///
/// At least write a line about safety:
///
/// ```rust
///# type Universe = ();
/// /// # Safety
/// ///
/// /// This function should not be called before the horsemen are ready.
/// pub unsafe fn start_apocalypse(u: &mut Universe) {
/// unimplemented!();
/// }
/// ```
pub MISSING_SAFETY_DOC,
style,
"`pub unsafe fn` without `# Safety` docs"
}
declare_clippy_lint! {
/// **What it does:** Checks the doc comments of publicly visible functions that
/// return a `Result` type and warns if there is no `# Errors` section.
///
/// **Why is this bad?** Documenting the type of errors that can be returned from a
/// function can help callers write code to handle the errors appropriately.
///
/// **Known problems:** None.
///
/// **Examples:**
///
/// Since the following function returns a `Result` it has an `# Errors` section in
/// its doc comment:
///
/// ```rust
///# use std::io;
/// /// # Errors
/// ///
/// /// Will return `Err` if `filename` does not exist or the user does not have
/// /// permission to read it.
/// pub fn read(filename: String) -> io::Result<String> {
/// unimplemented!();
/// }
/// ```
pub MISSING_ERRORS_DOC,
pedantic,
"`pub fn` returns `Result` without `# Errors` in doc comment"
}
declare_clippy_lint! {
/// **What it does:** Checks the doc comments of publicly visible functions that
/// may panic and warns if there is no `# Panics` section.
///
/// **Why is this bad?** Documenting the scenarios in which panicking occurs
/// can help callers who do not want to panic to avoid those situations.
///
/// **Known problems:** None.
///
/// **Examples:**
///
/// Since the following function may panic it has a `# Panics` section in
/// its doc comment:
///
/// ```rust
/// /// # Panics
/// ///
/// /// Will panic if y is 0
/// pub fn divide_by(x: i32, y: i32) -> i32 {
/// if y == 0 {
/// panic!("Cannot divide by 0")
/// } else {
/// x / y
/// }
/// }
/// ```
pub MISSING_PANICS_DOC,
pedantic,
"`pub fn` may panic without `# Panics` in doc comment"
}
declare_clippy_lint! {
/// **What it does:** Checks for `fn main() { .. }` in doctests
///
/// **Why is this bad?** The test can be shorter (and likely more readable)
/// if the `fn main()` is left implicit.
///
/// **Known problems:** None.
///
/// **Examples:**
/// ``````rust
/// /// An example of a doctest with a `main()` function
/// ///
/// /// # Examples
/// ///
/// /// ```
/// /// fn main() {
/// /// // this needs not be in an `fn`
/// /// }
/// /// ```
/// fn needless_main() {
/// unimplemented!();
/// }
/// ``````
pub NEEDLESS_DOCTEST_MAIN,
style,
"presence of `fn main() {` in code examples"
}
#[allow(clippy::module_name_repetitions)]
#[derive(Clone)]
pub struct DocMarkdown {
valid_idents: FxHashSet<String>,
in_trait_impl: bool,
}
impl DocMarkdown {
pub fn new(valid_idents: FxHashSet<String>) -> Self {
Self {
valid_idents,
in_trait_impl: false,
}
}
}
impl_lint_pass!(DocMarkdown =>
[DOC_MARKDOWN, MISSING_SAFETY_DOC, MISSING_ERRORS_DOC, MISSING_PANICS_DOC, NEEDLESS_DOCTEST_MAIN]
);
impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
fn check_crate(&mut self, cx: &LateContext<'tcx>, _: &'tcx hir::Crate<'_>) {
let attrs = cx.tcx.hir().attrs(hir::CRATE_HIR_ID);
check_attrs(cx, &self.valid_idents, attrs);
}
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
let attrs = cx.tcx.hir().attrs(item.hir_id());
let headers = check_attrs(cx, &self.valid_idents, attrs);
match item.kind {
hir::ItemKind::Fn(ref sig, _, body_id) => {
if !(is_entrypoint_fn(cx, item.def_id.to_def_id()) || in_external_macro(cx.tcx.sess, item.span)) {
let body = cx.tcx.hir().body(body_id);
let mut fpu = FindPanicUnwrap {
cx,
typeck_results: cx.tcx.typeck(item.def_id),
panic_span: None,
};
fpu.visit_expr(&body.value);
lint_for_missing_headers(
cx,
item.hir_id(),
item.span,
sig,
headers,
Some(body_id),
fpu.panic_span,
);
}
},
hir::ItemKind::Impl(ref impl_) => {
self.in_trait_impl = impl_.of_trait.is_some();
},
_ => {},
}
}
fn check_item_post(&mut self, _cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
if let hir::ItemKind::Impl { .. } = item.kind {
self.in_trait_impl = false;
}
}
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
let attrs = cx.tcx.hir().attrs(item.hir_id());
let headers = check_attrs(cx, &self.valid_idents, attrs);
if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
if !in_external_macro(cx.tcx.sess, item.span) {
lint_for_missing_headers(cx, item.hir_id(), item.span, sig, headers, None, None);
}
}
}
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
let attrs = cx.tcx.hir().attrs(item.hir_id());
let headers = check_attrs(cx, &self.valid_idents, attrs);
if self.in_trait_impl || in_external_macro(cx.tcx.sess, item.span) {
return;
}
if let hir::ImplItemKind::Fn(ref sig, body_id) = item.kind {
let body = cx.tcx.hir().body(body_id);
let mut fpu = FindPanicUnwrap {
cx,
typeck_results: cx.tcx.typeck(item.def_id),
panic_span: None,
};
fpu.visit_expr(&body.value);
lint_for_missing_headers(
cx,
item.hir_id(),
item.span,
sig,
headers,
Some(body_id),
fpu.panic_span,
);
}
}
}
fn lint_for_missing_headers<'tcx>(
cx: &LateContext<'tcx>,
hir_id: hir::HirId,
span: impl Into<MultiSpan> + Copy,
sig: &hir::FnSig<'_>,
headers: DocHeaders,
body_id: Option<hir::BodyId>,
panic_span: Option<Span>,
) {
if !cx.access_levels.is_exported(hir_id) {
return; // Private functions do not require doc comments
}
if !headers.safety && sig.header.unsafety == hir::Unsafety::Unsafe {
span_lint(
cx,
MISSING_SAFETY_DOC,
span,
"unsafe function's docs miss `# Safety` section",
);
}
if !headers.panics && panic_span.is_some() {
span_lint_and_note(
cx,
MISSING_PANICS_DOC,
span,
"docs for function which may panic missing `# Panics` section",
panic_span,
"first possible panic found here",
);
}
if !headers.errors {
if is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym::result_type) {
span_lint(
cx,
MISSING_ERRORS_DOC,
span,
"docs for function returning `Result` missing `# Errors` section",
);
} else {
if_chain! {
if let Some(body_id) = body_id;
if let Some(future) = cx.tcx.lang_items().future_trait();
let typeck = cx.tcx.typeck_body(body_id);
let body = cx.tcx.hir().body(body_id);
let ret_ty = typeck.expr_ty(&body.value);
if implements_trait(cx, ret_ty, future, &[]);
if let ty::Opaque(_, subs) = ret_ty.kind();
if let Some(gen) = subs.types().next();
if let ty::Generator(_, subs, _) = gen.kind();
if is_type_diagnostic_item(cx, subs.as_generator().return_ty(), sym::result_type);
then {
span_lint(
cx,
MISSING_ERRORS_DOC,
span,
"docs for function returning `Result` missing `# Errors` section",
);
}
}
}
}
}
/// Cleanup documentation decoration.
///
/// We can't use `rustc_ast::attr::AttributeMethods::with_desugared_doc` or
/// `rustc_ast::parse::lexer::comments::strip_doc_comment_decoration` because we
/// need to keep track of
/// the spans but this function is inspired from the later.
#[allow(clippy::cast_possible_truncation)]
#[must_use]
pub fn strip_doc_comment_decoration(doc: &str, comment_kind: CommentKind, span: Span) -> (String, Vec<(usize, Span)>) {
// one-line comments lose their prefix
if comment_kind == CommentKind::Line {
let mut doc = doc.to_owned();
doc.push('\n');
let len = doc.len();
// +3 skips the opening delimiter
return (doc, vec![(len, span.with_lo(span.lo() + BytePos(3)))]);
}
let mut sizes = vec![];
let mut contains_initial_stars = false;
for line in doc.lines() {
let offset = line.as_ptr() as usize - doc.as_ptr() as usize;
debug_assert_eq!(offset as u32 as usize, offset);
contains_initial_stars |= line.trim_start().starts_with('*');
// +1 adds the newline, +3 skips the opening delimiter
sizes.push((line.len() + 1, span.with_lo(span.lo() + BytePos(3 + offset as u32))));
}
if !contains_initial_stars {
return (doc.to_string(), sizes);
}
// remove the initial '*'s if any
let mut no_stars = String::with_capacity(doc.len());
for line in doc.lines() {
let mut chars = line.chars();
while let Some(c) = chars.next() {
if c.is_whitespace() {
no_stars.push(c);
} else {
no_stars.push(if c == '*' { ' ' } else { c });
break;
}
}
no_stars.push_str(chars.as_str());
no_stars.push('\n');
}
(no_stars, sizes)
}
#[derive(Copy, Clone)]
struct DocHeaders {
safety: bool,
errors: bool,
panics: bool,
}
fn check_attrs<'a>(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, attrs: &'a [Attribute]) -> DocHeaders {
let mut doc = String::new();
let mut spans = vec![];
for attr in attrs {
if let AttrKind::DocComment(comment_kind, comment) = attr.kind {
let (comment, current_spans) = strip_doc_comment_decoration(&comment.as_str(), comment_kind, attr.span);
spans.extend_from_slice(&current_spans);
doc.push_str(&comment);
} else if attr.has_name(sym::doc) {
// ignore mix of sugared and non-sugared doc
// don't trigger the safety or errors check
return DocHeaders {
safety: true,
errors: true,
panics: true,
};
}
}
let mut current = 0;
for &mut (ref mut offset, _) in &mut spans {
let offset_copy = *offset;
*offset = current;
current += offset_copy;
}
if doc.is_empty() {
return DocHeaders {
safety: false,
errors: false,
panics: false,
};
}
let parser = pulldown_cmark::Parser::new(&doc).into_offset_iter();
// Iterate over all `Events` and combine consecutive events into one
let events = parser.coalesce(|previous, current| {
use pulldown_cmark::Event::Text;
let previous_range = previous.1;
let current_range = current.1;
match (previous.0, current.0) {
(Text(previous), Text(current)) => {
let mut previous = previous.to_string();
previous.push_str(&current);
Ok((Text(previous.into()), previous_range))
},
(previous, current) => Err(((previous, previous_range), (current, current_range))),
}
});
check_doc(cx, valid_idents, events, &spans)
}
const RUST_CODE: &[&str] = &["rust", "no_run", "should_panic", "compile_fail"];
fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize>)>>(
cx: &LateContext<'_>,
valid_idents: &FxHashSet<String>,
events: Events,
spans: &[(usize, Span)],
) -> DocHeaders {
// true if a safety header was found
use pulldown_cmark::CodeBlockKind;
use pulldown_cmark::Event::{
Code, End, FootnoteReference, HardBreak, Html, Rule, SoftBreak, Start, TaskListMarker, Text,
};
use pulldown_cmark::Tag::{CodeBlock, Heading, Link};
let mut headers = DocHeaders {
safety: false,
errors: false,
panics: false,
};
let mut in_code = false;
let mut in_link = None;
let mut in_heading = false;
let mut is_rust = false;
let mut edition = None;
for (event, range) in events {
match event {
Start(CodeBlock(ref kind)) => {
in_code = true;
if let CodeBlockKind::Fenced(lang) = kind {
for item in lang.split(',') {
if item == "ignore" {
is_rust = false;
break;
}
if let Some(stripped) = item.strip_prefix("edition") {
is_rust = true;
edition = stripped.parse::<Edition>().ok();
} else if item.is_empty() || RUST_CODE.contains(&item) {
is_rust = true;
}
}
}
},
End(CodeBlock(_)) => {
in_code = false;
is_rust = false;
},
Start(Link(_, url, _)) => in_link = Some(url),
End(Link(..)) => in_link = None,
Start(Heading(_)) => in_heading = true,
End(Heading(_)) => in_heading = false,
Start(_tag) | End(_tag) => (), // We don't care about other tags
Html(_html) => (), // HTML is weird, just ignore it
SoftBreak | HardBreak | TaskListMarker(_) | Code(_) | Rule => (),
FootnoteReference(text) | Text(text) => {
if Some(&text) == in_link.as_ref() {
// Probably a link of the form `<http://example.com>`
// Which are represented as a link to "http://example.com" with
// text "http://example.com" by pulldown-cmark
continue;
}
headers.safety |= in_heading && text.trim() == "Safety";
headers.errors |= in_heading && text.trim() == "Errors";
headers.panics |= in_heading && text.trim() == "Panics";
let index = match spans.binary_search_by(|c| c.0.cmp(&range.start)) {
Ok(o) => o,
Err(e) => e - 1,
};
let (begin, span) = spans[index];
if in_code {
if is_rust {
let edition = edition.unwrap_or_else(|| cx.tcx.sess.edition());
check_code(cx, &text, edition, span);
}
} else {
// Adjust for the beginning of the current `Event`
let span = span.with_lo(span.lo() + BytePos::from_usize(range.start - begin));
check_text(cx, valid_idents, &text, span);
}
},
}
}
headers
}
fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
fn has_needless_main(code: &str, edition: Edition) -> bool {
rustc_driver::catch_fatal_errors(|| {
rustc_span::with_session_globals(edition, || {
let filename = FileName::anon_source_code(code);
let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
let emitter = EmitterWriter::new(box io::sink(), None, false, false, false, None, false);
let handler = Handler::with_emitter(false, None, box emitter);
let sess = ParseSess::with_span_handler(handler, sm);
let mut parser = match maybe_new_parser_from_source_str(&sess, filename, code.into()) {
Ok(p) => p,
Err(errs) => {
for mut err in errs {
err.cancel();
}
return false;
},
};
let mut relevant_main_found = false;
loop {
match parser.parse_item(ForceCollect::No) {
Ok(Some(item)) => match &item.kind {
// Tests with one of these items are ignored
ItemKind::Static(..)
| ItemKind::Const(..)
| ItemKind::ExternCrate(..)
| ItemKind::ForeignMod(..) => return false,
// We found a main function ...
ItemKind::Fn(box FnKind(_, sig, _, Some(block))) if item.ident.name == sym::main => {
let is_async = matches!(sig.header.asyncness, Async::Yes { .. });
let returns_nothing = match &sig.decl.output {
FnRetTy::Default(..) => true,
FnRetTy::Ty(ty) if ty.kind.is_unit() => true,
FnRetTy::Ty(_) => false,
};
if returns_nothing && !is_async && !block.stmts.is_empty() {
// This main function should be linted, but only if there are no other functions
relevant_main_found = true;
} else {
// This main function should not be linted, we're done
return false;
}
},
// Another function was found; this case is ignored too
ItemKind::Fn(..) => return false,
_ => {},
},
Ok(None) => break,
Err(mut e) => {
e.cancel();
return false;
},
}
}
relevant_main_found
})
})
.ok()
.unwrap_or_default()
}
if has_needless_main(text, edition) {
span_lint(cx, NEEDLESS_DOCTEST_MAIN, span, "needless `fn main` in doctest");
}
}
fn check_text(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, text: &str, span: Span) {
for word in text.split(|c: char| c.is_whitespace() || c == '\'') {
// Trim punctuation as in `some comment (see foo::bar).`
// ^^
// Or even as in `_foo bar_` which is emphasized.
let word = word.trim_matches(|c: char| !c.is_alphanumeric());
if valid_idents.contains(word) {
continue;
}
// Adjust for the current word
let offset = word.as_ptr() as usize - text.as_ptr() as usize;
let span = Span::new(
span.lo() + BytePos::from_usize(offset),
span.lo() + BytePos::from_usize(offset + word.len()),
span.ctxt(),
);
check_word(cx, word, span);
}
}
fn check_word(cx: &LateContext<'_>, word: &str, span: Span) {
/// Checks if a string is camel-case, i.e., contains at least two uppercase
/// letters (`Clippy` is ok) and one lower-case letter (`NASA` is ok).
/// Plurals are also excluded (`IDs` is ok).
fn is_camel_case(s: &str) -> bool {
if s.starts_with(|c: char| c.is_digit(10)) {
return false;
}
let s = s.strip_suffix('s').unwrap_or(s);
s.chars().all(char::is_alphanumeric)
&& s.chars().filter(|&c| c.is_uppercase()).take(2).count() > 1
&& s.chars().filter(|&c| c.is_lowercase()).take(1).count() > 0
}
fn has_underscore(s: &str) -> bool {
s != "_" && !s.contains("\\_") && s.contains('_')
}
fn has_hyphen(s: &str) -> bool {
s != "-" && s.contains('-')
}
if let Ok(url) = Url::parse(word) {
// try to get around the fact that `foo::bar` parses as a valid URL
if !url.cannot_be_a_base() {
span_lint(
cx,
DOC_MARKDOWN,
span,
"you should put bare URLs between `<`/`>` or make a proper Markdown link",
);
return;
}
}
// We assume that mixed-case words are not meant to be put inside bacticks. (Issue #2343)
if has_underscore(word) && has_hyphen(word) {
return;
}
if has_underscore(word) || word.contains("::") || is_camel_case(word) {
span_lint(
cx,
DOC_MARKDOWN,
span,
&format!("you should put `{}` between ticks in the documentation", word),
);
}
}
struct FindPanicUnwrap<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
panic_span: Option<Span>,
typeck_results: &'tcx ty::TypeckResults<'tcx>,
}
impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
type Map = Map<'tcx>;
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if self.panic_span.is_some() {
return;
}
// check for `begin_panic`
if_chain! {
if let ExprKind::Call(ref func_expr, _) = expr.kind;
if let ExprKind::Path(QPath::Resolved(_, ref path)) = func_expr.kind;
if let Some(path_def_id) = path.res.opt_def_id();
if match_panic_def_id(self.cx, path_def_id);
if is_expn_of(expr.span, "unreachable").is_none();
if !is_expn_of_debug_assertions(expr.span);
then {
self.panic_span = Some(expr.span);
}
}
// check for `unwrap`
if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
let reciever_ty = self.typeck_results.expr_ty(&arglists[0][0]).peel_refs();
if is_type_diagnostic_item(self.cx, reciever_ty, sym::option_type)
|| is_type_diagnostic_item(self.cx, reciever_ty, sym::result_type)
{
self.panic_span = Some(expr.span);
}
}
// and check sub-expressions
intravisit::walk_expr(self, expr);
}
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
}
}
fn is_expn_of_debug_assertions(span: Span) -> bool {
const MACRO_NAMES: &[&str] = &["debug_assert", "debug_assert_eq", "debug_assert_ne"];
MACRO_NAMES.iter().any(|name| is_expn_of(span, name).is_some())
}