src/librustdoc/passes/check_code_block_syntax.rs

   1 //! Validates syntax inside Rust code blocks (\`\`\`rust).
   2 use rustc_data_structures::sync::{Lock, Lrc};
   3 use rustc_errors::{emitter::Emitter, Applicability, Diagnostic, Handler, LazyFallbackBundle};
   4 use rustc_middle::lint::LintDiagnosticBuilder;
   5 use rustc_parse::parse_stream_from_source_str;
   6 use rustc_session::parse::ParseSess;
   7 use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId};
   8 use rustc_span::source_map::{FilePathMapping, SourceMap};
   9 use rustc_span::{FileName, InnerSpan, DUMMY_SP};
  10
  11 use crate::clean;
  12 use crate::core::DocContext;
  13 use crate::html::markdown::{self, RustCodeBlock};
  14 use crate::passes::Pass;
  15 use crate::visit::DocVisitor;
  16
  17 pub(crate) const CHECK_CODE_BLOCK_SYNTAX: Pass = Pass {
  18     name: "check-code-block-syntax",
  19     run: check_code_block_syntax,
  20     description: "validates syntax inside Rust code blocks",
  21 };
  22
  23 pub(crate) fn check_code_block_syntax(
  24     krate: clean::Crate,
  25     cx: &mut DocContext<'_>,
  26 ) -> clean::Crate {
  27     SyntaxChecker { cx }.visit_crate(&krate);
  28     krate
  29 }
  30
  31 struct SyntaxChecker<'a, 'tcx> {
  32     cx: &'a DocContext<'tcx>,
  33 }
  34
  35 impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
  36     fn check_rust_syntax(&self, item: &clean::Item, dox: &str, code_block: RustCodeBlock) {
  37         let buffer = Lrc::new(Lock::new(Buffer::default()));
  38         let fallback_bundle =
  39             rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
  40         let emitter = BufferEmitter { buffer: Lrc::clone(&buffer), fallback_bundle };
  41
  42         let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
  43         let handler = Handler::with_emitter(false, None, Box::new(emitter));
  44         let source = dox[code_block.code].to_owned();
  45         let sess = ParseSess::with_span_handler(handler, sm);
  46
  47         let edition = code_block.lang_string.edition.unwrap_or_else(|| self.cx.tcx.sess.edition());
  48         let expn_data = ExpnData::default(
  49             ExpnKind::AstPass(AstPass::TestHarness),
  50             DUMMY_SP,
  51             edition,
  52             None,
  53             None,
  54         );
  55         let expn_id = LocalExpnId::fresh(expn_data, self.cx.tcx.create_stable_hashing_context());
  56         let span = DUMMY_SP.fresh_expansion(expn_id);
  57
  58         let is_empty = rustc_driver::catch_fatal_errors(|| {
  59             parse_stream_from_source_str(
  60                 FileName::Custom(String::from("doctest")),
  61                 source,
  62                 &sess,
  63                 Some(span),
  64             )
  65             .is_empty()
  66         })
  67         .unwrap_or(false);
  68         let buffer = buffer.borrow();
  69
  70         if !buffer.has_errors && !is_empty {
  71             // No errors in a non-empty program.
  72             return;
  73         }
  74
  75         let Some(local_id) = item.item_id.as_def_id().and_then(|x| x.as_local())
  76         else {
  77             // We don't need to check the syntax for other crates so returning
  78             // without doing anything should not be a problem.
  79             return;
  80         };
  81
  82         let hir_id = self.cx.tcx.hir().local_def_id_to_hir_id(local_id);
  83         let empty_block = code_block.lang_string == Default::default() && code_block.is_fenced;
  84         let is_ignore = code_block.lang_string.ignore != markdown::Ignore::None;
  85
  86         // The span and whether it is precise or not.
  87         let (sp, precise_span) = match super::source_span_for_markdown_range(
  88             self.cx.tcx,
  89             dox,
  90             &code_block.range,
  91             &item.attrs,
  92         ) {
  93             Some(sp) => (sp, true),
  94             None => (item.attr_span(self.cx.tcx), false),
  95         };
  96
  97         // lambda that will use the lint to start a new diagnostic and add
  98         // a suggestion to it when needed.
  99         let diag_builder = |lint: LintDiagnosticBuilder<'_, ()>| {
 100             let explanation = if is_ignore {
 101                 "`ignore` code blocks require valid Rust code for syntax highlighting; \
 102                     mark blocks that do not contain Rust code as text"
 103             } else {
 104                 "mark blocks that do not contain Rust code as text"
 105             };
 106             let msg = if buffer.has_errors {
 107                 "could not parse code block as Rust code"
 108             } else {
 109                 "Rust code block is empty"
 110             };
 111             let mut diag = lint.build(msg);
 112
 113             if precise_span {
 114                 if is_ignore {
 115                     // giving an accurate suggestion is hard because `ignore` might not have come first in the list.
 116                     // just give a `help` instead.
 117                     diag.span_help(
 118                         sp.from_inner(InnerSpan::new(0, 3)),
 119                         &format!("{}: ```text", explanation),
 120                     );
 121                 } else if empty_block {
 122                     diag.span_suggestion(
 123                         sp.from_inner(InnerSpan::new(0, 3)).shrink_to_hi(),
 124                         explanation,
 125                         "text",
 126                         Applicability::MachineApplicable,
 127                     );
 128                 }
 129             } else if empty_block || is_ignore {
 130                 diag.help(&format!("{}: ```text", explanation));
 131             }
 132
 133             // FIXME(#67563): Provide more context for these errors by displaying the spans inline.
 134             for message in buffer.messages.iter() {
 135                 diag.note(message);
 136             }
 137
 138             diag.emit();
 139         };
 140
 141         // Finally build and emit the completed diagnostic.
 142         // All points of divergence have been handled earlier so this can be
 143         // done the same way whether the span is precise or not.
 144         self.cx.tcx.struct_span_lint_hir(
 145             crate::lint::INVALID_RUST_CODEBLOCKS,
 146             hir_id,
 147             sp,
 148             diag_builder,
 149         );
 150     }
 151 }
 152
 153 impl<'a, 'tcx> DocVisitor for SyntaxChecker<'a, 'tcx> {
 154     fn visit_item(&mut self, item: &clean::Item) {
 155         if let Some(dox) = &item.attrs.collapsed_doc_value() {
 156             let sp = item.attr_span(self.cx.tcx);
 157             let extra = crate::html::markdown::ExtraInfo::new_did(
 158                 self.cx.tcx,
 159                 item.item_id.expect_def_id(),
 160                 sp,
 161             );
 162             for code_block in markdown::rust_code_blocks(dox, &extra) {
 163                 self.check_rust_syntax(item, dox, code_block);
 164             }
 165         }
 166
 167         self.visit_item_recur(item)
 168     }
 169 }
 170
 171 #[derive(Default)]
 172 struct Buffer {
 173     messages: Vec<String>,
 174     has_errors: bool,
 175 }
 176
 177 struct BufferEmitter {
 178     buffer: Lrc<Lock<Buffer>>,
 179     fallback_bundle: LazyFallbackBundle,
 180 }
 181
 182 impl Emitter for BufferEmitter {
 183     fn emit_diagnostic(&mut self, diag: &Diagnostic) {
 184         let mut buffer = self.buffer.borrow_mut();
 185         // FIXME(davidtwco): need to support translation here eventually
 186         buffer.messages.push(format!("error from rustc: {}", diag.message[0].0.expect_str()));
 187         if diag.is_error() {
 188             buffer.has_errors = true;
 189         }
 190     }
 191
 192     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
 193         None
 194     }
 195
 196     fn fluent_bundle(&self) -> Option<&Lrc<rustc_errors::FluentBundle>> {
 197         None
 198     }
 199
 200     fn fallback_fluent_bundle(&self) -> &rustc_errors::FluentBundle {
 201         &**self.fallback_bundle
 202     }
 203 }