compiler/rustc_errors/src/json.rs

   1 //! A JSON emitter for errors.
   2 //!
   3 //! This works by converting errors to a simplified structural format (see the
   4 //! structs at the start of the file) and then serializing them. These should
   5 //! contain as much information about the error as possible.
   6 //!
   7 //! The format of the JSON output should be considered *unstable*. For now the
   8 //! structs at the end of this file (Diagnostic*) specify the error format.
   9
  10 // FIXME: spec the JSON output properly.
  11
  12 use rustc_span::source_map::{FilePathMapping, SourceMap};
  13
  14 use crate::emitter::{Emitter, HumanReadableErrorType};
  15 use crate::registry::Registry;
  16 use crate::DiagnosticId;
  17 use crate::ToolMetadata;
  18 use crate::{CodeSuggestion, SubDiagnostic};
  19 use rustc_lint_defs::Applicability;
  20
  21 use rustc_data_structures::sync::Lrc;
  22 use rustc_span::hygiene::ExpnData;
  23 use rustc_span::{MultiSpan, Span, SpanLabel};
  24 use std::io::{self, Write};
  25 use std::path::Path;
  26 use std::sync::{Arc, Mutex};
  27 use std::vec;
  28
  29 use rustc_serialize::json::{as_json, as_pretty_json};
  30 use rustc_serialize::{Encodable, Encoder};
  31
  32 #[cfg(test)]
  33 mod tests;
  34
  35 pub struct JsonEmitter {
  36     dst: Box<dyn Write + Send>,
  37     registry: Option<Registry>,
  38     sm: Lrc<SourceMap>,
  39     pretty: bool,
  40     ui_testing: bool,
  41     json_rendered: HumanReadableErrorType,
  42     terminal_width: Option<usize>,
  43     macro_backtrace: bool,
  44 }
  45
  46 impl JsonEmitter {
  47     pub fn stderr(
  48         registry: Option<Registry>,
  49         source_map: Lrc<SourceMap>,
  50         pretty: bool,
  51         json_rendered: HumanReadableErrorType,
  52         terminal_width: Option<usize>,
  53         macro_backtrace: bool,
  54     ) -> JsonEmitter {
  55         JsonEmitter {
  56             dst: Box::new(io::BufWriter::new(io::stderr())),
  57             registry,
  58             sm: source_map,
  59             pretty,
  60             ui_testing: false,
  61             json_rendered,
  62             terminal_width,
  63             macro_backtrace,
  64         }
  65     }
  66
  67     pub fn basic(
  68         pretty: bool,
  69         json_rendered: HumanReadableErrorType,
  70         terminal_width: Option<usize>,
  71         macro_backtrace: bool,
  72     ) -> JsonEmitter {
  73         let file_path_mapping = FilePathMapping::empty();
  74         JsonEmitter::stderr(
  75             None,
  76             Lrc::new(SourceMap::new(file_path_mapping)),
  77             pretty,
  78             json_rendered,
  79             terminal_width,
  80             macro_backtrace,
  81         )
  82     }
  83
  84     pub fn new(
  85         dst: Box<dyn Write + Send>,
  86         registry: Option<Registry>,
  87         source_map: Lrc<SourceMap>,
  88         pretty: bool,
  89         json_rendered: HumanReadableErrorType,
  90         terminal_width: Option<usize>,
  91         macro_backtrace: bool,
  92     ) -> JsonEmitter {
  93         JsonEmitter {
  94             dst,
  95             registry,
  96             sm: source_map,
  97             pretty,
  98             ui_testing: false,
  99             json_rendered,
 100             terminal_width,
 101             macro_backtrace,
 102         }
 103     }
 104
 105     pub fn ui_testing(self, ui_testing: bool) -> Self {
 106         Self { ui_testing, ..self }
 107     }
 108 }
 109
 110 impl Emitter for JsonEmitter {
 111     fn emit_diagnostic(&mut self, diag: &crate::Diagnostic) {
 112         let data = Diagnostic::from_errors_diagnostic(diag, self);
 113         let result = if self.pretty {
 114             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
 115         } else {
 116             writeln!(&mut self.dst, "{}", as_json(&data))
 117         }
 118         .and_then(|_| self.dst.flush());
 119         if let Err(e) = result {
 120             panic!("failed to print diagnostics: {:?}", e);
 121         }
 122     }
 123
 124     fn emit_artifact_notification(&mut self, path: &Path, artifact_type: &str) {
 125         let data = ArtifactNotification { artifact: path, emit: artifact_type };
 126         let result = if self.pretty {
 127             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
 128         } else {
 129             writeln!(&mut self.dst, "{}", as_json(&data))
 130         }
 131         .and_then(|_| self.dst.flush());
 132         if let Err(e) = result {
 133             panic!("failed to print notification: {:?}", e);
 134         }
 135     }
 136
 137     fn emit_future_breakage_report(&mut self, diags: Vec<crate::Diagnostic>) {
 138         let data: Vec<FutureBreakageItem> = diags
 139             .into_iter()
 140             .map(|mut diag| {
 141                 if diag.level == crate::Level::Allow {
 142                     diag.level = crate::Level::Warning;
 143                 }
 144                 FutureBreakageItem { diagnostic: Diagnostic::from_errors_diagnostic(&diag, self) }
 145             })
 146             .collect();
 147         let report = FutureIncompatReport { future_incompat_report: data };
 148         let result = if self.pretty {
 149             writeln!(&mut self.dst, "{}", as_pretty_json(&report))
 150         } else {
 151             writeln!(&mut self.dst, "{}", as_json(&report))
 152         }
 153         .and_then(|_| self.dst.flush());
 154         if let Err(e) = result {
 155             panic!("failed to print future breakage report: {:?}", e);
 156         }
 157     }
 158
 159     fn emit_unused_externs(&mut self, lint_level: &str, unused_externs: &[&str]) {
 160         let data = UnusedExterns { lint_level, unused_extern_names: unused_externs };
 161         let result = if self.pretty {
 162             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
 163         } else {
 164             writeln!(&mut self.dst, "{}", as_json(&data))
 165         }
 166         .and_then(|_| self.dst.flush());
 167         if let Err(e) = result {
 168             panic!("failed to print unused externs: {:?}", e);
 169         }
 170     }
 171
 172     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
 173         Some(&self.sm)
 174     }
 175
 176     fn should_show_explain(&self) -> bool {
 177         !matches!(self.json_rendered, HumanReadableErrorType::Short(_))
 178     }
 179 }
 180
 181 // The following data types are provided just for serialisation.
 182
 183 // NOTE: this has a manual implementation of Encodable which needs to be updated in
 184 // parallel.
 185 struct Diagnostic {
 186     /// The primary error message.
 187     message: String,
 188     code: Option<DiagnosticCode>,
 189     /// "error: internal compiler error", "error", "warning", "note", "help".
 190     level: &'static str,
 191     spans: Vec<DiagnosticSpan>,
 192     /// Associated diagnostic messages.
 193     children: Vec<Diagnostic>,
 194     /// The message as rustc would render it.
 195     rendered: Option<String>,
 196     /// Extra tool metadata
 197     tool_metadata: ToolMetadata,
 198 }
 199
 200 macro_rules! encode_fields {
 201     (
 202         $enc:expr,                  // encoder
 203         $idx:expr,                  // starting field index
 204         $struct:expr,               // struct we're serializing
 205         $struct_name:ident,         // struct name
 206         [ $($name:ident),+$(,)? ],  // fields to encode
 207         [ $($ignore:ident),+$(,)? ] // fields we're skipping
 208     ) => {
 209         {
 210             // Pattern match to make sure all fields are accounted for
 211             let $struct_name { $($name,)+ $($ignore: _,)+ } = $struct;
 212             let mut idx = $idx;
 213             $(
 214                 $enc.emit_struct_field(
 215                     stringify!($name),
 216                     idx == 0,
 217                     |enc| $name.encode(enc),
 218                 )?;
 219                 idx += 1;
 220             )+
 221             idx
 222         }
 223     };
 224 }
 225
 226 // Special-case encoder to skip tool_metadata if not set
 227 impl<E: Encoder> Encodable<E> for Diagnostic {
 228     fn encode(&self, s: &mut E) -> Result<(), E::Error> {
 229         s.emit_struct(false, |s| {
 230             let mut idx = 0;
 231
 232             idx = encode_fields!(
 233                 s,
 234                 idx,
 235                 self,
 236                 Self,
 237                 [message, code, level, spans, children, rendered],
 238                 [tool_metadata]
 239             );
 240             if self.tool_metadata.is_set() {
 241                 idx = encode_fields!(
 242                     s,
 243                     idx,
 244                     self,
 245                     Self,
 246                     [tool_metadata],
 247                     [message, code, level, spans, children, rendered]
 248                 );
 249             }
 250
 251             let _ = idx;
 252             Ok(())
 253         })
 254     }
 255 }
 256
 257 #[derive(Encodable)]
 258 struct DiagnosticSpan {
 259     file_name: String,
 260     byte_start: u32,
 261     byte_end: u32,
 262     /// 1-based.
 263     line_start: usize,
 264     line_end: usize,
 265     /// 1-based, character offset.
 266     column_start: usize,
 267     column_end: usize,
 268     /// Is this a "primary" span -- meaning the point, or one of the points,
 269     /// where the error occurred?
 270     is_primary: bool,
 271     /// Source text from the start of line_start to the end of line_end.
 272     text: Vec<DiagnosticSpanLine>,
 273     /// Label that should be placed at this location (if any)
 274     label: Option<String>,
 275     /// If we are suggesting a replacement, this will contain text
 276     /// that should be sliced in atop this span.
 277     suggested_replacement: Option<String>,
 278     /// If the suggestion is approximate
 279     suggestion_applicability: Option<Applicability>,
 280     /// Macro invocations that created the code at this span, if any.
 281     expansion: Option<Box<DiagnosticSpanMacroExpansion>>,
 282 }
 283
 284 #[derive(Encodable)]
 285 struct DiagnosticSpanLine {
 286     text: String,
 287
 288     /// 1-based, character offset in self.text.
 289     highlight_start: usize,
 290
 291     highlight_end: usize,
 292 }
 293
 294 #[derive(Encodable)]
 295 struct DiagnosticSpanMacroExpansion {
 296     /// span where macro was applied to generate this code; note that
 297     /// this may itself derive from a macro (if
 298     /// `span.expansion.is_some()`)
 299     span: DiagnosticSpan,
 300
 301     /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
 302     macro_decl_name: String,
 303
 304     /// span where macro was defined (if known)
 305     def_site_span: DiagnosticSpan,
 306 }
 307
 308 #[derive(Encodable)]
 309 struct DiagnosticCode {
 310     /// The code itself.
 311     code: String,
 312     /// An explanation for the code.
 313     explanation: Option<&'static str>,
 314 }
 315
 316 #[derive(Encodable)]
 317 struct ArtifactNotification<'a> {
 318     /// The path of the artifact.
 319     artifact: &'a Path,
 320     /// What kind of artifact we're emitting.
 321     emit: &'a str,
 322 }
 323
 324 #[derive(Encodable)]
 325 struct FutureBreakageItem {
 326     diagnostic: Diagnostic,
 327 }
 328
 329 #[derive(Encodable)]
 330 struct FutureIncompatReport {
 331     future_incompat_report: Vec<FutureBreakageItem>,
 332 }
 333
 334 // NOTE: Keep this in sync with the equivalent structs in rustdoc's
 335 // doctest component (as well as cargo).
 336 // We could unify this struct the one in rustdoc but they have different
 337 // ownership semantics, so doing so would create wasteful allocations.
 338 #[derive(Encodable)]
 339 struct UnusedExterns<'a, 'b, 'c> {
 340     /// The severity level of the unused dependencies lint
 341     lint_level: &'a str,
 342     /// List of unused externs by their names.
 343     unused_extern_names: &'b [&'c str],
 344 }
 345
 346 impl Diagnostic {
 347     fn from_errors_diagnostic(diag: &crate::Diagnostic, je: &JsonEmitter) -> Diagnostic {
 348         let sugg = diag.suggestions.iter().map(|sugg| Diagnostic {
 349             message: sugg.msg.clone(),
 350             code: None,
 351             level: "help",
 352             spans: DiagnosticSpan::from_suggestion(sugg, je),
 353             children: vec![],
 354             rendered: None,
 355             tool_metadata: sugg.tool_metadata.clone(),
 356         });
 357
 358         // generate regular command line output and store it in the json
 359
 360         // A threadsafe buffer for writing.
 361         #[derive(Default, Clone)]
 362         struct BufWriter(Arc<Mutex<Vec<u8>>>);
 363
 364         impl Write for BufWriter {
 365             fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 366                 self.0.lock().unwrap().write(buf)
 367             }
 368             fn flush(&mut self) -> io::Result<()> {
 369                 self.0.lock().unwrap().flush()
 370             }
 371         }
 372         let buf = BufWriter::default();
 373         let output = buf.clone();
 374         je.json_rendered
 375             .new_emitter(
 376                 Box::new(buf),
 377                 Some(je.sm.clone()),
 378                 false,
 379                 je.terminal_width,
 380                 je.macro_backtrace,
 381             )
 382             .ui_testing(je.ui_testing)
 383             .emit_diagnostic(diag);
 384         let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
 385         let output = String::from_utf8(output).unwrap();
 386
 387         Diagnostic {
 388             message: diag.message(),
 389             code: DiagnosticCode::map_opt_string(diag.code.clone(), je),
 390             level: diag.level.to_str(),
 391             spans: DiagnosticSpan::from_multispan(&diag.span, je),
 392             children: diag
 393                 .children
 394                 .iter()
 395                 .map(|c| Diagnostic::from_sub_diagnostic(c, je))
 396                 .chain(sugg)
 397                 .collect(),
 398             rendered: Some(output),
 399             tool_metadata: ToolMetadata::default(),
 400         }
 401     }
 402
 403     fn from_sub_diagnostic(diag: &SubDiagnostic, je: &JsonEmitter) -> Diagnostic {
 404         Diagnostic {
 405             message: diag.message(),
 406             code: None,
 407             level: diag.level.to_str(),
 408             spans: diag
 409                 .render_span
 410                 .as_ref()
 411                 .map(|sp| DiagnosticSpan::from_multispan(sp, je))
 412                 .unwrap_or_else(|| DiagnosticSpan::from_multispan(&diag.span, je)),
 413             children: vec![],
 414             rendered: None,
 415             tool_metadata: ToolMetadata::default(),
 416         }
 417     }
 418 }
 419
 420 impl DiagnosticSpan {
 421     fn from_span_label(
 422         span: SpanLabel,
 423         suggestion: Option<(&String, Applicability)>,
 424         je: &JsonEmitter,
 425     ) -> DiagnosticSpan {
 426         Self::from_span_etc(span.span, span.is_primary, span.label, suggestion, je)
 427     }
 428
 429     fn from_span_etc(
 430         span: Span,
 431         is_primary: bool,
 432         label: Option<String>,
 433         suggestion: Option<(&String, Applicability)>,
 434         je: &JsonEmitter,
 435     ) -> DiagnosticSpan {
 436         // obtain the full backtrace from the `macro_backtrace`
 437         // helper; in some ways, it'd be better to expand the
 438         // backtrace ourselves, but the `macro_backtrace` helper makes
 439         // some decision, such as dropping some frames, and I don't
 440         // want to duplicate that logic here.
 441         let backtrace = span.macro_backtrace();
 442         DiagnosticSpan::from_span_full(span, is_primary, label, suggestion, backtrace, je)
 443     }
 444
 445     fn from_span_full(
 446         span: Span,
 447         is_primary: bool,
 448         label: Option<String>,
 449         suggestion: Option<(&String, Applicability)>,
 450         mut backtrace: impl Iterator<Item = ExpnData>,
 451         je: &JsonEmitter,
 452     ) -> DiagnosticSpan {
 453         let start = je.sm.lookup_char_pos(span.lo());
 454         let end = je.sm.lookup_char_pos(span.hi());
 455         let backtrace_step = backtrace.next().map(|bt| {
 456             let call_site = Self::from_span_full(bt.call_site, false, None, None, backtrace, je);
 457             let def_site_span =
 458                 Self::from_span_full(bt.def_site, false, None, None, vec![].into_iter(), je);
 459             Box::new(DiagnosticSpanMacroExpansion {
 460                 span: call_site,
 461                 macro_decl_name: bt.kind.descr(),
 462                 def_site_span,
 463             })
 464         });
 465
 466         DiagnosticSpan {
 467             file_name: je.sm.filename_for_diagnostics(&start.file.name).to_string(),
 468             byte_start: start.file.original_relative_byte_pos(span.lo()).0,
 469             byte_end: start.file.original_relative_byte_pos(span.hi()).0,
 470             line_start: start.line,
 471             line_end: end.line,
 472             column_start: start.col.0 + 1,
 473             column_end: end.col.0 + 1,
 474             is_primary,
 475             text: DiagnosticSpanLine::from_span(span, je),
 476             suggested_replacement: suggestion.map(|x| x.0.clone()),
 477             suggestion_applicability: suggestion.map(|x| x.1),
 478             expansion: backtrace_step,
 479             label,
 480         }
 481     }
 482
 483     fn from_multispan(msp: &MultiSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 484         msp.span_labels()
 485             .into_iter()
 486             .map(|span_str| Self::from_span_label(span_str, None, je))
 487             .collect()
 488     }
 489
 490     fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 491         suggestion
 492             .substitutions
 493             .iter()
 494             .flat_map(|substitution| {
 495                 substitution.parts.iter().map(move |suggestion_inner| {
 496                     let span_label =
 497                         SpanLabel { span: suggestion_inner.span, is_primary: true, label: None };
 498                     DiagnosticSpan::from_span_label(
 499                         span_label,
 500                         Some((&suggestion_inner.snippet, suggestion.applicability)),
 501                         je,
 502                     )
 503                 })
 504             })
 505             .collect()
 506     }
 507 }
 508
 509 impl DiagnosticSpanLine {
 510     fn line_from_source_file(
 511         sf: &rustc_span::SourceFile,
 512         index: usize,
 513         h_start: usize,
 514         h_end: usize,
 515     ) -> DiagnosticSpanLine {
 516         DiagnosticSpanLine {
 517             text: sf.get_line(index).map_or_else(String::new, |l| l.into_owned()),
 518             highlight_start: h_start,
 519             highlight_end: h_end,
 520         }
 521     }
 522
 523     /// Creates a list of DiagnosticSpanLines from span - each line with any part
 524     /// of `span` gets a DiagnosticSpanLine, with the highlight indicating the
 525     /// `span` within the line.
 526     fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
 527         je.sm
 528             .span_to_lines(span)
 529             .map(|lines| {
 530                 // We can't get any lines if the source is unavailable.
 531                 if !je.sm.ensure_source_file_source_present(lines.file.clone()) {
 532                     return vec![];
 533                 }
 534
 535                 let sf = &*lines.file;
 536                 lines
 537                     .lines
 538                     .iter()
 539                     .map(|line| {
 540                         DiagnosticSpanLine::line_from_source_file(
 541                             sf,
 542                             line.line_index,
 543                             line.start_col.0 + 1,
 544                             line.end_col.0 + 1,
 545                         )
 546                     })
 547                     .collect()
 548             })
 549             .unwrap_or_else(|_| vec![])
 550     }
 551 }
 552
 553 impl DiagnosticCode {
 554     fn map_opt_string(s: Option<DiagnosticId>, je: &JsonEmitter) -> Option<DiagnosticCode> {
 555         s.map(|s| {
 556             let s = match s {
 557                 DiagnosticId::Error(s) => s,
 558                 DiagnosticId::Lint { name, .. } => name,
 559             };
 560             let je_result =
 561                 je.registry.as_ref().map(|registry| registry.try_find_description(&s)).unwrap();
 562
 563             DiagnosticCode { code: s, explanation: je_result.unwrap_or(None) }
 564         })
 565     }
 566 }