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