src/librustc_errors/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::{Applicability, DiagnosticId};
  17 use crate::{CodeSuggestion, SubDiagnostic};
  18
  19 use rustc_data_structures::sync::Lrc;
  20 use rustc_span::hygiene::ExpnData;
  21 use rustc_span::{MultiSpan, Span, SpanLabel};
  22 use std::io::{self, Write};
  23 use std::path::Path;
  24 use std::sync::{Arc, Mutex};
  25 use std::vec;
  26
  27 use rustc_serialize::json::{as_json, as_pretty_json};
  28
  29 #[cfg(test)]
  30 mod tests;
  31
  32 pub struct JsonEmitter {
  33     dst: Box<dyn Write + Send>,
  34     registry: Option<Registry>,
  35     sm: Lrc<SourceMap>,
  36     pretty: bool,
  37     ui_testing: bool,
  38     json_rendered: HumanReadableErrorType,
  39     macro_backtrace: bool,
  40 }
  41
  42 impl JsonEmitter {
  43     pub fn stderr(
  44         registry: Option<Registry>,
  45         source_map: Lrc<SourceMap>,
  46         pretty: bool,
  47         json_rendered: HumanReadableErrorType,
  48         macro_backtrace: bool,
  49     ) -> JsonEmitter {
  50         JsonEmitter {
  51             dst: Box::new(io::stderr()),
  52             registry,
  53             sm: source_map,
  54             pretty,
  55             ui_testing: false,
  56             json_rendered,
  57             macro_backtrace,
  58         }
  59     }
  60
  61     pub fn basic(
  62         pretty: bool,
  63         json_rendered: HumanReadableErrorType,
  64         macro_backtrace: bool,
  65     ) -> JsonEmitter {
  66         let file_path_mapping = FilePathMapping::empty();
  67         JsonEmitter::stderr(
  68             None,
  69             Lrc::new(SourceMap::new(file_path_mapping)),
  70             pretty,
  71             json_rendered,
  72             macro_backtrace,
  73         )
  74     }
  75
  76     pub fn new(
  77         dst: Box<dyn Write + Send>,
  78         registry: Option<Registry>,
  79         source_map: Lrc<SourceMap>,
  80         pretty: bool,
  81         json_rendered: HumanReadableErrorType,
  82         macro_backtrace: bool,
  83     ) -> JsonEmitter {
  84         JsonEmitter {
  85             dst,
  86             registry,
  87             sm: source_map,
  88             pretty,
  89             ui_testing: false,
  90             json_rendered,
  91             macro_backtrace,
  92         }
  93     }
  94
  95     pub fn ui_testing(self, ui_testing: bool) -> Self {
  96         Self { ui_testing, ..self }
  97     }
  98 }
  99
 100 impl Emitter for JsonEmitter {
 101     fn emit_diagnostic(&mut self, diag: &crate::Diagnostic) {
 102         let data = Diagnostic::from_errors_diagnostic(diag, self);
 103         let result = if self.pretty {
 104             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
 105         } else {
 106             writeln!(&mut self.dst, "{}", as_json(&data))
 107         };
 108         if let Err(e) = result {
 109             panic!("failed to print diagnostics: {:?}", e);
 110         }
 111     }
 112
 113     fn emit_artifact_notification(&mut self, path: &Path, artifact_type: &str) {
 114         let data = ArtifactNotification { artifact: path, emit: artifact_type };
 115         let result = if self.pretty {
 116             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
 117         } else {
 118             writeln!(&mut self.dst, "{}", as_json(&data))
 119         };
 120         if let Err(e) = result {
 121             panic!("failed to print notification: {:?}", e);
 122         }
 123     }
 124
 125     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
 126         Some(&self.sm)
 127     }
 128
 129     fn should_show_explain(&self) -> bool {
 130         match self.json_rendered {
 131             HumanReadableErrorType::Short(_) => false,
 132             _ => true,
 133         }
 134     }
 135 }
 136
 137 // The following data types are provided just for serialisation.
 138
 139 #[derive(RustcEncodable)]
 140 struct Diagnostic {
 141     /// The primary error message.
 142     message: String,
 143     code: Option<DiagnosticCode>,
 144     /// "error: internal compiler error", "error", "warning", "note", "help".
 145     level: &'static str,
 146     spans: Vec<DiagnosticSpan>,
 147     /// Associated diagnostic messages.
 148     children: Vec<Diagnostic>,
 149     /// The message as rustc would render it.
 150     rendered: Option<String>,
 151 }
 152
 153 #[derive(RustcEncodable)]
 154 struct DiagnosticSpan {
 155     file_name: String,
 156     byte_start: u32,
 157     byte_end: u32,
 158     /// 1-based.
 159     line_start: usize,
 160     line_end: usize,
 161     /// 1-based, character offset.
 162     column_start: usize,
 163     column_end: usize,
 164     /// Is this a "primary" span -- meaning the point, or one of the points,
 165     /// where the error occurred?
 166     is_primary: bool,
 167     /// Source text from the start of line_start to the end of line_end.
 168     text: Vec<DiagnosticSpanLine>,
 169     /// Label that should be placed at this location (if any)
 170     label: Option<String>,
 171     /// If we are suggesting a replacement, this will contain text
 172     /// that should be sliced in atop this span.
 173     suggested_replacement: Option<String>,
 174     /// If the suggestion is approximate
 175     suggestion_applicability: Option<Applicability>,
 176     /// Macro invocations that created the code at this span, if any.
 177     expansion: Option<Box<DiagnosticSpanMacroExpansion>>,
 178 }
 179
 180 #[derive(RustcEncodable)]
 181 struct DiagnosticSpanLine {
 182     text: String,
 183
 184     /// 1-based, character offset in self.text.
 185     highlight_start: usize,
 186
 187     highlight_end: usize,
 188 }
 189
 190 #[derive(RustcEncodable)]
 191 struct DiagnosticSpanMacroExpansion {
 192     /// span where macro was applied to generate this code; note that
 193     /// this may itself derive from a macro (if
 194     /// `span.expansion.is_some()`)
 195     span: DiagnosticSpan,
 196
 197     /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
 198     macro_decl_name: String,
 199
 200     /// span where macro was defined (if known)
 201     def_site_span: DiagnosticSpan,
 202 }
 203
 204 #[derive(RustcEncodable)]
 205 struct DiagnosticCode {
 206     /// The code itself.
 207     code: String,
 208     /// An explanation for the code.
 209     explanation: Option<&'static str>,
 210 }
 211
 212 #[derive(RustcEncodable)]
 213 struct ArtifactNotification<'a> {
 214     /// The path of the artifact.
 215     artifact: &'a Path,
 216     /// What kind of artifact we're emitting.
 217     emit: &'a str,
 218 }
 219
 220 impl Diagnostic {
 221     fn from_errors_diagnostic(diag: &crate::Diagnostic, je: &JsonEmitter) -> Diagnostic {
 222         let sugg = diag.suggestions.iter().map(|sugg| Diagnostic {
 223             message: sugg.msg.clone(),
 224             code: None,
 225             level: "help",
 226             spans: DiagnosticSpan::from_suggestion(sugg, je),
 227             children: vec![],
 228             rendered: None,
 229         });
 230
 231         // generate regular command line output and store it in the json
 232
 233         // A threadsafe buffer for writing.
 234         #[derive(Default, Clone)]
 235         struct BufWriter(Arc<Mutex<Vec<u8>>>);
 236
 237         impl Write for BufWriter {
 238             fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 239                 self.0.lock().unwrap().write(buf)
 240             }
 241             fn flush(&mut self) -> io::Result<()> {
 242                 self.0.lock().unwrap().flush()
 243             }
 244         }
 245         let buf = BufWriter::default();
 246         let output = buf.clone();
 247         je.json_rendered
 248             .new_emitter(Box::new(buf), Some(je.sm.clone()), false, None, je.macro_backtrace)
 249             .ui_testing(je.ui_testing)
 250             .emit_diagnostic(diag);
 251         let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
 252         let output = String::from_utf8(output).unwrap();
 253
 254         Diagnostic {
 255             message: diag.message(),
 256             code: DiagnosticCode::map_opt_string(diag.code.clone(), je),
 257             level: diag.level.to_str(),
 258             spans: DiagnosticSpan::from_multispan(&diag.span, je),
 259             children: diag
 260                 .children
 261                 .iter()
 262                 .map(|c| Diagnostic::from_sub_diagnostic(c, je))
 263                 .chain(sugg)
 264                 .collect(),
 265             rendered: Some(output),
 266         }
 267     }
 268
 269     fn from_sub_diagnostic(diag: &SubDiagnostic, je: &JsonEmitter) -> Diagnostic {
 270         Diagnostic {
 271             message: diag.message(),
 272             code: None,
 273             level: diag.level.to_str(),
 274             spans: diag
 275                 .render_span
 276                 .as_ref()
 277                 .map(|sp| DiagnosticSpan::from_multispan(sp, je))
 278                 .unwrap_or_else(|| DiagnosticSpan::from_multispan(&diag.span, je)),
 279             children: vec![],
 280             rendered: None,
 281         }
 282     }
 283 }
 284
 285 impl DiagnosticSpan {
 286     fn from_span_label(
 287         span: SpanLabel,
 288         suggestion: Option<(&String, Applicability)>,
 289         je: &JsonEmitter,
 290     ) -> DiagnosticSpan {
 291         Self::from_span_etc(span.span, span.is_primary, span.label, suggestion, je)
 292     }
 293
 294     fn from_span_etc(
 295         span: Span,
 296         is_primary: bool,
 297         label: Option<String>,
 298         suggestion: Option<(&String, Applicability)>,
 299         je: &JsonEmitter,
 300     ) -> DiagnosticSpan {
 301         // obtain the full backtrace from the `macro_backtrace`
 302         // helper; in some ways, it'd be better to expand the
 303         // backtrace ourselves, but the `macro_backtrace` helper makes
 304         // some decision, such as dropping some frames, and I don't
 305         // want to duplicate that logic here.
 306         let backtrace = span.macro_backtrace();
 307         DiagnosticSpan::from_span_full(span, is_primary, label, suggestion, backtrace, je)
 308     }
 309
 310     fn from_span_full(
 311         span: Span,
 312         is_primary: bool,
 313         label: Option<String>,
 314         suggestion: Option<(&String, Applicability)>,
 315         mut backtrace: impl Iterator<Item = ExpnData>,
 316         je: &JsonEmitter,
 317     ) -> DiagnosticSpan {
 318         let start = je.sm.lookup_char_pos(span.lo());
 319         let end = je.sm.lookup_char_pos(span.hi());
 320         let backtrace_step = backtrace.next().map(|bt| {
 321             let call_site = Self::from_span_full(bt.call_site, false, None, None, backtrace, je);
 322             let def_site_span =
 323                 Self::from_span_full(bt.def_site, false, None, None, vec![].into_iter(), je);
 324             Box::new(DiagnosticSpanMacroExpansion {
 325                 span: call_site,
 326                 macro_decl_name: bt.kind.descr(),
 327                 def_site_span,
 328             })
 329         });
 330
 331         DiagnosticSpan {
 332             file_name: start.file.name.to_string(),
 333             byte_start: start.file.original_relative_byte_pos(span.lo()).0,
 334             byte_end: start.file.original_relative_byte_pos(span.hi()).0,
 335             line_start: start.line,
 336             line_end: end.line,
 337             column_start: start.col.0 + 1,
 338             column_end: end.col.0 + 1,
 339             is_primary,
 340             text: DiagnosticSpanLine::from_span(span, je),
 341             suggested_replacement: suggestion.map(|x| x.0.clone()),
 342             suggestion_applicability: suggestion.map(|x| x.1),
 343             expansion: backtrace_step,
 344             label,
 345         }
 346     }
 347
 348     fn from_multispan(msp: &MultiSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 349         msp.span_labels()
 350             .into_iter()
 351             .map(|span_str| Self::from_span_label(span_str, None, je))
 352             .collect()
 353     }
 354
 355     fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 356         suggestion
 357             .substitutions
 358             .iter()
 359             .flat_map(|substitution| {
 360                 substitution.parts.iter().map(move |suggestion_inner| {
 361                     let span_label =
 362                         SpanLabel { span: suggestion_inner.span, is_primary: true, label: None };
 363                     DiagnosticSpan::from_span_label(
 364                         span_label,
 365                         Some((&suggestion_inner.snippet, suggestion.applicability)),
 366                         je,
 367                     )
 368                 })
 369             })
 370             .collect()
 371     }
 372 }
 373
 374 impl DiagnosticSpanLine {
 375     fn line_from_source_file(
 376         sf: &rustc_span::SourceFile,
 377         index: usize,
 378         h_start: usize,
 379         h_end: usize,
 380     ) -> DiagnosticSpanLine {
 381         DiagnosticSpanLine {
 382             text: sf.get_line(index).map_or(String::new(), |l| l.into_owned()),
 383             highlight_start: h_start,
 384             highlight_end: h_end,
 385         }
 386     }
 387
 388     /// Creates a list of DiagnosticSpanLines from span - each line with any part
 389     /// of `span` gets a DiagnosticSpanLine, with the highlight indicating the
 390     /// `span` within the line.
 391     fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
 392         je.sm
 393             .span_to_lines(span)
 394             .map(|lines| {
 395                 let sf = &*lines.file;
 396                 lines
 397                     .lines
 398                     .iter()
 399                     .map(|line| {
 400                         DiagnosticSpanLine::line_from_source_file(
 401                             sf,
 402                             line.line_index,
 403                             line.start_col.0 + 1,
 404                             line.end_col.0 + 1,
 405                         )
 406                     })
 407                     .collect()
 408             })
 409             .unwrap_or_else(|_| vec![])
 410     }
 411 }
 412
 413 impl DiagnosticCode {
 414     fn map_opt_string(s: Option<DiagnosticId>, je: &JsonEmitter) -> Option<DiagnosticCode> {
 415         s.map(|s| {
 416             let s = match s {
 417                 DiagnosticId::Error(s) => s,
 418                 DiagnosticId::Lint(s) => s,
 419             };
 420             let explanation =
 421                 je.registry.as_ref().and_then(|registry| registry.find_description(&s));
 422
 423             DiagnosticCode { code: s, explanation }
 424         })
 425     }
 426 }