src/libsyntax/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 crate::source_map::{SourceMap, FilePathMapping};
  13
  14 use errors::registry::Registry;
  15 use errors::{SubDiagnostic, CodeSuggestion, SourceMapper};
  16 use errors::{DiagnosticId, Applicability};
  17 use errors::emitter::{Emitter, HumanReadableErrorType};
  18
  19 use syntax_pos::{MacroBacktrace, Span, SpanLabel, MultiSpan};
  20 use rustc_data_structures::sync::{self, Lrc};
  21 use std::io::{self, Write};
  22 use std::path::Path;
  23 use std::vec;
  24 use std::sync::{Arc, Mutex};
  25
  26 use rustc_serialize::json::{as_json, as_pretty_json};
  27
  28 pub struct JsonEmitter {
  29     dst: Box<dyn Write + Send>,
  30     registry: Option<Registry>,
  31     sm: Lrc<dyn SourceMapper + sync::Send + sync::Sync>,
  32     pretty: bool,
  33     ui_testing: bool,
  34     json_rendered: HumanReadableErrorType,
  35     external_macro_backtrace: bool,
  36 }
  37
  38 impl JsonEmitter {
  39     pub fn stderr(
  40         registry: Option<Registry>,
  41         source_map: Lrc<SourceMap>,
  42         pretty: bool,
  43         json_rendered: HumanReadableErrorType,
  44         external_macro_backtrace: bool,
  45     ) -> JsonEmitter {
  46         JsonEmitter {
  47             dst: Box::new(io::stderr()),
  48             registry,
  49             sm: source_map,
  50             pretty,
  51             ui_testing: false,
  52             json_rendered,
  53             external_macro_backtrace,
  54         }
  55     }
  56
  57     pub fn basic(
  58         pretty: bool,
  59         json_rendered: HumanReadableErrorType,
  60         external_macro_backtrace: bool,
  61     ) -> JsonEmitter {
  62         let file_path_mapping = FilePathMapping::empty();
  63         JsonEmitter::stderr(None, Lrc::new(SourceMap::new(file_path_mapping)),
  64                             pretty, json_rendered, external_macro_backtrace)
  65     }
  66
  67     pub fn new(
  68         dst: Box<dyn Write + Send>,
  69         registry: Option<Registry>,
  70         source_map: Lrc<SourceMap>,
  71         pretty: bool,
  72         json_rendered: HumanReadableErrorType,
  73         external_macro_backtrace: bool,
  74     ) -> JsonEmitter {
  75         JsonEmitter {
  76             dst,
  77             registry,
  78             sm: source_map,
  79             pretty,
  80             ui_testing: false,
  81             json_rendered,
  82             external_macro_backtrace,
  83         }
  84     }
  85
  86     pub fn ui_testing(self, ui_testing: bool) -> Self {
  87         Self { ui_testing, ..self }
  88     }
  89 }
  90
  91 impl Emitter for JsonEmitter {
  92     fn emit_diagnostic(&mut self, db: &errors::Diagnostic) {
  93         let data = Diagnostic::from_errors_diagnostic(db, self);
  94         let result = if self.pretty {
  95             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
  96         } else {
  97             writeln!(&mut self.dst, "{}", as_json(&data))
  98         };
  99         if let Err(e) = result {
 100             panic!("failed to print diagnostics: {:?}", e);
 101         }
 102     }
 103
 104     fn emit_artifact_notification(&mut self, path: &Path, artifact_type: &str) {
 105         let data = ArtifactNotification { artifact: path, emit: artifact_type };
 106         let result = if self.pretty {
 107             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
 108         } else {
 109             writeln!(&mut self.dst, "{}", as_json(&data))
 110         };
 111         if let Err(e) = result {
 112             panic!("failed to print notification: {:?}", e);
 113         }
 114     }
 115
 116     fn should_show_explain(&self) -> bool {
 117         match self.json_rendered {
 118             HumanReadableErrorType::Short(_) => false,
 119             _ => true,
 120         }
 121     }
 122 }
 123
 124 // The following data types are provided just for serialisation.
 125
 126 #[derive(RustcEncodable)]
 127 struct Diagnostic {
 128     /// The primary error message.
 129     message: String,
 130     code: Option<DiagnosticCode>,
 131     /// "error: internal compiler error", "error", "warning", "note", "help".
 132     level: &'static str,
 133     spans: Vec<DiagnosticSpan>,
 134     /// Associated diagnostic messages.
 135     children: Vec<Diagnostic>,
 136     /// The message as rustc would render it.
 137     rendered: Option<String>,
 138 }
 139
 140 #[derive(RustcEncodable)]
 141 struct DiagnosticSpan {
 142     file_name: String,
 143     byte_start: u32,
 144     byte_end: u32,
 145     /// 1-based.
 146     line_start: usize,
 147     line_end: usize,
 148     /// 1-based, character offset.
 149     column_start: usize,
 150     column_end: usize,
 151     /// Is this a "primary" span -- meaning the point, or one of the points,
 152     /// where the error occurred?
 153     is_primary: bool,
 154     /// Source text from the start of line_start to the end of line_end.
 155     text: Vec<DiagnosticSpanLine>,
 156     /// Label that should be placed at this location (if any)
 157     label: Option<String>,
 158     /// If we are suggesting a replacement, this will contain text
 159     /// that should be sliced in atop this span.
 160     suggested_replacement: Option<String>,
 161     /// If the suggestion is approximate
 162     suggestion_applicability: Option<Applicability>,
 163     /// Macro invocations that created the code at this span, if any.
 164     expansion: Option<Box<DiagnosticSpanMacroExpansion>>,
 165 }
 166
 167 #[derive(RustcEncodable)]
 168 struct DiagnosticSpanLine {
 169     text: String,
 170
 171     /// 1-based, character offset in self.text.
 172     highlight_start: usize,
 173
 174     highlight_end: usize,
 175 }
 176
 177 #[derive(RustcEncodable)]
 178 struct DiagnosticSpanMacroExpansion {
 179     /// span where macro was applied to generate this code; note that
 180     /// this may itself derive from a macro (if
 181     /// `span.expansion.is_some()`)
 182     span: DiagnosticSpan,
 183
 184     /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
 185     macro_decl_name: String,
 186
 187     /// span where macro was defined (if known)
 188     def_site_span: DiagnosticSpan,
 189 }
 190
 191 #[derive(RustcEncodable)]
 192 struct DiagnosticCode {
 193     /// The code itself.
 194     code: String,
 195     /// An explanation for the code.
 196     explanation: Option<&'static str>,
 197 }
 198
 199 #[derive(RustcEncodable)]
 200 struct ArtifactNotification<'a> {
 201     /// The path of the artifact.
 202     artifact: &'a Path,
 203     /// What kind of artifact we're emitting.
 204     emit: &'a str,
 205 }
 206
 207 impl Diagnostic {
 208     fn from_errors_diagnostic(db: &errors::Diagnostic,
 209                                je: &JsonEmitter)
 210                                -> Diagnostic {
 211         let sugg = db.suggestions.iter().map(|sugg| {
 212             Diagnostic {
 213                 message: sugg.msg.clone(),
 214                 code: None,
 215                 level: "help",
 216                 spans: DiagnosticSpan::from_suggestion(sugg, je),
 217                 children: vec![],
 218                 rendered: None,
 219             }
 220         });
 221
 222         // generate regular command line output and store it in the json
 223
 224         // A threadsafe buffer for writing.
 225         #[derive(Default, Clone)]
 226         struct BufWriter(Arc<Mutex<Vec<u8>>>);
 227
 228         impl Write for BufWriter {
 229             fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 230                 self.0.lock().unwrap().write(buf)
 231             }
 232             fn flush(&mut self) -> io::Result<()> {
 233                 self.0.lock().unwrap().flush()
 234             }
 235         }
 236         let buf = BufWriter::default();
 237         let output = buf.clone();
 238         je.json_rendered.new_emitter(
 239             Box::new(buf), Some(je.sm.clone()), false, None, je.external_macro_backtrace
 240         ).ui_testing(je.ui_testing).emit_diagnostic(db);
 241         let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
 242         let output = String::from_utf8(output).unwrap();
 243
 244         Diagnostic {
 245             message: db.message(),
 246             code: DiagnosticCode::map_opt_string(db.code.clone(), je),
 247             level: db.level.to_str(),
 248             spans: DiagnosticSpan::from_multispan(&db.span, je),
 249             children: db.children.iter().map(|c| {
 250                 Diagnostic::from_sub_diagnostic(c, je)
 251             }).chain(sugg).collect(),
 252             rendered: Some(output),
 253         }
 254     }
 255
 256     fn from_sub_diagnostic(db: &SubDiagnostic, je: &JsonEmitter) -> Diagnostic {
 257         Diagnostic {
 258             message: db.message(),
 259             code: None,
 260             level: db.level.to_str(),
 261             spans: db.render_span.as_ref()
 262                      .map(|sp| DiagnosticSpan::from_multispan(sp, je))
 263                      .unwrap_or_else(|| DiagnosticSpan::from_multispan(&db.span, je)),
 264             children: vec![],
 265             rendered: None,
 266         }
 267     }
 268 }
 269
 270 impl DiagnosticSpan {
 271     fn from_span_label(span: SpanLabel,
 272                        suggestion: Option<(&String, Applicability)>,
 273                        je: &JsonEmitter)
 274                        -> DiagnosticSpan {
 275         Self::from_span_etc(span.span,
 276                             span.is_primary,
 277                             span.label,
 278                             suggestion,
 279                             je)
 280     }
 281
 282     fn from_span_etc(span: Span,
 283                      is_primary: bool,
 284                      label: Option<String>,
 285                      suggestion: Option<(&String, Applicability)>,
 286                      je: &JsonEmitter)
 287                      -> DiagnosticSpan {
 288         // obtain the full backtrace from the `macro_backtrace`
 289         // helper; in some ways, it'd be better to expand the
 290         // backtrace ourselves, but the `macro_backtrace` helper makes
 291         // some decision, such as dropping some frames, and I don't
 292         // want to duplicate that logic here.
 293         let backtrace = span.macro_backtrace().into_iter();
 294         DiagnosticSpan::from_span_full(span,
 295                                        is_primary,
 296                                        label,
 297                                        suggestion,
 298                                        backtrace,
 299                                        je)
 300     }
 301
 302     fn from_span_full(span: Span,
 303                       is_primary: bool,
 304                       label: Option<String>,
 305                       suggestion: Option<(&String, Applicability)>,
 306                       mut backtrace: vec::IntoIter<MacroBacktrace>,
 307                       je: &JsonEmitter)
 308                       -> DiagnosticSpan {
 309         let start = je.sm.lookup_char_pos(span.lo());
 310         let end = je.sm.lookup_char_pos(span.hi());
 311         let backtrace_step = backtrace.next().map(|bt| {
 312             let call_site =
 313                 Self::from_span_full(bt.call_site,
 314                                      false,
 315                                      None,
 316                                      None,
 317                                      backtrace,
 318                                      je);
 319             let def_site_span =
 320                 Self::from_span_full(bt.def_site_span,
 321                                      false,
 322                                      None,
 323                                      None,
 324                                      vec![].into_iter(),
 325                                      je);
 326             Box::new(DiagnosticSpanMacroExpansion {
 327                 span: call_site,
 328                 macro_decl_name: bt.macro_decl_name,
 329                 def_site_span,
 330             })
 331         });
 332
 333         DiagnosticSpan {
 334             file_name: start.file.name.to_string(),
 335             byte_start: span.lo().0 - start.file.start_pos.0,
 336             byte_end: span.hi().0 - start.file.start_pos.0,
 337             line_start: start.line,
 338             line_end: end.line,
 339             column_start: start.col.0 + 1,
 340             column_end: end.col.0 + 1,
 341             is_primary,
 342             text: DiagnosticSpanLine::from_span(span, je),
 343             suggested_replacement: suggestion.map(|x| x.0.clone()),
 344             suggestion_applicability: suggestion.map(|x| x.1),
 345             expansion: backtrace_step,
 346             label,
 347         }
 348     }
 349
 350     fn from_multispan(msp: &MultiSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 351         msp.span_labels()
 352            .into_iter()
 353            .map(|span_str| Self::from_span_label(span_str, None, je))
 354            .collect()
 355     }
 356
 357     fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter)
 358                        -> Vec<DiagnosticSpan> {
 359         suggestion.substitutions
 360                       .iter()
 361                       .flat_map(|substitution| {
 362                           substitution.parts.iter().map(move |suggestion_inner| {
 363                               let span_label = SpanLabel {
 364                                   span: suggestion_inner.span,
 365                                   is_primary: true,
 366                                   label: None,
 367                               };
 368                               DiagnosticSpan::from_span_label(span_label,
 369                                                               Some((&suggestion_inner.snippet,
 370                                                                    suggestion.applicability)),
 371                                                               je)
 372                           })
 373                       })
 374                       .collect()
 375     }
 376 }
 377
 378 impl DiagnosticSpanLine {
 379     fn line_from_source_file(fm: &syntax_pos::SourceFile,
 380                          index: usize,
 381                          h_start: usize,
 382                          h_end: usize)
 383                          -> DiagnosticSpanLine {
 384         DiagnosticSpanLine {
 385             text: fm.get_line(index).map_or(String::new(), |l| l.into_owned()),
 386             highlight_start: h_start,
 387             highlight_end: h_end,
 388         }
 389     }
 390
 391     /// Creates a list of DiagnosticSpanLines from span - each line with any part
 392     /// of `span` gets a DiagnosticSpanLine, with the highlight indicating the
 393     /// `span` within the line.
 394     fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
 395         je.sm.span_to_lines(span)
 396             .map(|lines| {
 397                 let fm = &*lines.file;
 398                 lines.lines
 399                     .iter()
 400                     .map(|line| DiagnosticSpanLine::line_from_source_file(
 401                         fm,
 402                         line.line_index,
 403                         line.start_col.0 + 1,
 404                         line.end_col.0 + 1,
 405                     )).collect()
 406             }).unwrap_or_else(|_| vec![])
 407     }
 408 }
 409
 410 impl DiagnosticCode {
 411     fn map_opt_string(s: Option<DiagnosticId>, je: &JsonEmitter) -> Option<DiagnosticCode> {
 412         s.map(|s| {
 413             let s = match s {
 414                 DiagnosticId::Error(s) => s,
 415                 DiagnosticId::Lint(s) => s,
 416             };
 417             let explanation = je.registry
 418                                 .as_ref()
 419                                 .and_then(|registry| registry.find_description(&s));
 420
 421             DiagnosticCode {
 422                 code: s,
 423                 explanation,
 424             }
 425         })
 426     }
 427 }