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