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