src/libsyntax/json.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A JSON emitter for errors.
  12 //!
  13 //! This works by converting errors to a simplified structural format (see the
  14 //! structs at the start of the file) and then serialising them. These should
  15 //! contain as much information about the error as possible.
  16 //!
  17 //! The format of the JSON output should be considered *unstable*. For now the
  18 //! structs at the end of this file (Diagnostic*) specify the error format.
  19
  20 // FIXME spec the JSON output properly.
  21
  22 use codemap::{CodeMap, FilePathMapping};
  23 use syntax_pos::{self, MacroBacktrace, Span, SpanLabel, MultiSpan};
  24 use errors::registry::Registry;
  25 use errors::{DiagnosticBuilder, SubDiagnostic, RenderSpan, CodeSuggestion, CodeMapper};
  26 use errors::emitter::Emitter;
  27
  28 use std::rc::Rc;
  29 use std::io::{self, Write};
  30 use std::vec;
  31
  32 use rustc_serialize::json::as_json;
  33
  34 pub struct JsonEmitter {
  35     dst: Box<Write + Send>,
  36     registry: Option<Registry>,
  37     cm: Rc<CodeMapper + 'static>,
  38 }
  39
  40 impl JsonEmitter {
  41     pub fn stderr(registry: Option<Registry>,
  42                   code_map: Rc<CodeMap>) -> JsonEmitter {
  43         JsonEmitter {
  44             dst: Box::new(io::stderr()),
  45             registry: registry,
  46             cm: code_map,
  47         }
  48     }
  49
  50     pub fn basic() -> JsonEmitter {
  51         let file_path_mapping = FilePathMapping::empty();
  52         JsonEmitter::stderr(None, Rc::new(CodeMap::new(file_path_mapping)))
  53     }
  54
  55     pub fn new(dst: Box<Write + Send>,
  56                registry: Option<Registry>,
  57                code_map: Rc<CodeMap>) -> JsonEmitter {
  58         JsonEmitter {
  59             dst: dst,
  60             registry: registry,
  61             cm: code_map,
  62         }
  63     }
  64 }
  65
  66 impl Emitter for JsonEmitter {
  67     fn emit(&mut self, db: &DiagnosticBuilder) {
  68         let data = Diagnostic::from_diagnostic_builder(db, self);
  69         if let Err(e) = writeln!(&mut self.dst, "{}", as_json(&data)) {
  70             panic!("failed to print diagnostics: {:?}", e);
  71         }
  72     }
  73 }
  74
  75 // The following data types are provided just for serialisation.
  76
  77 #[derive(RustcEncodable)]
  78 struct Diagnostic {
  79     /// The primary error message.
  80     message: String,
  81     code: Option<DiagnosticCode>,
  82     /// "error: internal compiler error", "error", "warning", "note", "help".
  83     level: &'static str,
  84     spans: Vec<DiagnosticSpan>,
  85     /// Associated diagnostic messages.
  86     children: Vec<Diagnostic>,
  87     /// The message as rustc would render it. Currently this is only
  88     /// `Some` for "suggestions", but eventually it will include all
  89     /// snippets.
  90     rendered: Option<String>,
  91 }
  92
  93 #[derive(RustcEncodable)]
  94 struct DiagnosticSpan {
  95     file_name: String,
  96     byte_start: u32,
  97     byte_end: u32,
  98     /// 1-based.
  99     line_start: usize,
 100     line_end: usize,
 101     /// 1-based, character offset.
 102     column_start: usize,
 103     column_end: usize,
 104     /// Is this a "primary" span -- meaning the point, or one of the points,
 105     /// where the error occurred?
 106     is_primary: bool,
 107     /// Source text from the start of line_start to the end of line_end.
 108     text: Vec<DiagnosticSpanLine>,
 109     /// Label that should be placed at this location (if any)
 110     label: Option<String>,
 111     /// If we are suggesting a replacement, this will contain text
 112     /// that should be sliced in atop this span. You may prefer to
 113     /// load the fully rendered version from the parent `Diagnostic`,
 114     /// however.
 115     suggested_replacement: Option<String>,
 116     /// Macro invocations that created the code at this span, if any.
 117     expansion: Option<Box<DiagnosticSpanMacroExpansion>>,
 118 }
 119
 120 #[derive(RustcEncodable)]
 121 struct DiagnosticSpanLine {
 122     text: String,
 123
 124     /// 1-based, character offset in self.text.
 125     highlight_start: usize,
 126
 127     highlight_end: usize,
 128 }
 129
 130 #[derive(RustcEncodable)]
 131 struct DiagnosticSpanMacroExpansion {
 132     /// span where macro was applied to generate this code; note that
 133     /// this may itself derive from a macro (if
 134     /// `span.expansion.is_some()`)
 135     span: DiagnosticSpan,
 136
 137     /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
 138     macro_decl_name: String,
 139
 140     /// span where macro was defined (if known)
 141     def_site_span: Option<DiagnosticSpan>,
 142 }
 143
 144 #[derive(RustcEncodable)]
 145 struct DiagnosticCode {
 146     /// The code itself.
 147     code: String,
 148     /// An explanation for the code.
 149     explanation: Option<&'static str>,
 150 }
 151
 152 impl Diagnostic {
 153     fn from_diagnostic_builder(db: &DiagnosticBuilder,
 154                                je: &JsonEmitter)
 155                                -> Diagnostic {
 156         Diagnostic {
 157             message: db.message(),
 158             code: DiagnosticCode::map_opt_string(db.code.clone(), je),
 159             level: db.level.to_str(),
 160             spans: DiagnosticSpan::from_multispan(&db.span, je),
 161             children: db.children.iter().map(|c| {
 162                 Diagnostic::from_sub_diagnostic(c, je)
 163             }).collect(),
 164             rendered: None,
 165         }
 166     }
 167
 168     fn from_sub_diagnostic(db: &SubDiagnostic, je: &JsonEmitter) -> Diagnostic {
 169         Diagnostic {
 170             message: db.message(),
 171             code: None,
 172             level: db.level.to_str(),
 173             spans: db.render_span.as_ref()
 174                      .map(|sp| DiagnosticSpan::from_render_span(sp, je))
 175                      .unwrap_or_else(|| DiagnosticSpan::from_multispan(&db.span, je)),
 176             children: vec![],
 177             rendered: db.render_span.as_ref()
 178                                     .and_then(|rsp| je.render(rsp)),
 179         }
 180     }
 181 }
 182
 183 impl DiagnosticSpan {
 184     fn from_span_label(span: SpanLabel,
 185                        suggestion: Option<&String>,
 186                        je: &JsonEmitter)
 187                        -> DiagnosticSpan {
 188         Self::from_span_etc(span.span,
 189                             span.is_primary,
 190                             span.label,
 191                             suggestion,
 192                             je)
 193     }
 194
 195     fn from_span_etc(span: Span,
 196                      is_primary: bool,
 197                      label: Option<String>,
 198                      suggestion: Option<&String>,
 199                      je: &JsonEmitter)
 200                      -> DiagnosticSpan {
 201         // obtain the full backtrace from the `macro_backtrace`
 202         // helper; in some ways, it'd be better to expand the
 203         // backtrace ourselves, but the `macro_backtrace` helper makes
 204         // some decision, such as dropping some frames, and I don't
 205         // want to duplicate that logic here.
 206         let backtrace = span.macro_backtrace().into_iter();
 207         DiagnosticSpan::from_span_full(span,
 208                                        is_primary,
 209                                        label,
 210                                        suggestion,
 211                                        backtrace,
 212                                        je)
 213     }
 214
 215     fn from_span_full(span: Span,
 216                       is_primary: bool,
 217                       label: Option<String>,
 218                       suggestion: Option<&String>,
 219                       mut backtrace: vec::IntoIter<MacroBacktrace>,
 220                       je: &JsonEmitter)
 221                       -> DiagnosticSpan {
 222         let start = je.cm.lookup_char_pos(span.lo);
 223         let end = je.cm.lookup_char_pos(span.hi);
 224         let backtrace_step = backtrace.next().map(|bt| {
 225             let call_site =
 226                 Self::from_span_full(bt.call_site,
 227                                      false,
 228                                      None,
 229                                      None,
 230                                      backtrace,
 231                                      je);
 232             let def_site_span = bt.def_site_span.map(|sp| {
 233                 Self::from_span_full(sp,
 234                                      false,
 235                                      None,
 236                                      None,
 237                                      vec![].into_iter(),
 238                                      je)
 239             });
 240             Box::new(DiagnosticSpanMacroExpansion {
 241                 span: call_site,
 242                 macro_decl_name: bt.macro_decl_name,
 243                 def_site_span: def_site_span,
 244             })
 245         });
 246         DiagnosticSpan {
 247             file_name: start.file.name.clone(),
 248             byte_start: span.lo.0,
 249             byte_end: span.hi.0,
 250             line_start: start.line,
 251             line_end: end.line,
 252             column_start: start.col.0 + 1,
 253             column_end: end.col.0 + 1,
 254             is_primary: is_primary,
 255             text: DiagnosticSpanLine::from_span(span, je),
 256             suggested_replacement: suggestion.cloned(),
 257             expansion: backtrace_step,
 258             label: label,
 259         }
 260     }
 261
 262     fn from_multispan(msp: &MultiSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 263         msp.span_labels()
 264            .into_iter()
 265            .map(|span_str| Self::from_span_label(span_str, None, je))
 266            .collect()
 267     }
 268
 269     fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter)
 270                        -> Vec<DiagnosticSpan> {
 271         assert_eq!(suggestion.msp.span_labels().len(), suggestion.substitutes.len());
 272         suggestion.msp.span_labels()
 273                       .into_iter()
 274                       .zip(&suggestion.substitutes)
 275                       .map(|(span_label, suggestion)| {
 276                           DiagnosticSpan::from_span_label(span_label,
 277                                                           Some(suggestion),
 278                                                           je)
 279                       })
 280                       .collect()
 281     }
 282
 283     fn from_render_span(rsp: &RenderSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
 284         match *rsp {
 285             RenderSpan::FullSpan(ref msp) =>
 286                 DiagnosticSpan::from_multispan(msp, je),
 287             RenderSpan::Suggestion(ref suggestion) =>
 288                 DiagnosticSpan::from_suggestion(suggestion, je),
 289         }
 290     }
 291 }
 292
 293 impl DiagnosticSpanLine {
 294     fn line_from_filemap(fm: &syntax_pos::FileMap,
 295                          index: usize,
 296                          h_start: usize,
 297                          h_end: usize)
 298                          -> DiagnosticSpanLine {
 299         DiagnosticSpanLine {
 300             text: fm.get_line(index).unwrap_or("").to_owned(),
 301             highlight_start: h_start,
 302             highlight_end: h_end,
 303         }
 304     }
 305
 306     /// Create a list of DiagnosticSpanLines from span - each line with any part
 307     /// of `span` gets a DiagnosticSpanLine, with the highlight indicating the
 308     /// `span` within the line.
 309     fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
 310         je.cm.span_to_lines(span)
 311              .map(|lines| {
 312                  let fm = &*lines.file;
 313                  lines.lines
 314                       .iter()
 315                       .map(|line| {
 316                           DiagnosticSpanLine::line_from_filemap(fm,
 317                                                                 line.line_index,
 318                                                                 line.start_col.0 + 1,
 319                                                                 line.end_col.0 + 1)
 320                       })
 321                      .collect()
 322              })
 323             .unwrap_or(vec![])
 324     }
 325 }
 326
 327 impl DiagnosticCode {
 328     fn map_opt_string(s: Option<String>, je: &JsonEmitter) -> Option<DiagnosticCode> {
 329         s.map(|s| {
 330
 331             let explanation = je.registry
 332                                 .as_ref()
 333                                 .and_then(|registry| registry.find_description(&s));
 334
 335             DiagnosticCode {
 336                 code: s,
 337                 explanation: explanation,
 338             }
 339         })
 340     }
 341 }
 342
 343 impl JsonEmitter {
 344     fn render(&self, render_span: &RenderSpan) -> Option<String> {
 345         use std::borrow::Borrow;
 346
 347         match *render_span {
 348             RenderSpan::FullSpan(_) => {
 349                 None
 350             }
 351             RenderSpan::Suggestion(ref suggestion) => {
 352                 Some(suggestion.splice_lines(self.cm.borrow()))
 353             }
 354         }
 355     }
 356 }
 357