Move JSON emitter to rustc_errors

1 files changed, 434 insertions, 0 deletions

diff --git a/src/librustc_errors/json.rs b/src/librustc_errors/json.rs
new file mode 100644
index 00000000000..ebbd49bd84a
--- /dev/null
+++ b/src/librustc_errors/json.rs
@@ -0,0 +1,434 @@
+//! A JSON emitter for errors.
+//!
+//! This works by converting errors to a simplified structural format (see the
+//! structs at the start of the file) and then serializing them. These should
+//! contain as much information about the error as possible.
+//!
+//! The format of the JSON output should be considered *unstable*. For now the
+//! structs at the end of this file (Diagnostic*) specify the error format.
+
+// FIXME: spec the JSON output properly.
+
+use syntax_pos::source_map::{SourceMap, FilePathMapping};
+
+use crate::registry::Registry;
+use crate::{SubDiagnostic, CodeSuggestion};
+use crate::{DiagnosticId, Applicability};
+use crate::emitter::{Emitter, HumanReadableErrorType};
+
+use syntax_pos::{MacroBacktrace, Span, SpanLabel, MultiSpan};
+use rustc_data_structures::sync::Lrc;
+use std::io::{self, Write};
+use std::path::Path;
+use std::vec;
+use std::sync::{Arc, Mutex};
+
+use rustc_serialize::json::{as_json, as_pretty_json};
+
+#[cfg(test)]
+mod tests;
+
+pub struct JsonEmitter {
+    dst: Box<dyn Write + Send>,
+    registry: Option<Registry>,
+    sm: Lrc<SourceMap>,
+    pretty: bool,
+    ui_testing: bool,
+    json_rendered: HumanReadableErrorType,
+    external_macro_backtrace: bool,
+}
+
+impl JsonEmitter {
+    pub fn stderr(
+        registry: Option<Registry>,
+        source_map: Lrc<SourceMap>,
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+        external_macro_backtrace: bool,
+    ) -> JsonEmitter {
+        JsonEmitter {
+            dst: Box::new(io::stderr()),
+            registry,
+            sm: source_map,
+            pretty,
+            ui_testing: false,
+            json_rendered,
+            external_macro_backtrace,
+        }
+    }
+
+    pub fn basic(
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+        external_macro_backtrace: bool,
+    ) -> JsonEmitter {
+        let file_path_mapping = FilePathMapping::empty();
+        JsonEmitter::stderr(None, Lrc::new(SourceMap::new(file_path_mapping)),
+                            pretty, json_rendered, external_macro_backtrace)
+    }
+
+    pub fn new(
+        dst: Box<dyn Write + Send>,
+        registry: Option<Registry>,
+        source_map: Lrc<SourceMap>,
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+        external_macro_backtrace: bool,
+    ) -> JsonEmitter {
+        JsonEmitter {
+            dst,
+            registry,
+            sm: source_map,
+            pretty,
+            ui_testing: false,
+            json_rendered,
+            external_macro_backtrace,
+        }
+    }
+
+    pub fn ui_testing(self, ui_testing: bool) -> Self {
+        Self { ui_testing, ..self }
+    }
+}
+
+impl Emitter for JsonEmitter {
+    fn emit_diagnostic(&mut self, diag: &crate::Diagnostic) {
+        let data = Diagnostic::from_errors_diagnostic(diag, self);
+        let result = if self.pretty {
+            writeln!(&mut self.dst, "{}", as_pretty_json(&data))
+        } else {
+            writeln!(&mut self.dst, "{}", as_json(&data))
+        };
+        if let Err(e) = result {
+            panic!("failed to print diagnostics: {:?}", e);
+        }
+    }
+
+    fn emit_artifact_notification(&mut self, path: &Path, artifact_type: &str) {
+        let data = ArtifactNotification { artifact: path, emit: artifact_type };
+        let result = if self.pretty {
+            writeln!(&mut self.dst, "{}", as_pretty_json(&data))
+        } else {
+            writeln!(&mut self.dst, "{}", as_json(&data))
+        };
+        if let Err(e) = result {
+            panic!("failed to print notification: {:?}", e);
+        }
+    }
+
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        Some(&self.sm)
+    }
+
+    fn should_show_explain(&self) -> bool {
+        match self.json_rendered {
+            HumanReadableErrorType::Short(_) => false,
+            _ => true,
+        }
+    }
+}
+
+// The following data types are provided just for serialisation.
+
+#[derive(RustcEncodable)]
+struct Diagnostic {
+    /// The primary error message.
+    message: String,
+    code: Option<DiagnosticCode>,
+    /// "error: internal compiler error", "error", "warning", "note", "help".
+    level: &'static str,
+    spans: Vec<DiagnosticSpan>,
+    /// Associated diagnostic messages.
+    children: Vec<Diagnostic>,
+    /// The message as rustc would render it.
+    rendered: Option<String>,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticSpan {
+    file_name: String,
+    byte_start: u32,
+    byte_end: u32,
+    /// 1-based.
+    line_start: usize,
+    line_end: usize,
+    /// 1-based, character offset.
+    column_start: usize,
+    column_end: usize,
+    /// Is this a "primary" span -- meaning the point, or one of the points,
+    /// where the error occurred?
+    is_primary: bool,
+    /// Source text from the start of line_start to the end of line_end.
+    text: Vec<DiagnosticSpanLine>,
+    /// Label that should be placed at this location (if any)
+    label: Option<String>,
+    /// If we are suggesting a replacement, this will contain text
+    /// that should be sliced in atop this span.
+    suggested_replacement: Option<String>,
+    /// If the suggestion is approximate
+    suggestion_applicability: Option<Applicability>,
+    /// Macro invocations that created the code at this span, if any.
+    expansion: Option<Box<DiagnosticSpanMacroExpansion>>,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticSpanLine {
+    text: String,
+
+    /// 1-based, character offset in self.text.
+    highlight_start: usize,
+
+    highlight_end: usize,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticSpanMacroExpansion {
+    /// span where macro was applied to generate this code; note that
+    /// this may itself derive from a macro (if
+    /// `span.expansion.is_some()`)
+    span: DiagnosticSpan,
+
+    /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
+    macro_decl_name: String,
+
+    /// span where macro was defined (if known)
+    def_site_span: DiagnosticSpan,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticCode {
+    /// The code itself.
+    code: String,
+    /// An explanation for the code.
+    explanation: Option<&'static str>,
+}
+
+#[derive(RustcEncodable)]
+struct ArtifactNotification<'a> {
+    /// The path of the artifact.
+    artifact: &'a Path,
+    /// What kind of artifact we're emitting.
+    emit: &'a str,
+}
+
+impl Diagnostic {
+    fn from_errors_diagnostic(diag: &crate::Diagnostic,
+                               je: &JsonEmitter)
+                               -> Diagnostic {
+        let sugg = diag.suggestions.iter().map(|sugg| {
+            Diagnostic {
+                message: sugg.msg.clone(),
+                code: None,
+                level: "help",
+                spans: DiagnosticSpan::from_suggestion(sugg, je),
+                children: vec![],
+                rendered: None,
+            }
+        });
+
+        // generate regular command line output and store it in the json
+
+        // A threadsafe buffer for writing.
+        #[derive(Default, Clone)]
+        struct BufWriter(Arc<Mutex<Vec<u8>>>);
+
+        impl Write for BufWriter {
+            fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+                self.0.lock().unwrap().write(buf)
+            }
+            fn flush(&mut self) -> io::Result<()> {
+                self.0.lock().unwrap().flush()
+            }
+        }
+        let buf = BufWriter::default();
+        let output = buf.clone();
+        je.json_rendered.new_emitter(
+            Box::new(buf), Some(je.sm.clone()), false, None, je.external_macro_backtrace
+        ).ui_testing(je.ui_testing).emit_diagnostic(diag);
+        let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
+        let output = String::from_utf8(output).unwrap();
+
+        Diagnostic {
+            message: diag.message(),
+            code: DiagnosticCode::map_opt_string(diag.code.clone(), je),
+            level: diag.level.to_str(),
+            spans: DiagnosticSpan::from_multispan(&diag.span, je),
+            children: diag.children.iter().map(|c| {
+                Diagnostic::from_sub_diagnostic(c, je)
+            }).chain(sugg).collect(),
+            rendered: Some(output),
+        }
+    }
+
+    fn from_sub_diagnostic(diag: &SubDiagnostic, je: &JsonEmitter) -> Diagnostic {
+        Diagnostic {
+            message: diag.message(),
+            code: None,
+            level: diag.level.to_str(),
+            spans: diag.render_span.as_ref()
+                     .map(|sp| DiagnosticSpan::from_multispan(sp, je))
+                     .unwrap_or_else(|| DiagnosticSpan::from_multispan(&diag.span, je)),
+            children: vec![],
+            rendered: None,
+        }
+    }
+}
+
+impl DiagnosticSpan {
+    fn from_span_label(span: SpanLabel,
+                       suggestion: Option<(&String, Applicability)>,
+                       je: &JsonEmitter)
+                       -> DiagnosticSpan {
+        Self::from_span_etc(span.span,
+                            span.is_primary,
+                            span.label,
+                            suggestion,
+                            je)
+    }
+
+    fn from_span_etc(span: Span,
+                     is_primary: bool,
+                     label: Option<String>,
+                     suggestion: Option<(&String, Applicability)>,
+                     je: &JsonEmitter)
+                     -> DiagnosticSpan {
+        // obtain the full backtrace from the `macro_backtrace`
+        // helper; in some ways, it'd be better to expand the
+        // backtrace ourselves, but the `macro_backtrace` helper makes
+        // some decision, such as dropping some frames, and I don't
+        // want to duplicate that logic here.
+        let backtrace = span.macro_backtrace().into_iter();
+        DiagnosticSpan::from_span_full(span,
+                                       is_primary,
+                                       label,
+                                       suggestion,
+                                       backtrace,
+                                       je)
+    }
+
+    fn from_span_full(span: Span,
+                      is_primary: bool,
+                      label: Option<String>,
+                      suggestion: Option<(&String, Applicability)>,
+                      mut backtrace: vec::IntoIter<MacroBacktrace>,
+                      je: &JsonEmitter)
+                      -> DiagnosticSpan {
+        let start = je.sm.lookup_char_pos(span.lo());
+        let end = je.sm.lookup_char_pos(span.hi());
+        let backtrace_step = backtrace.next().map(|bt| {
+            let call_site =
+                Self::from_span_full(bt.call_site,
+                                     false,
+                                     None,
+                                     None,
+                                     backtrace,
+                                     je);
+            let def_site_span =
+                Self::from_span_full(bt.def_site_span,
+                                     false,
+                                     None,
+                                     None,
+                                     vec![].into_iter(),
+                                     je);
+            Box::new(DiagnosticSpanMacroExpansion {
+                span: call_site,
+                macro_decl_name: bt.macro_decl_name,
+                def_site_span,
+            })
+        });
+
+        DiagnosticSpan {
+            file_name: start.file.name.to_string(),
+            byte_start: start.file.original_relative_byte_pos(span.lo()).0,
+            byte_end: start.file.original_relative_byte_pos(span.hi()).0,
+            line_start: start.line,
+            line_end: end.line,
+            column_start: start.col.0 + 1,
+            column_end: end.col.0 + 1,
+            is_primary,
+            text: DiagnosticSpanLine::from_span(span, je),
+            suggested_replacement: suggestion.map(|x| x.0.clone()),
+            suggestion_applicability: suggestion.map(|x| x.1),
+            expansion: backtrace_step,
+            label,
+        }
+    }
+
+    fn from_multispan(msp: &MultiSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
+        msp.span_labels()
+           .into_iter()
+           .map(|span_str| Self::from_span_label(span_str, None, je))
+           .collect()
+    }
+
+    fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter)
+                       -> Vec<DiagnosticSpan> {
+        suggestion.substitutions
+                      .iter()
+                      .flat_map(|substitution| {
+                          substitution.parts.iter().map(move |suggestion_inner| {
+                              let span_label = SpanLabel {
+                                  span: suggestion_inner.span,
+                                  is_primary: true,
+                                  label: None,
+                              };
+                              DiagnosticSpan::from_span_label(span_label,
+                                                              Some((&suggestion_inner.snippet,
+                                                                   suggestion.applicability)),
+                                                              je)
+                          })
+                      })
+                      .collect()
+    }
+}
+
+impl DiagnosticSpanLine {
+    fn line_from_source_file(fm: &syntax_pos::SourceFile,
+                         index: usize,
+                         h_start: usize,
+                         h_end: usize)
+                         -> DiagnosticSpanLine {
+        DiagnosticSpanLine {
+            text: fm.get_line(index).map_or(String::new(), |l| l.into_owned()),
+            highlight_start: h_start,
+            highlight_end: h_end,
+        }
+    }
+
+    /// Creates a list of DiagnosticSpanLines from span - each line with any part
+    /// of `span` gets a DiagnosticSpanLine, with the highlight indicating the
+    /// `span` within the line.
+    fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
+        je.sm.span_to_lines(span)
+            .map(|lines| {
+                let fm = &*lines.file;
+                lines.lines
+                    .iter()
+                    .map(|line| DiagnosticSpanLine::line_from_source_file(
+                        fm,
+                        line.line_index,
+                        line.start_col.0 + 1,
+                        line.end_col.0 + 1,
+                    )).collect()
+            }).unwrap_or_else(|_| vec![])
+    }
+}
+
+impl DiagnosticCode {
+    fn map_opt_string(s: Option<DiagnosticId>, je: &JsonEmitter) -> Option<DiagnosticCode> {
+        s.map(|s| {
+            let s = match s {
+                DiagnosticId::Error(s) => s,
+                DiagnosticId::Lint(s) => s,
+            };
+            let explanation = je.registry
+                                .as_ref()
+                                .and_then(|registry| registry.find_description(&s));
+
+            DiagnosticCode {
+                code: s,
+                explanation,
+            }
+        })
+    }
+}