Rollup merge of #59128 - oli-obk:colorful_json, r=mark-i-m,eddyb

Emit ansi color codes in the `rendered` field of json diagnostics

cc @ljedrz

Implemented for https://github.com/rust-lang/rust/pull/56595#issuecomment-447645115 (x.py clippy)

13 files changed, 287 insertions, 230 deletions

diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index d3a734cbc6e..dc1ceaf69f0 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -19,6 +19,7 @@ use syntax::parse::token;
 use syntax::parse;
 use syntax::symbol::Symbol;
 use syntax::feature_gate::UnstableFeatures;
+use errors::emitter::HumanReadableErrorType;
 
 use errors::{ColorConfig, FatalError, Handler};
 
@@ -219,14 +220,18 @@ impl OutputType {
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum ErrorOutputType {
-    HumanReadable(ColorConfig),
-    Json(bool),
-    Short(ColorConfig),
+    HumanReadable(HumanReadableErrorType),
+    Json {
+        /// Render the json in a human readable way (with indents and newlines)
+        pretty: bool,
+        /// The way the `rendered` field is created
+        json_rendered: HumanReadableErrorType,
+    },
 }
 
 impl Default for ErrorOutputType {
     fn default() -> ErrorOutputType {
-        ErrorOutputType::HumanReadable(ColorConfig::Auto)
+        ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(ColorConfig::Auto))
     }
 }
 
@@ -1372,6 +1377,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "print some statistics about AST and HIR"),
     always_encode_mir: bool = (false, parse_bool, [TRACKED],
         "encode MIR of all functions into the crate metadata"),
+    json_rendered: Option<String> = (None, parse_opt_string, [UNTRACKED],
+        "describes how to render the `rendered` field of json diagnostics"),
     unleash_the_miri_inside_of_you: bool = (false, parse_bool, [TRACKED],
         "take the breaks off const evaluation. NOTE: this is unsound"),
     osx_rpath_install_name: bool = (false, parse_bool, [TRACKED],
@@ -1825,6 +1832,12 @@ pub fn rustc_optgroups() -> Vec<RustcOptGroup> {
             "How errors and other messages are produced",
             "human|json|short",
         ),
+        opt::opt(
+            "",
+            "json-rendered",
+            "Choose `rendered` field of json diagnostics render scheme",
+            "plain|termcolor",
+        ),
         opt::opt_s(
             "",
             "color",
@@ -1965,6 +1978,17 @@ pub fn build_session_options_and_crate_config(
         )
     }
 
+    let json_rendered = matches.opt_str("json-rendered").and_then(|s| match s.as_str() {
+        "plain" => None,
+        "termcolor" => Some(HumanReadableErrorType::Default(ColorConfig::Always)),
+        _ => early_error(
+            ErrorOutputType::default(),
+            &format!(
+                "argument for --json-rendered must be `plain` or `termcolor` (instead was `{}`)",
+                s,
+            ),
+        ),
+    }).unwrap_or(HumanReadableErrorType::Default(ColorConfig::Never));
 
     // We need the opts_present check because the driver will send us Matches
     // with only stable options if no unstable options are used. Since error-format
@@ -1972,14 +1996,14 @@ pub fn build_session_options_and_crate_config(
     // opt_present because the latter will panic.
     let error_format = if matches.opts_present(&["error-format".to_owned()]) {
         match matches.opt_str("error-format").as_ref().map(|s| &s[..]) {
-            Some("human") => ErrorOutputType::HumanReadable(color),
-            Some("json") => ErrorOutputType::Json(false),
-            Some("pretty-json") => ErrorOutputType::Json(true),
-            Some("short") => ErrorOutputType::Short(color),
-            None => ErrorOutputType::HumanReadable(color),
+            None |
+            Some("human") => ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(color)),
+            Some("json") => ErrorOutputType::Json { pretty: false, json_rendered },
+            Some("pretty-json") => ErrorOutputType::Json { pretty: true, json_rendered },
+            Some("short") => ErrorOutputType::HumanReadable(HumanReadableErrorType::Short(color)),
 
             Some(arg) => early_error(
-                ErrorOutputType::HumanReadable(color),
+                ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(color)),
                 &format!(
                     "argument for --error-format must be `human`, `json` or \
                      `short` (instead was `{}`)",
@@ -1988,7 +2012,7 @@ pub fn build_session_options_and_crate_config(
             ),
         }
     } else {
-        ErrorOutputType::HumanReadable(color)
+        ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(color))
     };
 
     let unparsed_crate_types = matches.opt_strs("crate-type");
@@ -2000,11 +2024,16 @@ pub fn build_session_options_and_crate_config(
 
     let mut debugging_opts = build_debugging_options(matches, error_format);
 
-    if !debugging_opts.unstable_options && error_format == ErrorOutputType::Json(true) {
-        early_error(
-            ErrorOutputType::Json(false),
-            "--error-format=pretty-json is unstable",
-        );
+    if !debugging_opts.unstable_options {
+        if matches.opt_str("json-rendered").is_some() {
+            early_error(error_format, "`--json-rendered=x` is unstable");
+        }
+        if let ErrorOutputType::Json { pretty: true, json_rendered } = error_format {
+            early_error(
+                ErrorOutputType::Json { pretty: false, json_rendered },
+                "--error-format=pretty-json is unstable",
+            );
+        }
     }
 
     if debugging_opts.pgo_gen.enabled() && !debugging_opts.pgo_use.is_empty() {
@@ -2928,50 +2957,55 @@ mod tests {
         let mut v3 = Options::default();
         let mut v4 = Options::default();
 
+        const JSON: super::ErrorOutputType = super::ErrorOutputType::Json {
+            pretty: false,
+            json_rendered: super::HumanReadableErrorType::Default(super::ColorConfig::Never),
+        };
+
         // Reference
         v1.search_paths
-            .push(SearchPath::from_cli_opt("native=abc", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("native=abc", JSON));
         v1.search_paths
-            .push(SearchPath::from_cli_opt("crate=def", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("crate=def", JSON));
         v1.search_paths
-            .push(SearchPath::from_cli_opt("dependency=ghi", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("dependency=ghi", JSON));
         v1.search_paths
-            .push(SearchPath::from_cli_opt("framework=jkl", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("framework=jkl", JSON));
         v1.search_paths
-            .push(SearchPath::from_cli_opt("all=mno", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("all=mno", JSON));
 
         v2.search_paths
-            .push(SearchPath::from_cli_opt("native=abc", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("native=abc", JSON));
         v2.search_paths
-            .push(SearchPath::from_cli_opt("dependency=ghi", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("dependency=ghi", JSON));
         v2.search_paths
-            .push(SearchPath::from_cli_opt("crate=def", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("crate=def", JSON));
         v2.search_paths
-            .push(SearchPath::from_cli_opt("framework=jkl", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("framework=jkl", JSON));
         v2.search_paths
-            .push(SearchPath::from_cli_opt("all=mno", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("all=mno", JSON));
 
         v3.search_paths
-            .push(SearchPath::from_cli_opt("crate=def", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("crate=def", JSON));
         v3.search_paths
-            .push(SearchPath::from_cli_opt("framework=jkl", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("framework=jkl", JSON));
         v3.search_paths
-            .push(SearchPath::from_cli_opt("native=abc", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("native=abc", JSON));
         v3.search_paths
-            .push(SearchPath::from_cli_opt("dependency=ghi", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("dependency=ghi", JSON));
         v3.search_paths
-            .push(SearchPath::from_cli_opt("all=mno", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("all=mno", JSON));
 
         v4.search_paths
-            .push(SearchPath::from_cli_opt("all=mno", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("all=mno", JSON));
         v4.search_paths
-            .push(SearchPath::from_cli_opt("native=abc", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("native=abc", JSON));
         v4.search_paths
-            .push(SearchPath::from_cli_opt("crate=def", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("crate=def", JSON));
         v4.search_paths
-            .push(SearchPath::from_cli_opt("dependency=ghi", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("dependency=ghi", JSON));
         v4.search_paths
-            .push(SearchPath::from_cli_opt("framework=jkl", super::ErrorOutputType::Json(false)));
+            .push(SearchPath::from_cli_opt("framework=jkl", JSON));
 
         assert!(v1.dep_tracking_hash() == v2.dep_tracking_hash());
         assert!(v1.dep_tracking_hash() == v3.dep_tracking_hash());
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index a1966c02683..eed516a4381 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -1033,39 +1033,42 @@ fn default_emitter(
     emitter_dest: Option<Box<dyn Write + Send>>,
 ) -> Box<dyn Emitter + sync::Send> {
     match (sopts.error_format, emitter_dest) {
-        (config::ErrorOutputType::HumanReadable(color_config), None) => Box::new(
-            EmitterWriter::stderr(
-                color_config,
-                Some(source_map.clone()),
-                false,
-                sopts.debugging_opts.teach,
-            ).ui_testing(sopts.debugging_opts.ui_testing),
-        ),
-        (config::ErrorOutputType::HumanReadable(_), Some(dst)) => Box::new(
-            EmitterWriter::new(dst, Some(source_map.clone()), false, false)
-                .ui_testing(sopts.debugging_opts.ui_testing),
-        ),
-        (config::ErrorOutputType::Json(pretty), None) => Box::new(
+        (config::ErrorOutputType::HumanReadable(kind), dst) => {
+            let (short, color_config) = kind.unzip();
+            let emitter = match dst {
+                None => EmitterWriter::stderr(
+                    color_config,
+                    Some(source_map.clone()),
+                    short,
+                    sopts.debugging_opts.teach,
+                ),
+                Some(dst) => EmitterWriter::new(
+                    dst,
+                    Some(source_map.clone()),
+                    short,
+                    false, // no teach messages when writing to a buffer
+                    false, // no colors when writing to a buffer
+                ),
+            };
+            Box::new(emitter.ui_testing(sopts.debugging_opts.ui_testing))
+        },
+        (config::ErrorOutputType::Json { pretty, json_rendered }, None) => Box::new(
             JsonEmitter::stderr(
                 Some(registry),
                 source_map.clone(),
                 pretty,
+                json_rendered,
             ).ui_testing(sopts.debugging_opts.ui_testing),
         ),
-        (config::ErrorOutputType::Json(pretty), Some(dst)) => Box::new(
+        (config::ErrorOutputType::Json { pretty, json_rendered }, Some(dst)) => Box::new(
             JsonEmitter::new(
                 dst,
                 Some(registry),
                 source_map.clone(),
                 pretty,
+                json_rendered,
             ).ui_testing(sopts.debugging_opts.ui_testing),
         ),
-        (config::ErrorOutputType::Short(color_config), None) => Box::new(
-            EmitterWriter::stderr(color_config, Some(source_map.clone()), true, false),
-        ),
-        (config::ErrorOutputType::Short(_), Some(dst)) => {
-            Box::new(EmitterWriter::new(dst, Some(source_map.clone()), true, false))
-        }
     }
 }
 
@@ -1322,13 +1325,12 @@ pub enum IncrCompSession {
 
 pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
     let emitter: Box<dyn Emitter + sync::Send> = match output {
-        config::ErrorOutputType::HumanReadable(color_config) => {
-            Box::new(EmitterWriter::stderr(color_config, None, false, false))
-        }
-        config::ErrorOutputType::Json(pretty) => Box::new(JsonEmitter::basic(pretty)),
-        config::ErrorOutputType::Short(color_config) => {
-            Box::new(EmitterWriter::stderr(color_config, None, true, false))
+        config::ErrorOutputType::HumanReadable(kind) => {
+            let (short, color_config) = kind.unzip();
+            Box::new(EmitterWriter::stderr(color_config, None, short, false))
         }
+        config::ErrorOutputType::Json { pretty, json_rendered } =>
+            Box::new(JsonEmitter::basic(pretty, json_rendered)),
     };
     let handler = errors::Handler::with_emitter(true, None, emitter);
     handler.emit(&MultiSpan::new(), msg, errors::Level::Fatal);
@@ -1337,13 +1339,12 @@ pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
 
 pub fn early_warn(output: config::ErrorOutputType, msg: &str) {
     let emitter: Box<dyn Emitter + sync::Send> = match output {
-        config::ErrorOutputType::HumanReadable(color_config) => {
-            Box::new(EmitterWriter::stderr(color_config, None, false, false))
-        }
-        config::ErrorOutputType::Json(pretty) => Box::new(JsonEmitter::basic(pretty)),
-        config::ErrorOutputType::Short(color_config) => {
-            Box::new(EmitterWriter::stderr(color_config, None, true, false))
+        config::ErrorOutputType::HumanReadable(kind) => {
+            let (short, color_config) = kind.unzip();
+            Box::new(EmitterWriter::stderr(color_config, None, short, false))
         }
+        config::ErrorOutputType::Json { pretty, json_rendered } =>
+            Box::new(JsonEmitter::basic(pretty, json_rendered)),
     };
     let handler = errors::Handler::with_emitter(true, None, emitter);
     handler.emit(&MultiSpan::new(), msg, errors::Level::Warning);
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index ee2a1b69cbd..a1472479afa 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -16,9 +16,35 @@ use std::borrow::Cow;
 use std::io::prelude::*;
 use std::io;
 use std::cmp::{min, Reverse};
-use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter};
+use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter, Ansi};
 use termcolor::{WriteColor, Color, Buffer};
 
+/// Describes the way the content of the `rendered` field of the json output is generated
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum HumanReadableErrorType {
+    Default(ColorConfig),
+    Short(ColorConfig),
+}
+
+impl HumanReadableErrorType {
+    /// Returns a (`short`, `color`) tuple
+    pub fn unzip(self) -> (bool, ColorConfig) {
+        match self {
+            HumanReadableErrorType::Default(cc) => (false, cc),
+            HumanReadableErrorType::Short(cc) => (true, cc),
+        }
+    }
+    pub fn new_emitter(
+        self,
+        dst: Box<dyn Write + Send>,
+        source_map: Option<Lrc<SourceMapperDyn>>,
+        teach: bool,
+    ) -> EmitterWriter {
+        let (short, color_config) = self.unzip();
+        EmitterWriter::new(dst, source_map, short, teach, color_config.suggests_using_colors())
+    }
+}
+
 const ANONYMIZED_LINE_NUM: &str = "LL";
 
 /// Emitter trait for emitting errors.
@@ -104,8 +130,8 @@ pub enum ColorConfig {
 }
 
 impl ColorConfig {
-    fn to_color_choice(&self) -> ColorChoice {
-        match *self {
+    fn to_color_choice(self) -> ColorChoice {
+        match self {
             ColorConfig::Always => {
                 if atty::is(atty::Stream::Stderr) {
                     ColorChoice::Always
@@ -120,6 +146,14 @@ impl ColorConfig {
             ColorConfig::Auto => ColorChoice::Never,
         }
     }
+    fn suggests_using_colors(self) -> bool {
+        match self {
+            | ColorConfig::Always
+            | ColorConfig::Auto
+            => true,
+            ColorConfig::Never => false,
+        }
+    }
 }
 
 pub struct EmitterWriter {
@@ -152,13 +186,15 @@ impl EmitterWriter {
         }
     }
 
-    pub fn new(dst: Box<dyn Write + Send>,
-               source_map: Option<Lrc<SourceMapperDyn>>,
-               short_message: bool,
-               teach: bool)
-               -> EmitterWriter {
+    pub fn new(
+        dst: Box<dyn Write + Send>,
+        source_map: Option<Lrc<SourceMapperDyn>>,
+        short_message: bool,
+        teach: bool,
+        colored: bool,
+    ) -> EmitterWriter {
         EmitterWriter {
-            dst: Raw(dst),
+            dst: Raw(dst, colored),
             sm: source_map,
             short_message,
             teach,
@@ -1538,13 +1574,15 @@ fn emit_to_destination(rendered_buffer: &[Vec<StyledString>],
 pub enum Destination {
     Terminal(StandardStream),
     Buffered(BufferWriter),
-    Raw(Box<dyn Write + Send>),
+    // The bool denotes whether we should be emitting ansi color codes or not
+    Raw(Box<(dyn Write + Send)>, bool),
 }
 
 pub enum WritableDst<'a> {
     Terminal(&'a mut StandardStream),
     Buffered(&'a mut BufferWriter, Buffer),
-    Raw(&'a mut Box<dyn Write + Send>),
+    Raw(&'a mut (dyn Write + Send)),
+    ColoredRaw(Ansi<&'a mut (dyn Write + Send)>),
 }
 
 impl Destination {
@@ -1570,7 +1608,8 @@ impl Destination {
                 let buf = t.buffer();
                 WritableDst::Buffered(t, buf)
             }
-            Destination::Raw(ref mut t) => WritableDst::Raw(t),
+            Destination::Raw(ref mut t, false) => WritableDst::Raw(t),
+            Destination::Raw(ref mut t, true) => WritableDst::ColoredRaw(Ansi::new(t)),
         }
     }
 }
@@ -1628,6 +1667,7 @@ impl<'a> WritableDst<'a> {
         match *self {
             WritableDst::Terminal(ref mut t) => t.set_color(color),
             WritableDst::Buffered(_, ref mut t) => t.set_color(color),
+            WritableDst::ColoredRaw(ref mut t) => t.set_color(color),
             WritableDst::Raw(_) => Ok(())
         }
     }
@@ -1636,6 +1676,7 @@ impl<'a> WritableDst<'a> {
         match *self {
             WritableDst::Terminal(ref mut t) => t.reset(),
             WritableDst::Buffered(_, ref mut t) => t.reset(),
+            WritableDst::ColoredRaw(ref mut t) => t.reset(),
             WritableDst::Raw(_) => Ok(()),
         }
     }
@@ -1647,6 +1688,7 @@ impl<'a> Write for WritableDst<'a> {
             WritableDst::Terminal(ref mut t) => t.write(bytes),
             WritableDst::Buffered(_, ref mut buf) => buf.write(bytes),
             WritableDst::Raw(ref mut w) => w.write(bytes),
+            WritableDst::ColoredRaw(ref mut t) => t.write(bytes),
         }
     }
 
@@ -1655,6 +1697,7 @@ impl<'a> Write for WritableDst<'a> {
             WritableDst::Terminal(ref mut t) => t.flush(),
             WritableDst::Buffered(_, ref mut buf) => buf.flush(),
             WritableDst::Raw(ref mut w) => w.flush(),
+            WritableDst::ColoredRaw(ref mut w) => w.flush(),
         }
     }
 }
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index a4d2a3be863..769ea3ff7bc 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -3,7 +3,7 @@ use std::fmt;
 use std::path::PathBuf;
 
 use errors;
-use errors::emitter::ColorConfig;
+use errors::emitter::{ColorConfig, HumanReadableErrorType};
 use getopts;
 use rustc::lint::Level;
 use rustc::session::early_error;
@@ -254,12 +254,19 @@ impl Options {
                                       (instead was `{}`)", arg));
             }
         };
+        // FIXME: deduplicate this code from the identical code in librustc/session/config.rs
         let error_format = match matches.opt_str("error-format").as_ref().map(|s| &s[..]) {
-            Some("human") => ErrorOutputType::HumanReadable(color),
-            Some("json") => ErrorOutputType::Json(false),
-            Some("pretty-json") => ErrorOutputType::Json(true),
-            Some("short") => ErrorOutputType::Short(color),
-            None => ErrorOutputType::HumanReadable(color),
+            None |
+            Some("human") => ErrorOutputType::HumanReadable(HumanReadableErrorType::Default(color)),
+            Some("json") => ErrorOutputType::Json {
+                pretty: false,
+                json_rendered: HumanReadableErrorType::Default(ColorConfig::Never),
+            },
+            Some("pretty-json") => ErrorOutputType::Json {
+                pretty: true,
+                json_rendered: HumanReadableErrorType::Default(ColorConfig::Never),
+            },
+            Some("short") => ErrorOutputType::HumanReadable(HumanReadableErrorType::Short(color)),
             Some(arg) => {
                 early_error(ErrorOutputType::default(),
                             &format!("argument for --error-format must be `human`, `json` or \
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 3cf6b32b07c..c141b474815 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -299,15 +299,18 @@ pub fn new_handler(error_format: ErrorOutputType,
     // stick to the defaults
     let sessopts = Options::default();
     let emitter: Box<dyn Emitter + sync::Send> = match error_format {
-        ErrorOutputType::HumanReadable(color_config) => Box::new(
-            EmitterWriter::stderr(
-                color_config,
-                source_map.map(|cm| cm as _),
-                false,
-                sessopts.debugging_opts.teach,
-            ).ui_testing(ui_testing)
-        ),
-        ErrorOutputType::Json(pretty) => {
+        ErrorOutputType::HumanReadable(kind) => {
+            let (short, color_config) = kind.unzip();
+            Box::new(
+                EmitterWriter::stderr(
+                    color_config,
+                    source_map.map(|cm| cm as _),
+                    short,
+                    sessopts.debugging_opts.teach,
+                ).ui_testing(ui_testing)
+            )
+        },
+        ErrorOutputType::Json { pretty, json_rendered } => {
             let source_map = source_map.unwrap_or_else(
                 || Lrc::new(source_map::SourceMap::new(sessopts.file_path_mapping())));
             Box::new(
@@ -315,16 +318,10 @@ pub fn new_handler(error_format: ErrorOutputType,
                     None,
                     source_map,
                     pretty,
+                    json_rendered,
                 ).ui_testing(ui_testing)
             )
         },
-        ErrorOutputType::Short(color_config) => Box::new(
-            EmitterWriter::stderr(
-                color_config,
-                source_map.map(|cm| cm as _),
-                true,
-                false)
-        ),
     };
 
     errors::Handler::with_emitter_and_flags(
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 0bbc7c5c4b2..abf74158c93 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -381,7 +381,7 @@ pub fn make_test(s: &str,
         // Any errors in parsing should also appear when the doctest is compiled for real, so just
         // send all the errors that libsyntax emits directly into a `Sink` instead of stderr.
         let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-        let emitter = EmitterWriter::new(box io::sink(), None, false, false);
+        let emitter = EmitterWriter::new(box io::sink(), None, false, false, false);
         let handler = Handler::with_emitter(false, None, box emitter);
         let sess = ParseSess::with_span_handler(handler, cm);
 
diff --git a/src/libsyntax/json.rs b/src/libsyntax/json.rs
index 838dfc62646..c19b408442a 100644
--- a/src/libsyntax/json.rs
+++ b/src/libsyntax/json.rs
@@ -14,7 +14,7 @@ use crate::source_map::{SourceMap, FilePathMapping};
 use errors::registry::Registry;
 use errors::{DiagnosticBuilder, SubDiagnostic, CodeSuggestion, SourceMapper};
 use errors::{DiagnosticId, Applicability};
-use errors::emitter::{Emitter, EmitterWriter};
+use errors::emitter::{Emitter, HumanReadableErrorType};
 
 use syntax_pos::{MacroBacktrace, Span, SpanLabel, MultiSpan};
 use rustc_data_structures::sync::{self, Lrc};
@@ -30,37 +30,46 @@ pub struct JsonEmitter {
     sm: Lrc<dyn SourceMapper + sync::Send + sync::Sync>,
     pretty: bool,
     ui_testing: bool,
+    json_rendered: HumanReadableErrorType,
 }
 
 impl JsonEmitter {
-    pub fn stderr(registry: Option<Registry>,
-                  source_map: Lrc<SourceMap>,
-                  pretty: bool) -> JsonEmitter {
+    pub fn stderr(
+        registry: Option<Registry>,
+        source_map: Lrc<SourceMap>,
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+    ) -> JsonEmitter {
         JsonEmitter {
             dst: Box::new(io::stderr()),
             registry,
             sm: source_map,
             pretty,
             ui_testing: false,
+            json_rendered,
         }
     }
 
-    pub fn basic(pretty: bool) -> JsonEmitter {
+    pub fn basic(pretty: bool, json_rendered: HumanReadableErrorType) -> JsonEmitter {
         let file_path_mapping = FilePathMapping::empty();
         JsonEmitter::stderr(None, Lrc::new(SourceMap::new(file_path_mapping)),
-                            pretty)
+                            pretty, json_rendered)
     }
 
-    pub fn new(dst: Box<dyn Write + Send>,
-               registry: Option<Registry>,
-               source_map: Lrc<SourceMap>,
-               pretty: bool) -> JsonEmitter {
+    pub fn new(
+        dst: Box<dyn Write + Send>,
+        registry: Option<Registry>,
+        source_map: Lrc<SourceMap>,
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+    ) -> JsonEmitter {
         JsonEmitter {
             dst,
             registry,
             sm: source_map,
             pretty,
             ui_testing: false,
+            json_rendered,
         }
     }
 
@@ -190,7 +199,7 @@ impl Diagnostic {
         }
         let buf = BufWriter::default();
         let output = buf.clone();
-        EmitterWriter::new(Box::new(buf), Some(je.sm.clone()), false, false)
+        je.json_rendered.new_emitter(Box::new(buf), Some(je.sm.clone()), false)
             .ui_testing(je.ui_testing).emit(db);
         let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
         let output = String::from_utf8(output).unwrap();
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 5557e281a66..3b980fafc2f 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -1920,6 +1920,7 @@ mod tests {
         let emitter = errors::emitter::EmitterWriter::new(Box::new(io::sink()),
                                                           Some(sm.clone()),
                                                           false,
+                                                          false,
                                                           false);
         ParseSess {
             span_diagnostic: errors::Handler::with_emitter(true, None, Box::new(emitter)),
diff --git a/src/libsyntax/test_snippet.rs b/src/libsyntax/test_snippet.rs
index 86910ffd894..cba429068fd 100644
--- a/src/libsyntax/test_snippet.rs
+++ b/src/libsyntax/test_snippet.rs
@@ -57,6 +57,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
         let emitter = EmitterWriter::new(Box::new(Shared { data: output.clone() }),
                                         Some(source_map.clone()),
                                         false,
+                                        false,
                                         false);
         let handler = Handler::with_emitter(true, None, Box::new(emitter));
         handler.span_err(msp, "foo");
diff --git a/src/test/ui/lint/use_suggestion_json.rs b/src/test/ui/lint/use_suggestion_json.rs
index 3bdbaa55f2d..9679ce4a2ae 100644
--- a/src/test/ui/lint/use_suggestion_json.rs
+++ b/src/test/ui/lint/use_suggestion_json.rs
@@ -1,5 +1,6 @@
 // ignore-cloudabi
-// compile-flags: --error-format pretty-json -Zunstable-options
+// ignore-windows
+// compile-flags: --error-format pretty-json -Zunstable-options --json-rendered=termcolor
 
 // The output for humans should just highlight the whole span without showing
 // the suggested replacement, but we also want to test that suggested
diff --git a/src/test/ui/lint/use_suggestion_json.stderr b/src/test/ui/lint/use_suggestion_json.stderr
index dee7f2f9b16..632666db75b 100644
--- a/src/test/ui/lint/use_suggestion_json.stderr
+++ b/src/test/ui/lint/use_suggestion_json.stderr
@@ -73,10 +73,10 @@ mod foo {
   "spans": [
     {
       "file_name": "$DIR/use_suggestion_json.rs",
-      "byte_start": 440,
-      "byte_end": 444,
-      "line_start": 11,
-      "line_end": 11,
+      "byte_start": 484,
+      "byte_end": 488,
+      "line_start": 12,
+      "line_end": 12,
       "column_start": 12,
       "column_end": 16,
       "is_primary": true,
@@ -101,10 +101,10 @@ mod foo {
       "spans": [
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -124,10 +124,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -147,10 +147,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -170,10 +170,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -193,10 +193,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -216,10 +216,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -239,10 +239,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -262,10 +262,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -285,10 +285,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -308,10 +308,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -331,10 +331,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -354,10 +354,10 @@ mod foo {
         },
         {
           "file_name": "$DIR/use_suggestion_json.rs",
-          "byte_start": 417,
-          "byte_end": 417,
-          "line_start": 10,
-          "line_end": 10,
+          "byte_start": 461,
+          "byte_end": 461,
+          "line_start": 11,
+          "line_end": 11,
           "column_start": 1,
           "column_end": 1,
           "is_primary": true,
@@ -380,22 +380,22 @@ mod foo {
       "rendered": null
     }
   ],
-  "rendered": "error[E0412]: cannot find type `Iter` in this scope
-  --> $DIR/use_suggestion_json.rs:11:12
-   |
-LL |     let x: Iter;
-   |            ^^^^ not found in this scope
-help: possible candidates are found in other modules, you can import them into scope
-   |
-LL | use std::collections::binary_heap::Iter;
-   |
-LL | use std::collections::btree_map::Iter;
-   |
-LL | use std::collections::btree_set::Iter;
-   |
-LL | use std::collections::hash_map::Iter;
-   |
-and 8 other candidates
+  "rendered": "\u001b[0m\u001b[1m\u001b[38;5;9merror[E0412]\u001b[0m\u001b[0m\u001b[1m: cannot find type `Iter` in this scope\u001b[0m
+\u001b[0m  \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m--> \u001b[0m\u001b[0m$DIR/use_suggestion_json.rs:12:12\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0m    let x: Iter;\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0m           \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;9m^^^^\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;9mnot found in this scope\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;14mhelp\u001b[0m\u001b[0m: possible candidates are found in other modules, you can import them into scope\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0muse std::collections::binary_heap::Iter;\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0muse std::collections::btree_map::Iter;\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0muse std::collections::btree_set::Iter;\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0muse std::collections::hash_map::Iter;\u001b[0m
+\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
+\u001b[0mand 8 other candidates\u001b[0m
 
 "
 }
@@ -405,7 +405,7 @@ and 8 other candidates
   "level": "error",
   "spans": [],
   "children": [],
-  "rendered": "error: aborting due to previous error
+  "rendered": "\u001b[0m\u001b[1m\u001b[38;5;9merror\u001b[0m\u001b[0m\u001b[1m: aborting due to previous error\u001b[0m
 
 "
 }
@@ -415,6 +415,6 @@ and 8 other candidates
   "level": "",
   "spans": [],
   "children": [],
-  "rendered": "For more information about this error, try `rustc --explain E0412`.
+  "rendered": "\u001b[0m\u001b[1mFor more information about this error, try `rustc --explain E0412`.\u001b[0m
 "
 }
diff --git a/src/tools/compiletest/src/json.rs b/src/tools/compiletest/src/json.rs
index ba919f4c411..a7615f5f423 100644
--- a/src/tools/compiletest/src/json.rs
+++ b/src/tools/compiletest/src/json.rs
@@ -62,7 +62,7 @@ struct DiagnosticCode {
     explanation: Option<String>,
 }
 
-pub fn extract_rendered(output: &str, proc_res: &ProcRes) -> String {
+pub fn extract_rendered(output: &str) -> String {
     output
         .lines()
         .filter_map(|line| {
@@ -70,11 +70,12 @@ pub fn extract_rendered(output: &str, proc_res: &ProcRes) -> String {
                 match serde_json::from_str::<Diagnostic>(line) {
                     Ok(diagnostic) => diagnostic.rendered,
                     Err(error) => {
-                        proc_res.fatal(Some(&format!(
+                        print!(
                             "failed to decode compiler output as json: \
                              `{}`\nline: {}\noutput: {}",
                             error, line, output
-                        )));
+                        );
+                        panic!()
                     }
                 }
             } else {
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 369bb3fefe5..6df56168973 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2090,50 +2090,10 @@ impl<'test> TestCx<'test> {
     }
 
     fn fatal_proc_rec(&self, err: &str, proc_res: &ProcRes) -> ! {
-        self.try_print_open_handles();
         self.error(err);
         proc_res.fatal(None);
     }
 
-    // This function is a poor man's attempt to debug rust-lang/rust#38620, if
-    // that's closed then this should be deleted
-    //
-    // This is a very "opportunistic" debugging attempt, so we ignore all
-    // errors here.
-    fn try_print_open_handles(&self) {
-        if !cfg!(windows) {
-            return;
-        }
-        if self.config.mode != Incremental {
-            return;
-        }
-
-        let filename = match self.testpaths.file.file_stem() {
-            Some(path) => path,
-            None => return,
-        };
-
-        let mut cmd = Command::new("handle.exe");
-        cmd.arg("-a").arg("-u");
-        cmd.arg(filename);
-        cmd.arg("-nobanner");
-        cmd.stdout(Stdio::piped());
-        cmd.stderr(Stdio::piped());
-        let output = match cmd.spawn().and_then(read2_abbreviated) {
-            Ok(output) => output,
-            Err(_) => return,
-        };
-        println!("---------------------------------------------------");
-        println!("ran extra command to debug rust-lang/rust#38620: ");
-        println!("{:?}", cmd);
-        println!("result: {}", output.status);
-        println!("--- stdout ----------------------------------------");
-        println!("{}", String::from_utf8_lossy(&output.stdout));
-        println!("--- stderr ----------------------------------------");
-        println!("{}", String::from_utf8_lossy(&output.stderr));
-        println!("---------------------------------------------------");
-    }
-
     // codegen tests (using FileCheck)
 
     fn compile_test_and_save_ir(&self) -> ProcRes {
@@ -2844,7 +2804,7 @@ impl<'test> TestCx<'test> {
         let stderr = if explicit {
             proc_res.stderr.clone()
         } else {
-            json::extract_rendered(&proc_res.stderr, &proc_res)
+            json::extract_rendered(&proc_res.stderr)
         };
 
         let normalized_stderr = self.normalize_output(&stderr, &self.props.normalize_stderr);
@@ -3464,7 +3424,9 @@ impl ProcRes {
              {}\n\
              ------------------------------------------\n\
              \n",
-            self.status, self.cmdline, self.stdout, self.stderr
+            self.status, self.cmdline,
+            json::extract_rendered(&self.stdout),
+            json::extract_rendered(&self.stderr),
         );
         // Use resume_unwind instead of panic!() to prevent a panic message + backtrace from
         // compiletest, which is unnecessary noise.