Auto merge of #46450 - Gilnaa:libtest_json_output, r=nrc

Libtest json output

A revisit to my [last PR](#45923).

Events are now more atomic, printed in a flat hierarchy.

For the normal test output:
```
running 1 test
test f ... FAILED

failures:

---- f stdout ----
	thread 'f' panicked at 'assertion failed: `(left == right)`
  left: `3`,
 right: `4`', f.rs:3:1
note: Run with `RUST_BACKTRACE=1` for a backtrace.

failures:
    f

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
```

The JSON equivalent is:
```
{ "type": "suite", "event": "started", "test_count": "1" }
{ "type": "test", "event": "started", "name": "f" }
{ "type": "test", "event": "failed", "name": "f" }
{ "type": "suite", "event": "failed", "passed": 0, "failed": 1, "allowed_fail": 0, "ignored": 0,  "measured": 0, "filtered_out": "0" }
{ "type": "test_output", "name": "f", "output": "thread 'f' panicked at 'assertion failed: `(left == right)`
  left: `3`,
 right: `4`', f.rs:3:1
note: Run with `RUST_BACKTRACE=1` for a backtrace.
" }
```

src/libtest/formatters/json.rs

@@ -0,0 +1,229 @@
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use super::*;
+
+pub(crate) struct JsonFormatter<T> {
+    out: OutputLocation<T>,
+}
+
+impl<T: Write> JsonFormatter<T> {
+    pub fn new(out: OutputLocation<T>) -> Self {
+        Self { out }
+    }
+
+    fn write_message(&mut self, s: &str) -> io::Result<()> {
+        assert!(!s.contains('\n'));
+
+        self.out.write_all(s.as_ref())?;
+        self.out.write_all(b"\n")
+    }
+
+    fn write_event(
+        &mut self,
+        ty: &str,
+        name: &str,
+        evt: &str,
+        extra: Option<String>,
+    ) -> io::Result<()> {
+        if let Some(extras) = extra {
+            self.write_message(&*format!(
+                r#"{{ "type": "{}", "name": "{}", "event": "{}", {} }}"#,
+                ty,
+                name,
+                evt,
+                extras
+            ))
+        } else {
+            self.write_message(&*format!(
+                r#"{{ "type": "{}", "name": "{}", "event": "{}" }}"#,
+                ty,
+                name,
+                evt
+            ))
+        }
+    }
+}
+
+impl<T: Write> OutputFormatter for JsonFormatter<T> {
+    fn write_run_start(&mut self, test_count: usize) -> io::Result<()> {
+        self.write_message(&*format!(
+            r#"{{ "type": "suite", "event": "started", "test_count": "{}" }}"#,
+            test_count
+        ))
+    }
+
+    fn write_test_start(&mut self, desc: &TestDesc) -> io::Result<()> {
+        self.write_message(&*format!(
+            r#"{{ "type": "test", "event": "started", "name": "{}" }}"#,
+            desc.name
+        ))
+    }
+
+    fn write_result(
+        &mut self,
+        desc: &TestDesc,
+        result: &TestResult,
+        stdout: &[u8],
+    ) -> io::Result<()> {
+        match *result {
+            TrOk => self.write_event("test", desc.name.as_slice(), "ok", None),
+
+            TrFailed => {
+                let extra_data = if stdout.len() > 0 {
+                    Some(format!(
+                        r#""stdout": "{}""#,
+                        EscapedString(String::from_utf8_lossy(stdout))
+                    ))
+                } else {
+                    None
+                };
+
+                self.write_event("test", desc.name.as_slice(), "failed", extra_data)
+            }
+
+            TrFailedMsg(ref m) => {
+                self.write_event(
+                    "test",
+                    desc.name.as_slice(),
+                    "failed",
+                    Some(format!(r#""message": "{}""#, EscapedString(m))),
+                )
+            }
+
+            TrIgnored => self.write_event("test", desc.name.as_slice(), "ignored", None),
+
+            TrAllowedFail => {
+                self.write_event("test", desc.name.as_slice(), "allowed_failure", None)
+            }
+
+            TrBench(ref bs) => {
+                let median = bs.ns_iter_summ.median as usize;
+                let deviation = (bs.ns_iter_summ.max - bs.ns_iter_summ.min) as usize;
+
+                let mbps = if bs.mb_s == 0 {
+                    "".into()
+                } else {
+                    format!(r#", "mib_per_second": {}"#, bs.mb_s)
+                };
+
+                let line = format!(
+                    "{{ \"type\": \"bench\", \
+                                \"name\": \"{}\", \
+                                \"median\": {}, \
+                                \"deviation\": {}{} }}",
+                    desc.name,
+                    median,
+                    deviation,
+                    mbps
+                );
+
+                self.write_message(&*line)
+            }
+        }
+    }
+
+    fn write_timeout(&mut self, desc: &TestDesc) -> io::Result<()> {
+        self.write_message(&*format!(
+            r#"{{ "type": "test", "event": "timeout", "name": "{}" }}"#,
+            desc.name
+        ))
+    }
+
+    fn write_run_finish(&mut self, state: &ConsoleTestState) -> io::Result<bool> {
+
+        self.write_message(&*format!(
+            "{{ \"type\": \"suite\", \
+            \"event\": \"{}\", \
+            \"passed\": {}, \
+            \"failed\": {}, \
+            \"allowed_fail\": {}, \
+            \"ignored\": {}, \
+            \"measured\": {}, \
+            \"filtered_out\": \"{}\" }}",
+            if state.failed == 0 { "ok" } else { "failed" },
+            state.passed,
+            state.failed + state.allowed_fail,
+            state.allowed_fail,
+            state.ignored,
+            state.measured,
+            state.filtered_out
+        ))?;
+
+        Ok(state.failed == 0)
+    }
+}
+
+/// A formatting utility used to print strings with characters in need of escaping.
+/// Base code taken form `libserialize::json::escape_str`
+struct EscapedString<S: AsRef<str>>(S);
+
+impl<S: AsRef<str>> ::std::fmt::Display for EscapedString<S> {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        let mut start = 0;
+
+        for (i, byte) in self.0.as_ref().bytes().enumerate() {
+            let escaped = match byte {
+                b'"' => "\\\"",
+                b'\\' => "\\\\",
+                b'\x00' => "\\u0000",
+                b'\x01' => "\\u0001",
+                b'\x02' => "\\u0002",
+                b'\x03' => "\\u0003",
+                b'\x04' => "\\u0004",
+                b'\x05' => "\\u0005",
+                b'\x06' => "\\u0006",
+                b'\x07' => "\\u0007",
+                b'\x08' => "\\b",
+                b'\t' => "\\t",
+                b'\n' => "\\n",
+                b'\x0b' => "\\u000b",
+                b'\x0c' => "\\f",
+                b'\r' => "\\r",
+                b'\x0e' => "\\u000e",
+                b'\x0f' => "\\u000f",
+                b'\x10' => "\\u0010",
+                b'\x11' => "\\u0011",
+                b'\x12' => "\\u0012",
+                b'\x13' => "\\u0013",
+                b'\x14' => "\\u0014",
+                b'\x15' => "\\u0015",
+                b'\x16' => "\\u0016",
+                b'\x17' => "\\u0017",
+                b'\x18' => "\\u0018",
+                b'\x19' => "\\u0019",
+                b'\x1a' => "\\u001a",
+                b'\x1b' => "\\u001b",
+                b'\x1c' => "\\u001c",
+                b'\x1d' => "\\u001d",
+                b'\x1e' => "\\u001e",
+                b'\x1f' => "\\u001f",
+                b'\x7f' => "\\u007f",
+                _ => {
+                    continue;
+                }
+            };
+
+            if start < i {
+                f.write_str(&self.0.as_ref()[start..i])?;
+            }
+
+            f.write_str(escaped)?;
+
+            start = i + 1;
+        }
+
+        if start != self.0.as_ref().len() {
+            f.write_str(&self.0.as_ref()[start..])?;
+        }
+
+        Ok(())
+    }
+}

src/libtest/formatters/mod.rs

@@ -0,0 +1,32 @@
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use super::*;
+
+mod pretty;
+mod json;
+mod terse;
+
+pub(crate) use self::pretty::PrettyFormatter;
+pub(crate) use self::json::JsonFormatter;
+pub(crate) use self::terse::TerseFormatter;
+
+pub(crate) trait OutputFormatter {
+    fn write_run_start(&mut self, test_count: usize) -> io::Result<()>;
+    fn write_test_start(&mut self, desc: &TestDesc) -> io::Result<()>;
+    fn write_timeout(&mut self, desc: &TestDesc) -> io::Result<()>;
+    fn write_result(
+        &mut self,
+        desc: &TestDesc,
+        result: &TestResult,
+        stdout: &[u8],
+    ) -> io::Result<()>;
+    fn write_run_finish(&mut self, state: &ConsoleTestState) -> io::Result<bool>;
+}