Update to the new backtrace API

[thenorili]

This addresses Issue #97. Pardon the half-baked commit message for now, I'll write it out more thoroughly once it's ready. I wrote a minimal test that produces error and panic backtraces, where I'm struggling is capturing this output and comparing it to a snippet. Comparing an error backtrace seems really difficult without intercepting stderr with something like Gag, which I'd prefer to avoid. Comparing the panic backtrace seems promising but the panic hook I added is only sending me the actual panic text -- ie panic!("foo") -> foo.

trying for an error backtrace like..

    fn low(frame: FailFrame) -> Result<(), Report> {
        let e: Report = eyre!("This program's frameness is suspect!");
        if let FailFrame::Low = frame {
            Err::<(), Report>(e).wrap_err("The low-level code has failed!")
            //            panic!("hello");
            //            ()
        } else {
            Ok(())
        }
    }

            Box::new(move |info| {
                let mut global_buffer = global_buffer.lock().unwrap();

                if let Some(s) = info.payload().downcast_ref::<&str>() {
                    println!("PANIC: {}", *s);
                    *global_buffer = (*s).to_string()
                } else {
                    panic!("help!");
                }
            })
        });

        panic::catch_unwind(|| {
            high(FailFrame::Low).unwrap();
        })
        .expect_err("Backtrace test did not panic.");

returns "panicked while processing panic", aka the payload downcast returned None.

[thenorili]

comparison to a test working normally:

    #[cfg_attr(not(backtrace), ignore)]
    #[test]
    fn test_backtrace_simple() {
        high(FailFrame::Low).unwrap();
    }

produces

running 1 test
thread 'test_backtrace::test_backtrace_simple' panicked at eyre\tests\test_backtrace.rs:61:30:
called `Result::unwrap()` on an `Err` value: The low-level code has failed!

Caused by:
    This program's frameness is suspect!

Location:
    eyre\tests\test_backtrace.rs:14:25

Stack backtrace:
   0: std::backtrace_rs::backtrace::dbghelp::trace
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\..\..\backtrace\src\backtrace\dbghelp.rs:95
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66
   2: std::backtrace::Backtrace::create
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\backtrace.rs:331
   3: std::backtrace::Backtrace::capture
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\backtrace.rs:297
   4: eyre::DefaultHandler::default_with
             at .\src\lib.rs:762
   5: core::ops::function::Fn::call<alloc::boxed::Box<dyn$<eyre::EyreHandler>,alloc::alloc::Global> (*)(ref$<dyn$<core::error::Error> >),tuple$<ref$<dyn$<core::error::Error> > > >
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef\library\core\src\ops\function.rs:79
   6: eyre::capture_handler
             at .\src\lib.rs:597
   7: eyre::Report::from_adhoc<ref$<str$> >
             at .\src\error.rs:114
   8: eyre::Report::msg<ref$<str$> >
             at .\src\error.rs:70
   9: eyre::private::format_err
             at .\src\lib.rs:1229
  10: test_backtrace::test_backtrace::low
             at .\tests\test_backtrace.rs:14
  11: test_backtrace::test_backtrace::med
             at .\tests\test_backtrace.rs:29
  12: test_backtrace::test_backtrace::high
             at .\tests\test_backtrace.rs:37
  13: test_backtrace::test_backtrace::test_backtrace_simple
             at .\tests\test_backtrace.rs:61
  14: test_backtrace::test_backtrace::test_backtrace_simple::closure$0
             at .\tests\test_backtrace.rs:60
  15: core::ops::function::FnOnce::call_once<test_backtrace::test_backtrace::test_backtrace_simple::closure_env$0,tuple$<> >
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef\library\core\src\ops\function.rs:250
  16: core::ops::function::FnOnce::call_once
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\ops\function.rs:250
  17: test::__rust_begin_short_backtrace<enum2$<core::result::Result<tuple$<>,alloc::string::String> >,enum2$<core::result::Result<tuple$<>,alloc::string::String> > (*)()>
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:628
  18: test::run_test_in_process::closure$0
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:651
  19: core::panic::unwind_safe::impl$23::call_once
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\panic\unwind_safe.rs:272
  20: std::panicking::try::do_call
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:552
  21: std::panicking::try
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:516
  22: std::panic::catch_unwind
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panic.rs:142
  23: test::run_test_in_process
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:651
  24: test::run_test::closure$0
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:574
  25: test::run_test::closure$1
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:602
  26: std::sys_common::backtrace::__rust_begin_short_backtrace<test::run_test::closure_env$1,tuple$<> >
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys_common\backtrace.rs:154
  27: std::thread::impl$0::spawn_unchecked_::closure$1::closure$0
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\thread\mod.rs:529
  28: core::panic::unwind_safe::impl$23::call_once
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\panic\unwind_safe.rs:272
  29: std::panicking::try::do_call
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:552
  30: std::panicking::try
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:516
  31: std::panic::catch_unwind
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panic.rs:142
  32: std::thread::impl$0::spawn_unchecked_::closure$1
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\thread\mod.rs:528
  33: core::ops::function::FnOnce::call_once<std::thread::impl$0::spawn_unchecked_::closure_env$1<test::run_test::closure_env$1,tuple$<> >,tuple$<> >
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\ops\function.rs:250
  34: std::sys::windows::thread::impl$0::new::thread_start
             at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys\windows\thread.rs:58
  35: BaseThreadInitThunk
  36: RtlUserThreadStart

stack backtrace:
   0:     0x7ff6a5377cf3 - std::sys_common::backtrace::_print::impl$0::fmt
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys_common\backtrace.rs:44
   1:     0x7ff6a539615d - core::fmt::rt::Argument::fmt
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\fmt\rt.rs:142
   2:     0x7ff6a539615d - core::fmt::write
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\fmt\mod.rs:1117
   3:     0x7ff6a53741b1 - std::io::Write::write_fmt<std::sys::windows::stdio::Stderr>
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\io\mod.rs:1763
   4:     0x7ff6a5377afa - std::sys_common::backtrace::_print
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys_common\backtrace.rs:47
   5:     0x7ff6a5377afa - std::sys_common::backtrace::print
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys_common\backtrace.rs:34
   6:     0x7ff6a537a639 - std::panicking::default_hook::closure$1
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:272
   7:     0x7ff6a537a2fb - std::panicking::default_hook
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:292
   8:     0x7ff6a537ab24 - std::panicking::rust_panic_with_hook
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:779
   9:     0x7ff6a537a9f5 - std::panicking::begin_panic_handler::closure$0
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:657
  10:     0x7ff6a53785e9 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>      
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys_common\backtrace.rs:170
  11:     0x7ff6a537a704 - std::panicking::begin_panic_handler
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:645
  12:     0x7ff6a53a0577 - core::panicking::panic_fmt
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\panicking.rs:72
  13:     0x7ff6a53a0af3 - core::result::unwrap_failed
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\result.rs:1653
  14:     0x7ff6a53135f0 - enum2$<core::result::Result<tuple$<>,eyre::Report> >::unwrap<tuple$<>,eyre::Report>
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef\library\core\src\result.rs:1077
  15:     0x7ff6a5312ad1 - test_backtrace::test_backtrace::test_backtrace_simple
                               at C:\Users\nori\dev\eyre\eyre\tests\test_backtrace.rs:61
  16:     0x7ff6a53136c8 - test_backtrace::test_backtrace::test_backtrace_simple::closure$0
                               at C:\Users\nori\dev\eyre\eyre\tests\test_backtrace.rs:60
  17:     0x7ff6a5311052 - core::ops::function::FnOnce::call_once<test_backtrace::test_backtrace::test_backtrace_simple::closure_env$0,tuple$<> > 
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef\library\core\src\ops\function.rs:250
  18:     0x7ff6a53560df - core::ops::function::FnOnce::call_once
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\ops\function.rs:250
  19:     0x7ff6a53560df - test::__rust_begin_short_backtrace<enum2$<core::result::Result<tuple$<>,alloc::string::String> >,enum2$<core::result::Result<tuple$<>,alloc::string::String> > (*)()>
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:628
  20:     0x7ff6a5354b53 - test::run_test_in_process::closure$0
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:651
  21:     0x7ff6a5354b53 - core::panic::unwind_safe::impl$23::call_once
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\panic\unwind_safe.rs:272
  22:     0x7ff6a5354b53 - std::panicking::try::do_call
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:552
  23:     0x7ff6a5354b53 - std::panicking::try
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:516
  24:     0x7ff6a5354b53 - std::panic::catch_unwind
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panic.rs:142
  25:     0x7ff6a5354b53 - test::run_test_in_process
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:651
  26:     0x7ff6a5354b53 - test::run_test::closure$0
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:574
  27:     0x7ff6a5313b6a - test::run_test::closure$1
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\test\src\lib.rs:602
  28:     0x7ff6a5313b6a - std::sys_common::backtrace::__rust_begin_short_backtrace<test::run_test::closure_env$1,tuple$<> >
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys_common\backtrace.rs:154
  29:     0x7ff6a53196b0 - std::thread::impl$0::spawn_unchecked_::closure$1::closure$0
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\thread\mod.rs:529
  30:     0x7ff6a53196b0 - core::panic::unwind_safe::impl$23::call_once
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\panic\unwind_safe.rs:272
  31:     0x7ff6a53196b0 - std::panicking::try::do_call
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:552
  32:     0x7ff6a53196b0 - std::panicking::try
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panicking.rs:516
  33:     0x7ff6a53196b0 - std::panic::catch_unwind
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\panic.rs:142
  34:     0x7ff6a53196b0 - std::thread::impl$0::spawn_unchecked_::closure$1
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\thread\mod.rs:528
  35:     0x7ff6a53196b0 - core::ops::function::FnOnce::call_once<std::thread::impl$0::spawn_unchecked_::closure_env$1<test::run_test::closure_env$1,tuple$<> >,tuple$<> >
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\core\src\ops\function.rs:250
  36:     0x7ff6a538682c - std::sys::windows::thread::impl$0::new::thread_start
                               at /rustc/4b85902b438f791c5bfcb6b1c5b476d5b88e2bef/library\std\src\sys\windows\thread.rs:58
  37:     0x7ffcfc36257d - BaseThreadInitThunk
  38:     0x7ffcfd38aa58 - RtlUserThreadStart
test test_backtrace::test_backtrace_simple ... FAILED

failures:

failures:
    test_backtrace::test_backtrace_simple

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.05s

error: test failed, to rerun pass `-p eyre --test test_backtrace`

[thenorili]

Even if I set up gag to grab the output during this panic, I don't see how to keep getting that output with a panic handler that's been modified not to panic so that I can go on to test the output. I'm going to look at how std backtrace writes their unit tests.

[thenorili]

We fixed backtrace in #160 and determined that the UI test isn't a realistic goal.