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Provide custom frame filtering options (#37)
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* Mostly done

* Fix the actual filtering

* cleanup

* remove comment and add it to pr

* Add fancy placeholders for hidden frames

* Change decorator for hidden frames to `⋮`

* Use `&mut Vec<&Frame>` for frame filtering

* Update changelog

Co-authored-by: Joel Höner <athre0z@zyantific.com>
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@yaahc @athre0z
yaahc and athre0z committed May 5, 2020
1 parent c5f5e9c commit d8660e9
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Showing 2 changed files with 108 additions and 47 deletions.
17 changes: 11 additions & 6 deletions CHANGELOG.md
View file
Expand Up @@ -5,12 +5,17 @@ All notable changes to this project will be documented in this file.

#### Added
- `BacktracePrinter::format_trace_to_string`
- Ability to add custom frame filter callbacks
- `BacktracePrinter::add_frame_filter`
- `BacktracePrinter::clear_frame_filters`
- `default_frame_filter`
- Thanks to @yaahc for helping out with this!

#### Changed
- Rename `Settings` -> `BacktracePrinter`
- Move `print_backtrace` -> `BacktracePrinter::print_trace`
- Move `print_panic_info` -> `BacktracePrinter::print_panic_info`
- Move `color_backtrace::failure::print_backtrace` ->
- Rename `Settings` → `BacktracePrinter`
- Move `print_backtrace` → `BacktracePrinter::print_trace`
- Move `print_panic_info` → `BacktracePrinter::print_panic_info`
- Move `color_backtrace::failure::print_backtrace` →
`BacktracePrinter::print_failure_trace`
- The majority of old APIs have deprecated shims that forward calls to
their new place to ease porting
Expand Down Expand Up @@ -56,7 +61,7 @@ All notable changes to this project will be documented in this file.

#### Added
- Experimental support for [failure] error backtraces
- Contributed by Jane Lusby (@yaahallo)
- Contributed by Jane Lusby (@yaahc)

#### Changed
- Switch to [gimli] backend for backtraces on macOS and Linux
Expand All @@ -79,7 +84,7 @@ All notable changes to this project will be documented in this file.
- Improved {dependency code,post panic frame,runtime init} heuristics
- Changed default panic message to be more professional
- Relicensed from MIT to MIT/Apache-2.0 dual licensing
- Moved `get_verbosity` -> `Verbosity::from_env`
- Moved `get_verbosity` → `Verbosity::from_env`
- Fix readability on light terminal themes
- Fix deadlock when unwrapping an error while printing the panic
- Many internal tweaks
Expand Down
138 changes: 97 additions & 41 deletions src/lib.rs
View file
Expand Up @@ -135,10 +135,15 @@ pub fn install_with_settings(printer: BacktracePrinter) {
// [Backtrace frame] //
// ============================================================================================== //

struct Frame {
name: Option<String>,
lineno: Option<u32>,
filename: Option<PathBuf>,
pub type FilterCallback = dyn Fn(&mut Vec<&Frame>) + Send + Sync + 'static;

#[derive(Debug)]
pub struct Frame {
pub n: usize,
pub name: Option<String>,
pub lineno: Option<u32>,
pub filename: Option<PathBuf>,
_private_ctor: (),
}

impl Frame {
Expand Down Expand Up @@ -331,6 +336,25 @@ impl Frame {
}
}

/// The default frame filter. Heuristically determines whether a frame is likely to be an
/// uninteresting frame. This filters out post panic frames and runtime init frames and dependency
/// code.
pub fn default_frame_filter(frames: &mut Vec<&Frame>) {
let top_cutoff = frames
.iter()
.rposition(|x| x.is_post_panic_code())
.map(|x| x + 1)
.unwrap_or(0);

let bottom_cutoff = frames
.iter()
.position(|x| x.is_runtime_init_code())
.unwrap_or_else(|| frames.len());

let rng = top_cutoff..bottom_cutoff;
frames.retain(|x| rng.contains(&x.n))
}

// ============================================================================================== //
// [BacktracePrinter] //
// ============================================================================================== //
Expand Down Expand Up @@ -394,6 +418,7 @@ pub struct BacktracePrinter {
verbosity: Verbosity,
strip_function_hash: bool,
colors: ColorScheme,
filters: Vec<Box<FilterCallback>>,
}

impl Default for BacktracePrinter {
Expand All @@ -403,6 +428,7 @@ impl Default for BacktracePrinter {
message: "The application panicked (crashed).".to_owned(),
strip_function_hash: false,
colors: ColorScheme::classic(),
filters: vec![Box::new(default_frame_filter)],
}
}
}
Expand Down Expand Up @@ -438,13 +464,39 @@ impl BacktracePrinter {
self
}

/// Controls whether the hash part of functions is printed stripped.
/// Controls whether the hash part of functions is stripped.
///
/// Defaults to `false`.
pub fn strip_function_hash(mut self, strip: bool) -> Self {
self.strip_function_hash = strip;
self
}

/// Add a custom filter to the set of frame filters
///
/// Filters are run in the order they are added.
///
/// # Example
///
/// ```rust
/// use color_backtrace::{default_output_stream, BacktracePrinter};
///
/// BacktracePrinter::new()
/// .add_frame_filter(Box::new(|frames| {
/// frames.retain(|x| matches!(&x.name, Some(n) if !n.starts_with("blabla")))
/// }))
/// .install(default_output_stream());
/// ```
pub fn add_frame_filter(mut self, filter: Box<FilterCallback>) -> Self {
self.filters.push(filter);
self
}

/// Clears all filters associated with this printer, including the default filter
pub fn clear_frame_filters(mut self) -> Self {
self.filters.clear();
self
}
}

/// Routines for putting the panic printer to use.
Expand Down Expand Up @@ -485,54 +537,58 @@ impl BacktracePrinter {
.frames()
.iter()
.flat_map(|frame| frame.symbols())
.map(|sym| Frame {
.zip(1usize..)
.map(|(sym, n)| Frame {
name: sym.name().map(|x| x.to_string()),
lineno: sym.lineno(),
filename: sym.filename().map(|x| x.into()),
n,
_private_ctor: (),
})
.collect();

// Try to find where the interesting part starts...
let top_cutoff = frames
.iter()
.rposition(Frame::is_post_panic_code)
.map(|x| x + 1)
.unwrap_or(0);
let mut filtered_frames = frames.iter().collect();
for filter in &self.filters {
filter(&mut filtered_frames);
}

// Try to find where language init frames start ...
let bottom_cutoff = frames
.iter()
.position(Frame::is_runtime_init_code)
.unwrap_or_else(|| frames.len());
if filtered_frames.is_empty() {
// TODO: Would probably look better centered.
return writeln!(out, "<empty backtrace>");
}

if top_cutoff != 0 {
let text = format!("({} post panic frames hidden)", top_cutoff);
out.set_color(&self.colors.frames_omitted_msg)?;
writeln!(out, "{:^80}", text)?;
out.reset()?;
// Don't let filters mess with the order.
filtered_frames.sort_by_key(|x| x.n);

macro_rules! print_hidden {
($n:expr) => {
out.set_color(&self.colors.frames_omitted_msg)?;
let n = $n;
let text = format!(
"{decorator} {n} frame{plural} hidden {decorator}",
n = n,
plural = if n == 1 { "" } else { "s" },
decorator = "⋮",
);
writeln!(out, "{:^80}", text)?;
out.reset()?;
};
}

// Turn them into `Frame` objects and print them.
let num_frames = frames.len();
let frames = frames
.into_iter()
.skip(top_cutoff)
.take(bottom_cutoff - top_cutoff)
.zip(top_cutoff..);

// Print surviving frames.
for (frame, i) in frames {
frame.print(i, out, self)?;
let mut last_n = 0;
for frame in &filtered_frames {
let frame_delta = frame.n - last_n - 1;
if frame_delta != 0 {
print_hidden!(frame_delta);
}
frame.print(frame.n, out, self)?;
last_n = frame.n;
}

if bottom_cutoff != num_frames {
let text = format!(
"({} runtime init frames hidden)",
num_frames - bottom_cutoff
);
out.set_color(&self.colors.frames_omitted_msg)?;
writeln!(out, "{:^80}", text)?;
out.reset()?;
let last_filtered_n = filtered_frames.last().unwrap().n;
let last_unfiltered_n = frames.last().unwrap().n;
if last_filtered_n < last_unfiltered_n {
print_hidden!(last_unfiltered_n - last_filtered_n);
}

Ok(())
Expand Down

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