feat(color-eyre): Add pre-hook callbacks

color-eyre/examples/pre_hook_callbacks.rs

@@ -0,0 +1,49 @@
+use color_eyre::eyre::Report;
+use tracing::instrument;
+
+#[instrument]
+fn main() -> Result<(), Report> {
+    #[cfg(feature = "capture-spantrace")]
+    install_tracing();
+
+    color_eyre::config::HookBuilder::default()
+        .add_pre_hook_callback(Box::new(|| {
+            eprintln!("This is a pre hook callback");
+        }))
+        .install()
+        .unwrap();
+
+    read_config();
+
+    Ok(())
+}
+
+#[cfg(feature = "capture-spantrace")]
+fn install_tracing() {
+    use tracing_error::ErrorLayer;
+    use tracing_subscriber::prelude::*;
+    use tracing_subscriber::{fmt, EnvFilter};
+
+    let fmt_layer = fmt::layer().with_target(false);
+    let filter_layer = EnvFilter::try_from_default_env()
+        .or_else(|_| EnvFilter::try_new("info"))
+        .unwrap();
+
+    tracing_subscriber::registry()
+        .with(filter_layer)
+        .with(fmt_layer)
+        .with(ErrorLayer::default())
+        .init();
+}
+
+#[instrument]
+fn read_file(path: &str) {
+    if let Err(e) = std::fs::read_to_string(path) {
+        panic!("{}", e);
+    }
+}
+
+#[instrument]
+fn read_config() {
+    read_file("fake_file")
+}

color-eyre/src/config.rs

@@ -11,39 +11,6 @@ use std::env;
 use std::fmt::Write as _;
 use std::{fmt, path::PathBuf, sync::Arc};
 
-#[derive(Debug)]
-struct InstallError;
-
-impl fmt::Display for InstallError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("could not install the BacktracePrinter as another was already installed")
-    }
-}
-
-impl std::error::Error for InstallError {}
-
-#[derive(Debug)]
-struct InstallThemeError;
-
-impl fmt::Display for InstallThemeError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("could not set the provided `Theme` globally as another was already set")
-    }
-}
-
-impl std::error::Error for InstallThemeError {}
-
-#[derive(Debug)]
-struct InstallColorSpantraceThemeError;
-
-impl fmt::Display for InstallColorSpantraceThemeError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("could not set the provided `Theme` via `color_spantrace::set_theme` globally as another was already set")
-    }
-}
-
-impl std::error::Error for InstallColorSpantraceThemeError {}
-
 /// A struct that represents a theme that is used by `color_eyre`
 #[derive(Debug, Copy, Clone, Default)]
 pub struct Theme {
@@ -418,6 +385,7 @@ impl Frame {
 /// Builder for customizing the behavior of the global panic and error report hooks
 pub struct HookBuilder {
     filters: Vec<Box<FilterCallback>>,
+    pre_hook_callbacks: Vec<Box<PreHookCallback>>,
     capture_span_trace_by_default: bool,
     display_env_section: bool,
     #[cfg(feature = "track-caller")]
@@ -461,6 +429,7 @@ impl HookBuilder {
     pub fn blank() -> Self {
         HookBuilder {
             filters: vec![],
+            pre_hook_callbacks: vec![],
             capture_span_trace_by_default: false,
             display_env_section: true,
             #[cfg(feature = "track-caller")]
@@ -698,6 +667,28 @@ impl HookBuilder {
         self
     }
 
+    /// Add a custom pre-hook callback to the set of pre-hook callbacks
+    ///
+    /// This callback will be called before the panic / error hook is called. It can be used to
+    /// print additional information or perform other actions before the panic / error hook is
+    /// called (such as clearing the terminal, printing a message, etc.)
+    ///
+    /// **Note**: This callback will be called in the context of the panic hook, so it should be
+    /// fast and not panic.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// color_eyre::config::HookBuilder::default()
+    ///     .add_pre_hook_callback(Box::new(|| eprintln!("pre-hook callback")))
+    ///     .install()
+    ///     .unwrap();
+    /// ```
+    pub fn add_pre_hook_callback(mut self, callback: Box<PreHookCallback>) -> Self {
+        self.pre_hook_callbacks.push(callback);
+        self
+    }
+
     /// Install the given Hook as the global error report hook
     pub fn install(self) -> Result<(), crate::eyre::Report> {
         let (panic_hook, eyre_hook) = self.try_into_hooks()?;
@@ -726,6 +717,7 @@ impl HookBuilder {
         let metadata = Arc::new(self.issue_metadata);
         let panic_hook = PanicHook {
             filters: self.filters.into(),
+            pre_hook_callbacks: self.pre_hook_callbacks.into(),
             section: self.panic_section,
             #[cfg(feature = "capture-spantrace")]
             capture_span_trace_by_default: self.capture_span_trace_by_default,
@@ -744,6 +736,7 @@ impl HookBuilder {
 
         let eyre_hook = EyreHook {
             filters: panic_hook.filters.clone(),
+            // TODO pre_hook_callbacks: panic_hook.pre_hook_callbacks.clone(),
             #[cfg(feature = "capture-spantrace")]
             capture_span_trace_by_default: self.capture_span_trace_by_default,
             display_env_section: self.display_env_section,
@@ -941,6 +934,7 @@ impl fmt::Display for PanicReport<'_> {
 /// A panic reporting hook
 pub struct PanicHook {
     filters: Arc<[Box<FilterCallback>]>,
+    pre_hook_callbacks: Arc<[Box<PreHookCallback>]>,
     section: Option<Box<dyn Display + Send + Sync + 'static>>,
     panic_message: Box<dyn PanicMessage>,
     theme: Theme,
@@ -984,6 +978,9 @@ impl PanicHook {
         self,
     ) -> Box<dyn Fn(&std::panic::PanicInfo<'_>) + Send + Sync + 'static> {
         Box::new(move |panic_info| {
+            for callback in self.pre_hook_callbacks.iter() {
+                callback();
+            }
             eprintln!("{}", self.panic_report(panic_info));
         })
     }
@@ -1023,6 +1020,7 @@ impl PanicHook {
 /// An eyre reporting hook used to construct `EyreHandler`s
 pub struct EyreHook {
     filters: Arc<[Box<FilterCallback>]>,
+    // TODO pre_hook_callbacks: Arc<[Box<PreHookCallback>]>,
     #[cfg(feature = "capture-spantrace")]
     capture_span_trace_by_default: bool,
     display_env_section: bool,
@@ -1215,6 +1213,9 @@ pub(crate) fn lib_verbosity() -> Verbosity {
 /// Callback for filtering a vector of `Frame`s
 pub type FilterCallback = dyn Fn(&mut Vec<&Frame>) + Send + Sync + 'static;
 
+/// Callback to run before running the panic / error hook
+pub type PreHookCallback = dyn Fn() + Send + Sync + 'static;
+
 /// Callback for filtering issue url generation in error reports
 #[cfg(feature = "issue-url")]
 #[cfg_attr(docsrs, doc(cfg(feature = "issue-url")))]

color-eyre/src/writers.rs

@@ -28,11 +28,13 @@ impl<W> WriterExt for W {
     }
 }
 
+#[cfg(feature = "issue-url")]
 pub(crate) trait DisplayExt: Sized + Display {
     fn with_header<H: Display>(self, header: H) -> Header<Self, H>;
     fn with_footer<F: Display>(self, footer: F) -> Footer<Self, F>;
 }
 
+#[cfg(feature = "issue-url")]
 impl<T> DisplayExt for T
 where
     T: Display,
@@ -80,11 +82,13 @@ where
     }
 }
 
+#[cfg(feature = "issue-url")]
 pub(crate) struct FooterWriter<W> {
     inner: W,
     had_output: bool,
 }
 
+#[cfg(feature = "issue-url")]
 impl<W> fmt::Write for FooterWriter<W>
 where
     W: fmt::Write,
@@ -98,6 +102,7 @@ where
     }
 }
 
+#[cfg(feature = "issue-url")]
 #[allow(explicit_outlives_requirements)]
 pub(crate) struct Footer<B, H>
 where
@@ -108,6 +113,7 @@ where
     footer: H,
 }
 
+#[cfg(feature = "issue-url")]
 impl<B, H> fmt::Display for Footer<B, H>
 where
     B: Display,
@@ -129,6 +135,7 @@ where
     }
 }
 
+#[cfg(feature = "issue-url")]
 #[allow(explicit_outlives_requirements)]
 pub(crate) struct Header<B, H>
 where
@@ -139,6 +146,7 @@ where
     h: H,
 }
 
+#[cfg(feature = "issue-url")]
 impl<B, H> fmt::Display for Header<B, H>
 where
     B: Display,