Added extension methods for flattening `eyre::Result<eyre:Result<T>>`s and related constructs.

Fortune for collect's current commit: Curse − 凶

src/ext.rs

@@ -0,0 +1,110 @@
+//! Extensions
+use super::*;
+
+/// Essentially equivelant bound as `eyre::StdError` (private trait)
+///
+/// Useful for when using traits that convert a generic type into an `eyre::Report`.
+pub trait EyreError: std::error::Error + Send + Sync + 'static{}
+impl<T: ?Sized> EyreError for T
+where T: std::error::Error + Send + Sync + 'static{}
+
+pub trait IntoEyre<T>
+{
+    fn into_eyre(self) -> eyre::Result<T>;
+}
+
+impl<T, E: EyreError> IntoEyre<T> for Result<T, E>
+{
+    #[inline(always)] 
+    fn into_eyre(self) -> eyre::Result<T> {
+	match self {
+	    Err(e) => Err(eyre::Report::from(e)),
+	    Ok(y) => Ok(y),
+	}
+    }
+}
+
+pub trait FlattenReports<T>
+{
+    /// Flatten a `eyre::Result<eyre::Result<T>>` into an `eyre::Result<T>`
+    fn flatten(self) -> eyre::Result<T>;
+}
+
+pub trait FlattenEyreResult<T, E>
+where E: EyreError
+{
+    /// Flatten a `Result<Result<T, IE>, OE>` into an `eyre::Result<E>`
+    fn flatten(self) -> eyre::Result<T>;
+}
+
+pub trait FlattenResults<T, E>
+{
+    /// Flatten a `Result<Result<T, IE>, E>` into a `Result<T, E>`.
+    fn flatten(self) -> Result<T, E>;
+}
+
+impl<T, E, IE: Into<E>> FlattenResults<T, E> for Result<Result<T, IE>, E>
+{
+    /// Flatten a `Result<Result<T, impl Into<E>>, E>` into a `Result<T, E>`
+    ///
+    /// This will convert the inner error into the type of the outer error.
+    #[inline] 
+    fn flatten(self) -> Result<T, E> {
+	match self {
+	    Err(e) => Err(e),
+	    Ok(Ok(e)) => Ok(e),
+	    Ok(Err(e)) => Err(e.into())
+	}
+    }
+}
+
+impl<T, IE: EyreError, E: EyreError> FlattenEyreResult<T, E> for Result<Result<T, IE>, E>
+{
+    #[inline] 
+    fn flatten(self) -> eyre::Result<T> {
+	match self {
+	    Err(e) => Err(e).with_note(|| "Flattened report (outer)"),
+	    Ok(Err(e)) => Err(e).with_warning(|| "Flattened report (inner)"),
+	    Ok(Ok(a)) => Ok(a),
+	}	
+    }
+}
+
+impl<T> FlattenReports<T> for eyre::Result<eyre::Result<T>>
+{
+    #[inline] 
+    fn flatten(self) -> eyre::Result<T> {
+	match self {
+	    Err(e) => Err(e.with_note(|| "Flattened report (outer)")),
+	    Ok(Err(e)) => Err(e.with_warning(|| "Flattened report (inner)")),
+	    Ok(Ok(a)) => Ok(a),
+	}
+    }
+}
+
+impl<T> FlattenReports<T> for eyre::Result<Option<T>>
+{
+    #[inline] 
+    fn flatten(self) -> eyre::Result<T> {
+	match self {
+	    Err(e) => Err(e.with_note(|| "Flattened report (outer)")),
+	    Ok(None) => Err(eyre!("Value expected, but not found").with_section(|| format!("Option<{}>", std::any::type_name::<T>()).header("Option type was")).with_warning(|| "Flattened report (inner)")),
+	    Ok(Some(a)) => Ok(a),
+	}
+    }
+}
+
+impl<T, E: EyreError> FlattenEyreResult<T, E> for Result<Option<T>, E>
+{
+    #[inline] 
+    fn flatten(self) -> eyre::Result<T> {
+	match self {
+	    Err(e) => Err(e).with_note(|| "Flattened report (outer)"),
+	    Ok(None) => Err(eyre!("Value expected, but not found")
+			    .with_section(|| format!("Option<{}>", std::any::type_name::<T>())
+					  .header("Option type was"))
+			    .with_warning(|| "Flattened report (inner)")),
+	    Ok(Some(a)) => Ok(a),
+	}
+    }
+}

src/main.rs

@@ -65,6 +65,7 @@ macro_rules! function {
     }}
 }
 
+mod ext; use ext::*;
 mod sys;
 use sys::{
     try_get_size,

src/memfile/hp.rs

@@ -300,15 +300,12 @@ mod tests
     fn get_bytes<'a, P: 'a>(from: P) -> eyre::Result<impl Iterator<Item=eyre::Result<usize>> +'a>
 	where P: AsRef<Path>
     {
+	use crate::*;
 	let dir = from.as_ref().read_dir()?;
 	Ok(dir
 	    .map(|x| x.map(|n| n.file_name()))
 	    .map(|name| name.map(|name| super::find_size_bytes(name)))
-	    .map(|result| match result {
-		Ok(None) => Err(eyre!("Failed to extract bytes")),
-		Ok(Some(x)) => Ok(x),
-		Err(err) => Err(eyre::Report::from(err)),
-	    }))
+	    .map(|result| result.flatten()))
     }
     
     #[test]