add derive_err_kind() and more docs

examples/tutorial13.rs

@@ -21,11 +21,12 @@ pub mod mycrate {
         IO(String),
     }
 
-    pub type Error = ChainError<ErrorKind>;
+    derive_err_kind!(Error, ErrorKind);
+
     pub type Result<T> = std::result::Result<T, Error>;
 
-    impl ::std::fmt::Display for ErrorKind {
-        fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+    impl std::fmt::Display for ErrorKind {
+        fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
             match self {
                 ErrorKind::Func2 => write!(f, "func1 error calling func2"),
                 ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),

examples/tutorial14.rs

@@ -0,0 +1,217 @@
+pub mod mycrate {
+    use std::error::Error as StdError;
+
+    use func2mod::{do_some_io, func2};
+
+    pub mod func2mod {
+        use std::error::Error as StdError;
+        use std::io;
+
+        pub enum ErrorKind {
+            IO(String),
+        }
+
+        impl std::fmt::Display for ErrorKind {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
+                match self {
+                    ErrorKind::IO(s) => std::fmt::Display::fmt(s, f),
+                }
+            }
+        }
+
+        impl std::fmt::Debug for ErrorKind {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
+                match self {
+                    ErrorKind::IO(s) => std::fmt::Display::fmt(s, f),
+                }
+            }
+        }
+
+        macro_rules! mcherr {
+            ( $k:expr ) => {{
+                |e| {
+                    Error(
+                        $k,
+                        Some(Box::from(e)),
+                        Some(concat!(file!(), ":", line!(), ": ")),
+                    )
+                }
+            }};
+        }
+
+        pub struct Error(
+            ErrorKind,
+            Option<Box<dyn std::error::Error + 'static>>,
+            Option<&'static str>,
+        );
+
+        impl Error {
+            pub fn kind(&self) -> &ErrorKind {
+                &self.0
+            }
+        }
+
+        impl From<ErrorKind> for Error {
+            fn from(e: ErrorKind) -> Self {
+                Error(e, None, None)
+            }
+        }
+
+        impl std::error::Error for Error {
+            fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+                self.1.as_ref().map(|e| e.as_ref())
+            }
+        }
+
+        impl std::fmt::Display for Error {
+            fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+                std::fmt::Display::fmt(&self.0, f)
+            }
+        }
+
+        impl std::fmt::Debug for Error {
+            fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+                if let Some(ref o) = self.2 {
+                    std::fmt::Display::fmt(o, f)?;
+                }
+
+                std::fmt::Debug::fmt(&self.0, f)?;
+
+                if let Some(e) = self.source() {
+                    std::fmt::Display::fmt("\nCaused by:\n", f)?;
+                    std::fmt::Debug::fmt(&e, f)?;
+                }
+                Ok(())
+            }
+        }
+
+        pub fn do_some_io() -> std::result::Result<(), Box<dyn std::error::Error>> {
+            Err(io::Error::from(io::ErrorKind::NotFound))?;
+            Ok(())
+        }
+
+        pub fn func2() -> std::result::Result<(), Error> {
+            let filename = "foo.txt";
+            do_some_io().map_err(mcherr!(ErrorKind::IO(format!(
+                "Error reading '{}'",
+                filename
+            ))))?;
+            Ok(())
+        }
+    }
+
+    #[derive(Debug)]
+    pub enum ErrorKind {
+        Func2,
+        IO(String),
+    }
+
+    impl std::fmt::Display for ErrorKind {
+        fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
+            match self {
+                ErrorKind::Func2 => write!(f, "func1 error calling func2"),
+                ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),
+            }
+        }
+    }
+
+    macro_rules! mcherr {
+        ( $k:expr ) => {{
+            |e| {
+                Error(
+                    $k,
+                    Some(Box::from(e)),
+                    Some(concat!(file!(), ":", line!(), ": ")),
+                )
+            }
+        }};
+    }
+
+    pub struct Error(
+        ErrorKind,
+        Option<Box<dyn std::error::Error + 'static>>,
+        Option<&'static str>,
+    );
+
+    impl Error {
+        pub fn kind(&self) -> &ErrorKind {
+            &self.0
+        }
+    }
+
+    impl From<ErrorKind> for Error {
+        fn from(e: ErrorKind) -> Self {
+            Error(e, None, None)
+        }
+    }
+
+    impl std::error::Error for Error {
+        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+            self.1.as_ref().map(|e| e.as_ref())
+        }
+    }
+
+    impl std::fmt::Display for Error {
+        fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+            std::fmt::Display::fmt(&self.0, f)
+        }
+    }
+
+    impl std::fmt::Debug for Error {
+        fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+            if let Some(ref o) = self.2 {
+                std::fmt::Display::fmt(o, f)?;
+            }
+
+            std::fmt::Debug::fmt(&self.0, f)?;
+            if let Some(e) = self.source() {
+                std::fmt::Display::fmt("\nCaused by:\n", f)?;
+                std::fmt::Debug::fmt(&e, f)?;
+            }
+            Ok(())
+        }
+    }
+
+    pub type Result<T> = std::result::Result<T, Error>;
+
+    pub fn func1() -> Result<()> {
+        func2().map_err(mcherr!(ErrorKind::Func2))?;
+        let filename = String::from("bar.txt");
+        do_some_io().map_err(mcherr!(ErrorKind::IO(filename)))?;
+        Ok(())
+    }
+}
+
+fn main() -> Result<(), Box<std::error::Error>> {
+    use mycrate::func1;
+    use mycrate::ErrorKind;
+    use std::error::Error;
+    use std::io;
+
+    if let Err(e) = func1() {
+        match e.kind() {
+            ErrorKind::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
+            ErrorKind::IO(ref filename) => {
+                eprintln!("Main Error Report: func1 error reading '{}'", filename)
+            }
+        }
+
+        eprintln!();
+        let mut s: &Error = &e;
+        while let Some(c) = s.source() {
+            if let Some(ioerror) = c.downcast_ref::<io::Error>() {
+                eprintln!("caused by: std::io::Error: {}", ioerror);
+                match ioerror.kind() {
+                    io::ErrorKind::NotFound => eprintln!("of kind: std::io::ErrorKind::NotFound"),
+                    _ => {}
+                }
+            } else {
+                eprintln!("caused by: {}", c);
+            }
+            s = c;
+        }
+
+        eprintln!("\nDebug Error:\n{:?}", e);
+    }
+    Ok(())
+}