3 files changed, 63 insertions, 26 deletions

diff --git a/src/backends/dialog.rs b/src/backends/dialog.rs
index fb0f73f..da17ad1 100644
--- a/src/backends/dialog.rs
+++ b/src/backends/dialog.rs
@@ -1,11 +1,9 @@
 // Copyright (C) 2019 Robin Krahl <robin.krahl@ireas.org>
 // SPDX-License-Identifier: MIT
 
-use std::io;
-use std::io::Result;
 use std::process;
 
-use crate::{Choice, Input, Message, Question};
+use crate::{Choice, Error, Input, Message, Question, Result};
 
 /// The `dialog` backend.
 ///
@@ -75,7 +73,7 @@ impl Dialog {
         command.arg(&self.width);
         command.args(post_args);
 
-        command.output()
+        command.output().map_err(Error::IoError)
     }
 }
 
@@ -83,7 +81,7 @@ fn require_success(status: process::ExitStatus) -> Result<()> {
     if status.success() {
         Ok(())
     } else {
-        Err(io::Error::new(io::ErrorKind::Other, "dialog failed"))
+        Err(Error::from(("dialog", status)))
     }
 }
 
@@ -93,16 +91,10 @@ fn get_choice(status: process::ExitStatus) -> Result<Choice> {
             0 => Ok(Choice::Yes),
             1 => Ok(Choice::No),
             255 => Ok(Choice::Cancel),
-            code => Err(io::Error::new(
-                io::ErrorKind::Other,
-                format!("Could not execute dialog: {}", code),
-            )),
+            _ => Err(Error::from(("dialog", status))),
         }
     } else {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "dialog was terminated by a signal",
-        ))
+        Err(Error::from(("dialog", status)))
     }
 }
 
@@ -110,25 +102,17 @@ fn get_stderr(output: process::Output) -> Result<Option<String>> {
     if output.status.success() {
         String::from_utf8(output.stderr)
             .map(|s| Some(s))
-            .map_err(|_| {
-                io::Error::new(io::ErrorKind::Other, "Input contained invalid UTF-8 bytes")
-            })
+            .map_err(|err| Error::from(err))
     } else {
         if let Some(code) = output.status.code() {
             match code {
                 0 => Ok(None),
                 1 => Ok(None),
                 255 => Ok(None),
-                code => Err(io::Error::new(
-                    io::ErrorKind::Other,
-                    format!("Could not execute dialog: {}", code),
-                )),
+                _ => Err(Error::from(("dialog", output.status))),
             }
         } else {
-            Err(io::Error::new(
-                io::ErrorKind::Other,
-                "dialog was terminated by a signal",
-            ))
+            Err(Error::from(("dialog", output.status)))
         }
     }
 }
diff --git a/src/backends/mod.rs b/src/backends/mod.rs
index 12a178b..fd0ddcc 100644
--- a/src/backends/mod.rs
+++ b/src/backends/mod.rs
@@ -5,7 +5,7 @@ mod dialog;
 
 pub use crate::backends::dialog::Dialog;
 
-use std::io::Result;
+use crate::Result;
 
 /// A dialog backend.
 ///
diff --git a/src/lib.rs b/src/lib.rs
index b51a3cc..422252b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -79,7 +79,60 @@
 /// [`Backend`]: trait.Backend.html
 pub mod backends;
 
-use std::io::Result;
+use std::io;
+use std::process;
+use std::result;
+use std::str;
+use std::string;
+
+/// A result returned by `dialog`.
+pub type Result<T> = result::Result<T, Error>;
+
+/// An error returned by `dialog`.
+#[derive(Debug)]
+pub enum Error {
+    /// A general error with an error message.
+    Error(String),
+    /// An input or output error.
+    IoError(io::Error),
+    /// An UTF-8 error.
+    Utf8Error(str::Utf8Error),
+}
+
+impl From<&str> for Error {
+    fn from(string: &str) -> Error {
+        Error::Error(string.to_string())
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(error: io::Error) -> Error {
+        Error::IoError(error)
+    }
+}
+
+impl From<str::Utf8Error> for Error {
+    fn from(error: str::Utf8Error) -> Error {
+        Error::Utf8Error(error)
+    }
+}
+
+impl From<string::FromUtf8Error> for Error {
+    fn from(error: string::FromUtf8Error) -> Error {
+        Error::Utf8Error(error.utf8_error())
+    }
+}
+
+impl From<(&str, process::ExitStatus)> for Error {
+    fn from(data: (&str, process::ExitStatus)) -> Error {
+        let (command, status) = data;
+        let msg = match status.code() {
+            Some(code) => format!("Command {} failed with exit status {}", command, code),
+            None => format!("Command {} was terminated by a signal", command),
+        };
+        Error::Error(msg)
+    }
+}
 
 /// A dialog box that can be shown using a backend.
 ///