Better error model

src/error.rs

@@ -0,0 +1,80 @@
+use failure::{Backtrace, Context, Fail};
+use std::fmt::{self, Display};
+use std::process::ExitStatus;
+
+#[derive(Debug)]
+pub struct Error {
+    inner: Context<ErrorKind>,
+}
+
+#[derive(Copy, Clone, Eq, PartialEq, Debug, Fail)]
+pub enum ErrorKind {
+    #[fail(display = "Error asking the user for retry")]
+    Retry,
+
+    #[fail(display = "Cannot find the user base directories")]
+    NoBaseDirectories,
+
+    #[fail(display = "A step failed")]
+    StepFailed,
+
+    #[fail(display = "Error reading the configuration")]
+    Configuration,
+
+    #[fail(display = "A custom pre-command failed")]
+    PreCommand,
+
+    #[fail(display = "{}", _0)]
+    ProcessFailed(ExitStatus),
+
+    #[fail(display = "Unknown Linux Distribution")]
+    #[cfg(target_os = "linux")]
+    UnknownLinuxDistribution,
+
+    #[fail(display = "Detected Python is not the system Python")]
+    #[cfg(target_os = "linux")]
+    NotSystemPython,
+
+    #[fail(display = "Process execution failure")]
+    ProcessExecution,
+
+    #[fail(display = "Self-update failure")]
+    #[cfg(feature = "self-update")]
+    SelfUpdate,
+}
+
+impl Fail for Error {
+    fn cause(&self) -> Option<&Fail> {
+        self.inner.cause()
+    }
+
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.inner.backtrace()
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.inner, f)
+    }
+}
+
+impl Error {
+    pub fn kind(&self) -> ErrorKind {
+        *self.inner.get_context()
+    }
+}
+
+impl From<ErrorKind> for Error {
+    fn from(kind: ErrorKind) -> Error {
+        Error {
+            inner: Context::new(kind),
+        }
+    }
+}
+
+impl From<Context<ErrorKind>> for Error {
+    fn from(inner: Context<ErrorKind>) -> Error {
+        Error { inner }
+    }
+}