improve errors management

src/input.rs

@@ -1,72 +1,43 @@
+use error_chain::error_chain;
 use std::{
-    env, fmt,
+    env,
     fs::{remove_file, File},
     io::{self, Read, Write},
     process::Command,
-    result,
 };
 
-// Error wrapper
-
-#[derive(Debug)]
-pub enum Error {
-    IoError(io::Error),
-    GetEditorEnvVarNotFoundError(env::VarError),
-    AskForConfirmationDeniedError,
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "input: ")?;
-
-        match self {
-            Error::IoError(err) => err.fmt(f),
-            Error::GetEditorEnvVarNotFoundError(err) => err.fmt(f),
-            Error::AskForConfirmationDeniedError => write!(f, "action cancelled"),
-        }
-    }
-}
-
-impl From<io::Error> for Error {
-    fn from(err: io::Error) -> Error {
-        Error::IoError(err)
-    }
-}
-
-impl From<env::VarError> for Error {
-    fn from(err: env::VarError) -> Error {
-        Error::GetEditorEnvVarNotFoundError(err)
-    }
-}
-
-// Result wrapper
-
-type Result<T> = result::Result<T, Error>;
-
-// Utils
+error_chain! {}
 
 pub fn open_editor_with_tpl(tpl: &[u8]) -> Result<String> {
     // Creates draft file
     let mut draft_path = env::temp_dir();
     draft_path.push("himalaya-draft.mail");
-    File::create(&draft_path)?.write(tpl)?;
+    File::create(&draft_path)
+        .chain_err(|| format!("Cannot create file `{}`", draft_path.to_string_lossy()))?
+        .write(tpl)
+        .chain_err(|| format!("Cannot write file `{}`", draft_path.to_string_lossy()))?;
 
     // Opens editor and saves user input to draft file
-    Command::new(env::var("EDITOR")?)
+    Command::new(env::var("EDITOR").chain_err(|| "Cannot find `EDITOR` env var")?)
         .arg(&draft_path)
-        .status()?;
+        .status()
+        .chain_err(|| "Cannot start editor")?;
 
     // Extracts draft file content
     let mut draft = String::new();
-    File::open(&draft_path)?.read_to_string(&mut draft)?;
-    remove_file(&draft_path)?;
+    File::open(&draft_path)
+        .chain_err(|| format!("Cannot open file `{}`", draft_path.to_string_lossy()))?
+        .read_to_string(&mut draft)
+        .chain_err(|| format!("Cannot read file `{}`", draft_path.to_string_lossy()))?;
+    remove_file(&draft_path)
+        .chain_err(|| format!("Cannot remove file `{}`", draft_path.to_string_lossy()))?;
 
     Ok(draft)
 }
 
 pub fn ask_for_confirmation(prompt: &str) -> Result<()> {
     print!("{} (y/n) ", prompt);
-    io::stdout().flush()?;
+    io::stdout().flush().chain_err(|| "Cannot flush stdout")?;
 
     match io::stdin()
         .bytes()
@@ -75,6 +46,7 @@ pub fn ask_for_confirmation(prompt: &str) -> Result<()> {
         .map(|bytes| bytes as char)
     {
         Some('y') | Some('Y') => Ok(()),
-        _ => Err(Error::AskForConfirmationDeniedError),
+        Some(choice) => Err(format!("Invalid choice `{}`", choice).into()),
+        None => Err("Empty choice".into()),
     }
 }