feat(errors): Introduce error module with custom error type

Introduces an error type using the failure crate. This type has
foreign error links established to various errors that can occur
within Converse.

1 files changed, 75 insertions, 0 deletions

diff --git a/src/errors.rs b/src/errors.rs
new file mode 100644
index 0000000000..3cbda5f4e5
--- /dev/null
+++ b/src/errors.rs
@@ -0,0 +1,75 @@
+//! This module defines custom error types using the `failure`-crate.
+//! Links to foreign error types (such as database connection errors)
+//! are established in a similar way as was tradition in
+//! `error_chain`, albeit manually.
+
+use std::result;
+use actix_web::{ResponseError, HttpResponse};
+use actix_web::http::StatusCode;
+
+// Modules with foreign errors:
+use actix;
+use diesel;
+use r2d2;
+use tera;
+
+pub type Result<T> = result::Result<T, ConverseError>;
+
+#[derive(Debug, Fail)]
+pub enum ConverseError {
+    #[fail(display = "an internal Converse error occured: {}", reason)]
+    InternalError { reason: String },
+
+    #[fail(display = "a database error occured: {}", error)]
+    Database { error: diesel::result::Error },
+
+    #[fail(display = "a database connection pool error occured: {}", error)]
+    ConnectionPool { error: r2d2::Error },
+
+    #[fail(display = "a template rendering error occured: {}", reason)]
+    Template { reason: String },
+
+    // This variant is used as a catch-all for wrapping
+    // actix-web-compatible response errors, such as the errors it
+    // throws itself.
+    #[fail(display = "Actix response error: {}", error)]
+    ActixWeb { error: Box<ResponseError> },
+}
+
+// Establish conversion links to foreign errors:
+
+impl From<diesel::result::Error> for ConverseError {
+    fn from(error: diesel::result::Error) -> ConverseError {
+        ConverseError::Database { error }
+    }
+}
+
+impl From<r2d2::Error> for ConverseError {
+    fn from(error: r2d2::Error) -> ConverseError {
+        ConverseError::ConnectionPool { error }
+    }
+}
+
+impl From<tera::Error> for ConverseError {
+    fn from(error: tera::Error) -> ConverseError {
+        ConverseError::Template {
+            reason: format!("{}", error),
+        }
+    }
+}
+
+impl From<actix::MailboxError> for ConverseError {
+    fn from(error: actix::MailboxError) -> ConverseError {
+        ConverseError::ActixWeb { error: Box::new(error) }
+    }
+}
+
+// Support conversion of error type into HTTP error responses:
+
+impl ResponseError for ConverseError {
+    fn error_response(&self) -> HttpResponse {
+        // Everything is mapped to internal server errors for now.
+        HttpResponse::build(StatusCode::INTERNAL_SERVER_ERROR)
+            .body(format!("An error occured: {}", self))
+    }
+}