Converted error-chain based error to enum based error

- now implements `Send` + `Sync` + `'static`
- still implements `std::error::Error`, `Debug`,
  `Display`, `From<std::fmt::Error>`,
  `From<::serde_json::Error>`

3 files changed, 98 insertions, 14 deletions

diff --git a/askama_shared/src/error.rs b/askama_shared/src/error.rs
new file mode 100644
index 0000000..cdd6b55
--- /dev/null
+++ b/askama_shared/src/error.rs
@@ -0,0 +1,95 @@
+use std::fmt::{self, Display};
+use std::error::{Error as ErrorTrait};
+
+pub type Result<I> = ::std::result::Result<I, Error>;
+
+/// askama error type
+///
+/// # Feature Interaction
+///
+/// If the feature `serde-json` is enabled an
+/// additional error variant `Json` is added.
+///
+/// # Why not `failure`/`error-chain`?
+///
+/// Error from `error-chain` are not `Sync` which
+/// can lead to problems e.g. when this is used
+/// by a crate which use `failure`. Implementing
+/// `Fail` on the other hand prevents the implementation
+/// of `std::error::Error` until specialization lands
+/// on stable. While errors impl. `Fail` can be
+/// converted to a type impl. `std::error::Error`
+/// using a adapter the benefits `failure` would
+/// bring to this crate are small, which is why
+/// `std::error::Error` was used.
+///
+#[derive(Debug, )]
+pub enum Error {
+    /// formatting error
+    Fmt(fmt::Error),
+
+    /// json conversion error
+    #[cfg(feature = "serde-json")]
+    Json(::serde_json::Error),
+
+    /// This error needs to be non-exhaustive as
+    /// the `Json` variants existence depends on
+    /// a feature.
+    #[doc(hidden)]
+    __Nonexhaustive,
+}
+
+impl ErrorTrait for Error {
+
+    fn description(&self) -> &str {
+        match *self {
+            Error::Fmt(ref err) => err.description(),
+            #[cfg(feature = "serde-json")]
+            Error::Json(ref err) => err.description(),
+            _ => "unknown error: __Nonexhaustive"
+        }
+    }
+
+    fn cause(&self) -> Option<&ErrorTrait> {
+        match *self {
+            Error::Fmt(ref err) => err.cause(),
+             #[cfg(feature = "serde-json")]
+            Error::Json(ref err) => err.cause(),
+            _ => None
+        }
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Error::Fmt(ref err) => write!(formatter, "formatting error: {}", err),
+
+            #[cfg(feature = "serde-json")]
+            Error::Json(ref err) => write!(formatter, "json conversion error: {}", err),
+            _ => write!(formatter, "unknown error: __Nonexhaustive")
+        }
+    }
+}
+
+impl From<fmt::Error> for Error {
+    fn from(err: fmt::Error) -> Self {
+        Error::Fmt(err)
+    }
+}
+
+#[cfg(feature = "serde-json")]
+impl From<::serde_json::Error> for Error {
+    fn from(err: ::serde_json::Error) -> Self {
+        Error::Json(err)
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::Error;
+
+    trait AssertSendSyncStatic: Send + Sync + 'static {}
+    impl AssertSendSyncStatic for Error {}
+}
\ No newline at end of file
diff --git a/askama_shared/src/filters/json.rs b/askama_shared/src/filters/json.rs
index 6b818eb..5d1b3ac 100644
--- a/askama_shared/src/filters/json.rs
+++ b/askama_shared/src/filters/json.rs
@@ -1,6 +1,6 @@
 use serde::Serialize;
 use serde_json;
-use errors::{Error, Result};
+use error::{Error, Result};
 use MarkupDisplay;
 
 
diff --git a/askama_shared/src/lib.rs b/askama_shared/src/lib.rs
index 3213778..cbb99d9 100644
--- a/askama_shared/src/lib.rs
+++ b/askama_shared/src/lib.rs
@@ -1,25 +1,14 @@
 #![cfg_attr(feature = "cargo-clippy", allow(unused_parens))]
 
-#[macro_use]
-extern crate error_chain;
-
 #[cfg(feature = "serde-json")]
 extern crate serde;
 #[cfg(feature = "serde-json")]
 extern crate serde_json;
 
 pub use escaping::MarkupDisplay;
-pub use errors::{Error, Result};
+pub use error::{Error, Result};
+mod error;
 pub mod filters;
 pub mod path;
 
 mod escaping;
-
-mod errors {
-    error_chain! {
-        foreign_links {
-            Fmt(::std::fmt::Error);
-            Json(::serde_json::Error) #[cfg(feature = "serde-json")];
-        }
-    }
-}