From 5d71ac584c46de1c51baad7033eb229e377a81fb Mon Sep 17 00:00:00 2001
From: Ty Coghlan <Coghlan.Ty@gmail.com>
Date: Sat, 3 Nov 2018 01:08:57 -0400
Subject: [PATCH] gnome-podcasts: DRY out From impls in errors

From impls for errors generally just take some error type and map
it into a variant of some podcast error enum. This removes the duplicate
impls by using a pattern macro to make the impls from the type of the
enum, the given error type, and the desired enum variant.
---
 podcasts-data/src/errors.rs       | 98 +++++++++----------------------
 podcasts-downloader/src/errors.rs | 23 ++------
 podcasts-downloader/src/lib.rs    |  1 +
 3 files changed, 36 insertions(+), 86 deletions(-)

diff --git a/podcasts-data/src/errors.rs b/podcasts-data/src/errors.rs
index c24e05b..dd86f1e 100644
--- a/podcasts-data/src/errors.rs
+++ b/podcasts-data/src/errors.rs
@@ -71,74 +71,34 @@ pub enum DataError {
     EpisodeNotChanged,
 }
 
-impl From<RunMigrationsError> for DataError {
-    fn from(err: RunMigrationsError) -> Self {
-        DataError::DieselMigrationError(err)
-    }
+// Maps a type to a variant of the DataError enum
+#[macro_export]
+macro_rules! easy_from_impl {
+    ($outer_type:ty, $from:ty => $to:expr) => (
+        impl From<$from> for $outer_type {
+            fn from(err: $from) -> Self {
+                $to(err)
+            }
+        }
+    );
+    ($outer_type:ty, $from:ty => $to:expr, $($f:ty => $t:expr),+) => (
+        easy_from_impl!($outer_type, $from => $to);
+        easy_from_impl!($outer_type, $($f => $t),+);
+    );
 }
 
-impl From<diesel::result::Error> for DataError {
-    fn from(err: diesel::result::Error) -> Self {
-        DataError::DieselResultError(err)
-    }
-}
-
-impl From<r2d2::Error> for DataError {
-    fn from(err: r2d2::Error) -> Self {
-        DataError::R2D2Error(err)
-    }
-}
-
-impl From<r2d2::PoolError> for DataError {
-    fn from(err: r2d2::PoolError) -> Self {
-        DataError::R2D2PoolError(err)
-    }
-}
-
-impl From<hyper::Error> for DataError {
-    fn from(err: hyper::Error) -> Self {
-        DataError::HyperError(err)
-    }
-}
-
-impl From<http::header::ToStrError> for DataError {
-    fn from(err: http::header::ToStrError) -> Self {
-        DataError::HttpToStr(err)
-    }
-}
-
-impl From<url::ParseError> for DataError {
-    fn from(err: url::ParseError) -> Self {
-        DataError::UrlError(err)
-    }
-}
-
-impl From<native_tls::Error> for DataError {
-    fn from(err: native_tls::Error) -> Self {
-        DataError::TLSError(err)
-    }
-}
-
-impl From<io::Error> for DataError {
-    fn from(err: io::Error) -> Self {
-        DataError::IOError(err)
-    }
-}
-
-impl From<rss::Error> for DataError {
-    fn from(err: rss::Error) -> Self {
-        DataError::RssError(err)
-    }
-}
-
-impl From<xml::reader::Error> for DataError {
-    fn from(err: xml::reader::Error) -> Self {
-        DataError::XmlReaderError(err)
-    }
-}
-
-impl From<String> for DataError {
-    fn from(err: String) -> Self {
-        DataError::Bail(err)
-    }
-}
+easy_from_impl!(
+    DataError,
+    RunMigrationsError       => DataError::DieselMigrationError,
+    diesel::result::Error    => DataError::DieselResultError,
+    r2d2::Error              => DataError::R2D2Error,
+    r2d2::PoolError          => DataError::R2D2PoolError,
+    hyper::Error             => DataError::HyperError,
+    http::header::ToStrError => DataError::HttpToStr,
+    url::ParseError          => DataError::UrlError,
+    native_tls::Error        => DataError::TLSError,
+    io::Error                => DataError::IOError,
+    rss::Error               => DataError::RssError,
+    xml::reader::Error       => DataError::XmlReaderError,
+    String                   => DataError::Bail
+);
diff --git a/podcasts-downloader/src/errors.rs b/podcasts-downloader/src/errors.rs
index 5750ac5..51def53 100644
--- a/podcasts-downloader/src/errors.rs
+++ b/podcasts-downloader/src/errors.rs
@@ -24,20 +24,9 @@ pub enum DownloadError {
     InvalidCachedImageLocation,
 }
 
-impl From<reqwest::Error> for DownloadError {
-    fn from(err: reqwest::Error) -> Self {
-        DownloadError::RequestError(err)
-    }
-}
-
-impl From<io::Error> for DownloadError {
-    fn from(err: io::Error) -> Self {
-        DownloadError::IoError(err)
-    }
-}
-
-impl From<DataError> for DownloadError {
-    fn from(err: DataError) -> Self {
-        DownloadError::DataError(err)
-    }
-}
+easy_from_impl!(
+    DownloadError,
+    reqwest::Error => DownloadError::RequestError,
+    io::Error => DownloadError::IoError,
+    DataError => DownloadError::DataError
+);
diff --git a/podcasts-downloader/src/lib.rs b/podcasts-downloader/src/lib.rs
index d3e95fa..18cde54 100644
--- a/podcasts-downloader/src/lib.rs
+++ b/podcasts-downloader/src/lib.rs
@@ -36,6 +36,7 @@ extern crate pretty_assertions;
 
 extern crate glob;
 extern crate mime_guess;
+#[macro_use]
 extern crate podcasts_data;
 extern crate reqwest;
 extern crate tempdir;