Add "source" implementations everywhere

Author: palfrey

src/error_chain.rs

@@ -179,6 +179,7 @@ macro_rules! impl_error_chain_processed {
                 self.description()
             }
 
+            #[cfg(not(has_error_source))]
             #[allow(unknown_lints, renamed_and_removed_lints, unused_doc_comment, unused_doc_comments)]
             fn cause(&self) -> Option<&::std::error::Error> {
                 match self.1.next_error {
@@ -188,12 +189,26 @@ macro_rules! impl_error_chain_processed {
                             $(
                                 $(#[$meta_foreign_links])*
                                 $error_kind_name::$foreign_link_variant(ref foreign_err) => {
-                                    match () {
-                                        #[cfg(not(has_error_source))]
-                                        () => foreign_err.cause(),
-                                        #[cfg(has_error_source)]
-                                        () => foreign_err.source(),
-                                    }
+                                    foreign_err.cause()
+                                }
+                            ) *
+                            _ => None
+                        }
+                    }
+                }
+            }
+
+            #[cfg(has_error_source)]
+            #[allow(unknown_lints, renamed_and_removed_lints, unused_doc_comment, unused_doc_comments)]
+            fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+                match self.1.next_error {
+                    Some(ref c) => Some(&**c),
+                    None => {
+                        match self.0 {
+                            $(
+                                $(#[$meta_foreign_links])*
+                                $error_kind_name::$foreign_link_variant(ref foreign_err) => {
+                                    foreign_err.source()
                                 }
                             ) *
                             _ => None

tests/tests.rs

@@ -292,9 +292,15 @@ mod foreign_link_test {
             "Foreign error description"
         }
 
+        #[cfg(not(has_error_source))]
         fn cause(&self) -> Option<&::std::error::Error> {
             Some(&self.cause)
         }
+
+        #[cfg(has_error_source)]
+        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+            Some(&self.cause)
+        }
     }
 
     impl fmt::Display for ForeignError {
@@ -311,9 +317,15 @@ mod foreign_link_test {
             "Foreign error cause description"
         }
 
+        #[cfg(not(has_error_source))]
         fn cause(&self) -> Option<&::std::error::Error> {
             None
         }
+
+        #[cfg(has_error_source)]
+        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+            None
+        }
     }
 
     impl fmt::Display for ForeignErrorCause {
@@ -353,7 +365,8 @@ mod foreign_link_test {
     #[cfg(has_error_source)]
     fn finds_source() {
         let chained_error = try_foreign_error().err().unwrap();
-        assert!(::std::error::Error::source(&chained_error).is_none());
+        assert_eq!(format!("{}", ForeignErrorCause {}),
+                   format!("{}", ::std::error::Error::source(&chained_error).unwrap()));
     }
 
     #[test]
@@ -363,13 +376,8 @@ mod foreign_link_test {
         assert!(!format!("{:?}", error_iter).is_empty());
         assert_eq!(format!("{}", ForeignError { cause: ForeignErrorCause {} }),
                    format!("{}", error_iter.next().unwrap()));
-        match () {
-            #[cfg(not(has_error_source))]
-            () => assert_eq!(format!("{}", ForeignErrorCause {}),
-                             format!("{}", error_iter.next().unwrap())),
-            #[cfg(has_error_source)]
-            () => assert!(error_iter.next().is_none()),
-        };
+        assert_eq!(format!("{}", ForeignErrorCause {}),
+                   format!("{}", error_iter.next().unwrap()));
         assert_eq!(format!("{:?}", None as Option<&::std::error::Error>),
                    format!("{:?}", error_iter.next()));
     }