proper handling of has_error_source flag

Author: prekucki

src/error_chain.rs

@@ -1,3 +1,69 @@
+#[doc(hidden)]
+#[macro_export]
+#[cfg(not(has_error_source))]
+macro_rules! impl_error_chain_source {
+    (
+     types {
+            $error_kind_name:ident
+    }
+    foreign_links {
+        $( $foreign_link_variant:ident ( $foreign_link_error_path:path )
+            $( #[$meta_foreign_links:meta] )*; )*
+    }) => {
+
+    #[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 {
+            Some(ref c) => Some(&**c),
+            None => {
+                match self.0 {
+                    $(
+                        $(#[$meta_foreign_links])*
+                        $error_kind_name::$foreign_link_variant(ref foreign_err) => {
+                        foreign_err.cause()
+                        }
+                    ) *
+                _ => None
+                }
+            }
+        }
+    }
+    };
+}
+
+#[cfg(has_error_source)]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_error_chain_source {
+    (
+     types {
+            $error_kind_name:ident
+    }
+    foreign_links {
+        $( $foreign_link_variant:ident ( $foreign_link_error_path:path )
+            $( #[$meta_foreign_links:meta] )*; )*
+    }) => {
+
+            #[allow(unknown_lints, renamed_and_removed_lints, unused_doc_comment, unused_doc_comments)]
+            fn source(&self) -> Option<&(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
+                        }
+                    }
+                }
+            }
+        };
+}
+
 /// Prefer to use `error_chain` instead of this macro.
 #[doc(hidden)]
 #[macro_export]
@@ -179,41 +245,13 @@ 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 {
-                    Some(ref c) => Some(&**c),
-                    None => {
-                        match self.0 {
-                            $(
-                                $(#[$meta_foreign_links])*
-                                $error_kind_name::$foreign_link_variant(ref foreign_err) => {
-                                    foreign_err.cause()
-                                }
-                            ) *
-                            _ => None
-                        }
-                    }
+            $crate::impl_error_chain_source!{
+                types {
+                    $error_kind_name
                 }
-            }
-
-            #[cfg(has_error_source)]
-            #[allow(unknown_lints, renamed_and_removed_lints, unused_doc_comment, unused_doc_comments)]
-            fn source(&self) -> Option<&(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
-                        }
-                    }
+                foreign_links {
+                    $( $foreign_link_variant ( $foreign_link_error_path )
+                    $( #[$meta_foreign_links] )*; )*
                 }
             }
         }