Merge pull request #692 from matthiasbeyer/libimagerror/map_err_trace

Add Result helpers for trace()ing errors

libimagerror/src/trace.rs

@@ -87,3 +87,49 @@ fn print_trace_dbg(idx: u64, e: &Error) {
     }
 }
 
+/// Helper functions for `Result<T, E>` types to reduce overhead in the following situations:
+///
+/// ```ignore
+/// function().map_err(|e| { trace_error(&e); e })
+/// ```
+///
+/// and variants
+pub trait MapErrTrace {
+    fn map_err_trace(self) -> Self;
+    fn map_err_dbg_trace(self) -> Self;
+    fn map_err_trace_exit(self, code: i32) -> Self;
+    fn map_err_trace_maxdepth(self, max: u64) -> Self;
+}
+
+impl<U, E: Error> MapErrTrace for Result<U, E> {
+
+    /// Simply call `trace_error()` on the Err (if there is one) and return the error.
+    ///
+    /// This does nothing besides the side effect of printing the error trace
+    fn map_err_trace(self) -> Self {
+        self.map_err(|e| { trace_error(&e); e })
+    }
+
+    /// Simply call `trace_error_dbg()` on the Err (if there is one) and return the error.
+    ///
+    /// This does nothing besides the side effect of printing the error trace
+    fn map_err_dbg_trace(self) -> Self {
+        self.map_err(|e| { trace_error_dbg(&e); e })
+    }
+
+    /// Simply call `trace_error_exit(code)` on the Err (if there is one).
+    ///
+    /// This does not return if there is an Err(e).
+    fn map_err_trace_exit(self, code: i32) -> Self {
+        self.map_err(|e| { trace_error_exit(&e, code) })
+    }
+
+    /// Simply call `trace_error_maxdepth(max)` on the Err (if there is one) and return the error.
+    ///
+    /// This does nothing besides the side effect of printing the error trace to a certain depth
+    fn map_err_trace_maxdepth(self, max: u64) -> Self {
+        self.map_err(|e| { trace_error_maxdepth(&e, max); e })
+    }
+
+}
+