Got error source working.

src/morethantext/error.rs

@@ -1,39 +1,112 @@
-use std::{error::Error, fmt};
+use std::{error::Error, fmt, sync::Arc};
 
 #[derive(Debug)]
-pub struct MTTError {
-    detail: String,
+pub enum MTTError {
+    Generic(Generic),
 }
 
-impl MTTError {
-    fn new(detail: &str) -> Self {
-        Self {
-            detail: detail.to_string(),
+impl Error for MTTError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            MTTError::Generic(err) => err.source(),
         }
     }
 }
 
 impl fmt::Display for MTTError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            MTTError::Generic(err) => write!(f, "{}", err),
+        }
+    }
+}
+
+impl From<Generic> for MTTError {
+    fn from(err: Generic) -> Self {
+        MTTError::Generic(err)
+    }
+}
+
+#[derive(Debug)]
+pub struct Generic {
+    detail: String,
+    source: Option<Arc<MTTError>>,
+}
+
+impl Generic {
+    fn new(detail: &str) -> Self {
+        Self {
+            detail: detail.to_string(),
+            source: None,
+        }
+    }
+
+    fn add_source(&mut self, source: MTTError) {
+        self.source = Some(Arc::new(source));
+    }
+}
+
+impl Error for Generic {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match &self.source {
+            Some(err) => Some(err.as_ref()),
+            None => None,
+        }
+    }
+}
+
+impl fmt::Display for Generic {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.detail)
     }
 }
 
-impl Error for MTTError {}
-
 #[cfg(test)]
-mod errors {
+mod generics {
     use super::*;
 
     #[test]
     fn new_error() {
         let detail = "new error";
-        let err = MTTError::new(detail);
+        let err = Generic::new(detail);
         assert!(
             err.to_string() == detail,
             "\n\nGot:  {}\nWant: {}\n\n",
             err.to_string(),
             detail
         );
+        assert!(
+            err.source().is_none(),
+            "Error source should initialoze to None."
+        );
+        let error: MTTError = err.into();
+        assert!(
+            error.to_string() == detail,
+            "\n\nGot:  {}\nWant: {}\n\n",
+            error.to_string(),
+            detail
+        );
+    }
+
+    #[test]
+    fn error_with_source() {
+        let par_detail = "parent error";
+        let cld_detail = "child error";
+        let par_err = Generic::new(par_detail);
+        let mut cld_err = Generic::new(cld_detail);
+        cld_err.add_source(par_err.into());
+        assert!(
+            cld_err.source().unwrap().to_string() == par_detail,
+            "/n/nGot:  {}\nWant: {}\n\n",
+            cld_err.source().unwrap().to_string(),
+            par_detail
+        );
+        let error: MTTError = cld_err.into();
+        assert!(
+            error.source().unwrap().to_string() == par_detail,
+            "/n/nGot:  {}\nWant: {}\n\n",
+            error.source().unwrap().to_string(),
+            par_detail
+        );
     }
 }