Update Exercises Directory Names to Reflect Order

exercises/13_error_handling/errors1.rs

@@ -0,0 +1,43 @@
+// errors1.rs
+//
+// This function refuses to generate text to be printed on a nametag if you pass
+// it an empty string. It'd be nicer if it explained what the problem was,
+// instead of just sometimes returning `None`. Thankfully, Rust has a similar
+// construct to `Option` that can be used to express error conditions. Let's use
+// it!
+//
+// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+pub fn generate_nametag_text(name: String) -> Option<String> {
+    if name.is_empty() {
+        // Empty names aren't allowed.
+        None
+    } else {
+        Some(format!("Hi! My name is {}", name))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn generates_nametag_text_for_a_nonempty_name() {
+        assert_eq!(
+            generate_nametag_text("Beyoncé".into()),
+            Ok("Hi! My name is Beyoncé".into())
+        );
+    }
+
+    #[test]
+    fn explains_why_generating_nametag_text_fails() {
+        assert_eq!(
+            generate_nametag_text("".into()),
+            // Don't change this line
+            Err("`name` was empty; it must be nonempty.".into())
+        );
+    }
+}