fix test and formatting

src/cmd/serve.rs

@@ -83,7 +83,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
         .config
         .get("output.html.input-404")
         .map(toml::Value::as_str)
-        .flatten()
+        .and_then(std::convert::identity) // flatten
         .map(ToString::to_string);
     let file_404 = get_404_output_file(&input_404);
 

src/config.rs

@@ -1022,10 +1022,7 @@ mod tests {
         let got = Config::from_str(src).unwrap();
         let html_config = got.html_config().unwrap();
         assert_eq!(html_config.input_404, None);
-        assert_eq!(
-            &get_404_output_file(&html_config.input_404),
-            "404.html"
-        );
+        assert_eq!(&get_404_output_file(&html_config.input_404), "404.html");
     }
 
     #[test]
@@ -1039,9 +1036,6 @@ mod tests {
         let got = Config::from_str(src).unwrap();
         let html_config = got.html_config().unwrap();
         assert_eq!(html_config.input_404, Some("missing.md".to_string()));
-        assert_eq!(
-            &get_404_output_file(&html_config.input_404),
-            "missing.html"
-        );
+        assert_eq!(&get_404_output_file(&html_config.input_404), "missing.html");
     }
 }

src/utils/fs.rs

@@ -178,7 +178,10 @@ pub fn copy_files_except_ext(
 }
 
 pub fn get_404_output_file(input_404: &Option<String>) -> String {
-    input_404.as_ref().unwrap_or(&"404.md".to_string()).replace(".md", ".html")
+    input_404
+        .as_ref()
+        .unwrap_or(&"404.md".to_string())
+        .replace(".md", ".html")
 }
 
 #[cfg(test)]