nix package, better errors

flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "Rust flake";
+  description = "mdf-blog";
   inputs =
     {
       nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable"; # or whatever vers
@@ -16,6 +16,14 @@
         };
       in
       {
+        defaultPackage = pkgs.rustPlatform.buildRustPackage {
+          name = "mdf-blog";
+          pname = "mdf-blog";
+          src = ./.;
+          cargoLock = {
+            lockFile = ./Cargo.lock;
+          };
+        };
         devShell = pkgs.mkShell {
           packages = with pkgs; [ 
             rustc

src/main.rs

@@ -2,9 +2,10 @@ use std::{collections::HashMap, io, path::Path};
 use markdown::to_html;
 use rss::{Channel, ChannelBuilder, GuidBuilder, Item, ItemBuilder};
 
-fn main() -> io::Result<()> {
+fn main() -> Result<(), String> {
     let posts = std::env::args().skip(2).map(|f| {
-        let contents = std::fs::read_to_string(f.clone())?;
+        let contents = std::fs::read_to_string(f.clone()).map_err(|e| format!("when reading file {f} got {e}"))?;
+        
         // parse metadata, then the rest to html
         let mut metadata: HashMap<String, String> = contents.lines().take_while(|l| {
             // header ends here
@@ -26,7 +27,7 @@ fn main() -> io::Result<()> {
         }).concat();
 
         Ok((to_html(&body), metadata))
-    }).collect::<Result<Vec<(String, HashMap<String, String>)>, io::Error>>()?;
+    }).collect::<Result<Vec<(String, HashMap<String, String>)>, String>>()?;
 
     if let Some(mode) = std::env::args().skip(1).next() {
         match mode.as_str() {