Use nuget.org if no NuGet.config file specified

README.md

@@ -4,11 +4,11 @@ Generates a Nix expression for `buildDotnetModule`, with support for non `nuget.
 
 ## Usage
 
-Similar to the `nuget-to-nix` command available in Nixpkgs, you'll need a directory of packages. This can be achieved with `dotnet restore` (see [here](https://github.com/NixOS/nixpkgs/blob/3ecddf791da4d893beb35fb09eb9da55b326f4fb/pkgs/build-support/build-dotnet-module/default.nix#L142) for an example). Additionally, you'll need a path to the `NuGet.config` file for your package.
+Similar to the `nuget-to-nix` command available in Nixpkgs, you'll need a directory of packages. This can be achieved with `dotnet restore` (see [here](https://github.com/NixOS/nixpkgs/blob/3ecddf791da4d893beb35fb09eb9da55b326f4fb/pkgs/build-support/build-dotnet-module/default.nix#L142) for an example). Optionally, you can specify a path to the `NuGet.config` file for your package.
 
 Once you have these, the tool can be invoked like so:
 ```
-$ nuget2nix --directory /path/to/packages --nuget-config /path/to/NuGet.config
+$ nuget2nix --directory /path/to/packages <--nuget-config /path/to/NuGet.config>
 ```
 
 On completion, the Nix expression to pass to `nugetDeps` is output to stdout.

src/main.rs

@@ -81,9 +81,18 @@ async fn main() -> anyhow::Result<()> {
     let mut args = Arguments::from_env();
 
     let dir: Utf8PathBuf = args.value_from_str("--directory")?;
-    let nuget_config: Utf8PathBuf = args.value_from_str("--nuget-config")?;
+    let nuget_config = args.value_from_str::<_, Utf8PathBuf>("--nuget-config");
+
+    let mut repos = Vec::new();
+
+    if let Ok(nuget_config) = nuget_config {
+        repos = get_repos(nuget_config.as_std_path()).await?;
+    }
+
+    if repos.is_empty() {
+        repos.push(Arc::new(NuGet::nuget_org().await?));
+    }
 
-    let repos = get_repos(nuget_config.as_std_path()).await?;
     let mut packages = Vec::new();
 
     for mut path in glob(dir.join("**/*.nuspec").as_str())?.map(Result::unwrap) {

src/nuget.rs

@@ -2,6 +2,8 @@ use dashmap::DashMap;
 use serde::Deserialize;
 use url::Url;
 
+const NUGET_ORG_INDEX_URL: &str = "https://api.nuget.org/v3/index.json";
+
 pub struct NuGet {
     client: reqwest::Client,
     package_base_address: Url,
@@ -28,6 +30,10 @@ impl NuGet {
         })
     }
 
+    pub async fn nuget_org() -> anyhow::Result<NuGet> {
+        NuGet::new(Url::parse(NUGET_ORG_INDEX_URL)?).await
+    }
+
     pub async fn exists(&self, package: &str, version: &str) -> bool {
         if !self.package_cache.contains_key(package) {
             async fn get(this: &NuGet, package: &str) -> Option<Vec<String>> {