add --hash

src/cli.rs

@@ -25,8 +25,12 @@ pub struct Opts {
     #[arg(short, long, default_value_t = 0)]
     pub indent: usize,
 
+    /// only output the hash
+    #[arg(short = 'H', long, group = "format")]
+    pub hash: bool,
+
     /// output in json format
-    #[arg(short, long)]
+    #[arg(short, long, group = "format")]
     pub json: bool,
 
     /// additional arguments to pass to the fetcher

src/fetcher/mod.rs

@@ -40,6 +40,15 @@ pub trait Fetcher<'a> {
         indent: String,
     ) -> Result<()>;
 
+    fn fetch_hash(
+        &'a self,
+        out: &mut impl ::std::io::Write,
+        url: &'a Url,
+        rev: Option<String>,
+        args: Vec<(String, String)>,
+        args_str: Vec<(String, String)>,
+    ) -> Result<()>;
+
     fn fetch_json(
         &'a self,
         out: &mut impl Write,
@@ -96,6 +105,31 @@ macro_rules! impl_fetcher {
                 self.write_nix(out, values, rev, hash, args, args_str, overwrites, indent)
             }
 
+            fn fetch_hash(
+                &'a self,
+                out: &mut impl ::std::io::Write,
+                url: &'a ::url::Url,
+                rev: Option<String>,
+                args: Vec<(String, String)>,
+                args_str: Vec<(String, String)>,
+            ) -> ::anyhow::Result<()> {
+                use anyhow::Context;
+
+                let values = &self
+                    .get_values(url)
+                    .with_context(|| format!("failed to parse {url}"))?;
+
+                let rev = match rev {
+                    Some(rev) => rev,
+                    None => self.fetch_rev(values)?,
+                };
+
+                let hash = self.fetch(values, &rev, &args, &args_str)?;
+                write!(out, "{}", hash)?;
+
+                Ok(())
+            }
+
             fn fetch_json(
                 &'a self,
                 out: &mut impl ::std::io::Write,

src/main.rs

@@ -140,7 +140,9 @@ fn main() -> Result<()> {
     let out = &mut stdout().lock();
     let args = opts.args.into_iter().tuples().collect();
     let args_str = opts.args_str.into_iter().tuples().collect();
-    if opts.json {
+    if opts.hash {
+        fetcher.fetch_hash(out, &opts.url, opts.rev, args, args_str)
+    } else if opts.json {
         fetcher.fetch_json(
             out,
             &opts.url,
@@ -166,7 +168,5 @@ fn main() -> Result<()> {
             overwrites,
             " ".repeat(opts.indent),
         )
-    }?;
-
-    Ok(())
+    }
 }

tests/cmd/hash.stdout

@@ -0,0 +1 @@
+sha256-jZ+cCp1THDhfHH5yMmRPjGuthOqsgcF/3OjZ61FMdA4=

tests/cmd/hash.toml

@@ -0,0 +1 @@
+args = ["https://github.com/nix-community/nurl", "v0.3.0", "--hash"]

tests/integration.rs

@@ -15,9 +15,15 @@ fn integration() {
 fn verify_outputs() {
     for path in glob("tests/cmd/**/*.stdout").unwrap() {
         let path = path.unwrap();
-        let name = path.file_name().unwrap();
+        let name = path
+            .file_name()
+            .unwrap()
+            .to_str()
+            .unwrap()
+            .strip_suffix(".stdout")
+            .unwrap();
 
-        if name == "json.stdout" {
+        if matches!(name, "hash" | "json") {
             eprintln!("skipping {}", path.display());
             continue;
         }
@@ -27,9 +33,9 @@ fn verify_outputs() {
         let mut expr = String::from_utf8(fs::read(&path).unwrap()).unwrap();
         expr.insert_str(0, "(import <nixpkgs> { }).");
 
-        if name == "overwrite.stdout" {
+        if name == "overwrite" {
             expr.insert_str(0, r#"let pname = "nurl"; in "#);
-        } else if name == "overwrite_str.stdout" {
+        } else if name == "overwrite_str" {
             expr.insert_str(0, r#"let version = "0.3.0"; in "#);
         }