[#202] Provide '^out' suffix for deriver on newer nix

Problem: Since 2.15 nix no longer reference '.drv' as derivation
outputs. At the same time, nix before '2.13' doesn't support '.drv'
special suffix handling.

Solution: Provide '^out' suffix for the profile deriver in case
'nix path-info <...>.drv' returns the same '<...>.drv' path.
In other cases either an error about the build result not being present
in the /nix/store is returned or an actual build result path is
returned.

1 files changed, 24 insertions, 3 deletions

diff --git a/src/push.rs b/src/push.rs
index 6d9f10d..80fc537 100644
--- a/src/push.rs
+++ b/src/push.rs
@@ -238,19 +238,40 @@ pub async fn build_profile(data: PushProfileData<'_>) -> Result<(), PushProfileE
     )
     .map_err(PushProfileError::ShowDerivationParse)?;
 
-    let derivation_name = derivation_info
+    let &deriver = derivation_info
         .keys()
         .next()
         .ok_or(PushProfileError::ShowDerivationEmpty)?;
 
+    // Since nix 2.15.0 'nix build <path>.drv' will build only the .drv file itself, not the
+    // derivation outputs, '^out' is used to refer to outputs explicitly
+    let new_deriver = &(deriver.to_owned().to_string() + "^out");
+
+    let path_info_output = Command::new("nix")
+        .arg("--experimental-features").arg("nix-command")
+        .arg("path-info")
+        .arg(&deriver)
+        .output().await;
+
+    let deriver = match path_info_output {
+        // In this case we're on 2.15.0 or newer, because 'nix path-infonix path-info <...>.drv'
+        // returns the same '<...>.drv' path.
+        // If 'nix path-info <...>.drv' returns a different path, then we're on pre 2.15.0 nix and
+        // derivation build result is already present in the /nix/store.
+        Ok(path) if std::str::from_utf8(&path.stdout).map(|s| s.trim()) == Ok(deriver) => new_deriver,
+        // At this point, we're sure that derivation path is valid, but
+        // the result of the derivation build is not yet present in the /nix/store.
+        // In this case, 'nix path-info' returns 'error: path '...' is not valid'.
+        _ => deriver,
+    };
     if data.deploy_data.merged_settings.remote_build.unwrap_or(false) {
         if !data.supports_flakes {
             return Err(PushProfileError::RemoteBuildWithLegacyNix)
         }
 
-        build_profile_remotely(&data, derivation_name).await?;
+        build_profile_remotely(&data, &deriver).await?;
     } else {
-        build_profile_locally(&data, derivation_name).await?;
+        build_profile_locally(&data, &deriver).await?;
     }
 
     Ok(())