allow non-flake builds with flake-enabled nix

Adds a --file option, which forces the non-flake build logic to always
run, regardless of whether or not the current nix is flake-enabled.

This allows using deploy-rs with repositories which do not use flakes
at all but use an external source-managing tool such as niv or npins
(the previous behaviour could only really support flake-based
repositories with a flake-compat fallback defined in default.nix).

Author: stuebinm

nix/tests/default.nix

@@ -162,4 +162,9 @@ in {
     flakes = false;
     deployArgs = "-s .#server";
   };
+  non-flake-with-flakes = mkTest {
+    name = "non-flake-with-flakes";
+    flakes = true;
+    deployArgs = "--file . --targets server";
+  };
 }

src/cli.rs

@@ -30,6 +30,9 @@ pub struct Opts {
     /// A list of flakes to deploy alternatively
     #[clap(long, group = "deploy")]
     targets: Option<Vec<String>>,
+    /// Treat targets as files instead of flakes
+    #[clap(short, long)]
+    file: Option<String>,
     /// Check signatures when using `nix copy`
     #[clap(short, long)]
     checksigs: bool,
@@ -672,15 +675,28 @@ pub async fn run(args: Option<&ArgMatches>) -> Result<(), RunError> {
         error!("Cannot use both --dry-activate & --boot!");
     }
 
+    // if opts.file.is_some() && (opts.targets.is_some() || opts.target.is_some()) {
+    //     error!("When using --file, only one target is supported!")
+    // }
+
     let deploys = opts
         .clone()
         .targets
         .unwrap_or_else(|| vec![opts.clone().target.unwrap_or_else(|| ".".to_string())]);
 
-    let deploy_flakes: Vec<DeployFlake> = deploys
+    let deploy_flakes: Vec<DeployFlake> =
+        if let Some(file) = &opts.file {
+            deploys
+                .iter()
+                .map(|f| deploy::parse_file(file.as_str(), f.as_str()))
+                .collect::<Result<Vec<DeployFlake>, ParseFlakeError>>()?
+        }
+    else {
+        deploys
         .iter()
         .map(|f| deploy::parse_flake(f.as_str()))
-        .collect::<Result<Vec<DeployFlake>, ParseFlakeError>>()?;
+          .collect::<Result<Vec<DeployFlake>, ParseFlakeError>>()?
+    };
 
     let cmd_overrides = deploy::CmdOverrides {
         ssh_user: opts.ssh_user,
@@ -700,22 +716,29 @@ pub async fn run(args: Option<&ArgMatches>) -> Result<(), RunError> {
     };
 
     let supports_flakes = test_flake_support().await.map_err(RunError::FlakeTest)?;
+    let do_not_want_flakes = opts.file.is_some();
 
     if !supports_flakes {
         warn!("A Nix version without flakes support was detected, support for this is work in progress");
     }
 
+    if do_not_want_flakes {
+        warn!("The --file option for deployments without flakes is experimental");
+    }
+
+    let using_flakes = supports_flakes && !do_not_want_flakes;
+
     if !opts.skip_checks {
         for deploy_flake in &deploy_flakes {
-            check_deployment(supports_flakes, deploy_flake.repo, &opts.extra_build_args).await?;
+            check_deployment(using_flakes, deploy_flake.repo, &opts.extra_build_args).await?;
         }
     }
     let result_path = opts.result_path.as_deref();
-    let data = get_deployment_data(supports_flakes, &deploy_flakes, &opts.extra_build_args).await?;
+    let data = get_deployment_data(using_flakes, &deploy_flakes, &opts.extra_build_args).await?;
     run_deploy(
         deploy_flakes,
         data,
-        supports_flakes,
+        using_flakes,
         opts.checksigs,
         opts.interactive,
         &cmd_overrides,

src/lib.rs

@@ -315,6 +315,65 @@ fn test_parse_flake() {
     );
 }
 
+pub fn parse_file<'a>(file: &'a str, attribute: &'a str) -> Result<DeployFlake<'a>, ParseFlakeError> {
+    let repo = file; //format!("./{file}");
+
+    let mut node: Option<String> = None;
+    let mut profile: Option<String> = None;
+
+    let ast = rnix::parse(attribute);
+
+    let first_child = match ast.root().node().first_child() {
+        Some(x) => x,
+        None => {
+            return Ok(DeployFlake {
+                repo: &repo,
+                node: None,
+                profile: None,
+            })
+        }
+    };
+
+    let mut node_over = false;
+
+    for entry in first_child.children_with_tokens() {
+        let x: Option<String> = match (entry.kind(), node_over) {
+            (TOKEN_DOT, false) => {
+                node_over = true;
+                None
+            }
+            (TOKEN_DOT, true) => {
+                return Err(ParseFlakeError::PathTooLong);
+            }
+            (NODE_IDENT, _) => Some(entry.into_node().unwrap().text().to_string()),
+            (TOKEN_IDENT, _) => Some(entry.into_token().unwrap().text().to_string()),
+            (NODE_STRING, _) => {
+                let c = entry
+                    .into_node()
+                    .unwrap()
+                    .children_with_tokens()
+                    .nth(1)
+                    .unwrap();
+
+                Some(c.into_token().unwrap().text().to_string())
+            }
+            _ => return Err(ParseFlakeError::Unrecognized),
+        };
+
+        if !node_over {
+            node = x;
+        } else {
+            profile = x;
+        }
+    }
+
+    Ok(DeployFlake {
+        repo: &repo,
+        node,
+        profile,
+    })
+}
+
 #[derive(Debug, Clone)]
 pub struct DeployData<'a> {
     pub node_name: &'a str,