register flake inputs as gc roots

src/flake_writer.rs

@@ -577,6 +577,8 @@ fn copy_for_poetry(
             }
         }
     }
+    //I'd love to return these relative, but since we run ancient-poetry in a tmp dir, 
+    //this will fail.
     Ok(target_path.canonicalize()?.to_string_lossy().to_string())
 }
 

src/main.rs

@@ -352,6 +352,10 @@ fn inner_main() -> Result<()> {
         &mut out_non_spec_but_cached_values,
     )?;
 
+    if flake_changed.flake_nix_changed && !use_generated_file_instead {
+        register_flake_inputs_as_gc_root(&flake_dir)?;
+    }
+
     if out_non_spec_but_cached_values != in_non_spec_but_cached_values {
         save_cached_values(&flake_dir, &out_non_spec_but_cached_values)?;
     }
@@ -1407,6 +1411,9 @@ fn nix_build_flake(url: &str) -> Result<String> {
     })
 }
 
+////register the used tools and the flake itself as gcroots
+///our own flake is automatically gc rooted.
+///and teh flake-inputs are handled when/if the flake changed
 pub fn register_nix_gc_root(url: &str, flake_dir: impl AsRef<Path>) -> Result<()> {
     debug!("registering gc root for {}", url);
     //where we store this stuff
@@ -1416,13 +1423,14 @@ pub fn register_nix_gc_root(url: &str, flake_dir: impl AsRef<Path>) -> Result<()
     let (without_hash, _) = url
         .rsplit_once('#')
         .context("GC_root url should contain #")?;
-    //first we store and hash the flake itself and record tha.
+    //first we store and hash the flake itself and record that.
     let flake_symlink_here = gc_roots.join(without_hash.replace('/', "_"));
     if !flake_symlink_here.exists() {
         let store_path = prefetch_flake(without_hash)?;
         register_gc_root(&store_path, &flake_symlink_here)?;
     }
 
+    //then we record it's output
     let build_symlink_here = gc_roots.join(url.replace('/', "_"));
     if !build_symlink_here.exists() {
         let store_path = nix_build_flake(url)?;
@@ -1431,6 +1439,21 @@ pub fn register_nix_gc_root(url: &str, flake_dir: impl AsRef<Path>) -> Result<()
     Ok(())
 }
 
+fn register_flake_inputs_as_gc_root(flake_dir: impl AsRef<Path>) -> Result<()> {
+    //run nix build .#flake_inputs_for_gc_root wit han output dir
+    Command::new("nix")
+        .args([
+            "build",
+            ".#flake_inputs_for_gc_root",
+            "-o",
+            ".gcroot_for_flake_inputs",
+        ])
+        .current_dir(flake_dir)
+        .status()
+        .context("retrieving content for flake input gc root from nix failed")?;
+    Ok(())
+}
+
 fn attach_to_previous_container(flake_dir: impl AsRef<Path>) -> Result<()> {
     let mut available: Vec<_> = fs::read_dir(flake_dir.as_ref().join("dtach"))
         .context("Could not find dtach socket directory")?

src/nix/flake_template.nix

@@ -4,7 +4,7 @@
     #%INPUT_DEFS%
   };
 
-  outputs = {
+  outputs = flake_inputs @ {
     self,
     #%INPUTS%
   }:
@@ -27,13 +27,30 @@
       };
       helpers = import ./functions.nix {inherit pkgs;};
     in rec {
-      defaultPackage = (helpers.buildSymlinkImage _args).derivation;
-      oci_image = helpers.buildOCIimage _args;
+      packages = {
+        default = (helpers.buildSymlinkImage _args).derivation;
+        oci_image = helpers.buildOCIimage _args;
+        flake_inputs_for_gc_root = pkgs.stdenv.mkDerivation {
+          pname = "anysnake2-flake-inputs";
+          version = "0.1";
+          unpackPhase = ":";
+          buildPhase = let
+            str_inputs =
+              builtins.concatStringsSep "\n"
+              (map (key: "ln -s ${flake_inputs.${key}} ${key}") (builtins.attrNames flake_inputs));
+          in
+            ''
+              mkdir $out -p
+              cd $out/
+            ''
+            + str_inputs;
+        };
+      };
       devShell = pkgs.stdenv.mkDerivation {
         name = "anysnake2-devshell";
         shellHook =
           ''
-            export PATH=${defaultPackage}/rootfs/bin:$PATH;
+            export PATH=${packages.default}/rootfs/bin:$PATH;
             if test -f "develop_python_path.bash"; then
               source "develop_python_path.bash"
             fi