1 files changed, 19 insertions, 0 deletions
diff --git a/tvix/utils.nix b/tvix/utils.nix
index ed751566bd9c..5edc1dc2e856 100644
--- a/tvix/utils.nix
+++ b/tvix/utils.nix
@@ -20,4 +20,23 @@
         );
       })
       (powerset features));
+
+  # Filters the given source, only keeping files related to the build, preventing unnecessary rebuilds.
+  # Includes src in the root, all other .rs files, as well as Cargo.toml.
+  # Additional files to be included can be specified in extraFileset.
+  filterRustCrateSrc =
+    { root # The original src
+    , extraFileset ? null # Additional filesets to include (e.g. fileFilter for proto files)
+    }:
+    lib.fileset.toSource {
+      inherit root;
+      fileset = (lib.fileset.intersection
+        (lib.fileset.fromSource root) # We build our final fileset from the original src
+        (lib.fileset.unions ([
+          (root + "/src")
+          (lib.fileset.fileFilter (f: f.hasExt "rs") root)
+          # We assume that every Rust crate will at a minimum have .rs files and a Cargo.toml
+          (lib.fileset.fileFilter (f: f.name == "Cargo.toml") root)
+        ] ++ lib.optional (extraFileset != null) extraFileset)));
+    };
 }