1 files changed, 77 insertions, 0 deletions
diff --git a/third_party/nixpkgs/default.nix b/third_party/nixpkgs/default.nix
new file mode 100644
index 000000000000..747cf5a11480
--- /dev/null
+++ b/third_party/nixpkgs/default.nix
@@ -0,0 +1,77 @@
+# This file imports the pinned nixpkgs sets and applies relevant
+# modifications, such as our overlays.
+#
+# The actual source pinning happens via niv in //third_party/sources
+#
+# Note that the attribute exposed by this (third_party.nixpkgs) is
+# "special" in that the fixpoint used as readTree's config parameter
+# in //default.nix passes this attribute as the `pkgs` argument to all
+# readTree derivations.
+
+{ depot ? { }
+, externalArgs ? { }
+, depotOverlays ? true
+, localSystem ? externalArgs.localSystem or builtins.currentSystem
+, crossSystem ? externalArgs.crossSystem or localSystem
+, ...
+}:
+
+let
+  # Arguments passed to both the stable nixpkgs and the main, unstable one.
+  # Includes everything but overlays which are only passed to unstable nixpkgs.
+  commonNixpkgsArgs = {
+    # allow users to inject their config into builds (e.g. to test CA derivations)
+    config =
+      (if externalArgs ? nixpkgsConfig then externalArgs.nixpkgsConfig else { })
+      // {
+        allowUnfree = true;
+        allowUnfreeRedistributable = true;
+        allowBroken = true;
+        # Forbids our meta.ci attribute
+        # https://github.com/NixOS/nixpkgs/pull/191171#issuecomment-1260650771
+        checkMeta = false;
+      };
+
+    inherit localSystem crossSystem;
+  };
+
+  # import the nixos-unstable package set, or optionally use the
+  # source (e.g. a path) specified by the `nixpkgsBisectPath`
+  # argument. This is intended for use-cases where the depot is
+  # bisected against nixpkgs to find the root cause of an issue in a
+  # channel bump.
+  nixpkgsSrc = externalArgs.nixpkgsBisectPath or depot.third_party.sources.nixpkgs;
+
+  # Stable package set is imported, but not exposed, to overlay
+  # required packages into the unstable set.
+  stableNixpkgs = import depot.third_party.sources.nixpkgs-stable commonNixpkgsArgs;
+
+  # Overlay for packages that should come from the stable channel
+  # instead (e.g. because something is broken in unstable).
+  # Use `stableNixpkgs` from above.
+  stableOverlay = _unstableSelf: unstableSuper: {
+    # weird memory access issues in SBCL on AMD; 2024-02-01
+    sbcl = stableNixpkgs.sbcl;
+  };
+
+  # Overlay to expose the nixpkgs commits we are using to other Nix code.
+  commitsOverlay = _: _: {
+    nixpkgsCommits = {
+      unstable = depot.third_party.sources.nixpkgs.rev;
+      stable = depot.third_party.sources.nixpkgs-stable.rev;
+    };
+  };
+in
+import nixpkgsSrc (commonNixpkgsArgs // {
+  overlays = [
+    commitsOverlay
+    stableOverlay
+  ] ++ (if depotOverlays then [
+    depot.third_party.overlays.haskell
+    depot.third_party.overlays.emacs
+    depot.third_party.overlays.tvl
+    depot.third_party.overlays.ecl-static
+    depot.third_party.overlays.dhall
+    (import depot.third_party.sources.rust-overlay)
+  ] else [ ]);
+})