Add extra documentation of evalFlake

nbdd0121 · nbdd0121 · commit 98f54698717c · 2025-07-21T13:36:24.000Z
diff --git a/README.md b/README.md
@@ -10,3 +10,8 @@ This package repository is licensed under the [MIT License](LICENSE).
 The following important clarification made in the [`nixpkgs`](https://github.com/NixOS/nixpkgs/blob/master/README.md#license) repository applies to this repository as well:
 > MIT license does not apply to the packages built by Nixpkgs, merely to the files in this repository (the Nix expressions, build scripts, NixOS modules, etc.).
 > It also might not apply to patches included in Nixpkgs, which may be derivative works of the packages to which they apply.The aforementioned artifacts are all covered by the licenses of the respective packages.
+
+## Contributing
+
+The inputs to this flake is divided into public parts in `flake.nix` and private inputs in `private/flake.nix`.
+To update all inputs, make sure that `nix flake update` is performed in `private/flake.nix` as well.
diff --git a/flake.nix b/flake.nix
@@ -7,6 +7,10 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
     flake-utils.url = "github:numtide/flake-utils";
+
+    # We also have some additional dependencies in private/flake.nix.
+    # They're not exposed to the user to save downstream user from having a
+    # bloating flake.lock and having to override them.
   };
 
   nixConfig = {
diff --git a/lib/README.md b/lib/README.md
@@ -29,3 +29,20 @@ Notice, that `pkgs.mdbook` doesn't need to be given as part of the `nativeBuildI
 In this case, just python.
 
 `standardMdbookFileset` and `hasExts` are also provided to further help in creating derivations.
+
+## `evalFlake` function
+
+The `lowrisc-nix` provides a `evalFlake` function which is a more powerful version than the nix's `builtins.getFlake` function:
+* It allows a store path to be used (this includes flake sources which are copied to the store), which `builtins.getFlake` does not.
+* It allows dependency to be overriden, similar to `inputs.<name>.follows`.
+
+The signature is `{ src: path, inputOverride: attrsOf flake } -> flake`. An example of it use:
+```nix
+lib.evalFlake {
+    src = /path/to/flake;
+    inputOverride = {
+        nixpkgs = inputs.nixpkgs;
+    };
+}
+```
+
