mkLogosModule should auto-wire follows for delivery_module.logos-module-builder

[fryorcraken]

Summary

mkLogosModule / mkLogosQmlModule do not inject follows wiring for the logos-module-builder input of transitively pulled dependency flakes (notably delivery_module). As a result, every module that depends on delivery_module ends up with two logos-module-builder entries in its flake.lock — the one the user pinned, plus whatever default-branch rev delivery_module pulled in.

This silently breaks the tutorial-sanctioned local-dev workflow (nix build --override-input <module> path:../<module>) as soon as the user pins logos-module-builder to anything other than master HEAD (e.g. tutorial-v1), because the transitive rev fights the pinned one in dependent flakes.

Reproduction

Minimal tictactoe-style module, tictactoe/flake.nix:

{
  inputs = {
    logos-module-builder.url = "github:logos-co/logos-module-builder/tutorial-v1";
    delivery_module.url = "github:logos-co/logos-delivery-module/<some-pin>";
    # NOTE: no follows wiring
  };
  outputs = inputs@{ logos-module-builder, delivery_module, ... }:
    logos-module-builder.lib.mkLogosModule {
      src = ./.;
      configFile = ./metadata.json;
      flakeInputs = inputs;
    };
}

After nix flake lock:

$ python3 -c "
import json
lock = json.load(open('flake.lock'))
for k, v in lock['nodes'].items():
    if 'module-builder' in k:
        print(k, v.get('original',{}).get('ref','-'), v.get('locked',{}).get('rev','')[:12])
"
logos-module-builder    -              4987fed5b7a9   # transitive, via delivery_module (master HEAD)
logos-module-builder_2  tutorial-v1    46a51e5fc321   # root pin

Now a sibling UI flake that depends on this module:

# tictactoe-ui-qml/flake.nix
inputs = {
  logos-module-builder.url = "github:logos-co/logos-module-builder/tutorial-v1";
  tictactoe.url = "github:user/repo?dir=tictactoe";
};

nix build .#lgx-portable --override-input tictactoe path:../tictactoe now has three logos-module-builder entries in its flake.lock and the transitive one (from tictactoe.inputs.delivery_module) can silently win for parts of the build graph, producing wire-format mismatches at runtime.

Why the tutorial workflow hits this every time

tutorial-qml-ui-app.md §5.2 and tutorial-cpp-ui-app.md tell users to use --override-input <core_module> path:../<core_module> for local dev. This is the blessed workflow. But:

• The tutorial doesn't mention follows.
• mkLogosModule doesn't inject it.
• Any module that depends on delivery_module (or any other flake that itself depends on logos-module-builder) thus ships a duplicate in its flake.lock.
• Users who pin logos-module-builder (e.g. to tutorial-v1 to match basecamp v0.1.1's bundled delivery_module 1.0.0 wire format) hit this immediately.

Proposed fix

mkLogosModule / mkLogosQmlModule know the full flakeInputs set. For any entry in that set whose flake declares logos-module-builder as one of its inputs, the wrapper should inject follows = "logos-module-builder" so only the root pin survives in flake.lock.

Equivalently, the tutorial scaffold template could emit the follows line for known-to-be-affected deps (delivery_module for sure; probably others over time):

delivery_module = {
  url = "github:logos-co/logos-delivery-module/<pin>";
  inputs.logos-module-builder.follows = "logos-module-builder";
};

Either fix eliminates the duplicate entry and makes the tutorial's --override-input workflow robust against pin drift.

Workaround we're using in the meantime

Adding the follows by hand in every dependent flake:

delivery_module.inputs.logos-module-builder.follows = "logos-module-builder";

(tictactoe/flake.nix, tictactoe-ui-cpp/flake.nix, tictactoe-ui-qml/flake.nix.)

Why this matters for DX

Today a user following the tutorial sees a green nix build on the core module, a green nix build on the UI module, and a broken nix build --override-input combination — with no obvious explanation. Debugging required tracing the flake.lock by hand. Fixing this in mkLogosModule or the tutorial scaffold would make the sanctioned local-dev workflow work out of the box.

---

Context: hit while working on fryorcraken/logos-module-tictactoe (a three-flake tutorial example with core + QML UI + C++ UI).

[fryorcraken]

Marking critical because afaiu, this is part of the UI -> core -> core dependency path that needs to work.