Transitive follows

[diniamo]

Describe the bug

In a structure where flake A depends on B and D, B depends on C, C depends on D, A cannot override D to follow its own version, because that results in an error:

error: cannot find flake 'flake:C' in the flake registries

See upstream issues for more details: NixOS#5790 NixOS#8325 NixOS#12083

Steps To Reproduce

1. flake.nix

{
  inputs = {
    gitignore.url = "github:hercules-ci/gitignore.nix";
    lanzaboote = {
      url = "github:nix-community/lanzaboote";
      inputs.pre-commit-hooks-nix.inputs.gitignore.follows = "gitignore";
    };
  };
}

2. Run nix flake lock

Expected behavior

D follows A's version, and C uses that as well.

Metadata

Compiled from latest Git:

nix (Determinate Nix 3.6.2) 2.29.0

Additional context

Lix fixed this long ago, in case their code would be helpful.

Checklist

• checked latest Determinate Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

[grahamc]

Tracked internally as FH-822:

Triple nested follows overrides break

A top level flake that overrides deeply nested dependencies breaks on Determinate Nix.

The structure looks like this:

flowchart TD
    TopLevel --> DependencyUpper
    DependencyUpper --> DependencyLower
    DependencyLower --x TransitiveDependency

    TopLevel --> TransitiveDependencyAlternative

    DependencyLower -- replaced in TopLevel with a deeply nested follows --> TransitiveDependencyAlternative

Loading

Running nix flake lock on this produces this error:

error: cannot find flake 'flake:dependency_lower' in the flake registries

The following script reproduces the issue:

#!/bin/sh

set -eu
set -o pipefail

scratch=$(mktemp -d -t tmp.XXXXXXXXXX)
function finish {
  rm -rf "$scratch"
}
trap finish EXIT

cd "$scratch"

echo "Making the transitive_dependency"
(
    set -x
    mkdir transitive_dependency
    cd transitive_dependency

    git init

    cat <<EOF > flake.nix
{
  outputs = { self }: {
    an_output = ./flake.nix;
  };
}
EOF
  git add flake.nix
  git commit -m "init"
  nix build .#an_output
  cat ./result
  rm ./result
) 2>&1 | sed -e 's/^/    /'



echo "Making the transitive_dependency_alternative"
(
    set -x
    mkdir transitive_dependency_alternative
    cd transitive_dependency_alternative

    git init

    cat <<EOF > flake.nix
{
  # alternative :)
  outputs = { self }: {
    an_output = ./flake.nix;
  };
}
EOF
  git add flake.nix
  git commit -m "init"
  nix build .#an_output
  cat ./result
  rm ./result
) 2>&1 | sed -e 's/^/    /'



echo "Making the dependency_lower"
(
    set -x
    mkdir dependency_lower
    cd dependency_lower

    git init

    cat <<EOF > flake.nix
{
  inputs = {
    transitive_dependency.url = "git+file://$(realpath "$scratch")/transitive_dependency";
  };
  outputs = { transitive_dependency, self }: {
    an_output = transitive_dependency.an_output;
  };
}
EOF
  git add flake.nix
  git commit -m "init"
  nix build .#an_output
  git add flake.lock
  git commit -m "lock"
  cat ./result
  rm ./result
) 2>&1 | sed -e 's/^/    /'



echo "Making the dependency_upper"
(
    set -x
    mkdir dependency_upper
    cd dependency_upper

    git init

    cat <<EOF > flake.nix
{
  inputs = {
    dependency_lower.url = "git+file://$(realpath "$scratch")/dependency_lower";
  };
  outputs = { dependency_lower, self }: {
    an_output = dependency_lower.an_output;
  };
}
EOF
  git add flake.nix
  git commit -m "init"
  nix build .#an_output
  git add flake.lock
  git commit -m "lock"
  cat ./result
  rm ./result
) 2>&1 | sed -e 's/^/    /'





echo "Making the toplevel"
(
    set -x
    mkdir toplevel
    cd toplevel
    git init
    cat <<EOF > flake.nix
{
  inputs = {
    transitive_dependency_alternative.url = "git+file://$(realpath "$scratch")/transitive_dependency_alternative";
    dependency_upper.url = "git+file://$(realpath "$scratch")/dependency_upper";
    dependency_upper.inputs.dependency_lower.inputs.transitive_dependency.follows = "transitive_dependency_alternative";
  };
  outputs = { transitive_dependency_alternative, dependency_upper, self }: {
    hi = dependency_upper.an_output;
  };
}
EOF
  git add flake.nix
  git commit -m "init"
) 2>&1 | sed -e 's/^/    /'

cd toplevel

echo "--> Locking with Determinate Nix v3.5.2 and committing the flake.lock"
(
  set -x
  rm flake.lock
  nix run github:DeterminateSystems/nix-src/v3.5.2 -- flake lock
  git add flake.lock
  git commit -m "Built with Determinate Nix 3.5.2"
  echo 'it locked!'
) 2>&1 | sed -e 's/^/    /'

cat flake.lock

Related issues:

• Transitive inputs "not in registry" NixOS/nix#5790
• Allow overriding the follows of a transitive input without overriding its flakeref NixOS/nix#8325
• Can't chain flake inputs when overriding with follows. NixOS/nix#12083

---

This was at one point fixed in NixOS#6983, but our notes show the codebase has evolved enough that the PR / fix needs to be derived again.

[edolstra]

This is fixed by #108 which will be in the next release.