this derivation will be built:
  /nix/store/hajkx8nhsgf22hrhq87xn71x67hm4b7d-treefmt-check.drv
building '/nix/store/hajkx8nhsgf22hrhq87xn71x67hm4b7d-treefmt-check.drv' on 'ssh-ng://builder@build04.clan.lol'
building '/nix/store/hajkx8nhsgf22hrhq87xn71x67hm4b7d-treefmt-check.drv'
treefmt-check> treefmt v2.4.1traversed 87 files
treefmt-check> emitted 63 files for processing
treefmt-check> formatted 63 files (3 changed) in 197ms
treefmt-check>  M lib/zfs-storage/tests/eval-tests.nix
treefmt-check>  M lib/zfs-storage/tests/flake-module.nix
treefmt-check>  M lib/zfs-storage/tests/vm-runtime/service.nix
treefmt-check> diff --git a/lib/zfs-storage/tests/eval-tests.nix b/lib/zfs-storage/tests/eval-tests.nix
treefmt-check> index 2333693..88de88a 100644
treefmt-check> --- a/lib/zfs-storage/tests/eval-tests.nix
treefmt-check> +++ b/lib/zfs-storage/tests/eval-tests.nix
treefmt-check> @@ -16,23 +16,25 @@ let
treefmt-check>    # Used to evaluate raw inputs *through* the submodule types so that
treefmt-check>    # defaults surface (owner, zfs, mode) exactly as a real consumer sees
treefmt-check>    # them.
treefmt-check> -  mountsType = lib.types.attrsOf (lib.types.submodule {
treefmt-check> -    options = {
treefmt-check> -      path = lib.mkOption { type = lib.types.str; };
treefmt-check> -      mode = lib.mkOption {
treefmt-check> -        type = lib.types.str;
treefmt-check> -        default = "0750";
treefmt-check> -      };
treefmt-check> -      owner = lib.mkOption {
treefmt-check> -        type = zfsStorage.types.owner;
treefmt-check> -        default = { };
treefmt-check> -      };
treefmt-check> -      zfs = lib.mkOption {
treefmt-check> -        type = zfsStorage.types.zfs;
treefmt-check> -        default = { };
treefmt-check> +  mountsType = lib.types.attrsOf (
treefmt-check> +    lib.types.submodule {
treefmt-check> +      options = {
treefmt-check> +        path = lib.mkOption { type = lib.types.str; };
treefmt-check> +        mode = lib.mkOption {
treefmt-check> +          type = lib.types.str;
treefmt-check> +          default = "0750";
treefmt-check> +        };
treefmt-check> +        owner = lib.mkOption {
treefmt-check> +          type = zfsStorage.types.owner;
treefmt-check> +          default = { };
treefmt-check> +        };
treefmt-check> +        zfs = lib.mkOption {
treefmt-check> +          type = zfsStorage.types.zfs;
treefmt-check> +          default = { };
treefmt-check> +        };
treefmt-check>        };
treefmt-check> -    };
treefmt-check> -  });
treefmt-check> +    }
treefmt-check> +  );
treefmt-check>  
treefmt-check>    evalMounts =
treefmt-check>      raw:
treefmt-check> @@ -50,7 +52,9 @@ let
treefmt-check>  
treefmt-check>    # A single fully-defaulted mount, used by the defaults tests.
treefmt-check>    defaultedMounts = evalMounts {
treefmt-check> -    m = { path = "/x"; };
treefmt-check> +    m = {
treefmt-check> +      path = "/x";
treefmt-check> +    };
treefmt-check>    };
treefmt-check>  in
treefmt-check>  {
treefmt-check> @@ -166,7 +170,9 @@ in
treefmt-check>          };
treefmt-check>        };
treefmt-check>        # zfs.enable defaults to false → this entry must be dropped.
treefmt-check> -      drop = { path = "/srv/b"; };
treefmt-check> +      drop = {
treefmt-check> +        path = "/srv/b";
treefmt-check> +      };
treefmt-check>      });
treefmt-check>      expected = {
treefmt-check>        "srv-a" = {
treefmt-check> @@ -188,32 +194,38 @@ in
treefmt-check>    # ── mkDiskoDatasets key convention ────────────────────────────────
treefmt-check>  
treefmt-check>    testMkDiskoKey = {
treefmt-check> -    expr = builtins.attrNames (zfsStorage.mkDiskoDatasets (evalMounts {
treefmt-check> -      m = {
treefmt-check> -        path = "/srv/a";
treefmt-check> -        zfs = {
treefmt-check> -          enable = true;
treefmt-check> -          pool = "pool1";
treefmt-check> -          dataset = "data/a";
treefmt-check> +    expr = builtins.attrNames (
treefmt-check> +      zfsStorage.mkDiskoDatasets (evalMounts {
treefmt-check> +        m = {
treefmt-check> +          path = "/srv/a";
treefmt-check> +          zfs = {
treefmt-check> +            enable = true;
treefmt-check> +            pool = "pool1";
treefmt-check> +            dataset = "data/a";
treefmt-check> +          };
treefmt-check>          };
treefmt-check> -      };
treefmt-check> -    }));
treefmt-check> +      })
treefmt-check> +    );
treefmt-check>      expected = [ "pool1/data/a" ];
treefmt-check>    };
treefmt-check>  
treefmt-check>    # Disabled mount does not leak into mkDiskoDatasets output.
treefmt-check>    testMkDiskoFiltersDisabled = {
treefmt-check> -    expr = builtins.attrNames (zfsStorage.mkDiskoDatasets (evalMounts {
treefmt-check> -      keep = {
treefmt-check> -        path = "/srv/a";
treefmt-check> -        zfs = {
treefmt-check> -          enable = true;
treefmt-check> -          pool = "p";
treefmt-check> -          dataset = "a";
treefmt-check> +    expr = builtins.attrNames (
treefmt-check> +      zfsStorage.mkDiskoDatasets (evalMounts {
treefmt-check> +        keep = {
treefmt-check> +          path = "/srv/a";
treefmt-check> +          zfs = {
treefmt-check> +            enable = true;
treefmt-check> +            pool = "p";
treefmt-check> +            dataset = "a";
treefmt-check> +          };
treefmt-check>          };
treefmt-check> -      };
treefmt-check> -      drop = { path = "/srv/b"; };
treefmt-check> -    }));
treefmt-check> +        drop = {
treefmt-check> +          path = "/srv/b";
treefmt-check> +        };
treefmt-check> +      })
treefmt-check> +    );
treefmt-check>      expected = [ "p/a" ];
treefmt-check>    };
treefmt-check>  
treefmt-check> @@ -324,7 +336,9 @@ in
treefmt-check>            dataset = "a";
treefmt-check>          };
treefmt-check>        };
treefmt-check> -      drop = { path = "/srv/b"; };
treefmt-check> +      drop = {
treefmt-check> +        path = "/srv/b";
treefmt-check> +      };
treefmt-check>      });
treefmt-check>      expected = [ "d /srv/a 0750 app app -" ];
treefmt-check>    };
treefmt-check> @@ -345,7 +359,9 @@ in
treefmt-check>                dataset = "a";
treefmt-check>              };
treefmt-check>            };
treefmt-check> -          off = { path = "/var/cache/app"; };
treefmt-check> +          off = {
treefmt-check> +            path = "/var/cache/app";
treefmt-check> +          };
treefmt-check>          });
treefmt-check>        in
treefmt-check>        builtins.sort (a: b: a.label < b.label) out;
treefmt-check> diff --git a/lib/zfs-storage/tests/flake-module.nix b/lib/zfs-storage/tests/flake-module.nix
treefmt-check> index 0130c40..3ef9e55 100644
treefmt-check> --- a/lib/zfs-storage/tests/flake-module.nix
treefmt-check> +++ b/lib/zfs-storage/tests/flake-module.nix
treefmt-check> @@ -34,50 +34,49 @@ in
treefmt-check>        nix-unit.tests.zfs-storage = import ./eval-tests.nix { inherit (pkgs) lib; };
treefmt-check>  
treefmt-check>        # `nix flake check` coverage.
treefmt-check> -      checks =
treefmt-check> -        {
treefmt-check> -          # Eval tests: force every assertion at Nix eval time. Mirrors the
treefmt-check> -          # `eval-tests-import-flake` pattern in `tests/flake-module.nix`.
treefmt-check> -          eval-tests-zfs-storage =
treefmt-check> -            let
treefmt-check> -              tests = import ./eval-tests.nix { inherit (pkgs) lib; };
treefmt-check> -              results = lib.mapAttrs (
treefmt-check> -                name: test:
treefmt-check> -                let
treefmt-check> -                  pass = test.expr == test.expected;
treefmt-check> -                in
treefmt-check> -                if pass then
treefmt-check> -                  "pass"
treefmt-check> -                else
treefmt-check> -                  throw "eval test '${name}' failed:\n  expr:     ${builtins.toJSON test.expr}\n  expected: ${builtins.toJSON test.expected}"
treefmt-check> -              ) tests;
treefmt-check> -              summary = lib.concatStringsSep "\n" (
treefmt-check> -                lib.mapAttrsToList (name: status: "  ${name}: ${status}") results
treefmt-check> -              );
treefmt-check> -            in
treefmt-check> -            pkgs.runCommand "eval-tests-zfs-storage" { inherit summary; } ''
treefmt-check> -              echo "All zfs-storage eval tests passed:"
treefmt-check> -              echo "$summary"
treefmt-check> -              echo ""
treefmt-check> -              echo "${toString (builtins.length (builtins.attrNames tests))} tests passed."
treefmt-check> -              touch $out
treefmt-check> -            '';
treefmt-check> -        }
treefmt-check> -        # Test 2: build-only structural check that `mkDiskoDatasets` output
treefmt-check> -        # is a shape disko-zfs accepts. Forces `system.build.diskoScript` to
treefmt-check> -        # build; does NOT execute it. Linux-only because disko-zfs is Linux.
treefmt-check> -        // lib.optionalAttrs pkgs.stdenv.isLinux {
treefmt-check> -          zfs-storage-disko-build =
treefmt-check> -            let
treefmt-check> -              machine = inputs.nixpkgs.lib.nixosSystem {
treefmt-check> -                inherit system;
treefmt-check> -                modules = [ (import ./disko-build/machine.nix { inherit inputs; }) ];
treefmt-check> -              };
treefmt-check> -            in
treefmt-check> -            pkgs.runCommand "zfs-storage-disko-build" { } ''
treefmt-check> -              cp ${machine.config.system.build.diskoScript} $out
treefmt-check> -            '';
treefmt-check> -        };
treefmt-check> +      checks = {
treefmt-check> +        # Eval tests: force every assertion at Nix eval time. Mirrors the
treefmt-check> +        # `eval-tests-import-flake` pattern in `tests/flake-module.nix`.
treefmt-check> +        eval-tests-zfs-storage =
treefmt-check> +          let
treefmt-check> +            tests = import ./eval-tests.nix { inherit (pkgs) lib; };
treefmt-check> +            results = lib.mapAttrs (
treefmt-check> +              name: test:
treefmt-check> +              let
treefmt-check> +                pass = test.expr == test.expected;
treefmt-check> +              in
treefmt-check> +              if pass then
treefmt-check> +                "pass"
treefmt-check> +              else
treefmt-check> +                throw "eval test '${name}' failed:\n  expr:     ${builtins.toJSON test.expr}\n  expected: ${builtins.toJSON test.expected}"
treefmt-check> +            ) tests;
treefmt-check> +            summary = lib.concatStringsSep "\n" (
treefmt-check> +              lib.mapAttrsToList (name: status: "  ${name}: ${status}") results
treefmt-check> +            );
treefmt-check> +          in
treefmt-check> +          pkgs.runCommand "eval-tests-zfs-storage" { inherit summary; } ''
treefmt-check> +            echo "All zfs-storage eval tests passed:"
treefmt-check> +            echo "$summary"
treefmt-check> +            echo ""
treefmt-check> +            echo "${toString (builtins.length (builtins.attrNames tests))} tests passed."
treefmt-check> +            touch $out
treefmt-check> +          '';
treefmt-check> +      }
treefmt-check> +      # Test 2: build-only structural check that `mkDiskoDatasets` output
treefmt-check> +      # is a shape disko-zfs accepts. Forces `system.build.diskoScript` to
treefmt-check> +      # build; does NOT execute it. Linux-only because disko-zfs is Linux.
treefmt-check> +      // lib.optionalAttrs pkgs.stdenv.isLinux {
treefmt-check> +        zfs-storage-disko-build =
treefmt-check> +          let
treefmt-check> +            machine = inputs.nixpkgs.lib.nixosSystem {
treefmt-check> +              inherit system;
treefmt-check> +              modules = [ (import ./disko-build/machine.nix { inherit inputs; }) ];
treefmt-check> +            };
treefmt-check> +          in
treefmt-check> +          pkgs.runCommand "zfs-storage-disko-build" { } ''
treefmt-check> +            cp ${machine.config.system.build.diskoScript} $out
treefmt-check> +          '';
treefmt-check> +      };
treefmt-check>  
treefmt-check>        # Test 1: VM, runtime side, no disko. Linux-only via the
treefmt-check>        # `optionalAttrs pkgs.stdenv.isLinux` gate inside `clan-nixos-test.nix`.
treefmt-check> diff --git a/lib/zfs-storage/tests/vm-runtime/service.nix b/lib/zfs-storage/tests/vm-runtime/service.nix
treefmt-check> index 2e0050b..b92399c 100644
treefmt-check> --- a/lib/zfs-storage/tests/vm-runtime/service.nix
treefmt-check> +++ b/lib/zfs-storage/tests/vm-runtime/service.nix
treefmt-check> @@ -23,23 +23,25 @@
treefmt-check>        {
treefmt-check>          options.mounts = lib.mkOption {
treefmt-check>            default = { };
treefmt-check> -          type = lib.types.attrsOf (lib.types.submodule {
treefmt-check> -            options = {
treefmt-check> -              path = lib.mkOption { type = lib.types.str; };
treefmt-check> -              mode = lib.mkOption {
treefmt-check> -                type = lib.types.str;
treefmt-check> -                default = "0750";
treefmt-check> +          type = lib.types.attrsOf (
treefmt-check> +            lib.types.submodule {
treefmt-check> +              options = {
treefmt-check> +                path = lib.mkOption { type = lib.types.str; };
treefmt-check> +                mode = lib.mkOption {
treefmt-check> +                  type = lib.types.str;
treefmt-check> +                  default = "0750";
treefmt-check> +                };
treefmt-check> +                owner = lib.mkOption {
treefmt-check> +                  type = zfsStorage.types.owner;
treefmt-check> +                  default = { };
treefmt-check> +                };
treefmt-check> +                zfs = lib.mkOption {
treefmt-check> +                  type = zfsStorage.types.zfs;
treefmt-check> +                  default = { };
treefmt-check> +                };
treefmt-check>                };
treefmt-check> -              owner = lib.mkOption {
treefmt-check> -                type = zfsStorage.types.owner;
treefmt-check> -                default = { };
treefmt-check> -              };
treefmt-check> -              zfs = lib.mkOption {
treefmt-check> -                type = zfsStorage.types.zfs;
treefmt-check> -                default = { };
treefmt-check> -              };
treefmt-check> -            };
treefmt-check> -          });
treefmt-check> +            }
treefmt-check> +          );
treefmt-check>          };
treefmt-check>        };
treefmt-check>  
error: path '/nix/store/s7yd7ia641grkzm02fnwzrrf5kifik8w-treefmt-check' is not valid
error: Cannot build '/nix/store/hajkx8nhsgf22hrhq87xn71x67hm4b7d-treefmt-check.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/s7yd7ia641grkzm02fnwzrrf5kifik8w-treefmt-check