wip

Author: sandydoo

default.nix

@@ -1,13 +1,15 @@
 let
-  flake = (import
-    (
-      let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
-      fetchTarball {
-        url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
-        sha256 = lock.nodes.flake-compat.locked.narHash;
-      }
-    )
-    { src = ./.; }
-  ).defaultNix;
+  flake =
+    (import
+      (
+        let
+          lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+        in
+        fetchTarball {
+          url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+          sha256 = lock.nodes.flake-compat.locked.narHash;
+        }
+      )
+      { src = ./.; }).defaultNix;
 in
-flake.lib.${builtins.currentSystem} // flake.packages.${builtins.currentSystem}
+flake.lib.${builtins.currentSystem} // flake.legacyPackages.${builtins.currentSystem}

dev/flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "A very basic flake";
+  description = "An internal test flake for git-hooks.nix";
 
   inputs = {
     git-hooks.url = "path:..";

flake.nix

@@ -40,11 +40,16 @@
         '';
       };
 
-      legacyPackages = self.packages;
-
       # The set of tools exposed by git-hooks.
-      # Each entry is guaranteed to be a derivation, but broken packages are not filtered out.
-      # `nix flake check` will likely not work.
+      # We use legacyPackages because not all tools are derivations that evaluate.
+      legacyPackages = forAllSystems ({ pkgs, exposed, ... }: exposed.tools // {
+        pre-commit = pkgs.pre-commit;
+      });
+
+      # WARN: use `legacyPackages` instead to get error messages for deprecated packages
+      #
+      # Each entry is guaranteed to be a derivation that evaluates.
+      # TODO: this should be deprecated as it exposes a subset of nixpkgs, which is incompatbile with the packages output.
       packages = forAllSystems ({ exposed, ... }: exposed.packages // {
         default = exposed.packages.pre-commit;
       });
@@ -59,6 +64,7 @@
 
       lib = forAllSystems ({ exposed, ... }: { inherit (exposed) run; });
 
+      # TODO: remove and expose a `lib` function is needed
       exposed = forAllSystems ({ exposed, ... }: exposed);
     };
 }

nix/call-tools.nix

@@ -1,17 +1,21 @@
 pkgs:
 pkgs.lib.flip builtins.removeAttrs [ "override" "overrideDerivation" ] (
   pkgs.callPackage ./tools.nix {
-    placeholder = name: {
-      # Allows checking without forcing evaluation
-      meta.isPlaceholder = true;
+    placeholder =
+      name:
+      let
+        errorMsg = ''
+          git-hooks: the package `${name}` is not available in your nixpkgs revision.
+        '';
+      in
+      {
+        # Allows checking without forcing evaluation
+        meta.isPlaceholder = true;
 
-      # Throw when the package is actually used
-      outPath = throw ''
-        git-hooks: the package `${name} is not available in your nixpkgs revision.
-      '';
-
-      type = "derivation";
-      name = name + "placeholder";
-    };
+        type = "derivation";
+        name = name + "-placeholder";
+        outPath = throw errorMsg;
+        drvPath = throw errorMsg;
+      };
   }
 )

nix/default.nix

@@ -19,8 +19,14 @@ let
           ;
       };
 
+      removeInvalidPackage = removeInvalidPackageWith { };
+      removeInvalidPackageQuiet = removeInvalidPackageWith { warn = false; };
+
       # Filter out broken and placeholder packages.
-      filterPackageForCheck =
+      removeInvalidPackageWith =
+        { warn ? true
+        ,
+        }:
         name: package:
         let
           isPlaceholder = package.meta.isPlaceholder or false;
@@ -46,19 +52,18 @@ let
               ""; # Not used
 
         in
-        lib.warnIf (!result) message result;
+        if warn then lib.warnIfNot result message result else result;
     in
     {
       inherit tools run;
 
       # Flake-style attributes
-      # Do not remove: these are exposed in the flake.
-      # Each should also be a valid derivation.
-      packages = tools // {
+      # Each should strictly be a valid derivation that evaluates.
+      packages = (lib.filterAttrs removeInvalidPackageQuiet tools) // {
         inherit (pkgs) pre-commit;
       };
 
-      checks = (lib.filterAttrs filterPackageForCheck tools) // {
+      checks = (lib.filterAttrs removeInvalidPackage tools) // {
         # A pre-commit-check for nix-pre-commit itself
         pre-commit-check = run {
           src = ../.;
@@ -87,7 +92,7 @@ let
               f n h.package;
 
             allEntryPoints = lib.pipe allHooks [
-              (lib.filterAttrs (getPackage filterPackageForCheck))
+              (lib.filterAttrs (getPackage (removeInvalidPackageQuiet)))
               (lib.mapAttrsToList getEntry)
             ];
           in