From e9e5ce266e4288474d5ebb5e36f54b6caa43d49f Mon Sep 17 00:00:00 2001
From: adisbladis <adisbladis@gmail.com>
Date: Thu, 2 Jan 2020 21:56:08 +0000
Subject: [PATCH] Allow taking functors as overlays

This allows for making the default overrides customisable by exposing
them as a set with an override function.
---
 default.nix       | 49 +++++++++++++++++++++++++++++++----------------
 tests/default.nix |  1 +
 2 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/default.nix b/default.nix
index 40c1472..4f328c4 100644
--- a/default.nix
+++ b/default.nix
@@ -18,6 +18,8 @@ let
     stdenv = pkgs.stdenv;
   };
 
+  getFunctorFn = fn: if builtins.typeOf fn == "set" then fn.__functor else fn;
+
   getAttrDefault = attribute: set: default: (
     if builtins.hasAttr attribute set
     then builtins.getAttr attribute set
@@ -83,21 +85,23 @@ let
         in
           lockPkgs;
 
-      overlays = [
-        (
-          self: super: {
-            mkPoetryDep = self.callPackage ./mk-poetry-dep.nix {
-              inherit pkgs lib python poetryLib;
-            };
-            poetry = poetryPkg;
-          }
-        )
-        # Null out any filtered packages, we don't want python.pkgs from nixpkgs
-        (self: super: builtins.listToAttrs (builtins.map (x: { name = x.name; value = null; }) incompatible))
-        # Create poetry2nix layer
-        baseOverlay
-      ] ++ # User provided overrides
-      overrides;
+      overlays = builtins.map getFunctorFn (
+        [
+          (
+            self: super: {
+              mkPoetryDep = self.callPackage ./mk-poetry-dep.nix {
+                inherit pkgs lib python poetryLib;
+              };
+              poetry = poetryPkg;
+            }
+          )
+          # Null out any filtered packages, we don't want python.pkgs from nixpkgs
+          (self: super: builtins.listToAttrs (builtins.map (x: { name = x.name; value = null; }) incompatible))
+          # Create poetry2nix layer
+          baseOverlay
+        ] ++ # User provided overrides
+        overrides
+      );
 
       packageOverrides = lib.foldr lib.composeExtensions (self: super: {}) overlays;
 
@@ -231,5 +235,18 @@ let
 
 in
 {
-  inherit mkPoetryEnv mkPoetryApplication defaultPoetryOverrides cli doc;
+  inherit mkPoetryEnv mkPoetryApplication cli doc;
+
+  /*
+  The default list of poetry2nix override overlays
+
+  Can be overriden by calling defaultPoetryOverrides.overrideOverlay which takes an overlay function
+  */
+  defaultPoetryOverrides = {
+    __functor = defaultPoetryOverrides;
+    overrideOverlay = fn: self: super: let
+      defaultSet = defaultPoetryOverrides self super;
+      customSet = fn self super;
+    in defaultSet // customSet;
+  };
 }
diff --git a/tests/default.nix b/tests/default.nix
index 725eb27..8e3aacb 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -11,6 +11,7 @@ in
 {
   trivial = pkgs.callPackage ./trivial { inherit poetry2nix; };
   override = pkgs.callPackage ./override-support { inherit poetry2nix; };
+  override-default = pkgs.callPackage ./override-default-support { inherit poetry2nix; };
   top-packages-1 = pkgs.callPackage ./common-pkgs-1 { inherit poetry2nix; };
   top-packages-2 = pkgs.callPackage ./common-pkgs-2 { inherit poetry2nix; };
   pep425 = pkgs.callPackage ./pep425 { inherit pep425; inherit pep425OSX; inherit pep425Python37; };