Unify flag substitution functionality

lib/flags.nix

@@ -1,28 +0,0 @@
-{ nixpkgs, ... }:
-
-let
-  inherit (builtins)
-    filter isList
-    isString stringLength
-    unsafeDiscardStringContext;
-
-  inherit (nixpkgs.lib.lists) flatten subtractLists;
-  inherit (nixpkgs.lib.strings) addContextFrom;
-
-  split = strOrList:
-    if isList strOrList then flatten strOrList
-    else builtins.split "[[:space:]]+" strOrList
-      |> filter (flag: isString flag && stringLength flag > 0);
-
-  remerge = strOrList: list:
-    if isList strOrList then list
-    else toString list |> addContextFrom strOrList;
-in {
-  remove = rem: strOrList: split strOrList
-    |> subtractLists rem
-    |> remerge strOrList;
-
-  subst = sub: strOrList: split strOrList
-    |> map (flag: sub.${unsafeDiscardStringContext flag} or flag)
-    |> remerge strOrList;
-}

lib/substituteFlags.nix

@@ -0,0 +1,32 @@
+{ nixpkgs, ... }:
+
+let
+  inherit (builtins)
+    isFunction
+    filter isList
+    match isString stringLength
+    unsafeDiscardStringContext;
+
+  inherit (nixpkgs.lib.attrsets) foldlAttrs;
+  inherit (nixpkgs.lib.lists) flatten subtractLists;
+  inherit (nixpkgs.lib.strings) addContextFrom;
+
+  split = strOrList:
+    if isList strOrList then flatten strOrList
+    else builtins.split "[[:space:]]+" strOrList
+      |> filter (flag: isString flag && stringLength flag > 0);
+
+  merge = strOrList: list:
+    if isList strOrList then list
+    else toString list |> addContextFrom strOrList;
+in substAttrs: strOrList: split strOrList
+  |> map (flag: let subst = foldlAttrs (result: regex: subst:
+      if result != false then result
+      else let groups = match regex flag;
+        in if groups == null then false
+        else if isFunction subst then subst groups
+        else subst)
+      false substAttrs;
+    in if subst != false then subst else flag)
+  |> filter (flag: flag != null)
+  |> merge strOrList

overlay/no-x.nix

@@ -5,7 +5,7 @@ let
   inherit (nixpkgs.lib.attrsets) genAttrs;
   inherit (nixpkgs.lib.lists) remove toList;
   inherit (nixpkgs.lib.strings) mesonBool mesonEnable;
-  inherit (self.lib) flags packages;
+  inherit (self.lib) substituteFlags packages;
 
   final' = final;
   prev' = prev;
@@ -89,7 +89,7 @@ in genAttrs [
     buildInputs = prevAttrs.buildInputs or [ ]
       ++ [ final.libGL ];
     mesonFlags = prevAttrs.mesonFlags or [ ]
-      |> flags.subst { "-Degl=no" = "-Degl=yes"; };
+      |> substituteFlags { "-Degl=.*" = "-Degl=yes"; };
   })).override {
     x11Support = false;
   };
@@ -132,12 +132,14 @@ in genAttrs [
     qtbase = (prev.qtbase.overrideAttrs (prevAttrs: {
       env = prevAttrs.env or { } // {
         NIX_CFLAGS_COMPILE = prevAttrs.env.NIX_CFLAGS_COMPILE or ""
-          |> flags.remove [ "-DUSE_X11" ];
+          |> substituteFlags { "-DUSE_X11" = null; };
       };
 
       configureFlags = prevAttrs.configureFlags or [ ]
-        |> flags.remove [ "-qpa xcb" ]
-        |> flags.subst { "-xcb" = "-no-xcb"; };
+        |> substituteFlags {
+          "-qpa .*" = null;
+          "-xcb" = "-no-xcb";
+        };
     })).override {
       withGtk3 = false;
       withQttranslation = false;
@@ -153,7 +155,7 @@ in genAttrs [
     buildInputs = prevAttrs.buildInputs or [ ]
       |> packages.remove [ "gtkmm" ];
     configureFlags = prevAttrs.configureFlags or [ ]
-      |> flags.remove [ "--with-gtkmm" ];
+      |> substituteFlags { "--with-gtkmm" = null; };
   });
 
   vim-full = prev.vim-full.override {