alacritty: fix toml escape generation

modules/programs/alacritty.nix

@@ -100,8 +100,20 @@ in
         _finalAttrs: prevAttrs: {
           buildCommand = lib.concatStringsSep "\n" [
             prevAttrs.buildCommand
-            # TODO: why is this needed? Is there a better way to retain escape sequences?
-            "substituteInPlace $out --replace-quiet '\\\\' '\\'"
+            # Nix cannot spell TOML escape sequences like "\u001d" directly:
+            # "\\u001d" is a literal backslash-u string, while fromJSON creates
+            # a control character and fails for "\u0000". Normalize both TOML
+            # generator outputs to the Alacritty escape form:
+            #   chars = "\\u001d" -> chars = "\u001d"
+            #   chars = '\u001d'  -> chars = "\u001d"
+            ''
+              sed \
+                -E \
+                -e "s/= \"\\\\\\\\u([0-9a-fA-F]{4})\"\$/= \"\\\\u\1\"/" \
+                -e "s/= '\\\\u([0-9a-fA-F]{4})'\$/= \"\\\\u\1\"/" \
+                "$out" > "$TMPDIR/alacritty.toml"
+              cp "$TMPDIR/alacritty.toml" "$out"
+            ''
           ];
         }
       );

tests/modules/programs/alacritty/settings-merging.nix

@@ -15,6 +15,11 @@
           mods = "Control";
           chars = "\\u000c";
         }
+        {
+          key = "RBracket";
+          mods = "Alt";
+          chars = "\\u001d";
+        }
       ];
 
       font =

tests/modules/programs/alacritty/settings-toml-expected.toml

@@ -9,6 +9,11 @@ chars = "\u000c"
 key = "K"
 mods = "Control"
 
+[[keyboard.bindings]]
+chars = "\u001d"
+key = "RBracket"
+mods = "Alt"
+
 [window.dimensions]
 columns = 200
 lines = 3

tests/modules/programs/alacritty/toml-config.nix

@@ -13,6 +13,11 @@
           mods = "Control";
           chars = "\\u000c";
         }
+        {
+          key = "RBracket";
+          mods = "Alt";
+          chars = "\\u001d";
+        }
       ];
 
       font = {