escape json

flake.nix

@@ -1,6 +1,6 @@
 {
   inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
-  outputs = { nixpkgs, ... }@self: let
+  outputs = { nixpkgs, ... }: let
     supportedArchitectures = [
       "aarch64-darwin"
       "aarch64-linux"

lib.nix

@@ -1,4 +1,10 @@
 { pkgs, lib, nix_templater }:
+let
+  escapeJson = {
+    "\"" = ''\"'';
+    "\\" = ''\\'';
+  };
+in
 rec {
   # placeholder to be substituted with the content of a secret file
   fileContents = file: {
@@ -7,12 +13,12 @@ rec {
   };
 
   # make a template with placeholders
-  templateText = { name, text, outPath }:
+  templateText = { name, text, outPath, translations ? {} }:
     pkgs.runCommand name {
       textBeforeTemplate = text;
       script = ''
         #!/bin/sh
-        ${nix_templater}/bin/nix_templater ${builtins.placeholder "out"}/template ${builtins.placeholder "nix_template"} "${outPath}"
+        ${nix_templater}/bin/nix_templater ${builtins.placeholder "out"}/template ${builtins.placeholder "nix_template"} "${outPath}" '${lib.strings.toJSON translations}'
       '';
       passAsFile = [ "script" "textBeforeTemplate" ];
     } ''
@@ -22,14 +28,14 @@ rec {
       chmod +x $out/bin/${name}
     '';
 
-  templateGenerator = generator: { name, value, outPath }: templateText {
-    inherit name outPath;
+  templateGenerator = translations: generator: { name, value, outPath }: templateText {
+    inherit name outPath translations;
     text = generator value;
   };
 
-  templateJsonWith = options: templateGenerator (lib.generators.toJSON options);
-  templateYamlWith = options: templateGenerator (lib.generators.toYAML options); # just json
-  templateIniWith = options: templateGenerator (lib.generators.toINI options);
+  templateJsonWith = options: templateGenerator escapeJson (lib.generators.toJSON options);
+  templateYamlWith = options: templateGenerator escapeJson (lib.generators.toYAML options); # just json
+  templateIniWith = options: templateGenerator escapeJson (lib.generators.toINI options);
   templateJson = templateJsonWith { };
   templateYaml = templateYamlWith { };
   templateIni = templateIniWith { };

pkgs/nix_templater/replace.py

@@ -1,10 +1,12 @@
 # replace occurrences of a magic string in a template file
+from json import loads
 import sys
 from pathlib import Path
 
 template_file = sys.argv[1]
 magic_string = sys.argv[2]
 outfile = sys.argv[3]
+translations = loads(sys.argv[4]) if len(sys.argv) >= 4 else {}
 
 if Path(outfile).exists():
     print(f"{outfile} already exists, aborting")
@@ -26,7 +28,7 @@ while True:
     ]
     output += template_bytes[loc : loc + magic_start]
     # TODO handle errors better here
-    output += Path(magic_file.decode()).read_bytes()
+    output += Path(magic_file.decode()).read_bytes().decode().translate(str.maketrans(translations)).encode()
     loc = loc + magic_start + magic_end + len(magic_string) + 1
 
 Path(outfile).write_bytes(output)

tests/json.nix

@@ -1,9 +1,10 @@
 # test injecting a secret into a json template
 { legacyPackages, system, nixpkgs }:
 let
-  secret_file = (nixpkgs.legacyPackages.${system}.writeText "secret" "secret");
+  hostPkgs = nixpkgs.legacyPackages.${system};
+  secret_file = hostPkgs.writeText "secret" "secret\\needing\"escaping";
 in (nixpkgs.lib.nixos.runTest {
-    hostPkgs = nixpkgs.legacyPackages.${system};
+    inherit hostPkgs;
     name = "nix_templates";
 
     nodes.machine = {pkgs, ...}: {
@@ -33,6 +34,8 @@ in (nixpkgs.lib.nixos.runTest {
       start_all()
       print(machine.execute("uname -a"))
       machine.wait_for_unit("multi-user.target")
+      print(machine.succeed("cat /test"))
       print(machine.succeed("cat /test | grep -q secret"))
+      print(machine.succeed("cat /test | ${hostPkgs.jq}/bin/jq"))
     '';
   })