Need help understanding how to escape special characters in the list of str type

Hello everyone,

I’m trying to construct config for pleroma-otp package, that recently appeared in unstable branch.

There’s an option, called configs, which according to the module in nixpkgs github repository( is type of list of strings

According to Nix Expression Language manual(Nix Expression Language - NixOS Wiki) list is surrounded with [ and ]. I’m trying to get entire config from here as one string in this list.
That’s why, I build my list this way:

config = [
<code goes here>

But I get:

error: undefined variable 'ref' at /etc/nixos/social/pleroma.nix:679:77
(use '--show-trace' to show detailed location information)

on this line:

      "ref" => "master"

I clearly understand, that this text has to be correctly escaped because "ref" and operator => are being treated as two variables comparison operation.

Please suggest, how to escape all possible special characters and treat all data as regular text that means nothing.


Escaping rules are described in the Nix manual. For '' strings:

Since ${ and '' have special meaning in indented strings, you need a way to quote them. $ can be escaped by prefixing it with '' (that is, two single quotes), i.e., ''$ . '' can be escaped by prefixing it with ' , i.e., ''' . $ removes any special meaning from the following $ . Linefeed, carriage-return and tab characters can be written as ''\n , ''\r , ''\t , and ''\ escapes any other character.

You should replace ${ref} with ''${ref} in your example, so that it does not try to interpolate a Nix variable ref. The sequence => is not special. Unfortunately the escaping rules are different from double-quote " strings, where \ is used to escape ${ instead.


Is it possible to include contents from file in the element of the list in some way?

For example, something like this:

config = [
include ./config.exs

Because my config is pretty big and there will be a lot of characters to escape

As long as it resolves to a string on eval you can put any expression in parens, and you can import external text files like so:

  (builtins.readFile ./config.exs)
  # or using interpolation to blend strings with code
    some import string content
    ${lib.fileContents ./other.txt}

builtins.readFile adds an extra newline at the end of the file, if you need to avoid this you can use lib.fileContents from nixpkgs instead.

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