add a shortcut for

nix-editor /etc/nixos/configuration.nix -o /etc/nixos/configuration.nix networking.hostName -v '"hello"'

for example

nix-editor -i /etc/nixos/configuration.nix networking.hostName -v '"hello"'

this should work

$ echo '{}' | nix-editor --val 1 /dev/stdin a
error: reading '/dev/stdin': No such file

$ echo '{}' | nix-editor --val 1 - a
error: reading '-': No such file

$ nix-editor --val 1 <(echo '{}') a
error: reading '/dev/fd/63': No such file

this works with standard CLI tools like cat

$ echo foo | cat /dev/stdin | head -c1
f

$ echo foo | cat - | head -c1
f

$ cat <(echo foo) | head -c1
f

Currently, none of the public functions have proper documentation comments, so the generated docs are empty.
See: https://docs.rs/nix-editor/latest/nix_editor/

Documentation is needed describing what each function does, as well as providing some examples.
Getting started: https://doc.rust-lang.org/rustdoc/how-to-write-documentation.html

I have no idea how to use this and documentation will be helpful.

Something along the lines of:

nix-editor [OPTIONS] <FILE> [<ATTRIBUTE> [--val <VAL>]]...
nix-editor file.nix name1 --val 0 name2 --val 2

or even perhaps take a json?

{
"name1": 0,
"name2": 2
}

The latest version fixes many bugs and offers a better api.

the interface could be better - similar to jq

$ echo '{}' | jq  # identity
{}

$ echo '{}' | jq -c '.a=1 | .b=2' # set multiple values
{"a":1,"b":2}

$ echo '{}' | jq -c '.a=1 | .b=2' | jq -c '.c=3 | .d=4' # chaining
{"a":1,"b":2,"c":3,"d":4}

set multiple values

#5

see also jaq - A jq clone focussed on correctness, speed, and simplicity

https://github.com/clap-rs/clap is more widely used and supports more features. Using this along with refactoring the argument code can make the tool easier to use

it would be good if there was also a way to format using alejandra

when running using recommended flake one-liner, I get

$ nix run github:vlinkz/nix-editor
error: attribute 'defaultApp.x86_64-linux' should have type 'derivation'

Does it work for you?

nix run github:vlinkz/nix-editor#nix-editor runs fine.

Situation:

{
  outputs = {...}: {
     a = {};
  };
}

Running nix-editor test.nix outputs.a -v 1 produces:

{
  outputs = {...}: {
     a = 1;
  };
}

as expected. But nix-editor test.nix outputs.a.b -v 1 produces:

{
  outputs = {...}: {
     a = {};
  };
  outputs.a.b = 1;
}

where the attrset was not placed into the function call, but on the outside.

// main.rs
        println!("{}", output);

should be print or so

Currently reading or modifying a value only applies to a single configuration file. Being able to optionally modify attributes based on the import option would be useful for applications like nixos-conf-editor