Poetry2nix fails to grab hash of dependency

Building

{src,poetry2nix,pkgs,fetchFromGitHub}:
let
      inherit (poetry2nix.lib.mkPoetry2Nix { inherit pkgs; }) mkPoetryApplication overrides;
in
mkPoetryApplication {
	projectDir=src; #taken from flake input
	overrides = overrides.withDefaults(final: prev:{
		orjson = prev.orjson.overrideAttrs(old:{
			src=fetchFromGitHub{
				inherit(old.src)owner repo rev;
				hash = "sha256-gKcj4LbmEx1QiDObial0+OJJmcLpjox5rPqVSHuf6tk=";
			};
		});
	});
}

the build fails with :

; nix build '.#fabric'
error:
       … while evaluating the attribute 'drvPath'

         at /nix/store/0jr2kk95c34c0b6yxi75q4fqgb43kqkm-source/lib/customisation.nix:365:7:

          364|     in commonAttrs // {
          365|       drvPath = assert condition; drv.drvPath;
             |       ^
          366|       outPath = assert condition; drv.outPath;

       … while calling the 'derivationStrict' builtin

         at /builtin/derivation.nix:9:12: (source not available)

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: hash mismatch in fixed-output derivation '/nix/store/7q53lc055sa7d30im6jnngfskpbg0h5l-source.drv':
         specified: sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
            got:    sha256-gKcj4LbmEx1QiDObial0+OJJmcLpjox5rPqVSHuf6tk=
; nix log '/nix/store/7q53lc055sa7d30im6jnngfskpbg0h5l-source.drv'
warning: The interpretation of store paths arguments ending in `.drv` recently changed. If this command is now failing try again with '/nix/store/7q53lc055sa7d30im6jnngfskpbg0h5l-source.drv^*'
sourcing setup hook '/nix/store/dv5vgsw8naxnkcc88x78vprbnn1pp44y-patchelf-0.15.0/nix-support/setup-hook'
sourcing setup hook '/nix/store/i4iynx9axbq23sd0gyrc5wdb46zz6z8l-update-autotools-gnu-config-scripts-hook/nix-support/setup-hook'
sourcing setup hook '/nix/store/h9lc1dpi14z7is86ffhl3ld569138595-audit-tmpdir.sh'
sourcing setup hook '/nix/store/m54bmrhj6fqz8nds5zcj97w9s9bckc9v-compress-man-pages.sh'
sourcing setup hook '/nix/store/wgrbkkaldkrlrni33ccvm3b6vbxzb656-make-symlinks-relative.sh'
sourcing setup hook '/nix/store/5yzw0vhkyszf2d179m0qfkgxmp5wjjx4-move-docs.sh'
sourcing setup hook '/nix/store/fyaryjvghbkpfnsyw97hb3lyb37s1pd6-move-lib64.sh'
sourcing setup hook '/nix/store/kd4xwxjpjxi71jkm6ka0np72if9rm3y0-move-sbin.sh'
sourcing setup hook '/nix/store/pag6l61paj1dc9sv15l7bm5c17xn5kyk-move-systemd-user-units.sh'
sourcing setup hook '/nix/store/jivxp510zxakaaic7qkrb7v1dd2rdbw9-multiple-outputs.sh'
sourcing setup hook '/nix/store/ilaf1w22bxi6jsi45alhmvvdgy4ly3zs-patch-shebangs.sh'
sourcing setup hook '/nix/store/cickvswrvann041nqxb0rxilc46svw1n-prune-libtool-files.sh'
sourcing setup hook '/nix/store/xyff06pkhki3qy1ls77w10s0v79c9il0-reproducible-builds.sh'
sourcing setup hook '/nix/store/aazf105snicrlvyzzbdj85sx4179rpfp-set-source-date-epoch-to-latest.sh'
sourcing setup hook '/nix/store/gps9qrh99j7g02840wv5x78ykmz30byp-strip.sh'

trying https://github.com/ijl/orjson/archive/3.10.0.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
100  887k    0  887k    0     0  1016k      0 --:--:-- --:--:-- --:--:-- 1501k
evaling implicit 'postFetch' string hook
unpacking source archive /build/3.10.0.tar.gz
calling 'unpackCmd' function hook '_defaultUnpack' /build/3.10.0.tar.gz

Why

At this point you usually replace an empty hash attribute with the value of “got”.

ok but I only wrote the above file. I expected that poetry2nix would extract the hash from the lock file or at least that the overlay would correct it

Overlays have nothing to do with setting hashes. Also, please share an example that we can build ourselves, as this isn’t sufficient to help troubleshoot IMO.