Question: How to correctly resolve mill dependencies in develop shells?

[CSharperMantle]

Background

I am trying to get familiar with chisel-nix, and utilize it to spin up my next project. I have created a project with the chisel-nix template with its content left unmodified.

Problem

The template GCD code is building correctly. However, when I start a develop shell with nix develop ".#gcd.gcd-compiled", mill can't find the pulled Chisel dependency. Are there any points in initialization that I am missing?

Project creation:

mkdir test-chisel-nix
cd test-chisel-nix
git init
nix flake init -t github:chipsalliance/chisel-nix#chisel

Building:

$ nix build ".#gcd.rtl"

$ ls -la result/
total 960
dr-xr-xr-x    2 root root     4096 Jan  1  1970 .
drwxrwxr-t 1355 root nixbld 962560 Feb 26 10:46 ..
-r--r--r--    1 root root       22 Jan  1  1970 filelist.f
-r--r--r--    1 root root     3437 Jan  1  1970 GCD.sv
-r--r--r--    1 root root       48 Jan  1  1970 ref_GCD.sv

Develop shell: (Not working)

$ nix develop ".#gcd.gcd-compiled"

$ mill -i gcd.ivyDepsTree
[build.mill-64/68] compile
[build.mill-64] [info] compiling 2 Scala sources to /home/nixos/workspace/test-chisel-nix/out/mill-build/compile.dest/classes ...
[build.mill-64] [info] done compiling
[13/13] ============================== gcd.ivyDepsTree ============================== 10s
1 tasks failed
gcd.ivyDepsTree
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel_2.13:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/chisel_2.13-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

$ mill -i __.assembly
[138/138] ============================== __.assembly ============================== 4s
8 tasks failed
gcd.resolvedIvyDeps
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel_2.13:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/chisel_2.13-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

gcd.enablePluginScalacOptions.super.ScalaModule
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel-plugin_2.13.15:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/chisel-plugin_2.13.15-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

gcd.scalacPluginClasspath.super.ScalaModule
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel-plugin_2.13.15:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/chisel-plugin_2.13.15-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

elaborator.resolvedIvyDeps
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel_2.13:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/chisel_2.13-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

elaborator.enablePluginScalacOptions.super.ScalaModule
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel-plugin_2.13.15:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/chisel-plugin_2.13.15-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

elaborator.scalacPluginClasspath.super.ScalaModule
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel-plugin_2.13.15:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel-plugin_2.13.15/0.0.0+0-no-vcs-SNAPSHOT/chisel-plugin_2.13.15-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

elaborator.resolvedRunIvyDeps
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel_2.13:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/chisel_2.13-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

gcd.resolvedRunIvyDeps
Resolution failed for 1 modules:
--------------------------------------------
  org.chipsalliance:chisel_2.13:0.0.0+0-no-vcs-SNAPSHOT
        not found: /home/nixos/.ivy2/local/org.chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/ivys/ivy.xml
        not found: https://repo1.maven.org/maven2/org/chipsalliance/chisel_2.13/0.0.0+0-no-vcs-SNAPSHOT/chisel_2.13-0.0.0+0-no-vcs-SNAPSHOT.pom

--------------------------------------------

For additional information on library dependencies, see the docs at
https://mill-build.org/mill/Library_Dependencies.html

Extra information

If I softlink ~/.ivy2 to a Nix artifact store (in this case, ln -d -s /nix/store/pw42h0wlzmdh5lw70zn3xvfwvjgghcji-chisel-mill-local-ivy/.ivy2/ ./.ivy2), then mill works fine, but this solution is neither elegant nor robust.

I have also tried to use nix-direnv to setup a VSCode remote environment, but it seems to suffer from the same problem. My current .envrc is as follows:

use flake

I am rather new to Nix, so feel free to point out if my question is silly or wrong. Any suggestions is welcome. Many thanks in advance. 😉

[Avimitin]

We are now making efforts to make the mill dependencies resolve process much reproducible(see https://github.com/Avimitin/mill-ivy-fetcher and chipsalliance/t1#969), please wait until the workflow migrated to chisel-nix. This issue should be fixed after this workflow integrated into chisel-nix project. Currently I suggest checkout to revision 6a8222a.

CC @unlsycn.

[unlsycn]

As a workaround you can automatically link the .ivy2 directory in devShell:

diff --git a/templates/chisel/flake.nix b/templates/chisel/flake.nix
index fe19ac7..4091a61 100644
--- a/templates/chisel/flake.nix
+++ b/templates/chisel/flake.nix
@@ -28,6 +28,8 @@
         legacyPackages = pkgs;
         devShells.default = mkShell ({
           inputsFrom = [ gcd.gcd-compiled gcd.tb-dpi-lib ];
+          nativeBuildInputs = [ pkgs.xorg.lndir ];
+          shellHook = "lndir ${mill-dependencies.chisel}/.ivy2 ~/.ivy2";
           packages = [ cargo rustfmt rust-analyzer nixd nvfetcher ];
           RUST_SRC_PATH =
             "${rust.packages.stable.rustPlatform.rustLibSrc}";