fix loading Nix Flake shell via direnv, update readme

[jakubgs]

And some other Nix related fixes.

[jakubgs]

There is an issue with Nimble build and missing sat sources:

bin/nim c -o:bin/nimble -d:release --mm:refc --noNimblePath -d:release --skipUserCfg --skipParentCfg --warnings:off --hints:off dist/nimble/src/nimble.nim
/build/source/vendor/nimbus-build-system/vendor/Nim/dist/nimble/src/nimble.nim(14, 13) Error: cannot open file: sat/sat

This is caused by this import:

when defined(nimNimbleBootstrap):
  import ../dist/sat/src/sat/sat
else:
  import sat/sat

https://github.com/nim-lang/nimble/blob/46e2ae13eeb95619a371a74d16efc5aff30ea371/src/nimble.nim#L11-L14

Which hits the else because when I try to set -d:nimNimbleBootstrap=true in NIMFLAGS it doesn't seem to propagate to the build of Nimbus when using the nimbus-build-system. I'm not sure where sat sources are supposed to be for import sat/sat to work.

[github-actions]

Unit Test Results

       12 files  ±0    1 822 suites  ±0   55m 57s ⏱️ -16s
  5 327 tests ±0    4 980 ✔️ ±0  347 💤 ±0  0 ❌ ±0 
29 521 runs  ±0  29 077 ✔️ ±0  444 💤 ±0  0 ❌ ±0 

Results for commit 9583ed2. ± Comparison against base commit fb1c3ba.

♻️ This comment has been updated with latest results.

[jakubgs]

I have checked and indeed the hash issues appear to be caused by some Nix caching mechanism which messes with results.

Indeed use of fetchSubmodules = true here should be sufficient to provide sat sources:

nimbus-eth2/nix/nimble.nix

Line 9 in bfec79e

fetchSubmodules = true;

I need to research how to avoid these Nix caching confusion.

[tersec]

There is an issue with Nimble build and missing sat sources:

bin/nim c -o:bin/nimble -d:release --mm:refc --noNimblePath -d:release --skipUserCfg --skipParentCfg --warnings:off --hints:off dist/nimble/src/nimble.nim
/build/source/vendor/nimbus-build-system/vendor/Nim/dist/nimble/src/nimble.nim(14, 13) Error: cannot open file: sat/sat

This is caused by this import:

when defined(nimNimbleBootstrap):
  import ../dist/sat/src/sat/sat
else:
  import sat/sat

https://github.com/nim-lang/nimble/blob/46e2ae13eeb95619a371a74d16efc5aff30ea371/src/nimble.nim#L11-L14

Which hits the else because when I try to set -d:nimNimbleBootstrap=true in NIMFLAGS it doesn't seem to propagate to the build of Nimbus when using the nimbus-build-system. I'm not sure where sat sources are supposed to be for import sat/sat to work.

If you see the line 14 error, it's the wrong/old Nimble version. Nimble 0.16.2 attempts to import sat on either line 12 or 14; This code targets Nimble 0.16.4, which attempts to import sat on line 11.

[jakubgs]

Indeed, this is the hash caching behavior that we talked about. Did you review the PR?

[tersec]

Is there something specific/special about version 3.0.6 or is this a way of pinning a semi-arbitrary version?

[jakubgs]

It's the same version we've been using in all of our infra-* repositories for our Nix Flake shell for a few months now:
https://github.com/status-im/infra-template/blob/3c85b88671a8b48c5d267801bf0ad678f0e739d4/.envrc#L1-L3

So it's known to be stable.

[tersec]

Indeed, this is the hash caching behavior that we talked about. Did you review the PR?

Mostly fine/reasonable, a couple questions