How to override hackage depedency in Stack with git branch

Question

I am experiencing trouble with proto-lens library on GHC 8.10. It has not been supported. Team fixed issue, but didn't published update on Hackage and I am trying to pull the fix just from github tag.

I don't see any difference in building process after added following section to stack.yaml

allow-newer: true

extra-deps:
- github: google/proto-lens
  commit: 0bef8c2f3da645f068b8a26ac168c1da41608182
  subdirs: proto-lens

I guess I missed something. It is not clear for me how Stack sees this custom dependency. Where is association that it is source for proto-len? What if I made a typo in subdirs or url? So Stack could get something else and it could be even a correct Stack library, but not proto-lens.

Log of failing build

Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.0.2.0 supports
'ghc' version < 8.10): /opt/ghc/8.10.1/bin/ghc is version 8.10.1
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: megaexample-0.4.2 (user goal)
[__1] trying: base-4.14.0.0/installed-4.1... (dependency of megaexample)
[__2] trying: opentelemetry-extra-0.4.2 (user goal)
[__3] next goal: proto-lens (dependency of opentelemetry-extra)
[__3] rejecting: proto-lens-0.6.0.0 (conflict:
base==4.14.0.0/installed-4.1..., proto-lens => base>=4.10 && <4.14)
[__3] rejecting: proto-lens-0.5.1.0, proto-lens-0.5.0.1, proto-lens-0.5.0.0,
proto-lens-0.4.0.1 (conflict: base==4.14.0.0/installed-4.1..., proto-lens =>

Another supplementary question: where is library version in Stack specified? Stack starts with 0.6, but there is no such literal in the source tree.

Link to source

Should I tweak cabal file also? The proto-lens library is referenced in cabal file.

executable eventlog-to-opentelemetry
  import: options
  main-is:    Main.hs
  hs-source-dirs: exe/eventlog-to-opentelemetry
  other-modules: Console, Json, Resource, Attribute, Spans
  build-depends:
    aeson,
    base,
    bytestring,
    clock,
    filepath,
    microlens,
    microlens-th,
    opentelemetry >= 0.4.0,
    opentelemetry-extra,
    opentelemetry-proto,
    optparse-applicative,
    proto-lens,
    text,
    unordered-containers,
  default-language: Haskell2010

Answer 1

Log of failing build

That error log is from cabal, not stack. cabal doesn't read stack.yaml , but cabal.project .

Here is the relevant part of cabal's documentation to specify remote dependencies: Cabal user manual

stack wouldn't try different versions of packages. The stack.yaml file specifies package versions upfront: every package is set to at most one specific version, either via extra-deps (where you specify individual packages explicitly) or resolver (which is a whole set of specific package versions, that you can browse on https://stackage.org ).

I guess I missed something. It is not clear for me how Stack sees this custom dependency. Where is association that it is source for proto-len? What if I made a typo in subdirs or url? So Stack could get something else and it could be even a correct Stack library, but not proto-lens.

It is indeed strange that doesn't seem to have an option to explicitly name the expected remote packages. This is an issue worth bringing up to stack maintainers.