Allow `nix realisation info` to return partial results

[PkmX]

Is your feature request related to a problem?

We have a large number (~2K) of CA derivations, and our tool use nix realisation to mass check whether those derivations have been realised on the remote store.

However, nix realisation info will bail if any of the derivation is not realised on the remote store:

these 5 derivations will be built:
  /nix/store/<...>.drv
  /nix/store/<...>.drv
  /nix/store/<...>.drv
  /nix/store/<...>.drv
  /nix/store/<...>.drv
error: cannot operate on output 'out' of the unbuilt derivation '/nix/store/<...>.drv'

Proposed solution

Add an option --ignore-non-realised (name subject to change) to ignore the error and still output other realisations.

Alternative solutions

Run nix realisation info on each input derivation separately. This works but is really slow since there is a ton of duplicated work.

Additional context

Checklist

• checked latest Nix manual (source)
• checked open feature issues and pull requests for possible duplicates

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[Mic92]

Don't have a nix-native solution for you just now, but nix-eval-jobs --check-cache-status provides you this information as well, assuming you are using it for evaluation as well.

[PkmX]

@Mic92 Does it work with CA derivations? Last time I tried it always returned local for cacheStatus.

[Mic92]

Unsure. We fixed some support for ca derivation, but I don't know if we have bugs in https://github.com/nix-community/nix-eval-jobs/pulls?q=is%3Apr+ca+is%3Aclosed that I have not discovered yet in cacheStatus. How can I test?

[PkmX]

At the risk of getting off-topic, here are some simple tests:

$ nix run github:nix-community/nix-eval-jobs -- --expr 'derivation { name = "test"; builder = "/this/certainly/does/not/exist"; __contentAddressed = false; system = "x86_64-linux"; }' --check-cache-status | jq
{
  "attr": "",
  "attrPath": [],
  "cacheStatus": "notBuilt",
  "drvPath": "/nix/store/pjj51k74k6wvckpzp5kca7xgprn1xzjl-test.drv",
  "isCached": false,
  "name": "test",
  "neededBuilds": [],
  "neededSubstitutes": [],
  "outputs": {
    "out": "/nix/store/32yj8nmwjipcs18g88qf4q7kf80lbkfn-test"
  },
  "system": "x86_64-linux"
}

$ nix run github:nix-community/nix-eval-jobs -- --expr 'derivation { name = "test"; builder = "/this/certainly/does/not/exist"; __contentAddressed = true; system = "x86_64-linux"; }' --check-cache-status | jq
{
  "attr": "",
  "attrPath": [],
  "cacheStatus": "local",
  "drvPath": "/nix/store/hdprfagw99lzl7ypzzdmj482vh3g9gwj-test.drv",
  "isCached": true,
  "name": "test",
  "neededBuilds": [],
  "neededSubstitutes": [],
  "outputs": {
    "out": null
  },
  "system": "x86_64-linux"
}

I would expect that the CA derivation to also output notBuilt for cacheStatus.