lockFileMaintenance does not refresh Nix flake.lock files unless a string like "github:NixOS/nixpkgs/anything" is present in flake.nix

[rarkins]

Discussed in #29706

^{Originally posted by ipetkov June 16, 2024}

What would you like help with?

I think I found a bug

How are you running Renovate?

Self-hosted

If you're self-hosting Renovate, tell us which platform (GitHub, GitLab, etc) and which version of Renovate.

Gitea Action, container: ghcr.io/renovatebot/renovate:37.406.2

Please tell us more about your question or problem

https://github.com/ipetkov/renovate-reproduction-flake-maintenance

Current behavior

When lockFileMaintenance and the nix manager are enabled, flake.lock files
are only refreshed if flake.nix contains a string like
"github:NixOS/nixpkgs/anything" (including the double quotes.
anything can be replaced with any alpha-numeric string of characters).

Expected behavior

I would expect that when lockFileMaintenance and the nix manager are
enabled, then flake.lock will always be refreshed, regardless of the
contents/inputs defined in flake.nix.

A workaround for this bug is to inject a dummy string to satisfy Renovate's
hard-coded regex:

echo '# Trick renovate into working: "github:NixOS/nixpkgs/nixpkgs-unstable"' >> flake.nix

Suggested Alternative

Rather than using a regex to detect inputs to nixpkgs in flake.nix, Renovate can parse flake.lock (which is a JSON file) and detect all git project/repo/commit combinations.

Logs (if relevant)

Logs

 INFO: Repository started (repository=ipetkov/ism)
       "renovateVersion": "37.406.2"
... snip ...
DEBUG: Using file match: (^|/)flake\.nix$ for manager nix (repository=ipetkov/ism)
... snip ...
DEBUG: Matched 1 file(s) for manager nix: flake.nix (repository=ipetkov/ism)
DEBUG: manager extract durations (ms) (repository=ipetkov/ism)
       "managers": {"nix": 1, "github-actions": 1, "cargo": 40}
... snip ...
DEBUG: Found 5 package file(s) (repository=ipetkov/ism)
 INFO: Dependency extraction complete (repository=ipetkov/ism, baseBranch=main)
       "stats": {
         "managers": {
           "cargo": {"fileCount": 4, "depCount": 61},
           "github-actions": {"fileCount": 1, "depCount": 2}
         },
         "total": {"fileCount": 5, "depCount": 63}
       }
... snip ...
DEBUG: packageFiles with updates (repository=ipetkov/ism, baseBranch=main)
       "config": {
         "cargo": [
... snip ...
         ],
       }
DEBUG: Updated 3 package files (repository=ipetkov/ism, branch=renovate/cargo-and-nix)
DEBUG: Updated 7 lock files (repository=ipetkov/ism, branch=renovate/cargo-and-nix)
       "updatedArtifacts": [
         "redacted/Cargo.lock",
... snip ...
       ]

Logs with workaround applied

 INFO: Repository started (repository=ipetkov/ism)
       "renovateVersion": "37.406.2"
... snip ...
DEBUG: Using file match: (^|/)flake\.nix$ for manager nix (repository=ipetkov/ism)
... snip ...
DEBUG: Matched 1 file(s) for manager nix: flake.nix (repository=ipetkov/ism)
... snip ...
DEBUG: manager extract durations (ms) (repository=ipetkov/ism)
       "managers": {"nix": 1, "github-actions": 1, "cargo": 40}
... snip ...
DEBUG: Found nix package files (repository=ipetkov/ism)
DEBUG: Found 6 package file(s) (repository=ipetkov/ism)
 INFO: Dependency extraction complete (repository=ipetkov/ism, baseBranch=main)
       "stats": {
         "managers": {
           "cargo": {"fileCount": 4, "depCount": 61},
           "github-actions": {"fileCount": 1, "depCount": 2},
           "nix": {"fileCount": 1, "depCount": 1}
         },
         "total": {"fileCount": 6, "depCount": 64}
       }
... snip ...
DEBUG: packageFiles with updates (repository=ipetkov/ism, baseBranch=main)
       "config": {
         "cargo": [
... snip ...
         ],
         "github-actions": [
... snip ...
         ],
         "nix": [
           {
             "deps": [
               {
                 "depName": "nixpkgs",
                 "currentValue": "nixpkgs-unstable",
                 "datasource": "git-refs",
                 "packageName": "https://github.com/NixOS/nixpkgs",
                 "versioning": "nixpkgs",
                 "updates": [],
                 "warnings": [],
                 "sourceUrl": "https://github.com/NixOS/nixpkgs",
                 "currentVersion": "nixpkgs-unstable",
                 "fixedVersion": "nixpkgs-unstable"
               }
             ],
             "packageFile": "flake.nix"
           }
         ]
       }
DEBUG: updateArtifacts for lockFileMaintenanceFiles (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
DEBUG: Setting CONTAINERBASE_CACHE_DIR to /tmp/renovate/cache/containerbase (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
DEBUG: Using containerbase dynamic installs (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
... snip ...
DEBUG: Executing command (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
       "command": "install-tool nix 2.23.0"
DEBUG: exec completed (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
       "durationMs": 106,
       "stdout": "[16:24:54.133] INFO (359): Installing tool [email protected]...\ntool nix v2.23 is already installed\ntool is already linked: nix v2.23\n[16:24:54.149] INFO (359): Installed tool nix in 16ms.\n",
       "stderr": ""
DEBUG: Executing command (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
       "command": "nix     --extra-experimental-features nix-command     --extra-experimental-features flakes --extra-access-tokens github.com=**redacted** flake update"
... snip ...
DEBUG: Updated 5 lock files (repository=ipetkov/ism, branch=renovate/lock-file-maintenance)
       "updatedArtifacts": [
         "flake.lock",
         "redacted/Cargo.lock",
... snip ...
       ]