`nix path-info --json` output schema divergence from Nix #1100

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opened 2026-01-09 09:02:38 +00:00 by mnixry · 1 comment

mnixry commented

2026-01-09 09:02:38 +00:00

Describe the bug

Lix outputs a JSON array when running nix path-info --json. Upstream Nix (since approximately version 2.14) outputs a JSON object/dictionary keyed by the store path.

This schema mismatch breaks compatibility with external tooling and scripts written for modern Nix versions that expect Dict<StorePath, DerivationInfo>.

Steps To Reproduce

Install Lix.
Run a command like nix path-info --json nixpkgs#coreutils.

Observe the output structure:

 [
   {
     "deriver": "/nix/store/x9sg4ch6n7z3flypyf5s305wgib7dd6f-coreutils-9.8.drv",
     "narHash": "sha256-B5apxHSZXXbJB8Y6W8879l1epngxT5ku7l7S+d5uI/I=",
     "narSize": 1631120,
     "path": "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8",
     "references": [
       "/nix/store/42hsdp2wh69pclsi2flbarql4fls0sm8-acl-2.3.2",
       "/nix/store/6lnqmp6z002x7i7if04a8y7y4v29pv2k-attr-2.5.2",
       "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8",
       "/nix/store/j193mfi0f921y0kfs8vjc1znnr45ispv-glibc-2.40-66",
       "/nix/store/ysybzx4slid45akig0q5b89afh32ar6k-gmp-with-cxx-6.3.0"
     ],
     "registrationTime": 1767550172,
     "signatures": [
       "cache.nixos.org-1:ojXJgSyMLcluDYXw4tVZNXrC4JEVn/qK0plegg1Gvvkrcg3qhNeUzU8PNXTlf8GonTZqPFa8bJ3arB12LmYODg=="
     ],
     "valid": true
   }
 ]

Compare with upstream Nix output:

 {
   "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8": {
     "ca": null,
     "deriver": "/nix/store/x9sg4ch6n7z3flypyf5s305wgib7dd6f-coreutils-9.8.drv",
     "narHash": "sha256-B5apxHSZXXbJB8Y6W8879l1epngxT5ku7l7S+d5uI/I=",
     "narSize": 1631120,
     "references": [
       "/nix/store/42hsdp2wh69pclsi2flbarql4fls0sm8-acl-2.3.2",
       "/nix/store/6lnqmp6z002x7i7if04a8y7y4v29pv2k-attr-2.5.2",
       "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8",
       "/nix/store/j193mfi0f921y0kfs8vjc1znnr45ispv-glibc-2.40-66",
       "/nix/store/ysybzx4slid45akig0q5b89afh32ar6k-gmp-with-cxx-6.3.0"
     ],
     "registrationTime": 1767550172,
     "signatures": [
       "cache.nixos.org-1:ojXJgSyMLcluDYXw4tVZNXrC4JEVn/qK0plegg1Gvvkrcg3qhNeUzU8PNXTlf8GonTZqPFa8bJ3arB12LmYODg=="
     ],
     "ultimate": false
   }
 }

Expected behavior

Lix should output a JSON object keyed by the store path to match upstream behavior. The output should be Dict<str, DerivationInfo>, not Array<DerivationInfo>.

`nix --version` output

nix (Nix) 2.31.2+2

Additional context

This divergence stems from missing upstream commit cc46ea163024254d0b74646e1b38b19896d40040, which changed the output format. Lix appears to have dropped or missed this change, causing the API to drift for the last three years.

## Describe the bug Lix outputs a JSON array when running `nix path-info --json`. Upstream Nix (since approximately version 2.14) outputs a JSON object/dictionary keyed by the store path. This schema mismatch breaks compatibility with external tooling and scripts written for modern Nix versions that expect `Dict<StorePath, DerivationInfo>`. ## Steps To Reproduce 1. Install Lix. 2. Run a command like `nix path-info --json nixpkgs#coreutils`. 3. Observe the output structure: ```json [ { "deriver": "/nix/store/x9sg4ch6n7z3flypyf5s305wgib7dd6f-coreutils-9.8.drv", "narHash": "sha256-B5apxHSZXXbJB8Y6W8879l1epngxT5ku7l7S+d5uI/I=", "narSize": 1631120, "path": "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8", "references": [ "/nix/store/42hsdp2wh69pclsi2flbarql4fls0sm8-acl-2.3.2", "/nix/store/6lnqmp6z002x7i7if04a8y7y4v29pv2k-attr-2.5.2", "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8", "/nix/store/j193mfi0f921y0kfs8vjc1znnr45ispv-glibc-2.40-66", "/nix/store/ysybzx4slid45akig0q5b89afh32ar6k-gmp-with-cxx-6.3.0" ], "registrationTime": 1767550172, "signatures": [ "cache.nixos.org-1:ojXJgSyMLcluDYXw4tVZNXrC4JEVn/qK0plegg1Gvvkrcg3qhNeUzU8PNXTlf8GonTZqPFa8bJ3arB12LmYODg==" ], "valid": true } ] ``` 4. Compare with upstream Nix output: ```json { "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8": { "ca": null, "deriver": "/nix/store/x9sg4ch6n7z3flypyf5s305wgib7dd6f-coreutils-9.8.drv", "narHash": "sha256-B5apxHSZXXbJB8Y6W8879l1epngxT5ku7l7S+d5uI/I=", "narSize": 1631120, "references": [ "/nix/store/42hsdp2wh69pclsi2flbarql4fls0sm8-acl-2.3.2", "/nix/store/6lnqmp6z002x7i7if04a8y7y4v29pv2k-attr-2.5.2", "/nix/store/d75200gb22v7p0703h5jrkgg8bqydk5q-coreutils-9.8", "/nix/store/j193mfi0f921y0kfs8vjc1znnr45ispv-glibc-2.40-66", "/nix/store/ysybzx4slid45akig0q5b89afh32ar6k-gmp-with-cxx-6.3.0" ], "registrationTime": 1767550172, "signatures": [ "cache.nixos.org-1:ojXJgSyMLcluDYXw4tVZNXrC4JEVn/qK0plegg1Gvvkrcg3qhNeUzU8PNXTlf8GonTZqPFa8bJ3arB12LmYODg==" ], "ultimate": false } } ``` ## Expected behavior Lix should output a JSON object keyed by the store path to match upstream behavior. The output should be `Dict<str, DerivationInfo>`, not `Array<DerivationInfo>`. ## `nix --version` output nix (Nix) 2.31.2+2 ## Additional context This divergence stems from missing upstream commit [cc46ea163024254d0b74646e1b38b19896d40040](https://github.com/NixOS/nix/commit/cc46ea163024254d0b74646e1b38b19896d40040), which changed the output format. Lix appears to have dropped or missed this change, causing the API to drift for the last three years.

mnixry added the

bug

label

2026-01-09 09:02:38 +00:00

pennae commented

2026-01-09 13:24:16 +00:00

Owner

this is intentional. we never cherry-picked this change because it changed the output in a backwards-incompatible way that broke many CI systems, and we will not be changing the schema again before we have a way to request a specific, known version of the output (cf #901)