It's hard to track where a source came from inside the evaluator #669

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opened 2025-02-12 18:41:47 +00:00 by jade · 4 comments

jade commented

2025-02-12 18:41:47 +00:00

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Raised from #668: if you have some store path with busted nix code in it, it's really hard to find the code that fetched it to figure out why it even got evaluated. We can surely store that information in the evaluator and surface it somehow (maybe in stack traces?).

This is especially true of flakes where the path is just "source", which is useless. It should give the attr path from which it came.

Raised from https://git.lix.systems/lix-project/lix/issues/668: if you have some store path with busted nix code in it, it's really hard to find the code that fetched it to figure out why it even got evaluated. We can surely store that information in the evaluator and surface it somehow (maybe in stack traces?). This is especially true of flakes where the path is just "source", which is useless. It should give the attr path from which it came.

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2025-02-12 18:41:47 +00:00

jade added this to the Error reporting project

2025-02-12 18:41:47 +00:00

jade added the

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2025-02-12 18:44:45 +00:00

pennae commented

2025-02-12 21:08:18 +00:00

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the issue in #668 was even worse since the problematic code came in via an imperative nixpkgs overlay. provenance tracking that can detangle this mess is going to be extremely costly :( probably not a large issue is we can make it free unless a special flag is given, but oof.

jade commented

2025-02-12 23:12:47 +00:00

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I think theoretically we could track it as a map from each individual store path going into the evaluation to the positions it's from, or so. So the cost would be just related to the total number of store paths in the evaluation and then the usage side is only when there's failures or debugging happening.

pennae commented

2025-02-12 23:55:56 +00:00

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       … while importing nix code referenced here
         at /home/git/nixpkgs/pkgs/top-level/impure.nix:59:17
           58|          # it's a file, so the result is the contents of the file itself
           59|          import path;
             |                 ^
           60|    in

       error: URL literals are deprecated, allow using them with --extra-deprecated-features url-literals
       at /nix/store/rnglp5cjwkd406is981cvbghd0j8bmv8-source/firefox-overlay.nix:18:34:
           17|   firefox_versions = with builtins;
           18|     fromJSON (readFile (fetchurl https://product-details.mozilla.org/1.0/firefox_versions.json));
             |                                  ^
           19|

instead of

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: URL literals are deprecated, allow using them with --extra-deprecated-features url-literals
       at /nix/store/rnglp5cjwkd406is981cvbghd0j8bmv8-source/firefox-overlay.nix:18:34:
           17|   firefox_versions = with builtins;
           18|     fromJSON (readFile (fetchurl https://product-details.mozilla.org/1.0/firefox_versions.json));
             |                                  ^
           19|

with @piegames's position tracking improvements that haven't landed yet we'll also have the position of the path expression in source. if we were to just add an error frame to import and show *two* innermost frames stack frames instead of just one we could have something like ``` … while importing nix code referenced here at /home/git/nixpkgs/pkgs/top-level/impure.nix:59:17 58| # it's a file, so the result is the contents of the file itself 59| import path; | ^ 60| in error: URL literals are deprecated, allow using them with --extra-deprecated-features url-literals at /nix/store/rnglp5cjwkd406is981cvbghd0j8bmv8-source/firefox-overlay.nix:18:34: 17| firefox_versions = with builtins; 18| fromJSON (readFile (fetchurl https://product-details.mozilla.org/1.0/firefox_versions.json)); | ^ 19| ``` instead of ``` (stack trace truncated; use '--show-trace' to show the full trace) error: URL literals are deprecated, allow using them with --extra-deprecated-features url-literals at /nix/store/rnglp5cjwkd406is981cvbghd0j8bmv8-source/firefox-overlay.nix:18:34: 17| firefox_versions = with builtins; 18| fromJSON (readFile (fetchurl https://product-details.mozilla.org/1.0/firefox_versions.json)); | ^ 19| ```

jade commented

2025-06-25 20:36:12 +00:00

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Related: #625

Related: https://git.lix.systems/lix-project/lix/issues/625