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author | sterni <sternenseemann@systemli.org> | 2023-05-26T18·38+0200 |
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committer | clbot <clbot@tvl.fyi> | 2023-05-26T22·35+0000 |
commit | 3b33c19a9c43cf66c2d28ffa3d49bb6e8757d9b1 (patch) | |
tree | 27fa4f35dfe0e069bb1e79bf034ec3ff51bc0157 /tvix/cli/src/.skip-subtree | |
parent | a4d0a80466016281c3f2b90a1ade66338d258153 (diff) |
fix(tvix): don't call function eagerly in genList, map & mapAttrs r/6207
mapAttrs, map and genList call Nix functions provided by the caller and store the result of applying them in a Nix data structure that does not force all of its contents when forced itself. This means that when such a builtin application is forced, the Nix function calls performed by the builtin should not be forced: They may be forced later, but it is also possible that they will never be forced, e.g. in builtins.length (builtins.map (builtins.add 2) [ 1 2 3 ]) it is not necessary to compute a single application of builtins.add. Since request_call_with immediately performs the function call requested, Tvix would compute function applications unnecessarily before this change. Because this was not followed by a request_force, the impact of this was relatively low in Nix code (most functions return a new thunk after being applied), but it was enough to cause a lot of bogus builtins.trace applications when evaluating anything from `lib.modules`. The newly added test includes many cases where Tvix previously incorrectly applied a builtin, breaking a working expression. To fix this we add a new helper to construct a Thunk performing a function application at runtime from a function and argument given as `Value`s. This mimics the compiler's compile_apply(), but does itself not require a compiler, since the necessary Lambda can be constructed independently. I also looked into other builtins that call a Nix function to verify that they don't exhibit such a problem: - Many builtins immediately use the resulting value in a way that makes it necessary to compute all the function calls they do as soon as the outer builtin application is forced: * all * any * filter * groupBy * partition - concatMap needs to (shallowly) force the returned list for concatenation. - foldl' is strict in the application of `op` (I added a comment that makes this explicit). - genericClosure needs to (shallowly) force the resulting list and some keys of the attribute sets inside. Resolves b/272. Change-Id: I1fa53f744bcffc035da84c1f97ed25d146830446 Reviewed-on: https://cl.tvl.fyi/c/depot/+/8651 Autosubmit: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
Diffstat (limited to 'tvix/cli/src/.skip-subtree')
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