From 3b33c19a9c43cf66c2d28ffa3d49bb6e8757d9b1 Mon Sep 17 00:00:00 2001 From: sterni Date: Fri, 26 May 2023 20:38:24 +0200 Subject: fix(tvix): don't call function eagerly in genList, map & mapAttrs 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 Tested-by: BuildkiteCI Reviewed-by: tazjin --- .../eval-okay-builtins-thunked-function-calls.exp | 1 + .../eval-okay-builtins-thunked-function-calls.nix | 31 ++++++++++++++++++++++ 2 files changed, 32 insertions(+) create mode 100644 tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.exp create mode 100644 tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.nix (limited to 'tvix/eval/src/tests') diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.exp b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.exp new file mode 100644 index 000000000000..3d4204d5a83e --- /dev/null +++ b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.exp @@ -0,0 +1 @@ +[ 2 [ "Hans" "James" "Joachim" ] 2 [ "Clawdia" "Mynheer" ] 981 3 2 2 ] diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.nix b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.nix new file mode 100644 index 000000000000..d96ddb3bd16d --- /dev/null +++ b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-thunked-function-calls.nix @@ -0,0 +1,31 @@ +[ + # This is independent of builtins + (builtins.length [ (builtins.throw "Ferge") (builtins.throw "Wehsal") ]) + (builtins.attrNames { + Hans = throw "Castorp"; + Joachim = throw "Ziemßen"; + James = "Tienappel"; + }) + + (builtins.length (builtins.map builtins.throw [ "Settembrini" "Naphta" ])) + + (builtins.attrNames (builtins.mapAttrs builtins.throw { + Clawdia = "Chauchat"; + Mynheer = "Peeperkorn"; + })) + + (builtins.length (builtins.genList (builtins.add "Marusja") 981)) + (builtins.length (builtins.genList builtins.throw 3)) + + # These are hard to get wrong since the outer layer needs to be forced anyways + (builtins.length (builtins.genericClosure { + startSet = [ + { key = 1; initial = true; } + ]; + operator = { key, initial, ... }: + if initial + then [ { key = key - 1; initial = false; value = throw "lol"; } ] + else [ ]; + })) + (builtins.length (builtins.concatMap (m: [ m (builtins.throw m) ]) [ "Marusja" ])) +] -- cgit 1.4.1