From 87c345163a77e8bd39f54fb777a0896751f3e1b1 Mon Sep 17 00:00:00 2001 From: John Ericson Date: Wed, 10 Mar 2021 04:22:56 +0000 Subject: [PATCH] Create `outputOf` primop. In the Nix language, given a drv path, we should be able to construct another string referencing to one of its output. We can do this today with `(import drvPath).output`, but this only works for derivations we already have. With dynamic derivations, however, that doesn't work well because the `drvPath` isn't yet built: importing it like would need to trigger IFD, when the whole point of this feature is to do "dynamic build graph" without IFD! Instead, what we want to do is create a placeholder value with the right string context to refer to the output of the as-yet unbuilt derivation. A new primop in the language, analogous to `builtins.placeholder` can be used to create one. This will achieve all the right properties. The placeholder machinery also will match out the `outPath` attribute for CA derivations works. In 60b7121d2c6d4322b7c2e8e7acfec7b701b2d3a1 we added that type of placeholder, and the derived path and string holder changes necessary to support it. Then in the previous commit we cleaned up the code (inspiration finally hit me!) to deduplicate the code and expose exactly what we need. Now, we can wire up the primop trivally! Part of RFC 92: dynamic derivations (tracking issue #6316) Co-authored-by: Robert Hensing --- src/libexpr/primops.cc | 39 ++++++++++++++++++++ tests/dyn-drv/dep-built-drv.sh | 9 +++++ tests/dyn-drv/eval-outputOf.sh | 55 ++++++++++++++++++++++++++++ tests/dyn-drv/local.mk | 4 +- tests/dyn-drv/text-hashed-output.nix | 10 +++++ 5 files changed, 116 insertions(+), 1 deletion(-) create mode 100644 tests/dyn-drv/dep-built-drv.sh create mode 100644 tests/dyn-drv/eval-outputOf.sh diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc index be78bca024ad..4f61a3385083 100644 --- a/src/libexpr/primops.cc +++ b/src/libexpr/primops.cc @@ -1838,6 +1838,45 @@ static RegisterPrimOp primop_readDir({ .fun = prim_readDir, }); +/* Extend single element string context with another output. */ +static void prim_outputOf(EvalState & state, const PosIdx pos, Value * * args, Value & v) +{ + SingleDerivedPath drvPath = state.coerceToSingleDerivedPath(pos, *args[0], "while evaluating the first argument to builtins.outputOf"); + + std::string_view outputName = state.forceStringNoCtx(*args[1], pos, "while evaluating the second argument to builtins.outputOf"); + + state.mkSingleDerivedPathString( + SingleDerivedPath::Built { + .drvPath = make_ref(drvPath), + .output = std::string { outputName }, + }, + v); +} + +static RegisterPrimOp primop_outputOf({ + .name = "__outputOf", + .args = {"derivation reference", "output name"}, + .doc = R"( + Return the output path of a derivation, literally or using a placeholder if needed. + + If the derivation has a statically-known output path (i.e. the derivation output is input-addressed, or fixed content-addresed), the output path will just be used. + But if the derivation is content-addressed or if the derivation is itself not-statically produced (i.e. is the output of another derivation), a placeholder will be returned instead. + + *`derivation reference`* must be a string that may contain a regular store path to a derivation, or may be a placeholder reference. If the derivation is produced by a derivation, you must explicitly select `drv.outPath`. + This primop can be chained arbitrarily deeply. + For instance, + ```nix + builtins.outputOf + (builtins.outputOf myDrv "out) + "out" + ``` + will return a placeholder for the output of the output of `myDrv`. + + This primop corresponds to the `^` sigil for derivable paths, e.g. as part of installable syntax on the command line. + )", + .fun = prim_outputOf, + .experimentalFeature = Xp::DynamicDerivations, +}); /************************************************************* * Creating files diff --git a/tests/dyn-drv/dep-built-drv.sh b/tests/dyn-drv/dep-built-drv.sh new file mode 100644 index 000000000000..8c4a45e3b40c --- /dev/null +++ b/tests/dyn-drv/dep-built-drv.sh @@ -0,0 +1,9 @@ +#!/usr/bin/env bash + +source common.sh + +out1=$(nix-build ./text-hashed-output.nix -A hello --no-out-link) + +clearStore + +expectStderr 1 nix-build ./text-hashed-output.nix -A wrapper --no-out-link | grepQuiet "Dependencies on the outputs of dynamic derivations are not yet supported" diff --git a/tests/dyn-drv/eval-outputOf.sh b/tests/dyn-drv/eval-outputOf.sh new file mode 100644 index 000000000000..8aa0c8c03215 --- /dev/null +++ b/tests/dyn-drv/eval-outputOf.sh @@ -0,0 +1,55 @@ +#!/usr/bin/env bash + +source ./common.sh + +# Without the dynamic-derivations XP feature, we don't have the builtin. +nix --experimental-features 'nix-command' eval --impure --expr \ + 'assert ! (builtins ? outputOf); ""' + +# We currently require a string to be passed, rather than a derivation +# object that could be coerced to a string. We might liberalise this in +# the future so it does work, but there are some design questions to +# resolve first. Adding a test so we don't liberalise it by accident. +expectStderr 1 nix --experimental-features 'nix-command dynamic-derivations' eval --impure --expr \ + 'builtins.outputOf (import ../dependencies.nix).drvPath "out"' \ + "value is a set while a string was expected" + +# Test with a regular old input-addresed derivation: works without +# ca-derivations and doesn't create a placeholder but just returns the +# output path. +nix --experimental-features 'nix-command dynamic-derivations' eval --impure --expr \ + 'let + item = import ../dependencies.nix; + a = item.outPath; + b = builtins.outputOf (builtins.unsafeDiscardOutputDependency item.drvPath) "out"; + in builtins.trace a + (builtins.trace b + (assert a == b; null))' + +# Test with content addressed derivation. +nix eval --impure --expr \ + 'with (import ./text-hashed-output.nix); let + a = hello.outPath; + b = builtins.outputOf (builtins.unsafeDiscardOutputDependency hello.drvPath) "out"; + in builtins.trace a + (builtins.trace b + (assert a == b; null))' + +# Test with derivation-producing derivation. +nix eval --impure --expr \ + 'with (import ./text-hashed-output.nix); let + a = producingDrv.outPath; + b = builtins.outputOf (builtins.builtins.unsafeDiscardOutputDependency producingDrv.drvPath) "out"; + in builtins.trace a + (builtins.trace b + (assert a == b; null))' + +# Test with unbuilt output of derivation-producing derivation. +# This is similar to the previous test, but instead of checking the property on a constant derivation, we check it on a derivation that's from another derivation's output (outPath). +nix eval --impure --expr \ + 'with (import ./text-hashed-output.nix); let + a = builtins.outputOf producingDrv.out.outPath "out"; + b = builtins.outputOf (builtins.outputOf (builtins.unsafeDiscardOutputDependency producingDrv.drvPath) "out") "out"; + in builtins.trace a + (builtins.trace b + (assert a == b; null))' diff --git a/tests/dyn-drv/local.mk b/tests/dyn-drv/local.mk index b087ecd1c6b7..0ce7cd37dd35 100644 --- a/tests/dyn-drv/local.mk +++ b/tests/dyn-drv/local.mk @@ -1,7 +1,9 @@ dyn-drv-tests := \ $(d)/text-hashed-output.sh \ $(d)/recursive-mod-json.sh \ - $(d)/build-built-drv.sh + $(d)/build-built-drv.sh \ + $(d)/eval-outputOf.sh \ + $(d)/dep-built-drv.sh install-tests-groups += dyn-drv diff --git a/tests/dyn-drv/text-hashed-output.nix b/tests/dyn-drv/text-hashed-output.nix index a700fd102de0..6ce960200000 100644 --- a/tests/dyn-drv/text-hashed-output.nix +++ b/tests/dyn-drv/text-hashed-output.nix @@ -26,4 +26,14 @@ rec { outputHashMode = "text"; outputHashAlgo = "sha256"; }; + wrapper = mkDerivation { + name = "use-dynamic-drv-in-ca-drv"; + buildCommand = '' + echo "Copying the output of the dynamic derivation" + cp -r ${builtins.outputOf producingDrv.outPath "out"} $out + ''; + __contentAddressed = true; + outputHashMode = "recursive"; + outputHashAlgo = "sha256"; + }; }