Merge pull request #4093 from matthewbauer/eval-system

Add eval-system option

(cherry picked from commit 071dbbee33af9f27338c3e53e4ea067dbfa14010)
Change-Id: Ia81358c8cfb60241da07a4d0e84b9ee62a18a53f
This commit is contained in:
eldritch horrors 2024-03-04 07:21:01 +01:00
parent 64a269ef73
commit 7614aa9797
8 changed files with 89 additions and 6 deletions

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@ -0,0 +1,12 @@
---
synopsis: Add new `eval-system` setting
prs: 4093
---
Add a new `eval-system` option.
Unlike `system`, it just overrides the value of `builtins.currentSystem`.
This is more useful than overriding `system`, because you can build these derivations on remote builders which can work on the given system.
In contrast, `system` also effects scheduling which will cause Nix to build those derivations locally even if that doesn't make sense.
`eval-system` only takes effect if it is non-empty.
If empty (the default) `system` is used as before, so there is no breakage.

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@ -88,6 +88,12 @@ std::string EvalSettings::resolvePseudoUrl(std::string_view url)
return std::string(url); return std::string(url);
} }
const std::string & EvalSettings::getCurrentSystem()
{
const auto & evalSystem = currentSystem.get();
return evalSystem != "" ? evalSystem : settings.thisSystem.get();
}
EvalSettings evalSettings; EvalSettings evalSettings;
static GlobalConfig::Register rEvalSettings(&evalSettings); static GlobalConfig::Register rEvalSettings(&evalSettings);

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@ -25,6 +25,26 @@ struct EvalSettings : Config
[`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath). [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath).
)"}; )"};
Setting<std::string> currentSystem{
this, "", "eval-system",
R"(
This option defines
[`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem)
in the Nix language if it is set as a non-empty string.
Otherwise, if it is defined as the empty string (the default), the value of the
[`system` ](#conf-system)
configuration setting is used instead.
Unlike `system`, this setting does not change what kind of derivations can be built locally.
This is useful for evaluating Nix code on one system to produce derivations to be built on another type of system.
)"};
/**
* Implements the `eval-system` vs `system` defaulting logic
* described for `eval-system`.
*/
const std::string & getCurrentSystem();
Setting<bool> restrictEval{ Setting<bool> restrictEval{
this, false, "restrict-eval", this, false, "restrict-eval",
R"( R"(

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@ -4288,13 +4288,16 @@ void EvalState::createBaseEnv()
.impureOnly = true, .impureOnly = true,
}); });
if (!evalSettings.pureEval) { if (!evalSettings.pureEval)
v.mkString(settings.thisSystem.get()); v.mkString(evalSettings.getCurrentSystem());
}
addConstant("__currentSystem", v, { addConstant("__currentSystem", v, {
.type = nString, .type = nString,
.doc = R"( .doc = R"(
The value of the [`system` configuration option](@docroot@/command-ref/conf-file.md#conf-pure-eval). The value of the
[`eval-system`](@docroot@/command-ref/conf-file.md#conf-eval-system)
or else
[`system`](@docroot@/command-ref/conf-file.md#conf-system)
configuration option.
It can be used to set the `system` attribute for [`builtins.derivation`](@docroot@/language/derivations.md) such that the resulting derivation can be built on the same system that evaluates the Nix expression: It can be used to set the `system` attribute for [`builtins.derivation`](@docroot@/language/derivations.md) such that the resulting derivation can be built on the same system that evaluates the Nix expression:

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@ -210,7 +210,11 @@ public:
In general, you do not have to modify this setting. In general, you do not have to modify this setting.
While you can force Nix to run a Darwin-specific `builder` executable on a Linux machine, the result would obviously be wrong. While you can force Nix to run a Darwin-specific `builder` executable on a Linux machine, the result would obviously be wrong.
This value is available in the Nix language as [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem). This value is available in the Nix language as
[`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem)
if the
[`eval-system`](#conf-eval-system)
configuration option is set as the empty string.
)"}; )"};
Setting<time_t> maxSilentTime{ Setting<time_t> maxSilentTime{

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@ -0,0 +1,35 @@
source common.sh
export REMOTE_STORE="dummy://"
simpleTest () {
local expr=$1; shift
local result=$1; shift
# rest, extra args
[[ "$(nix eval --impure --raw "$@" --expr "$expr")" == "$result" ]]
}
# `builtins.storeDir`
## Store dir follows `store` store setting
simpleTest 'builtins.storeDir' '/foo' --store "$REMOTE_STORE?store=/foo"
simpleTest 'builtins.storeDir' '/bar' --store "$REMOTE_STORE?store=/bar"
# `builtins.currentSystem`
## `system` alone affects by default
simpleTest 'builtins.currentSystem' 'foo' --system 'foo'
simpleTest 'builtins.currentSystem' 'bar' --system 'bar'
## `system` affects if `eval-system` is an empty string
simpleTest 'builtins.currentSystem' 'foo' --system 'foo' --eval-system ''
simpleTest 'builtins.currentSystem' 'bar' --system 'bar' --eval-system ''
## `eval-system` alone affects
simpleTest 'builtins.currentSystem' 'foo' --eval-system 'foo'
simpleTest 'builtins.currentSystem' 'bar' --eval-system 'bar'
## `eval-system` overrides `system`
simpleTest 'builtins.currentSystem' 'bar' --system 'foo' --eval-system 'bar'
simpleTest 'builtins.currentSystem' 'baz' --system 'foo' --eval-system 'baz'

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@ -68,6 +68,7 @@ nix_tests = \
build-remote-trustless-should-pass-3.sh \ build-remote-trustless-should-pass-3.sh \
build-remote-trustless-should-fail-0.sh \ build-remote-trustless-should-fail-0.sh \
nar-access.sh \ nar-access.sh \
impure-eval.sh \
pure-eval.sh \ pure-eval.sh \
eval.sh \ eval.sh \
repl.sh \ repl.sh \

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@ -1,6 +1,8 @@
#include <gmock/gmock.h> #include <gmock/gmock.h>
#include <gtest/gtest.h> #include <gtest/gtest.h>
#include "eval-settings.hh"
#include "tests/libexpr.hh" #include "tests/libexpr.hh"
namespace nix { namespace nix {
@ -614,7 +616,7 @@ namespace nix {
TEST_F(PrimOpTest, currentSystem) { TEST_F(PrimOpTest, currentSystem) {
auto v = eval("builtins.currentSystem"); auto v = eval("builtins.currentSystem");
ASSERT_THAT(v, IsStringEq(settings.thisSystem.get())); ASSERT_THAT(v, IsStringEq(evalSettings.getCurrentSystem()));
} }
TEST_F(PrimOpTest, derivation) { TEST_F(PrimOpTest, derivation) {