allow flakes to trivially eval to attrsets

flake.nix has historically been required to be a literal attribute set
expression. This commit relaxes that requirement that it must trivially
evaluate to an attribute set. Thunks are still not allowed, so imports,
most function applications, etc are all still disallowed, but things
like trivial let expressions are.

I love deleting code ^_^

Change-Id: I3b66e2bacb58d1deadfb4a768cc3a356638aeec3
This commit is contained in:
Qyriad 2024-05-31 17:01:12 -06:00
parent c7ca87461d
commit bea69509a2
5 changed files with 60 additions and 18 deletions

View file

@ -1098,7 +1098,7 @@ Value * ExprPath::maybeThunk(EvalState & state, Env & env)
} }
void EvalState::evalFile(const SourcePath & path_, Value & v, bool mustBeTrivial) void EvalState::evalFile(const SourcePath & path_, Value & v)
{ {
auto path = checkSourcePath(path_); auto path = checkSourcePath(path_);
@ -1124,7 +1124,7 @@ void EvalState::evalFile(const SourcePath & path_, Value & v, bool mustBeTrivial
if (!e) if (!e)
e = parseExprFromFile(checkSourcePath(resolvedPath)); e = parseExprFromFile(checkSourcePath(resolvedPath));
cacheFile(path, resolvedPath, e, v, mustBeTrivial); cacheFile(path, resolvedPath, e, v);
} }
@ -1139,8 +1139,8 @@ void EvalState::cacheFile(
const SourcePath & path, const SourcePath & path,
const SourcePath & resolvedPath, const SourcePath & resolvedPath,
Expr * e, Expr * e,
Value & v, Value & v
bool mustBeTrivial) )
{ {
fileParseCache[resolvedPath] = e; fileParseCache[resolvedPath] = e;
@ -1153,12 +1153,6 @@ void EvalState::cacheFile(
e->getPos() ? std::make_shared<Pos>(positions[e->getPos()]) : nullptr, e->getPos() ? std::make_shared<Pos>(positions[e->getPos()]) : nullptr,
"while evaluating the file '%1%':", resolvedPath.to_string()) "while evaluating the file '%1%':", resolvedPath.to_string())
: nullptr; : nullptr;
// Enforce that 'flake.nix' is a direct attrset, not a
// computation.
if (mustBeTrivial &&
!(dynamic_cast<ExprAttrs *>(e)))
error<EvalError>("file '%s' must be an attribute set", path).debugThrow();
eval(e, v); eval(e, v);
} catch (Error & e) { } catch (Error & e) {
addErrorTrace(e, "while evaluating the file '%1%':", resolvedPath.to_string()); addErrorTrace(e, "while evaluating the file '%1%':", resolvedPath.to_string());

View file

@ -352,11 +352,9 @@ public:
Expr * parseStdin(); Expr * parseStdin();
/** /**
* Evaluate an expression read from the given file to normal * Evaluate an expression read from the given file to normal form.
* form. Optionally enforce that the top-level expression is
* trivial (i.e. doesn't require arbitrary computation).
*/ */
void evalFile(const SourcePath & path, Value & v, bool mustBeTrivial = false); void evalFile(const SourcePath & path, Value & v);
/** /**
* Like `evalFile`, but with an already parsed expression. * Like `evalFile`, but with an already parsed expression.
@ -365,8 +363,8 @@ public:
const SourcePath & path, const SourcePath & path,
const SourcePath & resolvedPath, const SourcePath & resolvedPath,
Expr * e, Expr * e,
Value & v, Value & v
bool mustBeTrivial = false); );
void resetFileCache(); void resetFileCache();

View file

@ -233,9 +233,13 @@ static Flake getFlake(
.sourceInfo = std::make_shared<fetchers::Tree>(std::move(sourceInfo)) .sourceInfo = std::make_shared<fetchers::Tree>(std::move(sourceInfo))
}; };
// NOTE evalFile forces vInfo to be an attrset because mustBeTrivial is true.
Value vInfo; Value vInfo;
state.evalFile(CanonPath(flakeFile), vInfo, true); // FIXME: symlink attack state.evalFile(CanonPath(flakeFile), vInfo); // FIXME: symlink attack
if (vInfo.type() != nAttrs) {
state.error<EvalError>(
"file '%s' must be an attribute set, but is %s", flakeFile, showType(vInfo)
).debugThrow();
}
if (auto description = vInfo.attrs->get(state.sDescription)) { if (auto description = vInfo.attrs->get(state.sDescription)) {
expectType(state, nString, *description->value, description->pos); expectType(state, nString, *description->value, description->pos);

View file

@ -0,0 +1,45 @@
# Allow trivial evaluation in flake metadata.
source ./common.sh
clearStore
flakeLetDir="$TEST_ROOT/flake-let"
flakeInterpDir="$TEST_ROOT/flake-interp"
for flakeDir in "$flakeLetDir" "$flakeInterpDir"; do
mkdir -vp "$flakeDir"
done
# let is trivial; this should succeed
cat > "$flakeLetDir/flake.nix" <<EOF
let
description = "meow";
in {
inherit description;
inputs = { };
outputs = { self }: {
};
}
EOF
# string interpolation thunks; this should fail
cat > "$flakeInterpDir/flake.nix" <<EOF
let
lix-forgejo = "git+https://git.lix.systems";
in {
inputs = {
lix.url = "\${lix-forgejo}/lix-project/lix";
};
outputs = { self, lix }: {
};
}
EOF
(cd "$flakeLetDir" && nix flake show)
(
cd "$flakeInterpDir"
expectStderr 1 nix flake show | grepQuiet "error: expected a string but got a thunk"
)

View file

@ -174,6 +174,7 @@ functional_tests_scripts = [
'fetchClosure.sh', 'fetchClosure.sh',
'completions.sh', 'completions.sh',
'flakes/show.sh', 'flakes/show.sh',
'flakes/trivial-flake.sh',
'impure-derivations.sh', 'impure-derivations.sh',
'path-from-hash-part.sh', 'path-from-hash-part.sh',
'toString-path.sh', 'toString-path.sh',