fix(tvix/eval): handle __toString when JSON-serialising attrsets

These must be serialised to a JSON string of the *result* of coercing
the function application to a string.

Change-Id: Ib7f49ccd950503ddbdbf99643cd59565e26b50da
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8204
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
This commit is contained in:
Vincent Ambo 2023-03-03 23:55:00 +03:00 committed by tazjin
parent a9f44721e5
commit 7d339d2762
5 changed files with 29 additions and 0 deletions

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@ -359,6 +359,15 @@ mod pure_builtins {
#[builtin("toJSON")]
async fn builtin_to_json(co: GenCo, val: Value) -> Result<Value, ErrorKind> {
if let Value::Attrs(attrs) = &val {
// Attribute sets with a callable `__toString` attribute
// serialise to the string-coerced version of the result of
// calling that.
if let Some(s) = attrs.try_to_string(&co, CoercionKind::Weak).await {
return Ok(Value::String(serde_json::to_string(&s)?.into()));
}
}
// All thunks need to be evaluated before serialising, as the
// data structure is fully traversed by the Serializer.
let val = generators::request_deep_force(&co, val, SharedThunkSet::default()).await;

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@ -0,0 +1,5 @@
# attribute sets with a non-callable `__toString` can not be
# serialised to JSON.
builtins.toJSON {
__toString = 42;
}

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@ -0,0 +1,6 @@
# String coercions when using builtins.toJSON on an attribute set with
# a `__toString` attribute should be weak.
builtins.toJSON {
__toString = self: self.x;
x = 42;
}

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@ -0,0 +1 @@
"\"it's 42\""

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@ -0,0 +1,8 @@
# Attribute sets with a `__toString` attribute JSON-serialise with a
# string coercion of the function call result.
builtins.toJSON {
__toString = self: "it's " + (builtins.toString (self.x * self.y));
x = 21;
y = 2;
}