refactor(tvix/eval): remove Value::Json and related functionality r/8890

Currently Value::Json is used in combination with VMRequest::ToJson to
recursively convert tvix Value to serde_json::Value. This functionality
is used in builtins.toJSON as well as derivation __structuredAttrs.

Both Value::Json and VMRequest::ToJson were removed in this commit.

Related functionality in vm.rs is also removed: vm.rs does not know
about JSON anymore.

Recursively converting to serde_json now happens without going through
the VM.

Thrown errors that are part of the value of toJSON are now directly
propagated as ErrorKind, were-as previously there was a split between
CatchableErrorKind and ErrorKind, where eventually CatchableErrorKind
would be converted to ErrorKind::Catchable.

Change-Id: I066f064926c491e4c087a984f07af43d19124cfe
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12732
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

2 files changed, 9 insertions, 7 deletions

diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index f130bbc5b15f..47c0f85b3c1b 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -442,17 +442,20 @@ mod pure_builtins {
     #[builtin("fromJSON")]
     async fn builtin_from_json(co: GenCo, json: Value) -> Result<Value, ErrorKind> {
         let json_str = json.to_str()?;
-
         serde_json::from_slice(&json_str).map_err(|err| err.into())
     }
 
     #[builtin("toJSON")]
     async fn builtin_to_json(co: GenCo, val: Value) -> Result<Value, ErrorKind> {
-        match val.into_contextful_json(&co).await? {
-            Err(cek) => Ok(Value::from(cek)),
-            Ok((json_value, ctx)) => {
-                let json_str = serde_json::to_string(&json_value)?;
-                Ok(NixString::new_context_from(ctx, json_str).into())
+        match val.into_contextful_json(&co).await {
+            Err(ErrorKind::CatchableError(catchable)) => Ok(Value::Catchable(Box::new(catchable))),
+            Err(err) => Err(err),
+            Ok((json, context)) => {
+                let json_str = serde_json::to_string(&json)
+                    .map_err(|err| ErrorKind::JsonError(err.to_string()))?;
+                Ok(Value::String(NixString::new_context_from(
+                    context, json_str,
+                )))
             }
         }
     }
diff --git a/tvix/eval/src/builtins/to_xml.rs b/tvix/eval/src/builtins/to_xml.rs
index 093e127fe25e..785992e457ac 100644
--- a/tvix/eval/src/builtins/to_xml.rs
+++ b/tvix/eval/src/builtins/to_xml.rs
@@ -122,7 +122,6 @@ fn value_variant_to_xml<W: Write>(w: &mut XmlEmitter<W>, value: &Value) -> Resul
         | Value::Blueprint(_)
         | Value::DeferredUpvalue(_)
         | Value::UnresolvedPath(_)
-        | Value::Json(..)
         | Value::FinaliseRequest(_) => {
             return Err(ErrorKind::TvixBug {
                 msg: "internal value variant encountered in builtins.toXML",