fix(error): avoid converting non-error into PyException (#991)

Author: georgeh0

src/builder/flow_builder.rs

@@ -18,7 +18,7 @@ use crate::{
     },
     lib_context::LibContext,
     ops::interface::FlowInstanceContext,
-    py::IntoPyResult,
+    py::{AnyhowIntoPyResult, IntoPyResult},
 };
 use crate::{lib_context::FlowContext, py};
 

src/execution/evaluator.rs

@@ -5,7 +5,7 @@ use futures::future::try_join_all;
 
 use crate::base::value::EstimatedByteSize;
 use crate::builder::{AnalyzedTransientFlow, plan::*};
-use crate::py::IntoPyResult;
+use crate::py::AnyhowIntoPyResult;
 use crate::{
     base::{schema, value},
     utils::immutable::RefList,
@@ -73,6 +73,7 @@ impl ScopeValueBuilder {
             .zip(&mut builder.fields)
         {
             r.set(augmented_value(v, &t.value_type.typ)?)
+                .map_err(|_| anyhow!("Value of field `{}` is already set", t.name))
                 .into_py_result()?;
         }
         Ok(builder)

src/py/convert.rs

@@ -12,7 +12,7 @@ use pythonize::{depythonize, pythonize};
 use serde::de::DeserializeOwned;
 use std::ops::Deref;
 
-use super::IntoPyResult;
+use super::{AnyhowIntoPyResult, IntoPyResult};
 
 #[derive(Debug)]
 pub struct Pythonized<T>(pub T);

src/py/mod.rs

@@ -72,7 +72,20 @@ pub trait IntoPyResult<T> {
     fn into_py_result(self) -> PyResult<T>;
 }
 
-impl<T, E: std::fmt::Debug> IntoPyResult<T> for Result<T, E> {
+impl<T, E: std::error::Error> IntoPyResult<T> for Result<T, E> {
+    fn into_py_result(self) -> PyResult<T> {
+        match self {
+            Ok(value) => Ok(value),
+            Err(err) => Err(PyException::new_err(format!("{err:?}"))),
+        }
+    }
+}
+
+pub trait AnyhowIntoPyResult<T> {
+    fn into_py_result(self) -> PyResult<T>;
+}
+
+impl<T> AnyhowIntoPyResult<T> for anyhow::Result<T> {
     fn into_py_result(self) -> PyResult<T> {
         match self {
             Ok(value) => Ok(value),