feat: add validation methods to python bindings (#305)

* add validation methods to python bindings

* centralize validation logic

* rename functions

* format

bindings/python/src/expression.rs

@@ -1,10 +1,11 @@
 use crate::variable::PyVariable;
 use anyhow::{anyhow, Context};
 use either::Either;
-use pyo3::types::PyDict;
+use pyo3::types::{PyAnyMethods, PyDict};
 use pyo3::{pyclass, pyfunction, pymethods, Bound, IntoPyObjectExt, Py, PyAny, PyResult, Python};
 use pythonize::depythonize;
 use zen_expression::expression::{Standard, Unary};
+use zen_expression::validate::{validate_expression, validate_unary_expression, ValidationError};
 use zen_expression::{Expression, Variable};
 
 #[pyfunction]
@@ -97,3 +98,31 @@ impl PyExpression {
         PyVariable(result).into_py_any(py)
     }
 }
+
+#[pyfunction]
+#[pyo3(name = "validate_expression")]
+pub fn py_validate_expression(py: Python, expression: String) -> PyResult<Option<Py<PyDict>>> {
+    let Some(err) = validate_expression(expression.as_str()) else {
+        return Ok(None);
+    };
+    return Ok(Some(convert_error_to_dict(py, &err)));
+}
+
+#[pyfunction]
+#[pyo3(name = "validate_unary_expression")]
+pub fn py_validate_unary_expression(
+    py: Python,
+    expression: String,
+) -> PyResult<Option<Py<PyDict>>> {
+    let Some(err) = validate_unary_expression(expression.as_str()) else {
+        return Ok(None);
+    };
+    return Ok(Some(convert_error_to_dict(py, &err)));
+}
+
+fn convert_error_to_dict(py: Python, err: &ValidationError) -> Py<PyDict> {
+    let dict = PyDict::new(py);
+    dict.set_item("type", &err.error_type).unwrap();
+    dict.set_item("source", &err.source).unwrap();
+    return dict.unbind();
+}

bindings/python/src/lib.rs

@@ -2,7 +2,7 @@ use crate::decision::PyZenDecision;
 use crate::engine::PyZenEngine;
 use crate::expression::{
     compile_expression, compile_unary_expression, evaluate_expression, evaluate_unary_expression,
-    render_template, PyExpression,
+    py_validate_expression, py_validate_unary_expression, render_template, PyExpression,
 };
 use pyo3::prelude::PyModuleMethods;
 use pyo3::types::PyModule;
@@ -28,6 +28,8 @@ fn zen(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(render_template, m)?)?;
     m.add_function(wrap_pyfunction!(compile_expression, m)?)?;
     m.add_function(wrap_pyfunction!(compile_unary_expression, m)?)?;
+    m.add_function(wrap_pyfunction!(py_validate_expression, m)?)?;
+    m.add_function(wrap_pyfunction!(py_validate_unary_expression, m)?)?;
 
     Ok(())
 }