feat(python): add validate

docs/python.md

@@ -11,3 +11,4 @@ python -m pip install cql2
 
 ::: cql2.Expr
 ::: cql2.SqlQuery
+::: cql2.ValidationError

python/cql2.pyi

@@ -41,6 +41,18 @@ class Expr:
             >>> expr = Expr({"op":"=","args":[{"property":"landsat:scene_id"},"LC82030282019133LGN00"]})
         """
 
+    def validate(self) -> None:
+        """Validates this expression using json-schema.
+
+        Raises:
+            ValidationError: Raised if the validation fails
+
+        Examples:
+            >>> from cql2 import Expr
+            >>> expr = Expr("landsat:scene_id = 'LC82030282019133LGN00'")
+            >>> expr.validate()
+        """
+
     def to_json(self) -> dict[str, Any]:
         """Converts this cql2 expression to a cql2-json dictionary.
 
@@ -81,3 +93,6 @@ class Expr:
             >>> q.params
             ['LC82030282019133LGN00']
         """
+
+class ValidationError(Exception):
+    """An error raised when cql2 json-schema validation fails."""

python/src/lib.rs

@@ -1,9 +1,12 @@
 use pyo3::{
+    create_exception,
     exceptions::{PyException, PyIOError, PyValueError},
     prelude::*,
 };
 use std::path::PathBuf;
 
+create_exception!(cql2, ValidationError, PyException);
+
 /// Crate-specific error enum.
 enum Error {
     Cql2(::cql2::Error),
@@ -46,6 +49,15 @@ impl Expr {
         }
     }
 
+    fn validate(&self) -> PyResult<()> {
+        let validator = ::cql2::Validator::new().map_err(Error::from)?;
+        if let Err(error) = validator.validate(&self.0.to_value().map_err(Error::from)?) {
+            Err(ValidationError::new_err(error.to_string()))
+        } else {
+            Ok(())
+        }
+    }
+
     /// Converts this expression to a cql2-json dictionary.
     fn to_json<'py>(&self, py: Python<'py>) -> Result<Bound<'py, PyAny>> {
         pythonize::pythonize(py, &self.0).map_err(Error::from)
@@ -104,8 +116,9 @@ impl From<pythonize::PythonizeError> for Error {
 
 /// A Python module implemented in Rust.
 #[pymodule]
-fn cql2(m: &Bound<'_, PyModule>) -> PyResult<()> {
+fn cql2(py: Python<'_>, m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_class::<Expr>()?;
     m.add_class::<SqlQuery>()?;
+    m.add("ValidationError", py.get_type_bound::<ValidationError>())?;
     Ok(())
 }

python/tests/test_expr.py

@@ -1,6 +1,7 @@
 from pathlib import Path
 
-from cql2 import Expr
+import pytest
+from cql2 import Expr, ValidationError
 
 
 def test_from_path(fixtures: Path) -> None:
@@ -26,3 +27,14 @@ def test_to_sql(example01_text: str) -> None:
     sql_query = Expr(example01_text).to_sql()
     assert sql_query.query == '("landsat:scene_id" = $1)'
     assert sql_query.params == ["LC82030282019133LGN00"]
+
+
+def test_validate() -> None:
+    expr = Expr(
+        {
+            "op": "t_before",
+            "args": [{"property": "updated_at"}, {"timestamp": "invalid-timestamp"}],
+        }
+    )
+    with pytest.raises(ValidationError):
+        expr.validate()