Fix baml validation imports (#1038)

<!-- ELLIPSIS_HIDDEN -->



> [!IMPORTANT]
> Fix import and definition of `BamlValidationError` by moving it to
`internal_monkeypatch.py` and updating related imports and Rust code.
> 
>   - **Imports and Definitions**:
> - Move `BamlValidationError` definition to `internal_monkeypatch.py`.
>     - Update import of `BamlValidationError` in `errors.py`.
>   - **File Deletions**:
>     - Remove `errors.pyi` as it is no longer needed.
>   - **Rust Code Adjustments**:
> - Modify `raise_baml_validation_error` in `errors.rs` to import
`BamlValidationError` from `internal_monkeypatch.py`.
> - Remove manual definition of `BamlValidationError` in `errors.rs`.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 17fd482. It will automatically
update as commits are pushed.</sup>

<!-- ELLIPSIS_HIDDEN -->

engine/language_client_python/python_src/baml_py/ctx_manager.py

@@ -40,31 +40,27 @@ def __ctx(self) -> RuntimeContextManager:
             ctx[thread_id] = self.rt.create_context_manager()
         return ctx[thread_id]
 
-
     def allow_reset(self) -> bool:
         ctx = self.ctx.get()
-        
+
         if len(ctx) > 1:
             print("Too many ctxs!")
             return False
 
-
         thread_id = current_thread_id()
         if thread_id not in ctx:
             print("Thread not in ctx!")
-            return False        
+            return False
 
         for c in ctx.values():
             if c.context_depth() > 0:
                 print("Context depth is greater than 0!")
                 return False
-
 
         return True
 
     def reset(self) -> None:
         self.ctx.set({current_thread_id(): self.rt.create_context_manager()})
-
 
     def upsert_tags(self, **tags: str) -> None:
         mngr = self.__ctx()

engine/language_client_python/python_src/baml_py/errors.py

@@ -4,9 +4,7 @@
     BamlClientHttpError,
     BamlInvalidArgumentError,
 )
-
-# hack to get the BamlValidationError class which is a custom error
-from .baml_py.errors import BamlValidationError
+from .internal_monkeypatch import BamlValidationError
 
 
 __all__ = [

engine/language_client_python/python_src/baml_py/internal_monkeypatch.py

@@ -0,0 +1,18 @@
+from .baml_py import BamlError
+
+
+# Define the BamlValidationError exception with additional fields
+# note on custom exceptions https://github.com/PyO3/pyo3/issues/295
+# can't use extends=PyException yet https://github.com/PyO3/pyo3/discussions/3838
+class BamlValidationError(BamlError):
+    def __init__(self, prompt: str, message: str, raw_output: str):
+        super().__init__(message)
+        self.prompt = prompt
+        self.message = message
+        self.raw_output = raw_output
+
+    def __str__(self):
+        return f"BamlValidationError(message={self.message}, raw_output={self.raw_output}, prompt={self.prompt})"
+
+    def __repr__(self):
+        return f"BamlValidationError(message={self.message}, raw_output={self.raw_output}, prompt={self.prompt})"

engine/language_client_python/src/errors.rs

@@ -17,76 +17,22 @@ create_exception!(baml_py, BamlClientHttpError, BamlClientError);
 
 // Define the BamlValidationError exception with additional fields
 // can't use extends=PyException yet https://github.com/PyO3/pyo3/discussions/3838
-#[pyfunction]
+
+#[allow(non_snake_case)]
 fn raise_baml_validation_error(prompt: String, message: String, raw_output: String) -> PyErr {
     Python::with_gil(|py| {
-        // Import the current module to access the BamlValidationError class
-        let module = PyModule::import(py, "baml_py.errors").unwrap();
-        let exception = module.getattr("BamlValidationError").unwrap();
+        let internal_monkeypatch = py.import("baml_py.internal_monkeypatch").unwrap();
+        let exception = internal_monkeypatch.getattr("BamlValidationError").unwrap();
         let args = (prompt, message, raw_output);
-        let instance = exception.call1(args).unwrap();
-        PyErr::from_value(instance.into())
+        let inst = exception.call1(args).unwrap();
+        PyErr::from_value(inst)
     })
 }
 
 /// Defines the errors module with the BamlValidationError exception.
 /// IIRC the name of this function is the name of the module that pyo3 generates (errors.py)
 #[pymodule]
 pub fn errors(parent_module: &Bound<'_, PyModule>) -> PyResult<()> {
-    // Define the BamlValidationError Python exception class in a hacky way first, manually into that errors module.
-    let errors_module = PyModule::from_code_bound(
-        parent_module.py(),
-        r#"
-class BamlValidationError(Exception):
-    def __init__(self, prompt, message, raw_output):
-        super().__init__(message)
-        self.prompt = prompt
-        self.message = message
-        self.raw_output = raw_output
-
-    def __str__(self):
-        return f"BamlValidationError(message={self.message}, raw_output={self.raw_output}, prompt={self.prompt})"
-
-    def __repr__(self):
-        return f"BamlValidationError(message={self.message}, raw_output={self.raw_output}, prompt={self.prompt})"
-"#,
-        "errors.py",
-        "errors",
-    )?;
-
-    // Add the raise_baml_validation_error function to the module
-    parent_module.add_wrapped(wrap_pyfunction!(raise_baml_validation_error))?;
-
-    // add the other exceptions in
-    errors_module.add(
-        "BamlError",
-        errors_module.py().get_type_bound::<BamlError>(),
-    )?;
-    errors_module.add(
-        "BamlInvalidArgumentError",
-        errors_module
-            .py()
-            .get_type_bound::<BamlInvalidArgumentError>(),
-    )?;
-    errors_module.add(
-        "BamlClientError",
-        errors_module.py().get_type_bound::<BamlClientError>(),
-    )?;
-    errors_module.add(
-        "BamlClientHttpError",
-        errors_module.py().get_type_bound::<BamlClientHttpError>(),
-    )?;
-
-    parent_module.add_submodule(&errors_module)?;
-
-    // we have to do this hack or python will complain the baml_py.errors is not a package.
-    parent_module
-        .py()
-        .import("sys")?
-        .getattr("modules")?
-        .set_item("baml_py.errors", errors_module.clone())?;
-
-    // now add the other errors again to the parent module
     parent_module.add(
         "BamlError",
         parent_module.py().get_type_bound::<BamlError>(),