Implement xpath error message handling

.gitignore

@@ -4,6 +4,7 @@
 *.rlib
 *.dll
 Cargo.lock
+.DS_Store
 
 # Executables
 *.exe

src/bindings.rs

@@ -14926,6 +14926,13 @@ extern "C" {
   pub fn xmlXPathSetContextNode(node: xmlNodePtr, ctx: xmlXPathContextPtr)
     -> ::std::os::raw::c_int;
 }
+extern "C" {
+  pub fn xmlXPathSetErrorHandler(
+    ctxt: xmlXPathContextPtr,
+    handler: xmlStructuredErrorFunc,
+    data: *mut ::std::os::raw::c_void,
+  );
+}
 extern "C" {
   pub fn xmlXPathNodeEval(
     node: xmlNodePtr,

src/schemas/mod.rs

@@ -16,3 +16,4 @@ use schema::Schema; // internally handled by SchemaValidationContext
 
 pub use parser::SchemaParserContext;
 pub use validation::SchemaValidationContext;
+pub use common::structured_error_handler;

src/xpath.rs

@@ -1,9 +1,13 @@
 //! The `XPath` functionality
 
-use crate::bindings::*;
-use crate::c_helpers::*;
-use crate::readonly::RoNode;
-use crate::tree::{Document, DocumentRef, DocumentWeak, Node};
+use crate::{
+  bindings::{self, *},
+  c_helpers::*,
+  error::StructuredError,
+  readonly::RoNode,
+  schemas::structured_error_handler,
+  tree::{Document, DocumentRef, DocumentWeak, Node},
+};
 use libc::{c_char, c_void, size_t};
 use std::cell::RefCell;
 use std::ffi::{CStr, CString};
@@ -33,6 +37,19 @@ pub struct Context {
   pub(crate) context_ptr: ContextRef,
   ///Document contains pointer, needed for ContextPtr, so we need to borrow Document to prevent it's freeing
   pub(crate) document: DocumentWeak,
+  ///Errors registered during libxml2 xpath processing3
+  pub(crate) errlog: *mut Vec<StructuredError>,
+}
+
+impl Drop for Context {
+  fn drop(&mut self) {
+    unsafe {
+      if !self.errlog.is_null() {
+        let errors: Box<Vec<StructuredError>> = std::mem::transmute(self.errlog);
+        drop(errors)
+      }
+    }
+  }
 }
 
 ///Essentially, the result of the evaluation of some xpath expression
@@ -50,21 +67,45 @@ impl Context {
     if ctxtptr.is_null() {
       Err(())
     } else {
-      Ok(Context {
-        context_ptr: Rc::new(RefCell::new(_Context(ctxtptr))),
-        document: Rc::downgrade(&doc.0),
-      })
+      let errors: Box<Vec<StructuredError>> = Box::default();
+
+      unsafe {
+        let reference: *mut Vec<StructuredError> = std::mem::transmute(errors);
+        bindings::xmlXPathSetErrorHandler(
+          ctxtptr,
+          Some(structured_error_handler),
+          reference as *mut _,
+        );
+        Ok(Context {
+          context_ptr: Rc::new(RefCell::new(_Context(ctxtptr))),
+          document: Rc::downgrade(&doc.0),
+          errlog: reference as *mut _,
+        })
+      }
     }
   }
+
   pub(crate) fn new_ptr(docref: &DocumentRef) -> Result<Context, ()> {
     let ctxtptr = unsafe { xmlXPathNewContext(docref.borrow().doc_ptr) };
     if ctxtptr.is_null() {
       Err(())
     } else {
-      Ok(Context {
-        context_ptr: Rc::new(RefCell::new(_Context(ctxtptr))),
-        document: Rc::downgrade(docref),
-      })
+      let errors: Box<Vec<StructuredError>> = Box::default();
+
+      unsafe {
+        let reference: *mut Vec<StructuredError> = std::mem::transmute(errors);
+        bindings::xmlXPathSetErrorHandler(
+          ctxtptr,
+          Some(structured_error_handler),
+          reference as *mut _,
+        );
+
+        Ok(Context {
+          context_ptr: Rc::new(RefCell::new(_Context(ctxtptr))),
+          document: Rc::downgrade(docref),
+          errlog: reference as *mut _,
+        })
+      }
     }
   }
 
@@ -73,6 +114,13 @@ impl Context {
     self.context_ptr.borrow().0
   }
 
+  /// Drains error log from errors that might have accumulated while evaluating an xpath
+  pub fn drain_errors(&mut self) -> Vec<StructuredError> {
+    assert!(!self.errlog.is_null());
+    let errors = unsafe { &mut *self.errlog };
+    std::mem::take(errors)
+  }
+
   /// Instantiate a new Context for the Document of a given Node.
   /// Note: the Context is root-level for that document, use `.set_context_node` to limit scope to this node
   pub fn from_node(node: &Node) -> Result<Context, ()> {
@@ -269,7 +317,6 @@ impl Object {
     }
     vec
   }
-
 }
 
 impl fmt::Display for Object {

tests/xpath_tests.rs

@@ -207,7 +207,11 @@
     let empty_values = xpath.findvalues(".//@xml:id", Some(empty_test));
     assert_eq!(empty_values, Ok(Vec::new()));
     let ids_values = xpath.findvalues(".//@xml:id", Some(ids_test));
-    let expected_ids = Ok(vec![String::from("start"),String::from("mid"),String::from("end")]);
+    let expected_ids = Ok(vec![
+      String::from("start"),
+      String::from("mid"),
+      String::from("end"),
+    ]);
     assert_eq!(ids_values, expected_ids);
     let node_ids_values = ids_test.findvalues(".//@xml:id");
     assert_eq!(node_ids_values, expected_ids);
@@ -216,6 +220,28 @@
   }
 }
 
+#[test]
+// brew install --HEAD libxml2
+// export LIBXML2=`ls /opt/homebrew/Cellar/libxml2/*/lib/libxml2.dylib` && echo $LIBXML2
+// cargo clean
+// cargo test
+fn xpath_context_new() {
+  let parser = Parser::default_html();
+  let doc_result = parser.parse_file("tests/resources/file02.xml");
+  assert!(doc_result.is_ok());
+  let doc = doc_result.unwrap();
+
+  // Xpath interface
+  let mut context = Context::new(&doc).unwrap();
+  match context.evaluate("/html/un:body") {
+    Ok(_) => assert!(false),
+    Err(e) => {
+      // for msg in context.drain_errors() {
+        // assert_eq!(1,msg.code);
+      // }
+    }
+  }
+}
 /// Tests for checking xpath well-formedness
 mod compile_tests {
   use libxml::xpath::is_well_formed_xpath;