Fix lol_html_take_last_error() after calling lol_html_element_add_end…

…_tag_handler() on element with no end tag (#187)

* Remove unused "No end tag" error

This was removed when the on_end_tag() API was switched to end_tag_handlers().

* Make lol_html_element_add_end_tag_handler() arm lol_html_take_last_error() on no end tag

Prior to the end_tag_handlers() refactor, calling lol_html_element_on_end_tag() on an element with no end tag would arm lol_html_take_last_error() with a "No end tag." string. The new lol_html_element_add_end_tag_handler() function inherited the previous function's doc comment describing this behavior, but not the actual behavior itself. This commit restores that behavior and adds a regression test.

c-api/include/lol_html.h

@@ -696,6 +696,10 @@ void *lol_html_element_user_data_get(const lol_html_element_t *element);
 // stops immediately and `write()` or `end()` of the rewriter methods
 // return an error code.
 //
+// Not all elements (for example, `<br>`) support end tags. If this function is
+// called on such an element, this function returns an error code as described
+// below.
+//
 // Returns 0 in case of success and -1 otherwise. The actual error message
 // can be obtained using `lol_html_take_last_error` function.
 //

c-api/src/element.rs

@@ -228,18 +228,18 @@ pub extern "C" fn lol_html_element_add_end_tag_handler(
 ) -> c_int {
     let element = to_ref_mut!(element);
 
-    match element.end_tag_handlers() {
-        Some(handlers) => {
-            handlers.push(Box::new(move |end_tag| {
-                match unsafe { handler(end_tag, user_data) } {
-                    RewriterDirective::Continue => Ok(()),
-                    RewriterDirective::Stop => Err("The rewriter has been stopped.".into()),
-                }
-            }));
-            0
+    let handlers = unwrap_or_ret_err_code! {
+        element.end_tag_handlers().ok_or("No end tag.")
+    };
+
+    handlers.push(Box::new(move |end_tag| {
+        match unsafe { handler(end_tag, user_data) } {
+            RewriterDirective::Continue => Ok(()),
+            RewriterDirective::Stop => Err("The rewriter has been stopped.".into()),
         }
-        None => -1,
-    }
+    }));
+
+    0
 }
 
 #[no_mangle]

c-api/tests/src/test_element_api.c

@@ -660,6 +660,36 @@ EXPECT_OUTPUT(
     sizeof(EXPECTED_USER_DATA)
 );
 
+static lol_html_rewriter_directive_t noop_end_tag_handler(lol_html_end_tag_t *end_tag, void *user_data) {
+  UNUSED(end_tag);
+  UNUSED(user_data);
+  return LOL_HTML_CONTINUE;
+}
+
+static lol_html_rewriter_directive_t add_end_tag_handler_to_element_with_no_end_tag(
+    lol_html_element_t *element,
+    void *user_data
+) {
+    UNUSED(user_data);
+
+    ok(lol_html_element_add_end_tag_handler(element, noop_end_tag_handler, NULL) == -1);
+
+    lol_html_str_t msg = lol_html_take_last_error();
+
+    str_eq(msg, "No end tag.");
+
+    lol_html_str_free(msg);
+
+    return LOL_HTML_CONTINUE;
+}
+
+EXPECT_OUTPUT(
+    no_end_tag,
+    "<br>",
+    &EXPECTED_USER_DATA,
+    sizeof(EXPECTED_USER_DATA)
+);
+
 void element_api_test() {
     int user_data = 43;
 
@@ -787,4 +817,30 @@ void element_api_test() {
         const char *input = "<div>42</div><div>some data</div>";
         run_rewriter(builder, input, modify_element_end_tag, &user_data);
     }
+
+    {
+        note("NoEndTag");
+
+        const char *selector_str = "br";
+        lol_html_selector_t *selector = lol_html_selector_parse(
+            selector_str,
+            strlen(selector_str)
+        );
+
+        lol_html_rewriter_builder_t *builder = lol_html_rewriter_builder_new();
+
+        lol_ok(lol_html_rewriter_builder_add_element_content_handlers(
+            builder,
+            selector,
+            add_end_tag_handler_to_element_with_no_end_tag,
+            NULL,
+            NULL,
+            NULL,
+            NULL,
+            NULL
+        ));
+
+        const char *input = "<br>";
+        run_rewriter(builder, input, no_end_tag, &user_data);
+    }
 }

src/lib.rs

@@ -52,8 +52,8 @@ pub mod errors {
 /// HTML content descriptors that can be produced and modified by a rewriter.
 pub mod html_content {
     pub use super::rewritable_units::{
-        Attribute, Comment, ContentType, Doctype, DocumentEnd, Element, EndTag, EndTagError,
-        StartTag, TextChunk, UserData,
+        Attribute, Comment, ContentType, Doctype, DocumentEnd, Element, EndTag, StartTag,
+        TextChunk, UserData,
     };
 
     pub use super::html::TextType;

src/rewritable_units/element.rs

@@ -30,14 +30,6 @@ pub enum TagNameError {
     UnencodableCharacter,
 }
 
-/// An error that occurs when invalid value is provided for the tag name.
-#[derive(Error, Debug, Eq, PartialEq, Copy, Clone)]
-pub enum EndTagError {
-    /// The tag has no end tag.
-    #[error("No end tag.")]
-    NoEndTag,
-}
-
 /// An HTML element rewritable unit.
 ///
 /// Exposes API for examination and modification of a parsed HTML element.