Fix some problems with bad mmultiscripts.

re-fixes #485
Fixes #544

Added/fixed tests for these.

Author: NSoiffer

src/canonicalize.rs

@@ -622,31 +622,30 @@ impl CanonicalizeContext {
 				"munderover" | "msubsup" => if n_children != 3 {
 					bail!("{} should have 3 children:\n{}", element_name, mml_to_string(mathml));
 				},
-				"mmultiscripts" => {
-					let has_prescripts = mathml.children().iter()
-							.any(|&child| name(as_element(child)) == "mprescripts");
-					if has_prescripts ^ (n_children.is_multiple_of(2)) {
-						bail!("{} has the wrong number of children:\n{}", element_name, mml_to_string(mathml));
-					}
-				},
-				"mlongdiv" => if n_children < 3 {
-					bail!("{} should have at least 3 children:\n{}", element_name, mml_to_string(mathml));
-				},
 				_ => if n_children != 2 {
 					bail!("{} should have 2 children:\n{}", element_name, mml_to_string(mathml));
 				},
 			}
-		}
-		if matches!(element_name, "mtd" | "mtr" | "mlabeledtr")  {
+		} else if matches!(element_name, "mtd" | "mtr" | "mlabeledtr")  {
 			let parent_name = name(get_parent(mathml));
 			if (element_name == "mtr" || element_name == "mlabeledtr") && parent_name != "mtable" {
 				bail!("Illegal MathML: {} is not a child of mtable. Parent is {}", element_name, mml_to_string(get_parent(mathml)));
 			} else if element_name == "mtd" && !(parent_name == "mtr" || parent_name == "mlabeledtr") {
 				bail!("Illegal MathML: mtd is not a child of {}. Parent is {}", parent_name, mml_to_string(get_parent(mathml)));
 			}
 		}
-		let children = mathml.children();
-		if element_name == "semantics" {
+		else if element_name == "mmultiscripts" {
+			let has_prescripts = mathml.children().iter()
+					.any(|&child| name(as_element(child)) == "mprescripts");
+			if has_prescripts ^ (n_children.is_multiple_of(2)) {
+				bail!("{} has the wrong number of children:\n{}", element_name, mml_to_string(mathml));
+			}
+		} else if element_name == "mlongdiv" {
+			if n_children < 3 {
+				bail!("{} should have at least 3 children:\n{}", element_name, mml_to_string(mathml));
+			}
+		} else if element_name == "semantics" {
+			let children = mathml.children();
 			if children.is_empty() {
 				return Ok( () );
 			} else {
@@ -662,16 +661,16 @@ impl CanonicalizeContext {
 				}
 				return CanonicalizeContext::assure_mathml(presentation_element);
 			}
-		}
-		if !IsNode::is_mathml(mathml) {
+		} else if !IsNode::is_mathml(mathml) {
 			if element_name == "annotation-xml" {
 				bail!("'annotation-xml' element is not child of 'semantics' element");
 			} else {
 				bail!("'{}' is not a valid MathML element", element_name);
 			}
 		}
+
 		// valid MathML element and not a leaf -- check the children
-		for child in children {
+		for child in mathml.children() {
 			CanonicalizeContext::assure_mathml( as_element(child) )?;
 		}
 		return Ok( () );
@@ -771,7 +770,8 @@ impl CanonicalizeContext {
 			name(parent).to_string()
 		};
 		let parent_requires_child = ELEMENTS_WITH_FIXED_NUMBER_OF_CHILDREN.contains(&parent_name) ||
-										  matches!(parent_name.as_ref(), "mtr" | "mlabeledtr" | "mtable");
+										  matches!(parent_name.as_ref(), "mtr" | "mlabeledtr" | "mtable") ||
+										  parent_name == "mmultiscripts";
 
 		// handle empty leaves -- leaving it empty causes problems with the speech rules
 		if is_leaf(mathml) && !EMPTY_ELEMENTS.contains(element_name) && as_text(mathml).is_empty() {
@@ -781,7 +781,9 @@ impl CanonicalizeContext {
 		if mathml.children().is_empty() && !EMPTY_ELEMENTS.contains(element_name) {
 			if element_name == "mrow" && mathml.attribute(INTENT_ATTR).is_none() {
 				// if it is an empty mrow that doesn't need to be there, get rid of it. Otherwise, replace it with an mtext
-				if parent_name == "mmultiscripts" {	// MathML Core dropped "none" in favor of <mrow/>, but MathCAT is written with <none/>
+				if parent_name == "mmultiscripts" && !mathml.preceding_siblings().is_empty() {
+					// MathML Core dropped "none" in favor of <mrow/>, but MathCAT is written with <none/>
+					// Do substitutions for the scripts, not the base
 					set_mathml_name(mathml, "none");
 					return Some(mathml);
 				}
@@ -1112,6 +1114,7 @@ impl CanonicalizeContext {
 				// cleaning children can add or delete subsequent children, so we need to constantly update the children (and mathml)
 				let mut children = mathml.children();
 				let mut i = 0;
+
 				while i < children.len() {
 					if let Some(child) = children[i].element() {
 						match self.clean_mathml(child) {
@@ -1418,7 +1421,7 @@ impl CanonicalizeContext {
 		}
 
 
-		/// looks for pairs of (letter, pseudoscript) such as x' or p'q' all inside of a single token element
+		/// looks for pairs of (letter, pseudo-script) such as x' or p'q' all inside of a single token element
 		fn split_apart_pseudo_scripts<'a>(mi: Element<'a>) -> Option<Element<'a>> {
 			static IS_DEGREES_C_OR_F: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"[°º][CF]").unwrap());
 
@@ -1562,7 +1565,7 @@ impl CanonicalizeContext {
 						i += 2;
 					}
 				}
-				if new_children.len() == 1 {
+				if new_children.len() <= 2 {  // base only, or base and </mprescripts>
 					mathml = as_element(new_children[0]);
 				} else {
 					mathml.replace_children(new_children);
@@ -6743,9 +6746,20 @@ mod canonicalize_tests {
 	#[test]
     fn empty_mmultiscripts_485() -> Result<()> {
         let test_str = "<math><mmultiscripts>   </mmultiscripts></math>";
-        let target_str = " <math>
-			<mtext data-added='missing-content' data-width='0.700'> </mtext>
-		</math>";
+        let target_str = ""; // shouldn't get to the point of comparing because the input is illegal.
+        let err = are_strs_canonically_equal_result(test_str, target_str, &[])
+            .expect_err("empty mmultiscripts should be rejected");
+        assert!(
+            err.to_string().contains("mmultiscripts has the wrong number of children:\n <mmultiscripts></mmultiscripts>"),
+            "unexpected error message: {err}"
+        );
+        Ok(())
+	}
+
+	#[test]
+    fn empty_mmultiscripts_544() -> Result<()> {
+        let test_str = "<math><mmultiscripts><mrow/><mprescripts></mprescripts><mrow/><mrow/></mmultiscripts></math>";
+        let target_str = "<math> <mtext data-changed='empty_content' data-width='0'> </mtext></math>";
         are_strs_canonically_equal_result(test_str, target_str, &[])
 	}