Add PMC stylechecker mathml checks

src/final-JATS-schematron.sch

@@ -2968,6 +2968,15 @@
 
       <report test="matches(.,'^\p{Zs}$')" role="error" id="math-mi-space-test">[math-mi-space-test] <name/> element contains only spaces. Has "\" been used for space in the tex editor, instead of "\,"?</report>
 
+    </rule></pattern><pattern id="math-empty-child-tests-pattern"><rule context="msub|msup|msubsup|munder|mover|munderover" id="math-empty-child-tests">
+      <let name="script-name" value="if (./name() = 'msub') then 'subscript'                                      else if (./name() = 'msup') then 'superscript'                                      else if (./name() = 'msubsup') then 'subscript'                                      else if (./name() = 'munder') then 'underscript'                                      else if (./name() = 'mover') then 'overscript'                                      else if (./name() = 'munderover') then 'underscript'                                      else 'second'"/>
+
+      <assert test="*[1][normalize-space(descendant-or-self::*[text()])]" role="error" id="math-empty-base-check">[math-empty-base-check] <name/> element must not have an empty base expression.</assert>
+
+      <assert test="*[2][normalize-space(descendant-or-self::*[text()])]" role="error" id="math-empty-script-check">[math-empty-script-check] <name/> element must not have an empty <value-of select="$script-name"/> expression.</assert>
+
+      <report test="name()=('msubsup','munderover') and not(*[3][normalize-space(descendant-or-self::*[text()])])" role="error" id="math-empty-second-script-check">[math-empty-second-script-check] <name/> element must not have an empty <value-of select="if (name()='msubsup') then 'superscript' else 'overscript'"/> expression.</report>
+
     </rule></pattern><pattern id="disp-formula-child-tests-pattern"><rule context="disp-formula/*" id="disp-formula-child-tests">
 
       <report see="https://elifeproduction.slab.com/posts/maths-0gfptlyl#disp-formula-child-test-1" test="not(local-name()=('label','math'))" role="error" id="disp-formula-child-test-1">[disp-formula-child-test-1] <name/> element is not allowed as a child of disp-formula.</report>

src/final-package-JATS-schematron.sch

@@ -2974,6 +2974,15 @@
 
       <report test="matches(.,'^\p{Zs}$')" role="error" id="math-mi-space-test"><name/> element contains only spaces. Has "\" been used for space in the tex editor, instead of "\,"?</report>
 
+    </rule></pattern><pattern id="math-empty-child-tests-pattern"><rule context="msub|msup|msubsup|munder|mover|munderover" id="math-empty-child-tests">
+      <let name="script-name" value="if (./name() = 'msub') then 'subscript'                                      else if (./name() = 'msup') then 'superscript'                                      else if (./name() = 'msubsup') then 'subscript'                                      else if (./name() = 'munder') then 'underscript'                                      else if (./name() = 'mover') then 'overscript'                                      else if (./name() = 'munderover') then 'underscript'                                      else 'second'"/>
+
+      <assert test="*[1][normalize-space(descendant-or-self::*[text()])]" role="error" id="math-empty-base-check"><name/> element must not have an empty base expression.</assert>
+
+      <assert test="*[2][normalize-space(descendant-or-self::*[text()])]" role="error" id="math-empty-script-check"><name/> element must not have an empty <value-of select="$script-name"/> expression.</assert>
+
+      <report test="name()=('msubsup','munderover') and not(*[3][normalize-space(descendant-or-self::*[text()])])" role="error" id="math-empty-second-script-check"><name/> element must not have an empty <value-of select="if (name()='msubsup') then 'superscript' else 'overscript'"/> expression.</report>
+
     </rule></pattern><pattern id="disp-formula-child-tests-pattern"><rule context="disp-formula/*" id="disp-formula-child-tests">
 
       <report see="https://elifeproduction.slab.com/posts/maths-0gfptlyl#disp-formula-child-test-1" test="not(local-name()=('label','math'))" role="error" id="disp-formula-child-test-1"><name/> element is not allowed as a child of disp-formula.</report>

src/pre-JATS-schematron.sch

@@ -2913,6 +2913,15 @@
 
       <report test="matches(.,'^\p{Zs}$')" role="error" id="math-mi-space-test">[math-mi-space-test] <name/> element contains only spaces. Has "\" been used for space in the tex editor, instead of "\,"?</report>
 
+    </rule></pattern><pattern id="math-empty-child-tests-pattern"><rule context="msub|msup|msubsup|munder|mover|munderover" id="math-empty-child-tests">
+      <let name="script-name" value="if (./name() = 'msub') then 'subscript'                                      else if (./name() = 'msup') then 'superscript'                                      else if (./name() = 'msubsup') then 'subscript'                                      else if (./name() = 'munder') then 'underscript'                                      else if (./name() = 'mover') then 'overscript'                                      else if (./name() = 'munderover') then 'underscript'                                      else 'second'"/>
+
+      <assert test="*[1][normalize-space(descendant-or-self::*[text()])]" role="error" id="math-empty-base-check">[math-empty-base-check] <name/> element must not have an empty base expression.</assert>
+
+      <assert test="*[2][normalize-space(descendant-or-self::*[text()])]" role="error" id="math-empty-script-check">[math-empty-script-check] <name/> element must not have an empty <value-of select="$script-name"/> expression.</assert>
+
+      <report test="name()=('msubsup','munderover') and not(*[3][normalize-space(descendant-or-self::*[text()])])" role="error" id="math-empty-second-script-check">[math-empty-second-script-check] <name/> element must not have an empty <value-of select="if (name()='msubsup') then 'superscript' else 'overscript'"/> expression.</report>
+
     </rule></pattern><pattern id="disp-formula-child-tests-pattern"><rule context="disp-formula/*" id="disp-formula-child-tests">
 
       <report see="https://elifeproduction.slab.com/posts/maths-0gfptlyl#disp-formula-child-test-1" test="not(local-name()=('label','math'))" role="error" id="disp-formula-child-test-1">[disp-formula-child-test-1] <name/> element is not allowed as a child of disp-formula.</report>