Create the mathml semantics block if it doesn't exist.

cnxpublishing/models.py

@@ -11,6 +11,30 @@
 from pyramid.threadlocal import get_current_registry
 
 
+MATHML_NAMESPACE = "http://www.w3.org/1998/Math/MathML"
+NSMAP = {'m': MATHML_NAMESPACE}
+
+
+def _find_or_create_semantics_block(math_block):
+    """Finds or creates the MathML semantics tag."""
+    try:
+        semantics_block = math_block.xpath(
+            '/m:samantics',
+            namespaces=NSMAP)[0]
+    except IndexError:
+        # Move all the contents of the math_block into a semantics wrapper.
+        children = []
+        for child in math_block.getchildren():
+            children.append(child)
+            math_block.remove(child)  # why no pop?
+        semantics_block = etree.SubElement(
+            math_block,
+            '{{{}}}semantics'.format(MATHML_NAMESPACE))
+        for child in children:
+            semantics_block.append(child)
+    return semantics_block
+
+
 def inject_mathml_svgs(content):
     """Inject MathML SVG annotations into HTML content."""
     settings = get_current_registry().settings
@@ -22,24 +46,23 @@ def inject_mathml_svgs(content):
         return content
 
     xml = etree.fromstring(content)
-    mathml_namespace = "http://www.w3.org/1998/Math/MathML"
-    mathml_blocks = xml.xpath(
+    math_blocks = xml.xpath(
         '//m:math[not(/m:annotation-xml[@encoding="image/svg+xml"])]',
-        namespaces={'m': mathml_namespace})
-    for mathml_block in mathml_blocks:
+        namespaces=NSMAP)
+    for math_block in math_blocks:
         # Submit the MathML block to the SVG generation service.
-        payload = {'MathML': etree.tostring(mathml_block)}
+        payload = {'MathML': etree.tostring(math_block)}
         response = requests.post(url, data=payload)
         # Inject the SVG into the MathML as an annotation
         # only if the resposne was good, otherwise skip over it.
-        semantic_block = mathml_block.getchildren()[0]
         if response.status_code == 200:
+            semantics_wrapper = _find_or_create_semantics_block(math_block)
             svg = response.text
             content_type = response.headers['content-type']
             # Insert the svg into the content
             annotation = etree.SubElement(
-                semantic_block,
-                '{{{}}}annotation-xml'.format(mathml_namespace))
+                semantics_wrapper,
+                '{{{}}}annotation-xml'.format(MATHML_NAMESPACE))
             annotation.set('encoding', content_type)
             annotation.append(etree.fromstring(svg))
     modified_content = etree.tostring(xml)

cnxpublishing/tests/test_models.py

@@ -60,3 +60,20 @@ def test_mathml2svg(self):
         expected = """<annotation-xml xmlns="http://www.w3.org/1998/Math/MathML" encoding="image/svg+xml"><svg>mocked</svg></annotation-xml>"""
 
         self.assertEqual(etree.tostring(annotation), expected)
+
+    def test_missing_semantics_wrapper(self):
+        content = """\
+<div class="equation">
+<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow> <mi>x</mi> <mo>=</mo> <mfrac> <mrow> <mo>&#8722;<!-- &#8722; --></mo> <mi>b</mi> <mo>&#177;<!-- &#177; --></mo> <msqrt> <msup> <mi>b</mi> <mn>2</mn> </msup> <mo>&#8722;<!-- &#8722; --></mo> <mn>4</mn> <mi>a</mi> <mi>c</mi> </msqrt> </mrow> <mrow> <mn>2</mn> <mi>a</mi> </mrow> </mfrac> </mrow></math>
+</div>"""
+
+        # Call the target function.
+        result = self.target(content)
+
+        elms = etree.fromstring(result)
+        annotation = elms.xpath(
+            '/div/m:math/m:semantics/m:annotation-xml[@encoding="image/svg+xml"]',
+            namespaces={'m': "http://www.w3.org/1998/Math/MathML"})[0]
+        expected = """<annotation-xml xmlns="http://www.w3.org/1998/Math/MathML" encoding="image/svg+xml"><svg>mocked</svg></annotation-xml>"""
+
+        self.assertEqual(etree.tostring(annotation), expected)