Fix verbatim tag handling in Doxygen bridge

Commit 2812109 added handling for
verbatim tags in doxybuilder_types.py, but did not check for tail
text.  This wasn't a problem in Doxygen 1.8 because its XML output
ended paragraph tags after verbatim tags, but that isn't the case in
Doxygen 1.9.  Move the is_tail check earlier so we don't have to check
for each tag type.

Also avoid putting spaces at the beginnings and ends of lines when
joining the elements of the result list, to avoid confusing the RST
parser at the end of literal blocks.

doc/tools/doxybuilder_types.py

@@ -268,38 +268,36 @@ def _get_detailed_description(self, node):
 
     def _process_paragraph_content(self, node):
 
+        def add_text(l, s):
+            # Add a space if it wouldn't be at the start or end of a line.
+            if l and not l[-1].endswith('\n') and not s.startswith('\n'):
+                l.append(' ')
+            l.append(s)
+
         result = list()
         content = node.xpath(".//text()")
         for e in content:
-            if node is e.getparent():
-                result.append(e.strip())
+            if e.is_tail or node is e.getparent():
+                add_text(result, e.strip())
             elif e.getparent().tag == 'ref':
-                if e.is_tail:
-                    result.append(e.strip())
-                elif e.strip().find('(') > 0:
-                    result.append(':c:func:`%s`' % e.strip())
+                if e.strip().find('(') > 0:
+                    add_text(result, ':c:func:`%s`' % e.strip())
                 elif e.isupper():
-                    result.append(':c:data:`%s`' % e.strip())
+                    add_text(result, ':c:data:`%s`' % e.strip())
                 else:
-                    result.append(':c:type:`%s`' % e.strip())
+                    add_text(result, ':c:type:`%s`' % e.strip())
             elif e.getparent().tag == 'emphasis':
-                if e.is_tail:
-                    result.append(e.strip())
-                else:
-                    result.append('*%s*' % e.strip())
+                add_text(result, '*%s*' % e.strip())
             elif e.getparent().tag == 'computeroutput':
-                if e.is_tail:
-                    result.append(e.strip())
-                else:
-                    result.append('*%s*' % e.strip())
-            elif  e.getparent().tag == 'defname':
-                result.append('%s, ' % e.strip())
+                add_text(result, '*%s*' % e.strip())
+            elif e.getparent().tag == 'defname':
+                add_text(result, '%s, ' % e.strip())
             elif e.getparent().tag == 'verbatim':
-                result.append('\n::\n\n')
-                result.append(textwrap.indent(e, '    ', lambda x: True))
-                result.append('\n')
+                add_text(result, '\n::\n\n')
+                add_text(result, textwrap.indent(e, '    ', lambda x: True))
+                add_text(result, '\n')
 
-        result = ' '.join(result)
+        result = ''.join(result)
 
         return result