docs: Allow multiple automarkup functions

The automarkup script previously matched expressions and substituted
them with markup to enable automatic cross-reference all in the same
function.

Split the expression matching iteration and the markup substitution into
different functions to make it easier to add new regular expressions and
functions to treat each of them.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@protonmail.com>
Link: https://lore.kernel.org/r/20200911133339.327721-2-nfraprado@protonmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/sphinx/automarkup.py

@@ -36,65 +36,78 @@ Skipfuncs = [ 'open', 'close', 'read', 'write', 'fcntl', 'mmap',
               'select', 'poll', 'fork', 'execve', 'clone', 'ioctl',
               'socket' ]
 
-#
-# Find all occurrences of C references (function() and struct/union/enum/typedef
-# type_name) and try to replace them with appropriate cross references.
-#
-def markup_c_refs(docname, app, node):
-    class_str = {RE_function: 'c-func', RE_type: 'c-type'}
-    reftype_str = {RE_function: 'function', RE_type: 'type'}
-
-    cdom = app.env.domains['c']
+def markup_refs(docname, app, node):
     t = node.astext()
     done = 0
     repl = [ ]
     #
-    # Sort all C references by the starting position in text
+    # Associate each regex with the function that will markup its matches
     #
-    sorted_matches = sorted(chain(RE_type.finditer(t), RE_function.finditer(t)),
-                            key=lambda m: m.start())
+    markup_func = {RE_type: markup_c_ref,
+                   RE_function: markup_c_ref}
+    match_iterators = [regex.finditer(t) for regex in markup_func]
+    #
+    # Sort all references by the starting position in text
+    #
+    sorted_matches = sorted(chain(*match_iterators), key=lambda m: m.start())
     for m in sorted_matches:
         #
         # Include any text prior to match as a normal text node.
         #
         if m.start() > done:
             repl.append(nodes.Text(t[done:m.start()]))
+
         #
-        # Go through the dance of getting an xref out of the C domain
+        # Call the function associated with the regex that matched this text and
+        # append its return to the text
         #
-        target = m.group(2)
-        target_text = nodes.Text(m.group(0))
-        xref = None
-        if not (m.re == RE_function and target in Skipfuncs):
-            lit_text = nodes.literal(classes=['xref', 'c', class_str[m.re]])
-            lit_text += target_text
-            pxref = addnodes.pending_xref('', refdomain = 'c',
-                                          reftype = reftype_str[m.re],
-                                          reftarget = target, modname = None,
-                                          classname = None)
-            #
-            # XXX The Latex builder will throw NoUri exceptions here,
-            # work around that by ignoring them.
-            #
-            try:
-                xref = cdom.resolve_xref(app.env, docname, app.builder,
-                                         reftype_str[m.re], target, pxref,
-                                         lit_text)
-            except NoUri:
-                xref = None
-        #
-        # Toss the xref into the list if we got it; otherwise just put
-        # the function text.
-        #
-        if xref:
-            repl.append(xref)
-        else:
-            repl.append(target_text)
+        repl.append(markup_func[m.re](docname, app, m))
+
         done = m.end()
     if done < len(t):
         repl.append(nodes.Text(t[done:]))
     return repl
 
+#
+# Try to replace a C reference (function() or struct/union/enum/typedef
+# type_name) with an appropriate cross reference.
+#
+def markup_c_ref(docname, app, match):
+    class_str = {RE_function: 'c-func', RE_type: 'c-type'}
+    reftype_str = {RE_function: 'function', RE_type: 'type'}
+
+    cdom = app.env.domains['c']
+    #
+    # Go through the dance of getting an xref out of the C domain
+    #
+    target = match.group(2)
+    target_text = nodes.Text(match.group(0))
+    xref = None
+    if not (match.re == RE_function and target in Skipfuncs):
+        lit_text = nodes.literal(classes=['xref', 'c', class_str[match.re]])
+        lit_text += target_text
+        pxref = addnodes.pending_xref('', refdomain = 'c',
+                                      reftype = reftype_str[match.re],
+                                      reftarget = target, modname = None,
+                                      classname = None)
+        #
+        # XXX The Latex builder will throw NoUri exceptions here,
+        # work around that by ignoring them.
+        #
+        try:
+            xref = cdom.resolve_xref(app.env, docname, app.builder,
+                                     reftype_str[match.re], target, pxref,
+                                     lit_text)
+        except NoUri:
+            xref = None
+    #
+    # Return the xref if we got it; otherwise just return the plain text.
+    #
+    if xref:
+        return xref
+    else:
+        return target_text
+
 def auto_markup(app, doctree, name):
     #
     # This loop could eventually be improved on.  Someday maybe we
@@ -108,7 +121,7 @@ def auto_markup(app, doctree, name):
     for para in doctree.traverse(nodes.paragraph):
         for node in para.traverse(nodes.Text):
             if not isinstance(node.parent, nodes.literal):
-                node.parent.replace(node, markup_c_refs(name, app, node))
+                node.parent.replace(node, markup_refs(name, app, node))
 
 def setup(app):
     app.connect('doctree-resolved', auto_markup)