[PATCH] docs: Make automarkup ready for Sphinx 3.1+

[Nícolas F. R. A. Prado]

While Sphinx 2 used a single c:type role for struct, union, enum and
typedef, Sphinx 3 uses a specific role for each one.
To keep backward compatibility, detect the Sphinx version and use the
correct roles for that version.

Also, Sphinx 3 is more strict with its C domain and generated warnings,
exposing issues in the parsing.
To fix the warnings, make the C regexes use ASCII, ensure the
expressions only match the beginning of words and skip trying to
cross-reference C reserved words.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxxx>
---

Hi,

after Mauro's series making everything ready for Sphinx 3.1, only the automarkup
was left to be ported.
This patch makes the needed changes to automarkup so that we can soon flip the
switch to Sphinx 3.1.

This change was tested both with Sphinx 2.4.4 and Sphinx 3.1.

This change doesn't add any warnings to the Documentation build.
I tested it with Mauro's series but later rebased it to docs-next, and it can be
accepted independently of that series.

I ended up doing more than one thing in this single patch, but since it was all
changing the same lines and for the same purpose, I felt it would be better to
keep it as a single commit.

Mauro,
if this patch is ok, the 3rd patch in your series, which disables automarkup for
sphinx 3, should be dropped.
Although I'm not sure what the implications of your patches adding namespaces
and using the c:macro for functions are.
All I did here was use the specific roles for sphinx 3 and fix the warnings, but
that was enough to get correct cross-references even after your series.

Thanks,
Nícolas


 Documentation/sphinx/automarkup.py | 69 ++++++++++++++++++++++++++----
 1 file changed, 60 insertions(+), 9 deletions(-)

diff --git a/Documentation/sphinx/automarkup.py b/Documentation/sphinx/automarkup.py
index a1b0f554cd82..fd1e927408ad 100644
--- a/Documentation/sphinx/automarkup.py
+++ b/Documentation/sphinx/automarkup.py
@@ -22,13 +22,34 @@ from itertools import chain
 # :c:func: block (i.e. ":c:func:`mmap()`s" flakes out), so the last
 # bit tries to restrict matches to things that won't create trouble.
 #
-RE_function = re.compile(r'(([\w_][\w\d_]+)\(\))')
-RE_type = re.compile(r'(struct|union|enum|typedef)\s+([\w_][\w\d_]+)')
+RE_function = re.compile(r'\b(([a-zA-Z_]\w+)\(\))', flags=re.ASCII)
+
+#
+# Sphinx 2 uses the same :c:type role for struct, union, enum and typedef
+#
+RE_generic_type = re.compile(r'\b(struct|union|enum|typedef)\s+([a-zA-Z_]\w+)',
+                             flags=re.ASCII)
+
+#
+# Sphinx 3 uses a different C role for each one of struct, union, enum and
+# typedef
+#
+RE_struct = re.compile(r'\b(struct)\s+([a-zA-Z_]\w+)', flags=re.ASCII)
+RE_union = re.compile(r'\b(union)\s+([a-zA-Z_]\w+)', flags=re.ASCII)
+RE_enum = re.compile(r'\b(enum)\s+([a-zA-Z_]\w+)', flags=re.ASCII)
+RE_typedef = re.compile(r'\b(typedef)\s+([a-zA-Z_]\w+)', flags=re.ASCII)
+
 #
 # Detects a reference to a documentation page of the form Documentation/... with
 # an optional extension
 #
-RE_doc = re.compile(r'Documentation(/[\w\-_/]+)(\.\w+)*')
+RE_doc = re.compile(r'\bDocumentation(/[\w\-_/]+)(\.\w+)*')
+
+#
+# Reserved C words that we should skip when cross-referencing
+#
+Skipnames = [ 'for', 'if', 'register', 'sizeof', 'struct', 'unsigned' ]
+
 
 #
 # Many places in the docs refer to common system calls.  It is
@@ -48,9 +69,22 @@ def markup_refs(docname, app, node):
     #
     # Associate each regex with the function that will markup its matches
     #
-    markup_func = {RE_type: markup_c_ref,
-                   RE_function: markup_c_ref,
-                   RE_doc: markup_doc_ref}
+    markup_func_sphinx2 = {RE_doc: markup_doc_ref,
+                           RE_function: markup_c_ref,
+                           RE_generic_type: markup_c_ref}
+
+    markup_func_sphinx3 = {RE_doc: markup_doc_ref,
+                           RE_function: markup_c_ref,
+                           RE_struct: markup_c_ref,
+                           RE_union: markup_c_ref,
+                           RE_enum: markup_c_ref,
+                           RE_typedef: markup_c_ref}
+
+    if sphinx.__version__[0] == '3':
+        markup_func = markup_func_sphinx3
+    else:
+        markup_func = markup_func_sphinx2
+
     match_iterators = [regex.finditer(t) for regex in markup_func]
     #
     # Sort all references by the starting position in text
@@ -79,8 +113,24 @@ def markup_refs(docname, app, node):
 # 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'}
+    class_str = {RE_function: 'c-func',
+                 # Sphinx 2 only
+                 RE_generic_type: 'c-type',
+                 # Sphinx 3+ only
+                 RE_struct: 'c-struct',
+                 RE_union: 'c-union',
+                 RE_enum: 'c-enum',
+                 RE_typedef: 'c-type',
+                 }
+    reftype_str = {RE_function: 'function',
+                   # Sphinx 2 only
+                   RE_generic_type: 'type',
+                   # Sphinx 3+ only
+                   RE_struct: 'struct',
+                   RE_union: 'union',
+                   RE_enum: 'enum',
+                   RE_typedef: 'type',
+                   }
 
     cdom = app.env.domains['c']
     #
@@ -89,7 +139,8 @@ def markup_c_ref(docname, app, match):
     target = match.group(2)
     target_text = nodes.Text(match.group(0))
     xref = None
-    if not (match.re == RE_function and target in Skipfuncs):
+    if not ((match.re == RE_function and target in Skipfuncs)
+            or (target in Skipnames)):
         lit_text = nodes.literal(classes=['xref', 'c', class_str[match.re]])
         lit_text += target_text
         pxref = addnodes.pending_xref('', refdomain = 'c',
-- 
2.28.0