qapi: clean up encoding of section kinds

We have several kinds of sections, and to tell them apart, we use
Section attribute @tag and also the section object's Python type:

              type        @tag
    untagged  Section     None
    @foo:     ArgSection  'foo'
    Returns:  Section     'Returns'
    Errors:   Section     'Errors'
    Since:    Section     'Since'
    TODO:     Section     'TODO'

Note:

* @foo can be a member or a feature description, depending on context.

* tag == 'Since' can be a Since: section or a member or feature
  description.  If it's a Section, it's the former, and if it's an
  ArgSection, it's the latter.

Clean this up as follows.  Move the member or feature name to new
ArgSection attribute @name, and replace @tag by enum @kind like this:

              type         kind     name
    untagged  Section      PLAIN
    @foo:     ArgSection   MEMBER   'foo'   if member or argument
              ArgSection   FEATURE  'foo'   if feature
    Returns:  Section      RETURNS
    Errors:   Section      ERRORS
    Since:    Section      SINCE
    TODO:     Section      TODO

The qapi-schema tests are updated to account for the new section names;
"TODO" becomes "Todo" and `None` becomes "Plain" there.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-ID: <20250311034303.75779-34-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/sphinx/qapidoc.py

@@ -35,6 +35,7 @@ from docutils.parsers.rst import Directive, directives
 from docutils.statemachine import ViewList
 from qapi.error import QAPIError, QAPISemError
 from qapi.gen import QAPISchemaVisitor
+from qapi.parser import QAPIDoc
 from qapi.schema import QAPISchema
 
 from sphinx import addnodes
@@ -258,11 +259,11 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
         """Return list of doctree nodes for additional sections"""
         nodelist = []
         for section in doc.sections:
-            if section.tag and section.tag == 'TODO':
+            if section.kind == QAPIDoc.Kind.TODO:
                 # Hide TODO: sections
                 continue
 
-            if not section.tag:
+            if section.kind == QAPIDoc.Kind.PLAIN:
                 # Sphinx cannot handle sectionless titles;
                 # Instead, just append the results to the prior section.
                 container = nodes.container()
@@ -270,7 +271,7 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
                 nodelist += container.children
                 continue
 
-            snode = self._make_section(section.tag)
+            snode = self._make_section(section.kind.name.title())
             self._parse_text_into_node(dedent(section.text), snode)
             nodelist.append(snode)
         return nodelist

scripts/qapi/parser.py

@@ -14,6 +14,7 @@
 # This work is licensed under the terms of the GNU GPL, version 2.
 # See the COPYING file in the top-level directory.
 
+import enum
 import os
 import re
 from typing import (
@@ -574,7 +575,10 @@ class QAPISchemaParser:
                         )
                         raise QAPIParseError(self, emsg)
 
-                    doc.new_tagged_section(self.info, match.group(1))
+                    doc.new_tagged_section(
+                        self.info,
+                        QAPIDoc.Kind.from_string(match.group(1))
+                    )
                     text = line[match.end():]
                     if text:
                         doc.append_line(text)
@@ -585,7 +589,7 @@ class QAPISchemaParser:
                         self,
                         "unexpected '=' markup in definition documentation")
                 else:
-                    # tag-less paragraph
+                    # plain paragraph
                     doc.ensure_untagged_section(self.info)
                     doc.append_line(line)
                     line = self.get_doc_paragraph(doc)
@@ -634,14 +638,33 @@ class QAPIDoc:
     Free-form documentation blocks consist only of a body section.
     """
 
+    class Kind(enum.Enum):
+        PLAIN = 0
+        MEMBER = 1
+        FEATURE = 2
+        RETURNS = 3
+        ERRORS = 4
+        SINCE = 5
+        TODO = 6
+
+        @staticmethod
+        def from_string(kind: str) -> 'QAPIDoc.Kind':
+            return QAPIDoc.Kind[kind.upper()]
+
+        def __str__(self) -> str:
+            return self.name.title()
+
     class Section:
         # pylint: disable=too-few-public-methods
-        def __init__(self, info: QAPISourceInfo,
+        def __init__(
-                     tag: Optional[str] = None):
+            self,
+            info: QAPISourceInfo,
+            kind: 'QAPIDoc.Kind',
+        ):
             # section source info, i.e. where it begins
             self.info = info
-            # section tag, if any ('Returns', '@name', ...)
+            # section kind
-            self.tag = tag
+            self.kind = kind
             # section text without tag
             self.text = ''
 
@@ -649,8 +672,14 @@ class QAPIDoc:
             self.text += line + '\n'
 
     class ArgSection(Section):
-        def __init__(self, info: QAPISourceInfo, tag: str):
+        def __init__(
-            super().__init__(info, tag)
+            self,
+            info: QAPISourceInfo,
+            kind: 'QAPIDoc.Kind',
+            name: str
+        ):
+            super().__init__(info, kind)
+            self.name = name
             self.member: Optional['QAPISchemaMember'] = None
 
         def connect(self, member: 'QAPISchemaMember') -> None:
@@ -662,7 +691,9 @@ class QAPIDoc:
         # definition doc's symbol, None for free-form doc
         self.symbol: Optional[str] = symbol
         # the sections in textual order
-        self.all_sections: List[QAPIDoc.Section] = [QAPIDoc.Section(info)]
+        self.all_sections: List[QAPIDoc.Section] = [
+            QAPIDoc.Section(info, QAPIDoc.Kind.PLAIN)
+        ]
         # the body section
         self.body: Optional[QAPIDoc.Section] = self.all_sections[0]
         # dicts mapping parameter/feature names to their description
@@ -679,12 +710,14 @@ class QAPIDoc:
     def end(self) -> None:
         for section in self.all_sections:
             section.text = section.text.strip('\n')
-            if section.tag is not None and section.text == '':
+            if section.kind != QAPIDoc.Kind.PLAIN and section.text == '':
                 raise QAPISemError(
-                    section.info, "text required after '%s:'" % section.tag)
+                    section.info, "text required after '%s:'" % section.kind)
 
     def ensure_untagged_section(self, info: QAPISourceInfo) -> None:
-        if self.all_sections and not self.all_sections[-1].tag:
+        kind = QAPIDoc.Kind.PLAIN
+
+        if self.all_sections and self.all_sections[-1].kind == kind:
             # extend current section
             section = self.all_sections[-1]
             if not section.text:
@@ -692,46 +725,56 @@ class QAPIDoc:
                 section.info = info
             section.text += '\n'
             return
+
         # start new section
-        section = self.Section(info)
+        section = self.Section(info, kind)
         self.sections.append(section)
         self.all_sections.append(section)
 
-    def new_tagged_section(self, info: QAPISourceInfo, tag: str) -> None:
+    def new_tagged_section(
-        section = self.Section(info, tag)
+        self,
-        if tag == 'Returns':
+        info: QAPISourceInfo,
+        kind: 'QAPIDoc.Kind',
+    ) -> None:
+        section = self.Section(info, kind)
+        if kind == QAPIDoc.Kind.RETURNS:
             if self.returns:
                 raise QAPISemError(
-                    info, "duplicated '%s' section" % tag)
+                    info, "duplicated '%s' section" % kind)
             self.returns = section
-        elif tag == 'Errors':
+        elif kind == QAPIDoc.Kind.ERRORS:
             if self.errors:
                 raise QAPISemError(
-                    info, "duplicated '%s' section" % tag)
+                    info, "duplicated '%s' section" % kind)
             self.errors = section
-        elif tag == 'Since':
+        elif kind == QAPIDoc.Kind.SINCE:
             if self.since:
                 raise QAPISemError(
-                    info, "duplicated '%s' section" % tag)
+                    info, "duplicated '%s' section" % kind)
             self.since = section
         self.sections.append(section)
         self.all_sections.append(section)
 
-    def _new_description(self, info: QAPISourceInfo, name: str,
+    def _new_description(
-                         desc: Dict[str, ArgSection]) -> None:
+        self,
+        info: QAPISourceInfo,
+        name: str,
+        kind: 'QAPIDoc.Kind',
+        desc: Dict[str, ArgSection]
+    ) -> None:
         if not name:
             raise QAPISemError(info, "invalid parameter name")
         if name in desc:
             raise QAPISemError(info, "'%s' parameter name duplicated" % name)
-        section = self.ArgSection(info, '@' + name)
+        section = self.ArgSection(info, kind, name)
         self.all_sections.append(section)
         desc[name] = section
 
     def new_argument(self, info: QAPISourceInfo, name: str) -> None:
-        self._new_description(info, name, self.args)
+        self._new_description(info, name, QAPIDoc.Kind.MEMBER, self.args)
 
     def new_feature(self, info: QAPISourceInfo, name: str) -> None:
-        self._new_description(info, name, self.features)
+        self._new_description(info, name, QAPIDoc.Kind.FEATURE, self.features)
 
     def append_line(self, line: str) -> None:
         self.all_sections[-1].append_line(line)
@@ -744,7 +787,7 @@ class QAPIDoc:
                                    "%s '%s' lacks documentation"
                                    % (member.role, member.name))
             self.args[member.name] = QAPIDoc.ArgSection(
-                self.info, '@' + member.name)
+                self.info, QAPIDoc.Kind.MEMBER, member.name)
         self.args[member.name].connect(member)
 
     def connect_feature(self, feature: 'QAPISchemaFeature') -> None:

tests/qapi-schema/doc-good.out

@@ -113,7 +113,7 @@ The _one_ {and only}, description on the same line
 Also _one_ {and only}
     feature=enum-member-feat
 a member feature
-    section=None
+    section=Plain
 @two is undocumented
 doc symbol=Base
     body=
@@ -171,15 +171,15 @@ description starts on the same line
 a feature
     feature=cmd-feat2
 another feature
-    section=None
+    section=Plain
 .. note:: @arg3 is undocumented
     section=Returns
 @Object
     section=Errors
 some
-    section=TODO
+    section=Todo
 frobnicate
-    section=None
+    section=Plain
 .. admonition:: Notes
 
  - Lorem ipsum dolor sit amet
@@ -212,7 +212,7 @@ If you're bored enough to read this, go see a video of boxed cats
 a feature
     feature=cmd-feat2
 another feature
-    section=None
+    section=Plain
 .. qmp-example::
 
    -> "this example"

tests/qapi-schema/test-qapi.py

@@ -122,7 +122,7 @@ def test_frontend(fname):
         for feat, section in doc.features.items():
             print('    feature=%s\n%s' % (feat, section.text))
         for section in doc.sections:
-            print('    section=%s\n%s' % (section.tag, section.text))
+            print('    section=%s\n%s' % (section.kind, section.text))
 
 
 def open_test_result(dir_name, file_name, update):