qapi: add doc comment "Intro" section parsing

Add parsing for explicit Intro section syntax.

A side effect of this patch is that we will (currently) always create
an empty Intro section, similar to how we used to have an empty Plain
section. The tests are adjusted accordingly, rendered document output
does not change at all.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-ID: <20260611042332.482979-14-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/devel/qapi-code-gen.rst

@@ -984,11 +984,11 @@ definition it documents.
 When documentation is required (see pragma_ 'doc-required'), every
 definition must have documentation.
 
-Definition documentation starts with a line naming the definition,
-followed by an optional overview, a description of each argument (for
-commands and events), member (for structs and unions), branch (for
-alternates), or value (for enums), a description of each feature (if
-any), and finally optional tagged sections.
+Definition documentation starts with a description naming the
+definition with an optional indented overview, a description of each
+argument (for commands and events), member (for structs and unions),
+branch (for alternates), or value (for enums), a description of each
+feature (if any), and finally optional tagged sections.
 
 Descriptions start with '\@name:'.  The description text must be
 indented like this::
@@ -1093,8 +1093,7 @@ Examples of complete definition documentation::
 
  ##
  # @BlockStats:
- #
- # Statistics of a virtual block device or a block backing device.
+ #     Statistics of a virtual block device or a block backing device.
  #
  # @device: If the stats are for a virtual block device, the name
  #     corresponding to the virtual block device.
@@ -1111,8 +1110,7 @@ Examples of complete definition documentation::
 
  ##
  # @query-blockstats:
- #
- # Query the @BlockStats for all virtual block devices.
+ #     Query the @BlockStats for all virtual block devices.
  #
  # @query-nodes: If true, the command will query all the block nodes
  #     ... explain, explain ...

scripts/qapi/parser.py

@@ -542,8 +542,8 @@ class QAPISchemaParser:
             if not symbol:
                 raise QAPIParseError(self, "name required after '@'")
             doc = QAPIDoc(info, symbol)
-            self.accept(False)
-            line = self.get_doc_line()
+            doc.all_sections.append(QAPIDoc.Section(info, QAPIDoc.Kind.INTRO))
+            line = self.get_doc_indented(doc)
             no_more_args = False
 
             while line is not None:

tests/qapi-schema/doc-good.out

@@ -106,6 +106,8 @@ Examples:
 - *verbatim*
 - {braces}
 doc symbol=Enum
+    Intro
+
     Member=one
 The _one_ {and only}, description on the same line
     Member=two
@@ -117,10 +119,14 @@ a member feature
     Plain
 @two is undocumented
 doc symbol=Base
+    Intro
+
     Member=base1
  description starts on a new line,
  minimally indented
 doc symbol=Variant1
+    Intro
+
     Plain
 A paragraph
 
@@ -134,10 +140,16 @@ a feature
     Feature=member-feat
 a member feature
 doc symbol=Variant2
+    Intro
+
 doc symbol=Object
+    Intro
+
     Feature=union-feat1
 a feature
 doc symbol=Alternate
+    Intro
+
     Member=i
 description starts on the same line
     remainder indented the same
@@ -151,6 +163,8 @@ doc freeform
 Another subsection
 ==================
 doc symbol=cmd
+    Intro
+
     Member=arg1
     description starts on a new line,
     indented
@@ -198,6 +212,8 @@ Note::
     Since
 2.10
 doc symbol=cmd-boxed
+    Intro
+
     Plain
 If you're bored enough to read this, go see a video of boxed cats
     Feature=cmd-feat1
@@ -211,5 +227,7 @@ another feature
 
    <- ... has no title ...
 doc symbol=EVT_BOXED
+    Intro
+
     Feature=feat3
 a feature