qapi/parser: preserve indentation in QAPIDoc sections

Change get_doc_indented() to preserve indentation on all subsequent text
lines, and create a compatibility dedent() function for qapidoc.py that
removes indentation the same way get_doc_indented() did.

This is being done for the benefit of a new qapidoc generator which
requires that indentation in argument and features sections are
preserved.

Prior to this patch, a section like this:

```
@name: lorem ipsum
   dolor sit amet
     consectetur adipiscing elit
```

would have its body text be parsed into:

```
lorem ipsum
dolor sit amet
  consectetur adipiscing elit
```

We want to preserve the indentation for even the first body line so that
the entire block can be parsed directly as rST. This patch would now
parse that segment into:

```
lorem ipsum
   dolor sit amet
     consectetur adipiscing elit
```

This is helpful for formatting arguments and features as field lists in
rST, where the new generator will format this information as:

```
:arg type name: lorem ipsum
   dolor sit amet
     consectetur apidiscing elit
```

...and can be formed by the simple concatenation of the field list
construct and the body text. The indents help preserve the continuation
of a block-level element, and further allow the use of additional rST
block-level constructs such as code blocks, lists, and other such
markup.

This understandably breaks the existing qapidoc.py; so a new function is
added there to dedent the text for compatibility. Once the new generator
is merged, this function will not be needed any longer and can be
dropped.

I verified this patch changes absolutely nothing by comparing the
md5sums of the QMP ref html pages both before and after the change, so
it's certified inert. QAPI test output has been updated to reflect the
new strategy of preserving indents for rST.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240626222128.406106-6-jsnow@redhat.com>
[Lost commit message paragraph restored]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/sphinx/qapidoc.py

@@ -26,6 +26,7 @@ https://www.sphinx-doc.org/en/master/development/index.html
 
 import os
 import re
+import textwrap
 
 from docutils import nodes
 from docutils.parsers.rst import Directive, directives
@@ -53,6 +54,19 @@ else:
 __version__ = "1.0"
 
 
+def dedent(text: str) -> str:
+    # Adjust indentation to make description text parse as paragraph.
+
+    lines = text.splitlines(True)
+    if re.match(r"\s+", lines[0]):
+        # First line is indented; description started on the line after
+        # the name. dedent the whole block.
+        return textwrap.dedent(text)
+
+    # Descr started on same line. Dedent line 2+.
+    return lines[0] + textwrap.dedent("".join(lines[1:]))
+
+
 # Disable black auto-formatter until re-enabled:
 # fmt: off
 
@@ -164,7 +178,7 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
             term = self._nodes_for_one_member(section.member)
             # TODO drop fallbacks when undocumented members are outlawed
             if section.text:
-                defn = section.text
+                defn = dedent(section.text)
             else:
                 defn = [nodes.Text('Not documented')]
 
@@ -202,7 +216,7 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
                 termtext.extend(self._nodes_for_ifcond(section.member.ifcond))
             # TODO drop fallbacks when undocumented members are outlawed
             if section.text:
-                defn = section.text
+                defn = dedent(section.text)
             else:
                 defn = [nodes.Text('Not documented')]
 
@@ -237,7 +251,7 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
         dlnode = nodes.definition_list()
         for section in doc.features.values():
             dlnode += self._make_dlitem(
-                [nodes.literal('', section.member.name)], section.text)
+                [nodes.literal('', section.member.name)], dedent(section.text))
             seen_item = True
 
         if not seen_item:
@@ -260,9 +274,12 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
                 continue
             snode = self._make_section(section.tag)
             if section.tag and section.tag.startswith('Example'):
-                snode += self._nodes_for_example(section.text)
+                snode += self._nodes_for_example(dedent(section.text))
             else:
-                self._parse_text_into_node(section.text, snode)
+                self._parse_text_into_node(
+                    dedent(section.text) if section.tag else section.text,
+                    snode,
+                )
             nodelist.append(snode)
         return nodelist
 

scripts/qapi/parser.py

@@ -448,7 +448,7 @@ class QAPISchemaParser:
         indent = must_match(r'\s*', line).end()
         if not indent:
             return line
-        doc.append_line(line[indent:])
+        doc.append_line(line)
         prev_line_blank = False
         while True:
             self.accept(False)
@@ -465,7 +465,7 @@ class QAPISchemaParser:
                     self,
                     "unexpected de-indent (expected at least %d spaces)" %
                     indent)
-            doc.append_line(line[indent:])
+            doc.append_line(line)
             prev_line_blank = True
 
     def get_doc_paragraph(self, doc: 'QAPIDoc') -> Optional[str]:

tests/qapi-schema/doc-good.out

@@ -117,8 +117,8 @@ doc symbol=Base
     body=
 
     arg=base1
-description starts on a new line,
-minimally indented
+ description starts on a new line,
+ minimally indented
 doc symbol=Variant1
     body=
 A paragraph
@@ -145,8 +145,8 @@ doc symbol=Alternate
 
     arg=i
 description starts on the same line
-remainder indented the same
-@b is undocumented
+    remainder indented the same
+    @b is undocumented
     arg=b
 
     feature=alt-feat
@@ -158,11 +158,11 @@ doc symbol=cmd
     body=
 
     arg=arg1
-description starts on a new line,
-indented
+    description starts on a new line,
+    indented
     arg=arg2
 description starts on the same line
-remainder indented differently
+    remainder indented differently
     arg=arg3
 
     feature=cmd-feat1
@@ -178,16 +178,16 @@ some
     section=TODO
 frobnicate
     section=Notes
-- Lorem ipsum dolor sit amet
-- Ut enim ad minim veniam
+ - Lorem ipsum dolor sit amet
+ - Ut enim ad minim veniam
 
-Duis aute irure dolor
+ Duis aute irure dolor
     section=Example
--> in
-<- out
+ -> in
+ <- out
     section=Examples
-- *verbatim*
-- {braces}
+ - *verbatim*
+ - {braces}
     section=Since
 2.10
 doc symbol=cmd-boxed
@@ -198,9 +198,9 @@ a feature
     feature=cmd-feat2
 another feature
     section=Example
--> in
+ -> in
 
-<- out
+ <- out
 doc symbol=EVT_BOXED
     body=