qapi: Relax doc string @name: description indentation rules
commit08349786c84306863a3b659c8a9b28bb74c405c6
authorMarkus Armbruster <armbru@redhat.com>
Fri, 28 Apr 2023 10:54:25 +0000 (28 12:54 +0200)
committerMarkus Armbruster <armbru@redhat.com>
Wed, 10 May 2023 08:00:40 +0000 (10 10:00 +0200)
tree0a70c0631a41f52c8ab6377778c0226ee89402dd
parent3e32dca3f0d1eddcfecf963d94b9ff60e3e08448
qapi: Relax doc string @name: description indentation rules

The QAPI schema doc comment language provides special syntax for
command and event arguments, struct and union members, alternate
branches, enumeration values, and features: descriptions starting with
"@name:".

By convention, we format them like this:

    # @name: Lorem ipsum dolor sit amet, consectetur adipiscing elit,
    #        sed do eiusmod tempor incididunt ut labore et dolore
    #        magna aliqua.

Okay for names as short as "name", but we have much longer ones.  Their
description gets squeezed against the right margin, like this:

    # @dirty-sync-missed-zero-copy: Number of times dirty RAM synchronization could
    #                               not avoid copying dirty pages. This is between
    #                               0 and @dirty-sync-count * @multifd-channels.
    #                               (since 7.1)

The description text is effectively just 50 characters wide.  Easy
enough to read, but can be cumbersome to write.

The awkward squeeze against the right margin makes people go beyond it,
which produces two undesirables: arguments about style, and descriptions
that are unnecessarily hard to read, like this one:

    # @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU.  This is
    #                           only present when the postcopy-blocktime migration capability
    #                           is enabled. (Since 3.0)

We could instead format it like

    # @postcopy-vcpu-blocktime:
    # list of the postcopy blocktime per vCPU.  This is only present
    # when the postcopy-blocktime migration capability is
    # enabled. (Since 3.0)

or, since the commit before previous, like

    # @postcopy-vcpu-blocktime:
    #    list of the postcopy blocktime per vCPU.  This is only present
    #    when the postcopy-blocktime migration capability is
    #    enabled. (Since 3.0)

However, I'd rather have

    # @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU.
    #     This is only present when the postcopy-blocktime migration
    #     capability is enabled.  (Since 3.0)

because this is how rST field and option lists work.

To get this, we need to let the first non-blank line after the
"@name:" line determine expected indentation.

This fills up the indentation pitfall mentioned in
docs/devel/qapi-code-gen.rst.  A related pitfall still exists.  Update
the text to show it.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230428105429.1687850-14-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[Work around lack of walrus operator in Python 3.7 and older]
docs/devel/qapi-code-gen.rst
scripts/qapi/parser.py
tests/qapi-schema/doc-bad-indent.err
tests/qapi-schema/doc-bad-indent.json
tests/qapi-schema/doc-good.json
tests/qapi-schema/doc-good.out