Simple unions predate flat unions.  Having both complicates the QAPI
schema language and the QAPI generator.  We haven't been using simple
unions in new code for a long time, because they are less flexible and
somewhat awkward on the wire.

To prepare for their removal, convert simple union TransactionAction
to an equivalent flat one.  Adds some boilerplate to the schema, which
is a bit ugly, but a lot easier to maintain than the simple union
feature.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210917143134.412106-11-armbru@redhat.com>
---
 qapi/transaction.json | 139 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 113 insertions(+), 26 deletions(-)

diff --git a/qapi/transaction.json b/qapi/transaction.json
index 894258d9e2..d175b5f863 100644
--- a/qapi/transaction.json
+++ b/qapi/transaction.json
@@ -38,41 +38,128 @@
 { 'enum': 'ActionCompletionMode',
   'data': [ 'individual', 'grouped' ] }
 
+##
+# @TransactionActionKind:
+#
+# @abort: Since 1.6
+# @block-dirty-bitmap-add: Since 2.5
+# @block-dirty-bitmap-remove: Since 4.2
+# @block-dirty-bitmap-clear: Since 2.5
+# @block-dirty-bitmap-enable: Since 4.0
+# @block-dirty-bitmap-disable: Since 4.0
+# @block-dirty-bitmap-merge: Since 4.0
+# @blockdev-backup: Since 2.3
+# @blockdev-snapshot: Since 2.5
+# @blockdev-snapshot-internal-sync: Since 1.7
+# @blockdev-snapshot-sync: since 1.1
+# @drive-backup: Since 1.6
+#
+# Since: 1.1
+##
+{ 'enum': 'TransactionActionKind',
+  'data': [ 'abort', 'block-dirty-bitmap-add', 'block-dirty-bitmap-remove',
+            'block-dirty-bitmap-clear', 'block-dirty-bitmap-enable',
+            'block-dirty-bitmap-disable', 'block-dirty-bitmap-merge',
+            'blockdev-backup', 'blockdev-snapshot',
+            'blockdev-snapshot-internal-sync', 'blockdev-snapshot-sync',
+            'drive-backup' ] }
+
+##
+# @AbortWrapper:
+#
+# Since: 1.6
+##
+{ 'struct': 'AbortWrapper',
+  'data': { 'data': 'Abort' } }
+
+##
+# @BlockDirtyBitmapAddWrapper:
+#
+# Since: 2.5
+##
+{ 'struct': 'BlockDirtyBitmapAddWrapper',
+  'data': { 'data': 'BlockDirtyBitmapAdd' } }
+
+##
+# @BlockDirtyBitmapWrapper:
+#
+# Since: 2.5
+##
+{ 'struct': 'BlockDirtyBitmapWrapper',
+  'data': { 'data': 'BlockDirtyBitmap' } }
+
+##
+# @BlockDirtyBitmapMergeWrapper:
+#
+# Since: 4.0
+##
+{ 'struct': 'BlockDirtyBitmapMergeWrapper',
+  'data': { 'data': 'BlockDirtyBitmapMerge' } }
+
+##
+# @BlockdevBackupWrapper:
+#
+# Since: 2.3
+##
+{ 'struct': 'BlockdevBackupWrapper',
+  'data': { 'data': 'BlockdevBackup' } }
+
+##
+# @BlockdevSnapshotWrapper:
+#
+# Since: 2.5
+##
+{ 'struct': 'BlockdevSnapshotWrapper',
+  'data': { 'data': 'BlockdevSnapshot' } }
+
+##
+# @BlockdevSnapshotInternalWrapper:
+#
+# Since: 1.7
+##
+{ 'struct': 'BlockdevSnapshotInternalWrapper',
+  'data': { 'data': 'BlockdevSnapshotInternal' } }
+
+##
+# @BlockdevSnapshotSyncWrapper:
+#
+# Since: 1.1
+##
+{ 'struct': 'BlockdevSnapshotSyncWrapper',
+  'data': { 'data': 'BlockdevSnapshotSync' } }
+
+##
+# @DriveBackupWrapper:
+#
+# Since: 1.6
+##
+{ 'struct': 'DriveBackupWrapper',
+  'data': { 'data': 'DriveBackup' } }
+
 ##
 # @TransactionAction:
 #
 # A discriminated record of operations that can be performed with
-# @transaction. Action @type can be:
-#
-# - @abort: since 1.6
-# - @block-dirty-bitmap-add: since 2.5
-# - @block-dirty-bitmap-remove: since 4.2
-# - @block-dirty-bitmap-clear: since 2.5
-# - @block-dirty-bitmap-enable: since 4.0
-# - @block-dirty-bitmap-disable: since 4.0
-# - @block-dirty-bitmap-merge: since 4.0
-# - @blockdev-backup: since 2.3
-# - @blockdev-snapshot: since 2.5
-# - @blockdev-snapshot-internal-sync: since 1.7
-# - @blockdev-snapshot-sync: since 1.1
-# - @drive-backup: since 1.6
+# @transaction.
 #
 # Since: 1.1
 ##
 { 'union': 'TransactionAction',
+  'base': { 'type': 'TransactionActionKind' },
+  'discriminator': 'type',
   'data': {
-       'abort': 'Abort',
-       'block-dirty-bitmap-add': 'BlockDirtyBitmapAdd',
-       'block-dirty-bitmap-remove': 'BlockDirtyBitmap',
-       'block-dirty-bitmap-clear': 'BlockDirtyBitmap',
-       'block-dirty-bitmap-enable': 'BlockDirtyBitmap',
-       'block-dirty-bitmap-disable': 'BlockDirtyBitmap',
-       'block-dirty-bitmap-merge': 'BlockDirtyBitmapMerge',
-       'blockdev-backup': 'BlockdevBackup',
-       'blockdev-snapshot': 'BlockdevSnapshot',
-       'blockdev-snapshot-internal-sync': 'BlockdevSnapshotInternal',
-       'blockdev-snapshot-sync': 'BlockdevSnapshotSync',
-       'drive-backup': 'DriveBackup'
+       'abort': 'AbortWrapper',
+       'block-dirty-bitmap-add': 'BlockDirtyBitmapAddWrapper',
+       'block-dirty-bitmap-remove': 'BlockDirtyBitmapWrapper',
+       'block-dirty-bitmap-clear': 'BlockDirtyBitmapWrapper',
+       'block-dirty-bitmap-enable': 'BlockDirtyBitmapWrapper',
+       'block-dirty-bitmap-disable': 'BlockDirtyBitmapWrapper',
+       'block-dirty-bitmap-merge': 'BlockDirtyBitmapMergeWrapper',
+       'blockdev-backup': 'BlockdevBackupWrapper',
+       'blockdev-snapshot': 'BlockdevSnapshotWrapper',
+       'blockdev-snapshot-internal-sync': 'BlockdevSnapshotInternalWrapper',
+       'blockdev-snapshot-sync': 'BlockdevSnapshotSyncWrapper',
+       'drive-backup': 'DriveBackupWrapper'
    } }
 
 ##
-- 
2.31.1