QEMU-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: Markus Armbruster <armbru@redhat.com>
To: qemu-devel@nongnu.org
Cc: marcandre.lureau@redhat.com, mdroth@linux.vnet.ibm.com
Subject: [Qemu-devel] [PATCH v3 09/16] qapi: Permit alternates with just one branch
Date: Fri, 13 Sep 2019 22:13:42 +0200
Message-ID: <20190913201349.24332-10-armbru@redhat.com> (raw)
In-Reply-To: <20190913201349.24332-1-armbru@redhat.com>

A union or alternate without branches makes no sense and doesn't work:
it can't be instantiated.  A union or alternate with just one branch
works, but is degenerate.  We accept the former, but reject the
latter.  Weird.  docs/devel/qapi-code-gen.txt doesn't mention the
difference.  It claims an alternate definition is "is similar to a
simple union type".

Permit degenerate alternates to make them consistent with unions.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 scripts/qapi/common.py                  | 6 ++----
 tests/qapi-schema/alternate-empty.err   | 2 +-
 tests/qapi-schema/alternate-empty.json  | 4 ++--
 tests/qapi-schema/qapi-schema-test.json | 4 +++-
 tests/qapi-schema/qapi-schema-test.out  | 6 ++++--
 5 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index c5c71287c3..99db18f3d6 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -920,11 +920,9 @@ def check_alternate(expr, info):
     members = expr['data']
     types_seen = {}
 
-    # Check every branch; require at least two branches
-    if len(members) < 2:
+    if len(members) == 0:
         raise QAPISemError(info,
-                           "Alternate '%s' should have at least two branches "
-                           "in 'data'" % name)
+                           "Alternate '%s' cannot have empty 'data'" % name)
     for (key, value) in members.items():
         check_name(info, "Member of alternate '%s'" % name, key)
         check_known_keys(info,
diff --git a/tests/qapi-schema/alternate-empty.err b/tests/qapi-schema/alternate-empty.err
index bb06c5bfec..86dbc666eb 100644
--- a/tests/qapi-schema/alternate-empty.err
+++ b/tests/qapi-schema/alternate-empty.err
@@ -1 +1 @@
-tests/qapi-schema/alternate-empty.json:2: Alternate 'Alt' should have at least two branches in 'data'
+tests/qapi-schema/alternate-empty.json:2: Alternate 'Alt' cannot have empty 'data'
diff --git a/tests/qapi-schema/alternate-empty.json b/tests/qapi-schema/alternate-empty.json
index fff15baf16..9f445474e6 100644
--- a/tests/qapi-schema/alternate-empty.json
+++ b/tests/qapi-schema/alternate-empty.json
@@ -1,2 +1,2 @@
-# alternates must list at least two types to be useful
-{ 'alternate': 'Alt', 'data': { 'i': 'int' } }
+# alternates cannot be empty
+{ 'alternate': 'Alt', 'data': { } }
diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index e6dbbbd328..8b0d47c4ab 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -186,19 +186,21 @@
 
 # test that we correctly compile downstream extensions, as well as munge
 # ticklish names
+# also test union and alternate with just one branch
 { 'enum': '__org.qemu_x-Enum', 'data': [ '__org.qemu_x-value' ] }
 { 'struct': '__org.qemu_x-Base',
   'data': { '__org.qemu_x-member1': '__org.qemu_x-Enum' } }
 { 'struct': '__org.qemu_x-Struct', 'base': '__org.qemu_x-Base',
   'data': { '__org.qemu_x-member2': 'str', '*wchar-t': 'int' } }
 { 'union': '__org.qemu_x-Union1', 'data': { '__org.qemu_x-branch': 'str' } }
+{ 'alternate': '__org.qemu_x-Alt1', 'data': { '__org.qemu_x-branch': 'str' } }
 { 'struct': '__org.qemu_x-Struct2',
   'data': { 'array': ['__org.qemu_x-Union1'] } }
 { 'union': '__org.qemu_x-Union2', 'base': '__org.qemu_x-Base',
   'discriminator': '__org.qemu_x-member1',
   'data': { '__org.qemu_x-value': '__org.qemu_x-Struct2' } }
 { 'alternate': '__org.qemu_x-Alt',
-  'data': { '__org.qemu_x-branch': 'str', 'b': '__org.qemu_x-Base' } }
+  'data': { '__org.qemu_x-branch': '__org.qemu_x-Base' } }
 { 'event': '__ORG.QEMU_X-EVENT', 'data': '__org.qemu_x-Struct' }
 { 'command': '__org.qemu_x-command',
   'data': { 'a': ['__org.qemu_x-Enum'], 'b': ['__org.qemu_x-Struct'],
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index fb00a21996..bea7976bbb 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -274,6 +274,9 @@ object __org.qemu_x-Union1
     member type: __org.qemu_x-Union1Kind optional=False
     tag type
     case __org.qemu_x-branch: q_obj_str-wrapper
+alternate __org.qemu_x-Alt1
+    tag type
+    case __org.qemu_x-branch: str
 array __org.qemu_x-Union1List __org.qemu_x-Union1
 object __org.qemu_x-Struct2
     member array: __org.qemu_x-Union1List optional=False
@@ -283,8 +286,7 @@ object __org.qemu_x-Union2
     case __org.qemu_x-value: __org.qemu_x-Struct2
 alternate __org.qemu_x-Alt
     tag type
-    case __org.qemu_x-branch: str
-    case b: __org.qemu_x-Base
+    case __org.qemu_x-branch: __org.qemu_x-Base
 event __ORG.QEMU_X-EVENT __org.qemu_x-Struct
    boxed=False
 array __org.qemu_x-EnumList __org.qemu_x-Enum
-- 
2.21.0



  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-13 20:13 [Qemu-devel] [PATCH v3 00/16] qapi: Schema language cleanups & doc improvements Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 01/16] scripts/git.orderfile: Match QAPI schema more precisely Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 02/16] qapi: Drop check_type()'s redundant parameter @allow_optional Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 03/16] qapi: Drop support for boxed alternate arguments Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 04/16] docs/devel/qapi-code-gen: Minor specification fixes Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 05/16] tests/qapi-schema: Demonstrate bad reporting of funny characters Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 06/16] qapi: Restrict strings to printable ASCII Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 07/16] qapi: Drop support for escape sequences other than \\ Markus Armbruster
2019-09-17 16:18   ` Eric Blake
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 08/16] qapi: Permit 'boxed' with empty type Markus Armbruster
2019-09-13 20:13 ` Markus Armbruster [this message]
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 10/16] qapi: Permit omitting all flat union branches Markus Armbruster
2019-09-17 16:20   ` Eric Blake
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 11/16] qapi: Adjust frontend errors to say enum value, not member Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 12/16] docs/devel/qapi-code-gen: Reorder sections for readability Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 13/16] docs/devel/qapi-code-gen: Rewrite compatibility considerations Markus Armbruster
2019-09-17 16:22   ` Eric Blake
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 14/16] docs/devel/qapi-code-gen: Rewrite introduction to schema Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 15/16] docs/devel/qapi-code-gen: Improve QAPI schema language doc Markus Armbruster
2019-09-13 20:13 ` [Qemu-devel] [PATCH v3 16/16] qapi: Tweak code to match docs/devel/qapi-code-gen.txt Markus Armbruster
2019-09-14  2:49 ` [Qemu-devel] [PATCH v3 00/16] qapi: Schema language cleanups & doc improvements no-reply
2019-09-17 16:31 ` Eric Blake

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190913201349.24332-10-armbru@redhat.com \
    --to=armbru@redhat.com \
    --cc=marcandre.lureau@redhat.com \
    --cc=mdroth@linux.vnet.ibm.com \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

QEMU-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/qemu-devel/0 qemu-devel/git/0.git
	git clone --mirror https://lore.kernel.org/qemu-devel/1 qemu-devel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 qemu-devel qemu-devel/ https://lore.kernel.org/qemu-devel \
		qemu-devel@nongnu.org qemu-devel@archiver.kernel.org
	public-inbox-index qemu-devel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.nongnu.qemu-devel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox