On 14/6/2018 10:19 AM, Markus Armbruster wrote:
Anton Nefedov <anton.nefe...@virtuozzo.com> writes:
It often happens that just a few discriminator values imply extra data in
a flat union. Existing checks did not make possible to leave other values
uncovered. Such cases had to be worked around by either stating a dummy
(empty) type or introducing another (subset) discriminator enumeration.
Both options create redundant entities in qapi files for little profit.
With this patch it is not necessary anymore to add designated union
fields for every possible value of a discriminator enumeration.
Signed-off-by: Anton Nefedov <anton.nefe...@virtuozzo.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
---
docs/devel/qapi-code-gen.txt | 8 +++++---
tests/qapi-schema/flat-union-incomplete-branch.json | 9 ---------
tests/qapi-schema/qapi-schema-test.json | 4 ++--
scripts/qapi/common.py | 11 ++++-------
scripts/qapi/types.py | 4 +++-
scripts/qapi/visit.py | 17 +++++++++++++----
tests/Makefile.include | 1 -
tests/qapi-schema/flat-union-incomplete-branch.err | 1 -
tests/qapi-schema/flat-union-incomplete-branch.exit | 1 -
tests/qapi-schema/flat-union-incomplete-branch.out | 0
tests/qapi-schema/qapi-schema-test.out | 3 ++-
11 files changed, 29 insertions(+), 30 deletions(-)
delete mode 100644 tests/qapi-schema/flat-union-incomplete-branch.json
delete mode 100644 tests/qapi-schema/flat-union-incomplete-branch.err
delete mode 100644 tests/qapi-schema/flat-union-incomplete-branch.exit
delete mode 100644 tests/qapi-schema/flat-union-incomplete-branch.out
diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
index 1366228..88a70e4 100644
--- a/docs/devel/qapi-code-gen.txt
+++ b/docs/devel/qapi-code-gen.txt
@@ -496,9 +496,11 @@ Resulting in these JSON objects:
Notice that in a flat union, the discriminator name is controlled by
the user, but because it must map to a base member with enum type, the
-code generator can ensure that branches exist for all values of the
-enum (although the order of the keys need not match the declaration of
-the enum). In the resulting generated C data types, a flat union is
+code generator ensures that branches match the existing values of the
+enum. The order of the keys need not match the declaration of the enum.
+The keys need not cover all possible enum values. Omitted enum values
+are still valid branches that add no additional members to the data type.
+In the resulting generated C data types, a flat union is
represented as a struct with the base members included directly, and
then a union of structures for each branch of the struct.
diff --git a/tests/qapi-schema/flat-union-incomplete-branch.json b/tests/qapi-schema/flat-union-incomplete-branch.json
deleted file mode 100644
index 25a411b..0000000
--- a/tests/qapi-schema/flat-union-incomplete-branch.json
+++ /dev/null
@@ -1,9 +0,0 @@
-# we require all branches of the union to be covered
-{ 'enum': 'TestEnum',
- 'data': [ 'value1', 'value2' ] }
-{ 'struct': 'TestTypeA',
- 'data': { 'string': 'str' } }
-{ 'union': 'TestUnion',
- 'base': { 'type': 'TestEnum' },
- 'discriminator': 'type',
- 'data': { 'value1': 'TestTypeA' } }
diff --git a/tests/qapi-schema/qapi-schema-test.json
b/tests/qapi-schema/qapi-schema-test.json
index 46c7282..881b53b 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -39,7 +39,7 @@
'*enum1': 'EnumOne' } } # intentional forward reference
{ 'enum': 'EnumOne',
- 'data': [ 'value1', 'value2', 'value3' ] }
+ 'data': [ 'value1', 'value2', 'value3', 'value4' ] }
{ 'struct': 'UserDefZero',
'data': { 'integer': 'int' } }
@@ -76,7 +76,7 @@
'discriminator': 'enum1',
'data': { 'value1' : 'UserDefA',
'value2' : 'UserDefB',
- 'value3' : 'UserDefB' } }
+ 'value3' : 'UserDefB' } } # skip 'value4'
Perhaps
'value3' : 'UserDefB'
# 'value4' defaults to empty
} }
would be clearer.
Sure
{ 'struct': 'UserDefUnionBase',
'base': 'UserDefZero',
diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index 2462fc0..0f3d89b 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -779,13 +779,6 @@ def check_union(expr, info):
"enum '%s'"
% (key, enum_define['enum']))
- # If discriminator is user-defined, ensure all values are covered
- if enum_define:
- for value in enum_define['data']:
- if value not in members.keys():
- raise QAPISemError(info, "Union '%s' data missing '%s' branch"
- % (name, value))
-
def check_alternate(expr, info):
name = expr['alternate']
@@ -1644,6 +1637,10 @@ class QAPISchema(object):
if tag_name:
variants = [self._make_variant(key, value)
for (key, value) in data.items()]
+ # branches that are not explicitly covered get an empty type
+ variants += [self._make_variant(key, 'q_empty')
+ for key in
discriminator_find_enum_define(expr)['data']
Long line, flagged by pycodestyle --diff.
Done.
+ if key not in data.keys()]
members = []
else:
variants = [self._make_simple_variant(key, value, info)
The way you desugar the union is simple enough, but it uses
discriminator_find_enum_define() outside check_exprs(), which I'd rather
avoid. Not something you could be reasonably expected to know.
We could desugar in QAPISchemaObjectTypeVariants.check(), where we have
self.tag_member.type.values.
@@ -1346,10 +1346,17 @@ class QAPISchemaObjectTypeVariants(object):
v.set_owner(name)
def check(self, schema, seen):
- if not self.tag_member: # flat union
+ if not self.tag_member: # flat union
self.tag_member = seen[c_name(self._tag_name)]
assert self._tag_name == self.tag_member.name
assert isinstance(self.tag_member.type, QAPISchemaEnumType)
+ if self._tag_name: # flat union
+ cases = set([v.name for v in self.variants])
+ for val in self.tag_member.type.values:
+ if val.name not in cases:
+ v = QAPISchemaObjectTypeVariant(val.name, 'q_empty')
+ v.set_owner(self.tag_member.owner)
+ self.variants.append(v)
for v in self.variants:
v.check(schema)
# Union names must match enum values; alternate names are
Not so simple anymore.
Simpler: desugar in check_union(), i.e. replace your two hunks by just
@@ -783,8 +783,7 @@ def check_union(expr, info):
if enum_define:
for value in enum_define['data']:
if value not in members.keys():
- raise QAPISemError(info, "Union '%s' data missing '%s'
branch"
- % (name, value))
+ members[value] = 'q_empty'
def check_alternate(expr, info):
What do you think?
it didn't feel right aesthetically to normalize by modifying the parsed
expressions especially at check_exprs() stage. But maybe using
discriminator_find_enum_define() is more sloppy, I can't quite see
diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
index 64d9c0f..1fb2b6d 100644
--- a/scripts/qapi/types.py
+++ b/scripts/qapi/types.py
@@ -124,7 +124,9 @@ def gen_variants(variants):
''',
c_name=c_name(variants.tag_member.name))
- for var in variants.variants:
+ # filter out the empty types
+ for var in filter(lambda var: var.type.name != 'q_empty',
+ variants.variants):
The comment's position suggests it tells what the loop does, but that's
not the case. Let's do it the old-fashioned obvious way instead:
for var in variants.variants:
if var.type.name == 'q_empty':
continue
Done.
Aside: we need to filter out q_empty, because we don't generate a C type
for it. Perhaps generating one would be simpler, but that's beyond the
scope of this patch.
ret += mcgen('''
%(c_type)s %(c_name)s;
''',
diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 5d72d89..96bd32c 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -81,14 +81,23 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s
*obj, Error **errp)
c_name=c_name(variants.tag_member.name))
for var in variants.variants:
- ret += mcgen('''
+ case_str = c_enum_const(variants.tag_member.type.name,
+ var.name,
+ variants.tag_member.type.prefix)
+ if var.type.name == 'q_empty':
+ # valid variant and nothing to do
+ ret += mcgen('''
+ case %(case)s:
+ break;
+''',
+ case=case_str)
+ else:
+ ret += mcgen('''
Aside: we need this, because we don't generate a visitor for q_empty.
case %(case)s:
visit_type_%(c_type)s_members(v, &obj->u.%(c_name)s, &err);
break;
''',
- case=c_enum_const(variants.tag_member.type.name,
- var.name,
- variants.tag_member.type.prefix),
+ case=case_str,
c_type=var.type.c_name(), c_name=c_name(var.name))
Indentation's off, flagged by pycodestyle --diff.
Done.
ret += mcgen('''
diff --git a/tests/Makefile.include b/tests/Makefile.include
index bb08e37..afdd0db 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -496,7 +496,6 @@ qapi-schema += flat-union-base-any.json
qapi-schema += flat-union-base-union.json
qapi-schema += flat-union-clash-member.json
qapi-schema += flat-union-empty.json
-qapi-schema += flat-union-incomplete-branch.json
qapi-schema += flat-union-inline.json
qapi-schema += flat-union-int-branch.json
qapi-schema += flat-union-invalid-branch-key.json
diff --git a/tests/qapi-schema/flat-union-incomplete-branch.err
b/tests/qapi-schema/flat-union-incomplete-branch.err
deleted file mode 100644
index e826bf0..0000000
--- a/tests/qapi-schema/flat-union-incomplete-branch.err
+++ /dev/null
@@ -1 +0,0 @@
-tests/qapi-schema/flat-union-incomplete-branch.json:6: Union 'TestUnion' data
missing 'value2' branch
diff --git a/tests/qapi-schema/flat-union-incomplete-branch.exit
b/tests/qapi-schema/flat-union-incomplete-branch.exit
deleted file mode 100644
index d00491f..0000000
--- a/tests/qapi-schema/flat-union-incomplete-branch.exit
+++ /dev/null
@@ -1 +0,0 @@
-1
diff --git a/tests/qapi-schema/flat-union-incomplete-branch.out
b/tests/qapi-schema/flat-union-incomplete-branch.out
deleted file mode 100644
index e69de29..0000000
diff --git a/tests/qapi-schema/qapi-schema-test.out
b/tests/qapi-schema/qapi-schema-test.out
index 542a19c..0dbcdaf 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -23,7 +23,7 @@ object UserDefOne
base UserDefZero
member string: str optional=False
member enum1: EnumOne optional=True
-enum EnumOne ['value1', 'value2', 'value3']
+enum EnumOne ['value1', 'value2', 'value3', 'value4']
object UserDefZero
member integer: int optional=False
object UserDefTwoDictDict
@@ -52,6 +52,7 @@ object UserDefFlatUnion
case value1: UserDefA
case value2: UserDefB
case value3: UserDefB
+ case value4: q_empty
object UserDefUnionBase
base UserDefZero
member string: str optional=False