tests/qapi-schema: Demonstrate misleading optional tag error

Test flat-union-optional-discriminator declares its union tag as
'*switch': 'Enum', and points to it with 'discriminator': '*switch'.
This gets rejected as "discriminator of flat union 'MyUnion' uses
invalid name '*switch'".  Correct; member 'discriminator' doesn't
accept a '*' prefix.

However, this merely tests name validity checking, which we already
cover elsewhere.  More interesting is testing the valid name 'switch'.
This reports "discriminator 'switch' is not a member of base struct
'Base'", which is misleading.

Copy the existing 'discriminator': '*switch' test to
flat-union-discriminator-bad-name, and rewrite its comment.  Change
flat-union-optional-discriminator to test 'discriminator': 'switch',
and mark it FIXME.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190914153506.2151-4-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

tests/Makefile.include

@@ -388,6 +388,7 @@ qapi-schema += flat-union-bad-discriminator.json
 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-discriminator-bad-name.json
 qapi-schema += flat-union-empty.json
 qapi-schema += flat-union-inline.json
 qapi-schema += flat-union-inline-invalid-dict.json

tests/qapi-schema/flat-union-discriminator-bad-name.err

@@ -0,0 +1 @@
+tests/qapi-schema/flat-union-discriminator-bad-name.json:7: Discriminator of flat union 'MyUnion' does not allow optional name '*switch'

tests/qapi-schema/flat-union-discriminator-bad-name.exit

@@ -0,0 +1 @@
+1

tests/qapi-schema/flat-union-discriminator-bad-name.json

@@ -0,0 +1,11 @@
+# discriminator '*switch' isn't a member of base, 'switch' is
+# reports "does not allow optional name", which is good enough
+{ 'enum': 'Enum', 'data': [ 'one', 'two' ] }
+{ 'struct': 'Base',
+  'data': { '*switch': 'Enum' } }
+{ 'struct': 'Branch', 'data': { 'name': 'str' } }
+{ 'union': 'MyUnion',
+  'base': 'Base',
+  'discriminator': '*switch',
+  'data': { 'one': 'Branch',
+            'two': 'Branch' } }

tests/qapi-schema/flat-union-optional-discriminator.err

@@ -1 +1 @@
-tests/qapi-schema/flat-union-optional-discriminator.json:6: Discriminator of flat union 'MyUnion' does not allow optional name '*switch'
+tests/qapi-schema/flat-union-optional-discriminator.json:7: Discriminator 'switch' is not a member of base struct 'Base'

tests/qapi-schema/flat-union-optional-discriminator.json

@@ -1,10 +1,11 @@
 # we require the discriminator to be non-optional
+# FIXME reports "discriminator 'switch' is not a member of base struct 'Base'"
 { 'enum': 'Enum', 'data': [ 'one', 'two' ] }
 { 'struct': 'Base',
   'data': { '*switch': 'Enum' } }
 { 'struct': 'Branch', 'data': { 'name': 'str' } }
 { 'union': 'MyUnion',
   'base': 'Base',
-  'discriminator': '*switch',
+  'discriminator': 'switch',
   'data': { 'one': 'Branch',
             'two': 'Branch' } }