qapi: Better error messages for bad enums

The previous commit demonstrated that the generator had several
flaws with less-than-perfect enums:
- an enum that listed the same string twice (or two variant
strings that map to the same C enumerator) ended up generating
an invalid C enum
- because the generator adds a _MAX terminator to each enum,
the use of an enum member 'max' can also cause this clash
- if an enum omits 'data', the generator left a python stack
trace rather than a graceful message
- an enum that used a non-array 'data' was silently accepted by
the parser
- an enum that used non-string members in the 'data' member
was silently accepted by the parser

Add check_enum to cover these situations, and update testcases
to match.  While valid .json files won't trigger any of these
cases, we might as well be nicer to developers that make a typo
while trying to add new QAPI code.

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

scripts/qapi.py

@@ -311,13 +311,37 @@ def check_union(expr, expr_info):
         # Todo: add checking for values. Key is checked as above, value can be
         # also checked here, but we need more functions to handle array case.
 
+def check_enum(expr, expr_info):
+    name = expr['enum']
+    members = expr.get('data')
+    values = { 'MAX': '(automatic)' }
+
+    if not isinstance(members, list):
+        raise QAPIExprError(expr_info,
+                            "Enum '%s' requires an array for 'data'" % name)
+    for member in members:
+        if not isinstance(member, str):
+            raise QAPIExprError(expr_info,
+                                "Enum '%s' member '%s' is not a string"
+                                % (name, member))
+        key = _generate_enum_string(member)
+        if key in values:
+            raise QAPIExprError(expr_info,
+                                "Enum '%s' member '%s' clashes with '%s'"
+                                % (name, member, values[key]))
+        values[key] = member
+
 def check_exprs(schema):
     for expr_elem in schema.exprs:
         expr = expr_elem['expr']
-        if expr.has_key('union'):
-            check_union(expr, expr_elem['info'])
-        if expr.has_key('event'):
-            check_event(expr, expr_elem['info'])
+        info = expr_elem['info']
+
+        if expr.has_key('enum'):
+            check_enum(expr, info)
+        elif expr.has_key('union'):
+            check_union(expr, info)
+        elif expr.has_key('event'):
+            check_event(expr, info)
 
 def parse_schema(input_file):
     try:
@@ -331,7 +355,7 @@ def parse_schema(input_file):
     for expr_elem in schema.exprs:
         expr = expr_elem['expr']
         if expr.has_key('enum'):
-            add_enum(expr['enum'], expr['data'])
+            add_enum(expr['enum'], expr.get('data'))
         elif expr.has_key('union'):
             add_union(expr)
         elif expr.has_key('type'):

tests/qapi-schema/enum-clash-member.err

@@ -0,0 +1 @@
+tests/qapi-schema/enum-clash-member.json:2: Enum 'MyEnum' member 'ONE' clashes with 'one'

tests/qapi-schema/enum-clash-member.exit

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

tests/qapi-schema/enum-clash-member.json

@@ -1,2 +1,2 @@
-# FIXME: we should reject enums where members will clash when mapped to C enum
+# we reject enums where members will clash when mapped to C enum
 { 'enum': 'MyEnum', 'data': [ 'one', 'ONE' ] }

tests/qapi-schema/enum-clash-member.out

@@ -1,3 +0,0 @@
-[OrderedDict([('enum', 'MyEnum'), ('data', ['one', 'ONE'])])]
-[{'enum_name': 'MyEnum', 'enum_values': ['one', 'ONE']}]
-[]

tests/qapi-schema/enum-dict-member.err

@@ -0,0 +1 @@
+tests/qapi-schema/enum-dict-member.json:2: Enum 'MyEnum' member 'OrderedDict([('value', 'str')])' is not a string

tests/qapi-schema/enum-dict-member.exit

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

tests/qapi-schema/enum-dict-member.json

@@ -1,2 +1,2 @@
-# FIXME: we should reject any enum member that is not a string
+# we reject any enum member that is not a string
 { 'enum': 'MyEnum', 'data': [ { 'value': 'str' } ] }

tests/qapi-schema/enum-dict-member.out

@@ -1,3 +0,0 @@
-[OrderedDict([('enum', 'MyEnum'), ('data', [OrderedDict([('value', 'str')])])])]
-[{'enum_name': 'MyEnum', 'enum_values': [OrderedDict([('value', 'str')])]}]
-[]

tests/qapi-schema/enum-max-member.err

@@ -0,0 +1 @@
+tests/qapi-schema/enum-max-member.json:3: Enum 'MyEnum' member 'max' clashes with '(automatic)'

tests/qapi-schema/enum-max-member.exit

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

tests/qapi-schema/enum-max-member.json

@@ -1,3 +1,3 @@
-# FIXME: we should reject user-supplied 'max' for clashing with implicit enum end
+# we reject user-supplied 'max' for clashing with implicit enum end
 # TODO: should we instead munge the implicit value to avoid the clash?
 { 'enum': 'MyEnum', 'data': [ 'max' ] }

tests/qapi-schema/enum-max-member.out

@@ -1,3 +0,0 @@
-[OrderedDict([('enum', 'MyEnum'), ('data', ['max'])])]
-[{'enum_name': 'MyEnum', 'enum_values': ['max']}]
-[]

tests/qapi-schema/enum-missing-data.err

@@ -1,6 +1 @@
-Traceback (most recent call last):
-  File "tests/qapi-schema/test-qapi.py", line 19, in <module>
-    exprs = parse_schema(sys.argv[1])
-  File "scripts/qapi.py", line 334, in parse_schema
-    add_enum(expr['enum'], expr['data'])
-KeyError: 'data'
+tests/qapi-schema/enum-missing-data.json:2: Enum 'MyEnum' requires an array for 'data'

tests/qapi-schema/enum-missing-data.json

@@ -1,2 +1,2 @@
-# FIXME: we should require that all QAPI enums have a data array
+# we require that all QAPI enums have a data array
 { 'enum': 'MyEnum' }

tests/qapi-schema/enum-wrong-data.err

@@ -0,0 +1 @@
+tests/qapi-schema/enum-wrong-data.json:2: Enum 'MyEnum' requires an array for 'data'

tests/qapi-schema/enum-wrong-data.exit

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

tests/qapi-schema/enum-wrong-data.json

@@ -1,2 +1,2 @@
-# FIXME: we should require that all qapi enums have an array for data
+# we require that all qapi enums have an array for data
 { 'enum': 'MyEnum', 'data': { 'value': 'str' } }

tests/qapi-schema/enum-wrong-data.out

@@ -1,3 +0,0 @@
-[OrderedDict([('enum', 'MyEnum'), ('data', OrderedDict([('value', 'str')]))])]
-[{'enum_name': 'MyEnum', 'enum_values': OrderedDict([('value', 'str')])}]
-[]