qapi: skip redundant includes

The purpose of this change is to help create a json file containing
common definitions; each bit of generated C code must be emitted
only one time.

A second history global to all QAPISchema instances has been added
to detect when a file is included more than one time and skip these
includes.
It does not act as a stack and the changes made to it by the
__init__ function are propagated back to the caller so it's really
a global state.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

tests/Makefile

@@ -193,7 +193,8 @@ check-qapi-schema-y := $(addprefix tests/qapi-schema/, \
         flat-union-string-discriminator.json \
         include-simple.json include-relpath.json include-format-err.json \
         include-non-file.json include-no-file.json include-before-err.json \
-        include-nested-err.json include-self-cycle.json include-cycle.json)
+        include-nested-err.json include-self-cycle.json include-cycle.json \
+        include-repetition.json)
 
 GENERATED_HEADERS += tests/test-qapi-types.h tests/test-qapi-visit.h tests/test-qmp-commands.h
 

tests/qapi-schema/include-repetition-sub.json

@@ -0,0 +1,2 @@
+{ 'include': 'comments.json' }
+{ 'include': 'comments.json' }

tests/qapi-schema/include-repetition.exit

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

tests/qapi-schema/include-repetition.json

@@ -0,0 +1,3 @@
+{ 'include': 'comments.json' }
+{ 'include': 'include-repetition-sub.json' }
+{ 'include': 'comments.json' }

tests/qapi-schema/include-repetition.out

@@ -0,0 +1,3 @@
+[OrderedDict([('enum', 'Status'), ('data', ['good', 'bad', 'ugly'])])]
+[{'enum_name': 'Status', 'enum_values': ['good', 'bad', 'ugly']}]
+[]