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>

docs/qapi-code-gen.txt

@@ -48,7 +48,7 @@ The QAPI schema definitions can be modularized using the 'include' directive:
  { 'include': 'path/to/file.json'}
 
 The directive is evaluated recursively, and include paths are relative to the
-file using the directive.
+file using the directive. Multiple includes of the same file are safe.
 
 
 === Complex types ===

scripts/qapi.py

@@ -73,13 +73,18 @@ def __str__(self):
 
 class QAPISchema:
 
-    def __init__(self, fp, input_relname=None, include_hist=[], parent_info=None):
+    def __init__(self, fp, input_relname=None, include_hist=[],
+                 previously_included=[], parent_info=None):
+        """ include_hist is a stack used to detect inclusion cycles
+            previously_included is a global state used to avoid multiple
+                                inclusions of the same file"""
         input_fname = os.path.abspath(fp.name)
         if input_relname is None:
             input_relname = fp.name
         self.input_dir = os.path.dirname(input_fname)
         self.input_file = input_relname
         self.include_hist = include_hist + [(input_relname, input_fname)]
+        previously_included.append(input_fname)
         self.parent_info = parent_info
         self.src = fp.read()
         if self.src == '' or self.src[-1] != '\n':
@@ -106,13 +111,16 @@ def __init__(self, fp, input_relname=None, include_hist=[], parent_info=None):
                        for elem in self.include_hist):
                     raise QAPIExprError(expr_info, "Inclusion loop for %s"
                                         % include)
+                # skip multiple include of the same file
+                if include_path in previously_included:
+                    continue
                 try:
                     fobj = open(include_path, 'r')
                 except IOError as e:
                     raise QAPIExprError(expr_info,
                                         '%s: %s' % (e.strerror, include))
-                exprs_include = QAPISchema(fobj, include,
-                                           self.include_hist, expr_info)
+                exprs_include = QAPISchema(fobj, include, self.include_hist,
+                                           previously_included, expr_info)
                 self.exprs.extend(exprs_include.exprs)
             else:
                 expr_elem = {'expr': expr,

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']}]
+[]