# vim:ts=4 sw=4 expandtab softtabstop=4 from collections import OrderedDict from jsonmerge.jsonvalue import JSONValue from jsonmerge.resolver import LocalRefResolver from jsonmerge import strategies from jsonmerge import descenders from jsonmerge.exceptions import SchemaError, JSONMergeError from jsonschema.validators import Draft4Validator import logging import warnings log = logging.getLogger(name=__name__) #logging.basicConfig(level=logging.DEBUG) class Walk(object): DESCENDERS = [ descenders.Ref, descenders.OneOf, descenders.AnyOfAllOf, ] def __init__(self, merger, merge_options): self.merger = merger self.merge_options = merge_options self.resolver = merger.validator.resolver self.lvl = -1 self.descenders = [ cls() for cls in self.DESCENDERS ] def _indent(self): return " " * self.lvl def is_type(self, instance, type): """Check if instance if a specific JSON type.""" assert isinstance(instance, JSONValue) if instance.is_undef(): return False return self.merger.validator.is_type(instance.val, type) def descend(self, schema, *args): assert isinstance(schema, JSONValue) self.lvl += 1 log.debug("descend: %sschema %s" % (self._indent(), schema.ref,)) if not schema.is_undef(): with self.resolver.resolving(schema.ref) as resolved: assert schema.val is resolved # backwards compatibility jsonmerge<=1.6.0 opts = {'meta': None} if not schema.is_undef(): for descender in self.descenders: rv = self.call_descender(descender, schema, *args) if rv is not None: self.lvl -= 1 return rv name = schema.val.get("mergeStrategy") for v in ( self.merge_options.get(name), schema.val.get("mergeOptions")): if v is not None: opts.update(v) else: name = None if name is None: name = self.default_strategy(schema, *args, **opts) log.debug("descend: %sinvoke strategy %s" % (self._indent(), name)) try: strategy = self.merger.strategies[name] except KeyError: raise SchemaError("Unknown strategy '%s'" % name, schema) try: rv = self.work(strategy, schema, *args, **opts) except JSONMergeError as exc: if exc.strategy_name is None: exc.strategy_name = name raise self.lvl -= 1 return rv class WalkInstance(Walk): def __init__(self, merger, base, head, merge_options): Walk.__init__(self, merger, merge_options) self.base_resolver = LocalRefResolver("", base.val) self.head_resolver = LocalRefResolver("", head.val) def default_strategy(self, schema, base, head, **kwargs): log.debug(" : %sdefault strategy" % (self._indent(),)) if self.is_type(head, "object"): return "objectMerge" else: return "overwrite" def call_descender(self, descender, schema, base, head): return descender.descend_instance(self, schema, base, head) def work(self, strategy, schema, base, head, **kwargs): assert isinstance(schema, JSONValue) assert isinstance(base, JSONValue) assert isinstance(head, JSONValue) log.debug("work : %sbase %s, head %s" % (self._indent(), base.ref, head.ref)) if not base.is_undef(): with self.base_resolver.resolving(base.ref) as resolved: assert base.val is resolved if not head.is_undef(): with self.head_resolver.resolving(head.ref) as resolved: assert head.val is resolved rv = strategy.merge(self, base, head, schema, objclass_menu=self.merger.objclass_menu, **kwargs) assert isinstance(rv, JSONValue) return rv class WalkSchema(Walk): def is_base_context(self): return self.resolver.base_uri == self.merger.schema.get('id', '') def resolve_refs(self, schema): # For backwards compatibility with jsonmerge <= 1.3.0 return schema def resolve_subschema_option_refs(self, subschema): # This is kind of ugly - schema for meta data # can again contain references to external schemas. # # Since we already have in place all the machinery # to resolve these references in the merge schema, # we (ab)use it here to do the same for meta data # schema. m = Merger(subschema) m.validator.resolver.store.update(self.resolver.store) w = WalkSchema(m, merge_options={}) subschema = w._resolve_refs(JSONValue(subschema), resolve_base=True).val return subschema def _resolve_refs(self, schema, resolve_base=False): assert isinstance(schema, JSONValue) if (not resolve_base) and self.is_base_context(): # no need to resolve refs in the context of the original schema - they # are still valid return schema elif self.is_type(schema, "array"): return JSONValue([ self._resolve_refs(v).val for v in schema ], schema.ref) elif self.is_type(schema, "object"): ref = schema.val.get("$ref") if ref is not None: with self.resolver.resolving(ref) as resolved: return self._resolve_refs(JSONValue(resolved, ref)) else: return JSONValue(dict( ((k, self._resolve_refs(v).val) for k, v in schema.items()) ), schema.ref) else: return schema def schema_is_object(self, schema): objonly = ( 'maxProperties', 'minProperties', 'required', 'additionalProperties', 'properties', 'patternProperties', 'dependencies') for k in objonly: if k in schema.val: return True if schema.val.get('type') == 'object': return True return False def default_strategy(self, schema, **kwargs): if self.schema_is_object(schema): return "objectMerge" else: return "overwrite" def call_descender(self, descender, schema): return descender.descend_schema(self, schema) def work(self, strategy, schema, **kwargs): assert isinstance(schema, JSONValue) schema = JSONValue(dict(schema.val), schema.ref) schema.val.pop("mergeStrategy", None) schema.val.pop("mergeOptions", None) rv = strategy.get_schema(self, schema, **kwargs) assert isinstance(rv, JSONValue) return rv class Merger(object): STRATEGIES = { "discard": strategies.Discard(), "overwrite": strategies.Overwrite(), "version": strategies.Version(), "append": strategies.Append(), "objectMerge": strategies.ObjectMerge(), "arrayMergeById": strategies.ArrayMergeById(), "arrayMergeByIndex": strategies.ArrayMergeByIndex(), } def __init__(self, schema, strategies=(), objclass_def='dict', objclass_menu=None, validatorclass=Draft4Validator): """Create a new Merger object. schema -- JSON schema to use when merging. strategies -- Any additional merge strategies to use during merge. objclass_def -- Name of the default class for JSON objects. objclass_menu -- Any additional classes for JSON objects. validatorclass -- JSON Schema validator class. strategies argument should be a dict mapping strategy names to instances of Strategy subclasses. objclass_def specifies the default class used for JSON objects when one is not specified in the schema. It should be 'dict' (dict built-in), 'OrderedDict' (collections.OrderedDict) or one of the names specified in the objclass_menu argument. If not specified, 'dict' is used. objclass_menu argument should be a dictionary that maps a string name to a function or class that will return an empty dictionary-like object to use as a JSON object. The function must accept either no arguments or a dictionary-like object. validatorclass argument can be used to supply a validator class from jsonschema. This can be used for example to specify which JSON Schema draft version will be used during merge. """ self.schema = schema if hasattr(validatorclass, 'ID_OF'): resolver = LocalRefResolver.from_schema(schema, id_of=validatorclass.ID_OF) else: # jsonschema<3.0.0 resolver = LocalRefResolver.from_schema(schema) self.validator = validatorclass(schema, resolver=resolver) self.strategies = dict(self.STRATEGIES) self.strategies.update(strategies) self.objclass_menu = { 'dict': dict, 'OrderedDict': OrderedDict } if objclass_menu: self.objclass_menu.update(objclass_menu) self.objclass_menu['_default'] = self.objclass_menu[objclass_def] def cache_schema(self, schema, uri=None): """Cache an external schema reference. schema -- JSON schema to cache uri -- Optional URI for the schema If the JSON schema for merging contains external references, they will be fetched using HTTP from their respective URLs. Alternatively, this method can be used to pre-populate the cache with any external schemas that are already known. If URI is omitted, it is obtained from the schema itself ('id' or '$id' keyword, depending on the JSON Schema draft used) """ if uri is None: if hasattr(self.validator, 'ID_OF'): uri = self.validator.ID_OF(schema) else: # jsonschema<3.0.0 uri = schema.get('id', '') self.validator.resolver.store.update(((uri, schema),)) def merge(self, base, head, meta=None, merge_options=None): """Merge head into base. base -- Old JSON document you are merging into. head -- New JSON document for merging into base. merge_options -- Optional dictionary with merge options. Keys of merge_options must be names of the strategies. Values must be dictionaries of merge options as in the mergeOptions schema element. Options in merge_options are applied to all instances of a strategy. Values in schema override values given in merge_options. Returns an updated base document """ schema = JSONValue(self.schema) if base is None: base = JSONValue(undef=True) else: base = JSONValue(base) head = JSONValue(head) if merge_options is None: merge_options = {} # backwards compatibility jsonmerge<=1.6.0 if meta is not None: warnings.warn("'meta' argument is deprecated. Please use " "merge_options={'version': {'metadata': ...}}.", DeprecationWarning, 2) merge_options['version'] = { 'metadata': meta } walk = WalkInstance(self, base, head, merge_options) return walk.descend(schema, base, head).val def get_schema(self, meta=None, merge_options=None): """Get JSON schema for the merged document. merge_options -- Optional dictionary with merge options. Keys of merge_options must be names of the strategies. Values must be dictionaries of merge options as in the mergeOptions schema element. Options in merge_options are applied to all instances of a strategy. Values in schema override values given in merge_options. Returns a JSON schema for documents returned by the merge() method. """ if merge_options is None: merge_options = {} # backwards compatibility jsonmerge<=1.6.0 if meta is not None: warnings.warn("'meta' argument is deprecated. Please use " "merge_options={'version': {'metadataSchema': ...}}.", DeprecationWarning, 2) merge_options['version'] = { 'metadataSchema': meta } schema = JSONValue(self.schema) walk = WalkSchema(self, merge_options) return walk.descend(schema).val def merge(base, head, schema={}): """Merge two JSON documents using strategies defined in schema. base -- Old JSON document you are merging into. head -- New JSON document for merging into base. schema -- JSON schema to use when merging. Merge strategy for each value can be specified in the schema using the "mergeStrategy" keyword. If not specified, default strategy is to use "objectMerge" for objects and "overwrite" for all other types. """ merger = Merger(schema) return merger.merge(base, head)