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Improved compatibility with the stdlib JSON gem.

Previously, calling `::JSON.{generate,dump}` sometimes causes
unexpected failures such as intridea/multi_json#86.

`::JSON.{generate,dump}` now bypasses the ActiveSupport JSON encoder
completely and yields the same result with or without ActiveSupport.
This means that it will **not** call `as_json` and will ignore any
options that the JSON gem does not natively understand. To invoke
ActiveSupport's JSON encoder instead, use `obj.to_json(options)` or
`ActiveSupport::JSON.encode(obj, options)`.
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1 parent 07996eb commit 0f33d70e89991711ff8b3dde134a61f4a5a0ec06 @chancancode chancancode committed Nov 12, 2013
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@@ -1,3 +1,17 @@
+* Improved compatibility with the stdlib JSON gem.
+
+ Previously, calling `::JSON.{generate,dump}` sometimes causes unexpected
+ failures such as intridea/multi_json#86.
+
+ `::JSON.{generate,dump}` now bypasses the ActiveSupport JSON encoder
+ completely and yields the same result with or without ActiveSupport. This
+ means that it will **not** call `as_json` and will ignore any options that
+ the JSON gem does not natively understand. To invoke ActiveSupport's JSON
+ encoder instead, use `obj.to_json(options)` or
+ `ActiveSupport::JSON.encode(obj, options)`.
+
+ *Godfrey Chan*
+
* Fix Active Support `Time#to_json` and `DateTime#to_json` to return 3 decimal
places worth of fractional seconds, similar to `TimeWithZone`.
@@ -9,18 +9,36 @@
require 'active_support/core_ext/time/conversions'
require 'active_support/core_ext/date_time/conversions'
require 'active_support/core_ext/date/conversions'
+require 'active_support/core_ext/module/aliasing'
# The JSON gem adds a few modules to Ruby core classes containing :to_json definition, overwriting
# their default behavior. That said, we need to define the basic to_json method in all of them,
# otherwise they will always use to_json gem implementation, which is backwards incompatible in
# several cases (for instance, the JSON implementation for Hash does not work) with inheritance
# and consequently classes as ActiveSupport::OrderedHash cannot be serialized to json.
+#
+# On the other hand, we should avoid conflict with ::JSON.{generate,dump}(obj). Unfortunately, the
+# JSON gem's encoder relies on its own to_json implementation to encode objects. Since it always
+# passes a ::JSON::State object as the only argument to to_json, we can detect that and forward the
+# calls to the original to_json method.
+#
+# It should be noted that when using ::JSON.{generate,dump} directly, ActiveSupport's encoder is
+# bypassed completely. This means that as_json won't be invoked and the JSON gem will simply
+# ignore any options it does not natively understand. This also means that ::JSON.{generate,dump}
+# should give exactly the same results with or without active support.
[Object, Array, FalseClass, Float, Hash, Integer, NilClass, String, TrueClass].each do |klass|
klass.class_eval do
- # Dumps object in JSON (JavaScript Object Notation). See www.json.org for more info.
- def to_json(options = nil)
- ActiveSupport::JSON.encode(self, options)
+ def to_json_with_active_support_encoder(options = nil)
+ if options.is_a?(::JSON::State)
+ # Called from JSON.{generate,dump}, forward it to JSON gem's to_json
+ self.to_json_without_active_support_encoder(options)
+ else
+ # to_json is being invoked directly, use ActiveSupport's encoder
+ ActiveSupport::JSON.encode(self, options)
+ end
end
+
+ alias_method_chain :to_json, :active_support_encoder
end
end
@@ -32,6 +32,19 @@ def as_json(options={})
end
end
+ class HashWithAsJson < Hash
+ attr_accessor :as_json_called
+
+ def initialize(*)
+ super
+ end
+
+ def as_json(options={})
+ @as_json_called = true
+ super
+ end
+ end
+
TrueTests = [[ true, %(true) ]]
FalseTests = [[ false, %(false) ]]
NilTests = [[ nil, %(null) ]]
@@ -367,6 +380,38 @@ def test_nil_true_and_false_represented_as_themselves
assert_equal false, false.as_json
end
+ def test_json_gem_dump_by_passing_active_support_encoder
+ h = HashWithAsJson.new
+ h[:foo] = "hello"
+ h[:bar] = "world"
+
+ assert_equal %({"foo":"hello","bar":"world"}), JSON.dump(h)
+ assert_nil h.as_json_called
+ end
+
+ def test_json_gem_generate_by_passing_active_support_encoder
+ h = HashWithAsJson.new
+ h[:foo] = "hello"
+ h[:bar] = "world"
+
+ assert_equal %({"foo":"hello","bar":"world"}), JSON.generate(h)
+ assert_nil h.as_json_called
+ end
+
+ def test_json_gem_pretty_generate_by_passing_active_support_encoder
+ h = HashWithAsJson.new
+ h[:foo] = "hello"
+ h[:bar] = "world"
+
+ assert_equal <<EXPECTED.chomp, JSON.pretty_generate(h)
+{
+ "foo": "hello",
+ "bar": "world"
+}
+EXPECTED
+ assert_nil h.as_json_called
+ end
+
protected
def object_keys(json_object)

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