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fix(kernel): Correct null handling in JSON types #523

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merged 3 commits into from
Jun 7, 2019

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@RomainMuller RomainMuller commented Jun 7, 2019

The JSON types were serialized "as-is" without touch, meaning if the
value was null, it would be forwarded as null, instead of undefined.
This caused some CDK usage patterns to crash at runtime. This changes
the behavior so that top-level nulls in JSON types turn into undefined,
while nulls nested in the JSON value will be preserved (they are valid
JSON after all!).

Additionally, tuned the Java code generator a little:
The serialization of structs creates a jackson ObjectNode to pass down
to the serialization layer, however those are turned to JSON without
processing and are not honoring the inclusion setting to ignore nulls.
Added some code in the Java generator to stop adding null values into
the ObjectNode.


By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

The serialization of structs creates a jackson ObjectNode to pass down
to the serialization layer, however those are turned to JSON without
processing and are not honoring the inclusion setting to ignore nulls.
Added some code in the Java generator to stop adding null values into
the ObjectNode.
@RomainMuller RomainMuller requested a review from a team as a code owner June 7, 2019 09:03
@RomainMuller RomainMuller changed the title fix(pacmak/java): Stop serializing null fix(kernel): Correct null handling in JSON types Jun 7, 2019
@RomainMuller RomainMuller merged commit 7ffa98d into master Jun 7, 2019
@RomainMuller RomainMuller deleted the rmuller/no-null-java branch June 7, 2019 12:22
RomainMuller added a commit to aws/aws-cdk that referenced this pull request Jun 7, 2019
There are a couple of places where fields accept values that are typed
as `Json` per the JSII type specification. This conveys that literal
`null` values may be passed and need to be preserved (as far as JSII is
concerned - see aws/jsii#523). However in the CloudFormation domain,
`null` is semantically equivalent to `undefined`.

Now enters Javascript's confusing type system, where `null` is an
`object` that cannot be converted to `object` (you read this correctly):

```js
typeof null === 'object'
// => true

Object.entries(null);
// => Thrown:
//    TypeError: Cannot convert undefined or null to object
//        at Function.entries (<anonymous>)
```

So this changes the `undefined` checks to the `null`-coercing way, so
that `null` and `undefined` are handled the same way.
RomainMuller added a commit to aws/aws-cdk that referenced this pull request Jun 7, 2019
There are a couple of places where fields accept values that are typed
as `Json` per the JSII type specification. This conveys that literal
`null` values may be passed and need to be preserved (as far as JSII is
concerned - see aws/jsii#523). However in the CloudFormation domain,
`null` is semantically equivalent to `undefined`.

Now enters Javascript's confusing type system, where `null` is an
`object` that cannot be converted to `object` (you read this correctly):

```js
typeof null === 'object'
// => true

Object.entries(null);
// => Thrown:
//    TypeError: Cannot convert undefined or null to object
//        at Function.entries (<anonymous>)
```

So this changes the `undefined` checks to the `null`-coercing way, so
that `null` and `undefined` are handled the same way.
rix0rrr pushed a commit to aws/aws-cdk that referenced this pull request Jun 7, 2019
There are a couple of places where fields accept values that are typed
as `Json` per the JSII type specification. This conveys that literal
`null` values may be passed and need to be preserved (as far as JSII is
concerned - see aws/jsii#523). However in the CloudFormation domain,
`null` is semantically equivalent to `undefined`.

Now enters Javascript's confusing type system, where `null` is an
`object` that cannot be converted to `object` (you read this correctly):

```js
typeof null === 'object'
// => true

Object.entries(null);
// => Thrown:
//    TypeError: Cannot convert undefined or null to object
//        at Function.entries (<canonymous>)
```

So this changes the `undefined` checks to the `null`-coercing way, so
that `null` and `undefined` are handled the same way.
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2 participants