Error serializing union types between class and boolean value types

[gregtyler]

Q	A
Bug report?	yes
Feature request?	no
BC Break report?	no
RFC?	no

As of 3.31.0, if you try to serialize a method that is a union type between a class a boolean value type (e.g. MyClass|false), JMS Serializer raises an exception.

This is because the value type is filtered out by TypedPropertiesDriver->shouldTypeHint() (because true and false aren't in the allowlist) so the only acceptable value becomes "MyClass".

Steps required to reproduce the problem

class SubClass {
}

class TestClass {
    public SubClass|false $falsableProp = false;
}

$serializer = JMS\Serializer\SerializerBuilder::create()->build();
$jsonContent = $serializer->serialize(new TestClass(), 'json');
echo $jsonContent;

Expected Result

{"falsable_prop":false}

Actual Result

Exception thrown:

JMS\Serializer\Exception\InvalidArgumentException: Value at TestClass is expected to be an object of class SubClass but is of type boolean

Workarounds

Changing the typehint to MyClass|bool fixes this, though means you're opening your type wider than needed.

Fix

I believe this can be fixed with two changes:

• Adding 'true' and 'false' to the TypedPropertiesDriver whitelist
• Adding 'true' and 'false' as cases to the graph navigator boolean acceptor (without, the navigator treats value types as objects)

I'm happy to raise a PR for this, but I'm not very familiar with the nuances of the codebase so I'm not confident this won't cause other issues.

[scyzoryck]

Hi! It looks like it will work :) I can help with reviewing the PR.

[gregtyler]

Thanks, I've created #1569. In doing so I realised that it also doesn't work for non-union value types, so I've generalised the PR slightly to acknowledge that.

For example, the following:

class TestClass {
    public false $falsableProp = false;
}

$serializer = JMS\Serializer\SerializerBuilder::create()->build();
$jsonContent = $serializer->serialize(new TestClass(), 'json');

Currently fails with:

ReflectionException: Class "false" does not exist