[Serializer] Add headers label support for CsvEncoder using csv_headers

[Seb33300]

Q	A
Branch?	7.2
Bug fix?	no
New feature?	yes
Deprecations?	no
Issues	Fix #55048
License	MIT

Improve the existing csv_headers option of CsvEncoder to pass CSV headers labels.

$contextBuilder = (new CsvEncoderContextBuilder())->withHeaders([
    'Prénom' => 'firstName',
    'Nom' => 'lastName',
    'Nested field label' => 'nested.field',
]);

[OskarStark]

Please move this to a new 7.2 section, thanks

[Seb33300]

I was hoping I still have a chance to see it merged in 7.1 branch since the final version is not released yet.

[Seb33300]

Done

[Seb33300]

I just added a test

[Seb33300]

Headers for nested data was already supported but not tested.

[valtzu]

Shouldn't the mapping be used in both, encoding & decoding? Or is that already the case 🤔

Also I'm wondering, would it make more sense to implement this mapping in MetadataAwareNameConverter so that it would work with any format, not only csv?

[Seb33300]

@valtzu not sure to understand your question.

This PR is not about mapping but adding labels to generated CSV, which is relevant only when exporting.

[valtzu]

adding labels

@Seb33300 I assume by adding labels you mean csv column names / header – and those may exist when exporting or importing csv data.

To me it feels quite unintuitive that you can not import the exported file using decode with the same context as was used with encode.

$data = [['firstName' => 'foo', 'lastName' => 'bar']];

$context = [
    CsvEncoder::HEADERS_KEY => [
        'Prénom' => 'firstName',
        'Nom' => 'lastName',
    ],
];

$encoded = $this->serializer->encode($data, 'csv', $context);

/* =
Prénom,Nom
foo,bar
*/


$decoded = $this->serializer->decode($encoded, 'csv', $context);

/* =
Array
(
    [0] => Array
        (
            [Prénom] => foo
            [Nom] => bar
        )

)
*/

I would expect $decoded be equal to $data.

If this was implemented in a name converter, it would work both ways. Basically same as #[SerializedName]/#[SerializedPath] – but just get those from context instead of static configuration. As I understood from your comment, you'd be happy with such approach.

It would be something like 👇 (such thing is not implemented)

$csv = $serializer->serialize($data, 'csv', [
    AbstractNormalizer::ATTRIBUTES => ['firstName', 'lastName'],
    MetadataAwareNameConverter::MAPPING => [
        YourEntity::class => [
            'Prénom' => 'firstName',
            'Nom' => 'lastName',
        ],
    ],
]);

[Seb33300]

You are right.
Thanks for the feedback.