feat: maintain placeholder order from template declaration

[metaforx]

• Keep the declaration order in the template similar to the output in the frontend.
• When we reuse placeholders in templates and add others, the order of placeholders is mixed up, likely because of sorting by creation and not by position in the template.

I could fix this behavior with the suggested PR. There might be a cleaner solution.

Summary by Sourcery

Enhancements:

• Adjust page content serialization to build the placeholders list based on the template-declared placeholders, ensuring consistent frontend ordering.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adjusts PageContentSerializer to preserve the placeholder order as declared in the template instead of relying on queryset ordering, by mapping existing placeholders to the template-declared placeholders and serializing them in that order.

Sequence diagram for PageContentSerializer placeholder ordering

sequenceDiagram
  actor FrontendClient
  participant APIView
  participant PageContentSerializer
  participant PageContent
  participant PlaceholderSerializer

  FrontendClient->>APIView: GET page_content
  APIView->>PageContentSerializer: instantiate with context(request)
  APIView->>PageContentSerializer: to_representation(page_content)

  PageContentSerializer->>PageContent: placeholders.all()
  PageContent-->>PageContentSerializer: placeholders_queryset
  PageContentSerializer->>PageContentSerializer: placeholder_map = {slot: placeholder}

  PageContentSerializer->>PageContentSerializer: declared_placeholders = get_declared_placeholders_for_obj(page_content)
  PageContentSerializer->>PageContentSerializer: placeholders = [placeholder_map[declared.slot] for declared in declared_placeholders if declared.slot in placeholder_map]

  PageContentSerializer->>PageContentSerializer: data = get_base_representation(page_content)
  PageContentSerializer->>PlaceholderSerializer: serialize(placeholders, many=True)
  PlaceholderSerializer-->>PageContentSerializer: placeholders_data
  PageContentSerializer-->>APIView: data with ordered placeholders
  APIView-->>FrontendClient: JSON response

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Class diagram for updated PageContentSerializer placeholder handling

classDiagram

  class BasePageSerializer

  class BasePageContentMixin

  class PageContentSerializer {
    +placeholders PlaceholderSerializer[]
    +request any
    +to_representation(page_content PageContent) dict
  }

  class PageContent {
    +placeholders Placeholder[]
  }

  class Placeholder {
    +slot str
  }

  class DeclaredPlaceholder {
    +slot str
  }

  class PlaceholderSerializer {
    +many bool
  }

  PageContentSerializer --|> BasePageSerializer
  PageContentSerializer ..|> BasePageContentMixin

  PageContent "1" --> "*" Placeholder : placeholders
  PageContentSerializer --> PageContent : serializes
  PageContentSerializer --> PlaceholderSerializer : uses
  PageContentSerializer --> DeclaredPlaceholder : orders_by

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File-Level Changes

Change	Details	Files
Preserve placeholder ordering in serialized page content to match template declaration order.	Add a class docstring to PageContentSerializer explaining that placeholders are serialized in template declaration order. Replace collection of declared placeholder slots with full declared placeholder objects from the template. Build a mapping from existing page placeholders to their slot names for efficient lookup. Construct the placeholders list by iterating over declared placeholders in order and selecting corresponding existing placeholders via the map, filtering out slots without an existing placeholder. Reuse PlaceholderSerializer on the reordered placeholder list so the API output reflects template order rather than database creation order.	djangocms_rest/serializers/pages.py

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[sourcery-ai]

Hey there - I've reviewed your changes and they look great!

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.98%. Comparing base (7f76592) to head (cf83eaf).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #91   +/-   ##
=======================================
  Coverage   91.98%   91.98%           
=======================================
  Files          19       19           
  Lines         886      886           
  Branches      100      100           
=======================================
  Hits          815      815           
  Misses         44       44           
  Partials       27       27           

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[fsbraun]

@metaforx This PR seems to be empty?

[metaforx]

@metaforx This PR seems to be empty?

This is strange. I see 2 commits. Pages.py contains the changes. I check why containing commit is not respected.

[fsbraun]

Maybe these commits have already been merged?

[fsbraun]

Are these changes contained in #83 ?

[metaforx]

@

@metaforx This PR seems to be empty?

This is strange. I see 2 commits. Pages.py contains the changes. I check why containing commit is not respected.

@fsbraun Yes. This is right. I think the reason was that my fork was not in sync with djangocms-rest main branch. :(
I will close PR.