The composeFilters() method was duplicated identically between doc-type/index.js and page/index.js, with TODO comments warning developers to 'keep in sync' between the two files. This is fragile — any change to filter composition logic requires updating two files, and forgetting one creates subtle inconsistencies in how filters behave for pages vs. other doc types.

This change extracts the shared logic into lib/compose-filters.js and replaces both implementations with a single call to the shared utility.

The extracted function:

• Transforms a filters object (keyed by name) into an array
• Normalizes inputType (defaults to 'select')
• Adds null choices for non-required filters
• Sets appropriate nullLabel for dynamic choices
• Sets default values for checkbox filters

Benefits:

• Single source of truth for filter composition logic
• Changes to filter behavior only need to be made in one place
• Eliminates the risk of the two implementations drifting apart
• Easier to unit test in isolation

Addresses the TODO comments in both files:
'keep in sync with page/index.js composeFilters' 'keep in sync with doc-type/index.js composeFilters'

Please indicate which branch this PR should merge into:

Check one

• main

• latest

• stable

• Check if this PR will be resubmitted against another branch

Summary

Summary

Extracts the duplicated composeFilters() method into a shared utility at
lib/compose-filters.js, replacing identical implementations in both
@apostrophecms/doc-type and @apostrophecms/page.

Problem

Both modules had identical 30+ line composeFilters() implementations with
TODO comments warning: "keep in sync with [other file] composeFilters". This is
fragile — any change requires updating two files, and forgetting one creates
subtle inconsistencies in how filters behave for pages vs. other doc types.

Solution

• New lib/compose-filters.js — pure function that takes a filters object and
  returns the composed array
• Both modules now call require('../../../../lib/compose-filters')(self.filters)
• Net reduction of 15 lines of code
• Fully backward compatible — same behavior, just DRY

Addresses

TODO comments in both files:

"keep in sync with page/index.js composeFilters"
"keep in sync with doc-type/index.js composeFilters"

What are the specific steps to test this change?

1. Run the website and log in as an admin

2. Open a piece manager (e.g., Articles) — verify that filters appear correctly in the manager toolbar (dropdowns, checkboxes, radio buttons all render as expected)

3. Verify that filters with explicit choices show a "None" option when not marked as required

4. Verify that filters with dynamic choices show the appropriate "Choose one" or "Any" null label

5. Verify that checkbox-type filters default to an empty array

6. Navigate to the Pages tree — verify that page-level filters (if configured) also render and behave identically to piece filters

7. Create a custom piece type with a filter configuration and verify it composes correctly:
   filters: {
   add: {
   myFilter: {
   label: 'My Filter',
   inputType: 'select',
   choices: [
   { value: 'a', label: 'Option A' },
   { value: 'b', label: 'Option B' }
   ]
   }
   }
   }

8. Confirm the filter shows "None" as an additional choice and functions correctly

What kind of change does this PR introduce?

(Check at least one)

• Bug fix
• New feature
• Refactor
• Documentation
• Build-related changes
• Other

Make sure the PR fulfills these requirements:

• It includes a) the existing issue ID being resolved, b) a convincing reason for adding this feature, or c) a clear description of the bug it resolves
• The changelog is updated
• Related documentation has been updated
• Related tests have been updated

If adding a new feature without an already open issue, it's best to open a feature request issue first and wait for approval before working on it.

Other information:
This is a pure refactoring with no behavioral change. The extracted lib/compose-filters.js is a pure function with JSDoc documentation that takes a filters object and returns the composed array. Both modules now delegate to this single implementation, ensuring they can never drift apart. Net result is a reduction of 15 lines of code while improving maintainability. Existing tests for both doc-type and page filter behavior should continue to pass without modification since the logic is identical.