Fix deprecation notices in the backend module

[austinderrick]

Summary

Fixes two families of deprecation notices in the backend module, found while auditing PHP 8.4/8.5 readiness (follow-up to #1489):

1. TranscodeFilter is missing the return types declared by php_user_filter. Loading the class raises three deprecations on PHP 8.1+:

Deprecated: Return type of ...TranscodeFilter::filter($in, $out, &$consumed, $closing) should either be compatible with php_user_filter::filter($in, $out, &$consumed, bool $closing): int, or the #[\ReturnTypeWillChange] attribute should be used...
Deprecated: Return type of ...TranscodeFilter::onCreate() should either be compatible with php_user_filter::onCreate(): bool, ...
Deprecated: Return type of ...TranscodeFilter::onClose() should either be compatible with php_user_filter::onClose(): void, ...

Since the repo's PHP floor is 8.1, this adds the real return types (: int, : bool, : void) rather than #[\ReturnTypeWillChange]. The existing bodies already return the right types (PSFS_PASS_ON, booleans, nothing).

2. displayAs() passes a null render mode into strtolower(). Lists::makeListColumn() and Filter::makeFilterScope() pass $config['type'] ?? null into displayAs(), and FormField, ListColumn, and FilterScope each do strtolower($type) ?: $this->type, so any column/scope/field config without an explicit type raises:

Deprecated: strtolower(): Passing null to parameter #1 ($string) of type string is deprecated

Fixed by typing the parameter natively (?string $type) in all three classes and coalescing inside (strtolower($type ?? '')), keeping identical semantics: null and '' both fall back to the existing type. Real argument types rather than a docblock-only change, per the direction from the storm#229 review. All in-repo callers already pass string-or-null (Form::makeFormField() validates the type before calling), and untyped subclass overrides remain legal (widening).

Verification

Reproduced all four deprecations on a clean develop checkout under PHP 8.5.5 with a small harness (load TranscodeFilter, call each displayAs(null)); after this change the same harness emits none. modules/backend PHPUnit suite shows an identical result before and after the change on the same machine (the handful of locally-failing tests are environment-related and untouched by this diff: FileUploadScoping, NavigationManager, WidgetManager).

Summary by CodeRabbit

• Bug Fixes

  • Improved null-safety for display/type selection in backend lists, forms, and filters to prevent errors when no render type is provided.

• Refactor

  • Added nullable support for display/type parameters across backend UI components.
  • Declared explicit return and parameter types for backend filter lifecycle methods for clearer, more predictable behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 5530d117-b34f-42fd-9537-b6641bdb358f

📥 Commits

Reviewing files that changed from the base of the PR and between 7684a13 and b545a05.

📒 Files selected for processing (4)

• modules/backend/behaviors/importexportcontroller/TranscodeFilter.php
• modules/backend/classes/FilterScope.php
• modules/backend/classes/FormField.php
• modules/backend/classes/ListColumn.php

🚧 Files skipped from review as they are similar to previous changes (3)

• modules/backend/classes/FilterScope.php
• modules/backend/classes/FormField.php
• modules/backend/classes/ListColumn.php

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Walkthrough

This PR strengthens type safety across the backend by adding explicit return type declarations to the TranscodeFilter stream processor class and making three displayAs() configuration methods null-safe. TranscodeFilter's filter(), onCreate(), and onClose() methods now declare their return types (int, bool, and void respectively). FormField, FilterScope, and ListColumn displayAs() methods now accept nullable type parameters and apply null-coalescing before string operations, preventing errors when null or empty values are passed while preserving the existing type as a fallback.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately captures the main objective of the PR: fixing PHP 8.4/8.5 deprecation notices in the backend module through type declaration updates.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@modules/backend/behaviors/importexportcontroller/TranscodeFilter.php`:
- Line 20: The filter method signature in TranscodeFilter::filter must match the
php_user_filter parent by adding the missing bool type hint for the fourth
parameter; update the method declaration from filter($in, $out, &$consumed,
$closing): int to include bool $closing so it reads filter($in, $out,
&$consumed, bool $closing): int, ensuring the parameter type aligns with the
parent and any callers remain compatible.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: dae7d38b-7200-4ba8-969d-ac7595131222

📥 Commits

Reviewing files that changed from the base of the PR and between 7c28580 and 7684a13.

📒 Files selected for processing (4)

• modules/backend/behaviors/importexportcontroller/TranscodeFilter.php
• modules/backend/classes/FilterScope.php
• modules/backend/classes/FormField.php
• modules/backend/classes/ListColumn.php

🚧 Files skipped from review as they are similar to previous changes (2)

• modules/backend/classes/ListColumn.php
• modules/backend/classes/FilterScope.php