fix: normalize empty input to empty array for schema-defining abilities

[galatanovidiu]

What

AbilityArgumentNormalizer::normalize() now converts null or an empty array to an empty array when the ability has an input_schema. Abilities without a schema keep the existing empty-to-null behavior.

Why

A zero-argument tool call sends {} (or omits arguments). For an ability that declares an input_schema, that value could reach WP_Ability::execute() as null, and validation rejected it:

Ability "example/get-info" has invalid input. Reason: input is not of type object.

An empty array is a valid empty object in WordPress (rest_is_object([]) is true), so passing [] instead of null lets a no-argument call through, while abilities with required properties still fail as they should.

Refs #229.

Testing

Verified live through the MCP Inspector over HTTP (default server, mcp-adapter-execute-ability and direct-tool paths), on WP 6.9 and 7.0:

Ability schema	Empty {} before	Empty {} after
object, all-optional	passed already	passes
array / non-object	failed ("not of type array")	passes

• PHPCS: clean
• PHPStan L8: clean
• Normalizer unit test updated (test_null_parameters_normalized_to_empty_array_with_schema)
• Full PHPUnit suite not run locally (tests wp-env would not start); please rely on CI.

Note on #229

I could not reproduce the reporter's exact case (an object schema failing on {}) on either v0.5.0 or trunk. This change fixes the real failure I did find (non-object schemas) and hardens the object path against null. It may not be the exact cause on their sites, so I'd keep #229 open until they share a failing ability's input_schema.

https://claude.ai/code/session_012RXWKvFkSm6LtNAYzPySHt

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.86%. Comparing base (90252e7) to head (05e0264).

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk     #230   +/-   ##
=========================================
  Coverage     87.86%   87.86%           
- Complexity     1245     1247    +2     
=========================================
  Files            53       53           
  Lines          4037     4039    +2     
=========================================
+ Hits           3547     3549    +2     
  Misses          490      490           

Flag	Coverage Δ
unit	87.86% <100.00%> (+<0.01%)	⬆️

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[Copilot]

Pull request overview

This PR adjusts how ability parameters are normalized when invoking WordPress Abilities through MCP, specifically ensuring schema-defining abilities receive an empty array ([]) instead of null for empty or omitted arguments to avoid schema validation failures (refs #229).

Changes:

• Update AbilityArgumentNormalizer::normalize() to return [] (instead of null) when an ability has an input_schema and parameters are null or [].
• Update the unit test to assert the new null → [] behavior for schema-defining abilities.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
includes/Domain/Utils/AbilityArgumentNormalizer.php	Changes normalization rules for empty inputs depending on whether an input_schema exists.
tests/phpunit/Unit/Domain/Utils/AbilityArgumentNormalizerTest.php	Updates unit test expectations to match the new normalization behavior.

Comments suppressed due to low confidence (1)

tests/phpunit/Unit/Domain/Utils/AbilityArgumentNormalizerTest.php:106

• This test covers the new null→[] behavior for an object schema, but the PR description also calls out non-object schemas (e.g. type=array) being fixed. Adding a second assertion for an array schema would lock in the intended behavior and prevent regressions.

	public function test_null_parameters_normalized_to_empty_array_with_schema(): void {
		$ability = $this->create_ability_mock(
			array(
				'type'       => 'object',
				'properties' => array(

---

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[gziolo]

Client side: always send a non-empty parameters object, e.g. {"refresh": true}.
Ability side: add 'default' => array() to every registered input_schema (what we shipped).

Reading the problem statement described by @pkhaninejad in #229, I would expect that {} (empty object) gets properly converted to new stdClass() so it can get recognized as an object.

What if the author defines that the type of the input schema is either null or object? Would it be possible to still pass null as an argument?