feat(wpmc S3): Helpers::alt_get_field with do_shortcode + filter

Implements alt_get_field(): applies wpmc_alt_get_field_post_id filter for
post_id remapping, guards against missing ACF, runs do_shortcode on string
results, passes arrays/null through unchanged.  4 new tests; full suite
22 tests / 58 assertions green.

Note: Brain Monkey FunctionStub::__construct calls function_exists()
internally; expect() calls must precede when('function_exists')->alias()
in each test to avoid the alias intercepting the stub-creation check and
causing eval redeclaration errors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

includes/class-helpers.php

@@ -72,4 +72,14 @@ final class Helpers
         $parts = array_values(array_filter(explode('/', $path), static fn(string $p) => $p !== ''));
         return $parts[0] ?? null;
     }
+
+    public static function alt_get_field(string $selector, $post_id = false, bool $format_value = true)
+    {
+        $post_id = \apply_filters('wpmc_alt_get_field_post_id', $post_id, $selector);
+        if (!\function_exists('get_field')) {
+            return null;
+        }
+        $value = \get_field($selector, $post_id, $format_value);
+        return is_string($value) ? \do_shortcode($value) : $value;
+    }
 }

tests/HelpersTest.php

@@ -129,4 +129,63 @@ final class HelpersTest extends TestCase
 
         self::assertTrue(true);
     }
+
+    public function test_alt_get_field_applies_do_shortcode_to_string_values(): void
+    {
+        // expect() must come before when('function_exists') so Brain Monkey's
+        // FunctionStub::__construct can eval-define get_field() before the shim
+        // fakes function_exists('get_field') === true.
+        \Brain\Monkey\Functions\expect('get_field')
+            ->once()
+            ->with('headline', 5, true)
+            ->andReturn('Hello [bar]');
+        \Brain\Monkey\Functions\expect('do_shortcode')
+            ->once()
+            ->with('Hello [bar]')
+            ->andReturn('Hello World');
+        \Brain\Monkey\Functions\when('function_exists')->alias(function ($name) {
+            return $name === 'get_field';
+        });
+
+        self::assertSame('Hello World', Helpers::alt_get_field('headline', 5));
+    }
+
+    public function test_alt_get_field_returns_arrays_as_is(): void
+    {
+        // expect() before when('function_exists') to avoid FunctionStub seeing
+        // the shim and skipping the eval-declaration of get_field.
+        // do_shortcode is intentionally NOT registered: if the implementation
+        // calls it for a non-string, Brain Monkey throws MissingFunctionExpectations.
+        \Brain\Monkey\Functions\expect('get_field')
+            ->once()
+            ->andReturn(['a', 'b']);
+        \Brain\Monkey\Functions\when('function_exists')->alias(fn($n) => $n === 'get_field');
+
+        self::assertSame(['a', 'b'], Helpers::alt_get_field('list'));
+    }
+
+    public function test_alt_get_field_post_id_filter_overrides_caller_id(): void
+    {
+        \Brain\Monkey\Functions\expect('get_field')
+            ->once()
+            ->with('title', 99, true)
+            ->andReturn(null);
+        \Brain\Monkey\Functions\when('function_exists')->alias(fn($n) => $n === 'get_field');
+        \Brain\Monkey\Filters\expectApplied('wpmc_alt_get_field_post_id')
+            ->once()
+            ->with(5, 'title')
+            ->andReturn(99);
+
+        Helpers::alt_get_field('title', 5);
+        self::assertTrue(true);
+    }
+
+    public function test_alt_get_field_returns_null_when_acf_get_field_missing(): void
+    {
+        \Brain\Monkey\Functions\when('function_exists')->justReturn(false);
+        // get_field must never be called; not registering it means Brain Monkey
+        // throws if it is, which is stronger than ->never().
+
+        self::assertNull(Helpers::alt_get_field('anything'));
+    }
 }