[6.x] Let modifiers opt into running on null

src/Modifiers/AcceptsNull.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Statamic\Modifiers;
+
+use Attribute;
+
+/**
+ * Runs the modifier for null values, which Antlers skips by default.
+ */
+#[Attribute(Attribute::TARGET_METHOD)]
+class AcceptsNull
+{
+}

src/Modifiers/CoreModifiers.php

@@ -345,6 +345,7 @@ public function bardHtml($value)
         return (new Augmentor(new Bard()))->augment($items);
     }
 
+    #[AcceptsNull]
     public function boolString($value)
     {
         if ($value == true) {
@@ -1296,6 +1297,7 @@ public function isBetween($value, $params, $context)
      *
      * @return bool
      */
+    #[AcceptsNull]
     public function isBlank($value)
     {
         return Stringy::isBlank($value);
@@ -2802,6 +2804,7 @@ public function toBool($value, $params)
      *
      * @return string
      */
+    #[AcceptsNull]
     public function toJson($value, $params)
     {
         $options = 0;

src/Modifiers/Loader.php

@@ -2,11 +2,14 @@
 
 namespace Statamic\Modifiers;
 
+use ReflectionMethod;
 use Statamic\Support\Str;
 use Statamic\View\State\StateManager;
 
 class Loader
 {
+    protected static $acceptsNull = [];
+
     /**
      * Loads a modifier.
      *
@@ -20,12 +23,31 @@ public function load($name)
             throw new ModifierNotFoundException($name);
         }
 
-        if (Str::contains($class = $modifiers->get($key), 'CoreModifiers@')) {
-            [$class, $method] = explode('@', $class);
-        }
+        [$class, $method] = $this->resolve($modifiers->get($key));
 
         StateManager::track($class);
 
-        return [app($class), $method ?? 'index'];
+        return [app($class), $method];
+    }
+
+    public function acceptsNull($name)
+    {
+        if (! $binding = app('statamic.modifiers')->get(Str::snake($name))) {
+            return false;
+        }
+
+        [$class, $method] = $this->resolve($binding);
+
+        return static::$acceptsNull[$binding] ??= method_exists($class, $method)
+            && (new ReflectionMethod($class, $method))->getAttributes(AcceptsNull::class);
+    }
+
+    protected function resolve($binding)
+    {
+        if (Str::contains($binding, 'CoreModifiers@')) {
+            return explode('@', $binding);
+        }
+
+        return [$binding, 'index'];
     }
 }

src/View/Antlers/Language/Runtime/ModifierManager.php

@@ -4,6 +4,7 @@
 
 use Illuminate\Support\Facades\Log;
 use Statamic\Fields\Value;
+use Statamic\Modifiers\Loader;
 use Statamic\Modifiers\ModifierException;
 use Statamic\Modifiers\Modify;
 use Statamic\Support\Str;
@@ -20,15 +21,6 @@ class ModifierManager
     public static $lastModifierName = null;
     const METHOD_MODIFIER = '{__method_args}';
 
-    /**
-     * Modifiers that should still run when the value is null.
-     *
-     * @var string[]
-     */
-    protected static $nullAwareModifiers = [
-        'bool_string',
-    ];
-
     public static function isModifier(ParameterNode $node)
     {
         if (self::$statamicModifiers == null) {
@@ -102,9 +94,9 @@ public static function guardRuntimeModifier($modifierName)
         return true;
     }
 
-    protected static function acceptsNull($modifierName)
+    public static function acceptsNull($modifierName)
     {
-        return in_array($modifierName, self::$nullAwareModifiers, true);
+        return app(Loader::class)->acceptsNull($modifierName);
     }
 
     public static function evaluate($value, Environment $env, ModifierChainNode $modifierChain, $context)

src/View/Antlers/Language/Runtime/NodeProcessor.php

@@ -2821,6 +2821,10 @@ protected function runModifier($modifier, $parameters, $data, $context = [])
             GlobalRuntimeState::$isEvaluatingUserData = $prevIsEvaluatingUserData;
         }
 
+        if ($value === null && ! ModifierManager::acceptsNull($modifier)) {
+            return null;
+        }
+
         try {
             return Modify::value($value)->context($context)->$modifier($parameters)->fetch();
         } catch (ModifierException $e) {

tests/Antlers/Runtime/CoreModifiersTest.php

@@ -10,6 +10,8 @@
 use Statamic\Fields\Fieldtype;
 use Statamic\Fields\Value;
 use Statamic\Fieldtypes\Text;
+use Statamic\Modifiers\AcceptsNull;
+use Statamic\Modifiers\Modifier;
 use Tests\Antlers\ParserTestCase;
 
 class CoreModifiersTest extends ParserTestCase
@@ -599,7 +601,7 @@ public function test_a_value_wrapping_null_short_circuits_modifiers_like_a_bare_
     {
         $data = ['wrapped' => new Value(null), 'bare' => null];
 
-        foreach (['sanitize', 'count', 'md5', 'is_blank', 'upper | md5'] as $modifiers) {
+        foreach (['sanitize', 'count', 'md5', 'is_alpha', 'upper | md5'] as $modifiers) {
             $this->assertSame('', $this->renderString("{{ bare | {$modifiers} }}", $data, true), $modifiers);
             $this->assertSame('', $this->renderString("{{ wrapped | {$modifiers} }}", $data, true), $modifiers);
         }
@@ -623,6 +625,34 @@ public function test_bool_string_outputs_false_for_null()
         $this->assertSame('FALSE', $this->renderString('{{ empty_field | bool_string | upper }}', $data, true));
         $this->assertSame('true', $this->renderString('{{ filled_field | bool_string }}', $data, true));
     }
+
+    public function test_core_modifiers_that_accept_null_run_for_empty_fields()
+    {
+        $data = ['empty_field' => new Value(null, 'empty_field', new Text)];
+
+        $this->assertSame('null', $this->renderString('{{ empty_field | to_json }}', $data, true));
+        $this->assertSame('null', $this->renderString('{{ empty_field | json }}', $data, true));
+        $this->assertSame('1', $this->renderString('{{ empty_field | is_blank }}', $data, true));
+    }
+
+    public function test_modifiers_marked_with_accepts_null_run_for_null()
+    {
+        (new class extends Modifier
+        {
+            protected static $handle = 'accepts_null';
+
+            #[AcceptsNull]
+            public function index($value)
+            {
+                return var_export($value, true);
+            }
+        })::register();
+
+        $data = ['bare' => null, 'wrapped' => new Value(null)];
+
+        $this->assertSame('NULL', $this->renderString('{{ bare | accepts_null }}', $data, true));
+        $this->assertSame('NULL', $this->renderString('{{ wrapped | accepts_null }}', $data, true));
+    }
 }
 
 class SimpleEntryObject implements Arrayable

tests/Antlers/Runtime/ParameterStyleModifierTest.php

@@ -4,6 +4,10 @@
 
 use Facades\Tests\Factories\EntryFactory;
 use Statamic\Entries\Collection;
+use Statamic\Fields\Value;
+use Statamic\Fieldtypes\Text;
+use Statamic\View\Antlers\Language\Exceptions\RuntimeException;
+use Statamic\View\Antlers\Language\Runtime\GlobalRuntimeState;
 use Statamic\View\Antlers\Language\Utilities\StringUtilities;
 use Tests\Antlers\Fixtures\Addon\Modifiers\VarTestModifier;
 use Tests\Antlers\ParserTestCase;
@@ -69,4 +73,27 @@ public function test_modifier_style_parameters_applies_brace_escape_sequences()
 
         $this->assertSame(['test{}', 'param_two{}'], VarTestModifier::$params);
     }
+
+    public function test_parameter_style_modifiers_skip_null_like_chained_modifiers()
+    {
+        $data = ['empty_field' => new Value(null, 'empty_field', new Text)];
+
+        $this->assertSame('', $this->renderString('{{ empty_field count="true" }}', $data, true));
+        $this->assertSame('null', $this->renderString('{{ empty_field to_json="true" }}', $data, true));
+    }
+
+    public function test_parameter_style_modifiers_check_access_before_skipping_null()
+    {
+        $banned = GlobalRuntimeState::$bannedModifierPaths;
+        GlobalRuntimeState::$bannedModifierPaths = ['upper'];
+        GlobalRuntimeState::$throwErrorOnAccessViolation = true;
+
+        $this->expectException(RuntimeException::class);
+
+        try {
+            $this->renderString('{{ empty_field upper="true" }}', ['empty_field' => new Value(null, 'empty_field', new Text)], true);
+        } finally {
+            GlobalRuntimeState::$bannedModifierPaths = $banned;
+        }
+    }
 }