feat: Add a way for Cast classes to express when an attribute should be unset (removed)

app/Casts/CastFloatOrUnset.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Carsdotcom\LaravelJsonModel\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsInboundAttributes;
+
+class CastFloatOrUnset implements ShouldUnset, CastsInboundAttributes
+{
+    public static function shouldUnset(mixed $value): bool
+    {
+        return ($value === null);
+    }
+
+    public function set($model, string $key, $value, array $attributes)
+    {
+        if ($this->shouldUnset($value)) {
+            return null;
+        }
+        return (float)$value;
+    }
+}

app/Casts/CastNonEmptyStringOrUnset.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Carsdotcom\LaravelJsonModel\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsInboundAttributes;
+
+class CastNonEmptyStringOrUnset implements ShouldUnset, CastsInboundAttributes
+{
+    public static function shouldUnset(mixed $value): bool
+    {
+        return ($value === null || $value === '');
+    }
+
+    public function set($model, string $key, $value, array $attributes)
+    {
+        if ($this->shouldUnset($value)) {
+            return null;
+        }
+        return (string)$value;
+    }
+}

app/Casts/CastStringOrUnset.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Carsdotcom\LaravelJsonModel\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsInboundAttributes;
+
+class CastStringOrUnset implements ShouldUnset, CastsInboundAttributes
+{
+    public static function shouldUnset(mixed $value): bool
+    {
+        return ($value === null);
+    }
+
+    public function set($model, string $key, $value, array $attributes)
+    {
+        if ($this->shouldUnset($value)) {
+            return null;
+        }
+        return (string)$value;
+    }
+}

app/Casts/ShouldUnset.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Carsdotcom\LaravelJsonModel\Casts;
+
+interface ShouldUnset
+{
+    static function shouldUnset(mixed $value): bool;
+}

app/JsonModel.php

@@ -20,6 +20,7 @@
 use ArrayAccess;
 use Carsdotcom\JsonSchemaValidation\Exceptions\JsonSchemaValidationException;
 use Carsdotcom\JsonSchemaValidation\Traits\ValidatesWithJsonSchema;
+use Carsdotcom\LaravelJsonModel\Casts\ShouldUnset;
 use Carsdotcom\LaravelJsonModel\Contracts\CanCascadeEvents;
 use Carsdotcom\JsonSchemaValidation\Contracts\CanValidate;
 use Carsdotcom\LaravelJsonModel\Helpers\ClassUsesTrait;
@@ -621,4 +622,24 @@ public function hasJsonModelAttributes(): bool
     {
         return (new ClassUsesTrait())(class: $this, trait: HasJsonModelAttributes::class);
     }
+
+    /**
+     * Extends setAttribute to cooperate with casts that implement ShouldUnset.
+     * If the cast wishes, we'll *remove* the attribute from the Json representation.
+     * This lets us implement things like PATCH {"zip":null} to mean "remove ZIP, return to default behavior"
+     */
+    use HasAttributes {
+        setAttribute as protected eloquentSetAttribute;
+    }
+
+    public function setAttribute($key, $value) {
+        $castType = $this->hasCast($key) ? $this->getCastType($key) : null;
+        if (is_a($castType, ShouldUnset::class, true) && $castType::shouldUnset($value)) {
+                unset($this->attributes[$key]);
+                return $this;
+        }
+
+        $this->eloquentSetAttribute($key, $value);
+        return $this;
+    }
 }

tests/Unit/JsonModelTest.php

@@ -9,6 +9,9 @@
 namespace Tests\Unit;
 
 use Carsdotcom\JsonSchemaValidation\Exceptions\JsonSchemaValidationException;
+use Carsdotcom\LaravelJsonModel\Casts\CastFloatOrUnset;
+use Carsdotcom\LaravelJsonModel\Casts\CastNonEmptyStringOrUnset;
+use Carsdotcom\LaravelJsonModel\Casts\CastStringOrUnset;
 use Carsdotcom\LaravelJsonModel\CollectionOfJsonModels;
 use Carsdotcom\JsonSchemaValidation\SchemaValidator as SchemaValidator;
 use Carsdotcom\LaravelJsonModel\JsonModel;
@@ -849,6 +852,79 @@ public function testSafeUpdateRecursive(): void
         self::assertSame('CA', $jsonModel->address->country, 'attribute is invalid, revert to previous value');
         self::assertSame('Jeremy', $jsonModel->first_name, 'attribute is valid, set');
     }
+
+    public function testCastFloatOrUnset(): void
+    {
+        $jsonModel = new class extends JsonModel{
+            protected $casts = [
+                'fou' => CastFloatOrUnset::class
+            ];
+        };
+
+        self::assertFalse(isset($jsonModel->fou), "Initializes unset");
+        $jsonModel->fou = null;
+        self::assertFalse(isset($jsonModel->fou), "Stays unset on initialize to null");
+        $jsonModel->fou = 6.9;
+        self::assertSame(6.9, $jsonModel->fou, "Float is unchanged");
+        $jsonModel->fou = '6';
+        self::assertSame(6.0, $jsonModel->fou, "String is cast");
+        $jsonModel->fou = 9;
+        self::assertSame(9.0, $jsonModel->fou, "int is cast");
+        self::assertStringContainsString('"fou":9', $jsonModel->toJson());
+        $jsonModel->fou = null;
+        self::assertFalse(isset($jsonModel->fou), "Set to null unsets attribute");
+        self::assertStringNotContainsString('fou', $jsonModel->toJson());
+    }
+
+    public function testCastStringOrUnset(): void
+    {
+        $jsonModel = new class extends JsonModel{
+            protected $casts = [
+                'sou' => CastStringOrUnset::class
+            ];
+        };
+
+        self::assertFalse(isset($jsonModel->sou), "Initializes unset");
+        $jsonModel->sou = null;
+        self::assertFalse(isset($jsonModel->sou), "Stays unset on initialize to null");
+        $jsonModel->sou = 'happy happy';
+        self::assertSame('happy happy', $jsonModel->sou, "String is unchanged");
+        $jsonModel->sou = 6;
+        self::assertSame('6', $jsonModel->sou, "int is cast");
+        $jsonModel->sou = false;
+        self::assertSame('', $jsonModel->sou, "bool is cast");
+        self::assertStringContainsString('"sou":""', $jsonModel->toJson());
+        $jsonModel->sou = null;
+        self::assertFalse(isset($jsonModel->sou), "Set to null unsets attribute");
+        self::assertStringNotContainsString('sou', $jsonModel->toJson());
+    }
+
+    public function testCastNonEmptyStringOrUnset(): void
+    {
+        $jsonModel = new class extends JsonModel{
+            protected $casts = [
+                'sou' => CastNonEmptyStringOrUnset::class
+            ];
+        };
+
+        self::assertFalse(isset($jsonModel->sou), "Initializes unset");
+        $jsonModel->sou = null;
+        self::assertFalse(isset($jsonModel->sou), "Stays unset on initialize to null");
+        $jsonModel->sou = 'happy happy';
+        self::assertSame('happy happy', $jsonModel->sou, "String is unchanged");
+
+        $jsonModel->sou = '';
+        self::assertFalse(isset($jsonModel->sou), "Set to empty string unsets attribute");
+        self::assertStringNotContainsString('sou', $jsonModel->toJson());
+
+        $jsonModel->sou = 6;
+        self::assertSame('6', $jsonModel->sou, "int is cast");
+        self::assertStringContainsString('"sou":"6"', $jsonModel->toJson());
+
+        $jsonModel->sou = null;
+        self::assertFalse(isset($jsonModel->sou), "Set to null unsets attribute");
+        self::assertStringNotContainsString('sou', $jsonModel->toJson());
+    }
 }
 /**
  * These are classes and models needed to test inheritance, etc.