[FIX][PHP-NEXTGEN] Missing tagged union discriminator literal (#20343) (#20356)

* fix: #20343

* chore: apply correct formatting
chore: build and package

---------

Co-authored-by: Christian Ascone <[email protected]>

---------

Co-authored-by: Christian Ascone <[email protected]>

Author: brianferri

modules/openapi-generator/src/main/resources/php-nextgen/model_generic.mustache

@@ -190,6 +190,12 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
         return self::$openAPIModelName;
     }
 
+{{#discriminator}}
+{{#discriminator.mappedModels}}
+    public const {{#lambda.uppercase}}{{discriminator.propertyName}}_{{#lambda.snakecase}}{{mappingName}}{{/lambda.snakecase}}{{/lambda.uppercase}} = '{{mappingName}}';
+{{/discriminator.mappedModels}}
+{{/discriminator}}
+{{^discriminator}}
     {{#vars}}
     {{#isEnum}}
     {{#allowableValues}}
@@ -199,6 +205,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
     {{/allowableValues}}
     {{/isEnum}}
     {{/vars}}
+{{/discriminator}}
 
     {{#vars}}
     {{#isEnum}}
@@ -210,8 +217,15 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
     public function {{getter}}AllowableValues()
     {
         return [
+{{#discriminator}}
+{{#discriminator.mappedModels}}
+            self::{{#lambda.uppercase}}{{discriminator.propertyName}}_{{#lambda.snakecase}}{{mappingName}}{{/lambda.snakecase}}{{/lambda.uppercase}},{{^-last}}
+{{/-last}}{{/discriminator.mappedModels}}
+{{/discriminator}}
+{{^discriminator}}
             {{#allowableValues}}{{#enumVars}}self::{{enumName}}_{{{name}}},{{^-last}}
             {{/-last}}{{/enumVars}}{{/allowableValues}}
+{{/discriminator}}
         ];
     }
 
@@ -233,18 +247,18 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
      */
     public function __construct(array $data = null)
     {
+        {{#discriminator}}
+        // Initialize discriminator property with the model name.
+        $this->container['{{discriminatorName}}'] = static::$openAPIModelName;
+
+        {{/discriminator}}
         {{#parentSchema}}
         parent::__construct($data);
 
         {{/parentSchema}}
         {{#vars}}
         $this->setIfExists('{{name}}', $data ?? [], {{#defaultValue}}{{{defaultValue}}}{{/defaultValue}}{{^defaultValue}}null{{/defaultValue}});
         {{/vars}}
-        {{#discriminator}}
-
-        // Initialize discriminator property with the model name.
-        $this->container['{{discriminatorName}}'] = static::$openAPIModelName;
-        {{/discriminator}}
     }
 
     /**

samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/Animal.php

@@ -233,6 +233,8 @@ public function getModelName(): string
         return self::$openAPIModelName;
     }
 
+    public const CLASS_NAME_CAT = 'CAT';
+    public const CLASS_NAME_DOG = 'DOG';
 
     /**
      * Associative array for storing property values
@@ -248,11 +250,11 @@ public function getModelName(): string
      */
     public function __construct(array $data = null)
     {
-        $this->setIfExists('class_name', $data ?? [], null);
-        $this->setIfExists('color', $data ?? [], 'red');
-
         // Initialize discriminator property with the model name.
         $this->container['class_name'] = static::$openAPIModelName;
+
+        $this->setIfExists('class_name', $data ?? [], null);
+        $this->setIfExists('color', $data ?? [], 'red');
     }
 
     /**

samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/ParentWithNullable.php

@@ -261,11 +261,11 @@ public function getTypeAllowableValues()
      */
     public function __construct(array $data = null)
     {
-        $this->setIfExists('type', $data ?? [], null);
-        $this->setIfExists('nullable_property', $data ?? [], null);
-
         // Initialize discriminator property with the model name.
         $this->container['type'] = static::$openAPIModelName;
+
+        $this->setIfExists('type', $data ?? [], null);
+        $this->setIfExists('nullable_property', $data ?? [], null);
     }
 
     /**