fix: coerce empty maps structurally instead of corrupting string payloads

src/Kinds/K8sResource.php

@@ -145,21 +145,49 @@ public function toJson($options = 0, ?string $kind = null): string|false
     }
 
     /**
-     * Convert the object to its JSON representation, but
-     * escaping [] for {}. Optionally, you can specify
+     * Convert the object to its JSON representation, coercing empty
+     * map fields from [] to {}. Optionally, you can specify
      * the Kind attribute to replace.
-     *
-     * @return string
      */
     public function toJsonPayload(?string $kind = null): string|false
     {
-        $attributes = $this->toJson(JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES, $kind);
+        $coerced = $this->coerceEmptyArraysToObjects($this->toArray($kind));
+
+        return json_encode($coerced, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
+    }
+
+    /**
+     * Kubernetes map fields are encoded by PHP's json_encode as `[]` when empty,
+     * but the API expects `{}` for objects. Walk the decoded structure and convert
+     * every empty array into an empty object so the byte sequence is only ever
+     * changed at structural positions — never inside string scalars (which would
+     * corrupt embedded scripts such as `glob(...) ?: []`).
+     *
+     * A handful of genuine list fields must stay as `[]` even when empty; those
+     * keys are exempted by name at any nesting depth.
+     *
+     * @param  array<array-key, mixed>  $attributes
+     * @return array<array-key, mixed>
+     */
+    protected function coerceEmptyArraysToObjects(array $attributes): array
+    {
+        $emptyArrayLists = ['allowedTopologies', 'mountOptions', 'accessModes'];
+
+        foreach ($attributes as $key => $value) {
+            if (! is_array($value)) {
+                continue;
+            }
 
-        $attributes = str_replace(': []', ': {}', $attributes);
+            if ($value === []) {
+                if (! in_array($key, $emptyArrayLists, true)) {
+                    $attributes[$key] = (object) [];
+                }
 
-        $attributes = str_replace('"allowedTopologies": {}', '"allowedTopologies": []', $attributes);
-        $attributes = str_replace('"mountOptions": {}', '"mountOptions": []', $attributes);
-        $attributes = str_replace('"accessModes": {}', '"accessModes": []', $attributes);
+                continue;
+            }
+
+            $attributes[$key] = $this->coerceEmptyArraysToObjects($value);
+        }
 
         return $attributes;
     }

tests/JsonPayloadTest.php

@@ -0,0 +1,113 @@
+<?php
+
+namespace RenokiCo\PhpK8s\Test;
+
+use RenokiCo\PhpK8s\K8s;
+
+class JsonPayloadTest extends TestCase
+{
+    public function test_string_values_containing_empty_array_literal_are_not_corrupted()
+    {
+        $container = K8s::container()
+            ->setName('backup')
+            ->setImage('public.ecr.aws/docker/library/php', '8.4')
+            ->setCommand(['php', '-r', 'foreach (glob("/x/*") ?: [] as $file) { echo $file; }']);
+
+        $pod = $this->cluster->pod()
+            ->setName('backup')
+            ->setContainers([$container]);
+
+        $job = $this->cluster->job()
+            ->setName('backup')
+            ->setTemplate($pod);
+
+        $payload = $job->toJsonPayload();
+        $decoded = json_decode($payload, true);
+
+        $command = $decoded['spec']['template']['spec']['containers'][0]['command'][2];
+
+        $this->assertSame('foreach (glob("/x/*") ?: [] as $file) { echo $file; }', $command);
+        $this->assertStringNotContainsString('?: {}', $payload);
+    }
+
+    public function test_generic_colon_space_bracket_string_is_preserved()
+    {
+        $container = K8s::container()
+            ->setName('echo')
+            ->setImage('public.ecr.aws/docker/library/busybox')
+            ->setCommand(['/bin/sh', '-c', 'echo arr: [] done']);
+
+        $pod = $this->cluster->pod()
+            ->setName('echo')
+            ->setContainers([$container]);
+
+        $decoded = json_decode($pod->toJsonPayload(), true);
+
+        $this->assertSame('echo arr: [] done', $decoded['spec']['containers'][0]['command'][2]);
+    }
+
+    public function test_non_empty_list_arrays_stay_lists()
+    {
+        $container = K8s::container()
+            ->setName('echo')
+            ->setImage('public.ecr.aws/docker/library/busybox')
+            ->setCommand(['/bin/sh', '-c', 'true']);
+
+        $pod = $this->cluster->pod()
+            ->setName('echo')
+            ->setContainers([$container]);
+
+        $decoded = json_decode($pod->toJsonPayload(), true);
+
+        $this->assertTrue(array_is_list($decoded['spec']['containers']));
+        $this->assertCount(1, $decoded['spec']['containers']);
+    }
+
+    public function test_empty_map_fields_are_coerced_to_objects()
+    {
+        $configMap = $this->cluster->configmap()
+            ->setName('settings')
+            ->setLabels([])
+            ->setData([]);
+
+        $payload = $configMap->toJsonPayload();
+
+        $this->assertStringContainsString('"data": {}', $payload);
+        $this->assertStringContainsString('"labels": {}', $payload);
+    }
+
+    public function test_exempted_list_fields_stay_empty_arrays()
+    {
+        $storageClass = $this->cluster->storageClass()
+            ->setName('standard')
+            ->setProvisioner('csi.example.com');
+
+        $storageClass->setAttribute('mountOptions', []);
+        $storageClass->setAttribute('allowedTopologies', []);
+        $storageClass->setAttribute('accessModes', []);
+
+        $payload = $storageClass->toJsonPayload();
+
+        $this->assertStringContainsString('"mountOptions": []', $payload);
+        $this->assertStringContainsString('"allowedTopologies": []', $payload);
+        $this->assertStringContainsString('"accessModes": []', $payload);
+    }
+
+    public function test_nested_empty_map_deep_in_spec_is_coerced()
+    {
+        $container = K8s::container()
+            ->setName('echo')
+            ->setImage('public.ecr.aws/docker/library/busybox')
+            ->setCommand(['/bin/sh', '-c', 'true']);
+
+        $pod = $this->cluster->pod()
+            ->setName('echo')
+            ->setContainers([$container]);
+
+        $pod->setAttribute('spec.nodeSelector', []);
+
+        $payload = $pod->toJsonPayload();
+
+        $this->assertStringContainsString('"nodeSelector": {}', $payload);
+    }
+}