Support restricting blocks to specific parents

README.md

@@ -25,6 +25,7 @@ Add blade templates to `views/blocks` which get and use ACF data. Each template
   EnqueueStyle:
   EnqueueScript:
   EnqueueAssets:
+  Parent:
 --}}
 ```
 
@@ -83,6 +84,7 @@ The options in the file header map to options in the [`acf_register_block_type`
 | `SupportsInnerBlocks` | This property allows the block to support the nesting of other blocks within it. | `true`  or `false` |_optional_ (defaults to `false`) |
 | `SupportsAlignText` | This property adds an alignment toolbar button similar to that seen when editing a paragraph of text. | `true`  or `false` |_optional_ (defaults to `false`) |
 | `SupportsAlignContent` | This property adds an alignment toolbar button similar to that seen when editing a core "Cover block" | `true`  or `false` |_optional_ (defaults to `false`) |
+| `Parent`           | An array of block types to restrict where this block can be used. Separate values with a space. | e.g. `core/column acf/parent-block` |_optional_ (defaults to usable anywhere)
 
 ## Creating ACF fields
 Once a block is created you'll be able to assign ACF fields to it using the standard Custom Fields interface in WordPress. We recommend using [sage-advanced-custom-fields](https://github.com/MWDelaney/sage-advanced-custom-fields) to keep your ACF fields in version control with Sage.

sage-acf-gutenberg-blocks.php

@@ -73,6 +73,7 @@
                     'enqueue_style'     => 'EnqueueStyle',
                     'enqueue_script'    => 'EnqueueScript',
                     'enqueue_assets'    => 'EnqueueAssets',
+                    'parent'            => 'Parent',
                 ]);
 
                 if (empty($file_headers['title'])) {
@@ -153,6 +154,13 @@
                     $data['supports']['multiple'] = $file_headers['supports_multiple'] === 'true' ? true : false;
                 }
 
+                // If the Parent header is set in the template, restrict this block to specific parent blocks
+                if (!empty($file_headers['parent'])) {
+                    $data['parent'] = array_map(function($name) {
+                        return validateBlockName($name);
+                    }, explode(' ', $file_headers['parent']));
+                }
+
                 // Register the block with ACF
                 \acf_register_block_type(apply_filters("sage/blocks/$slug/register-data", $data));
             }
@@ -236,6 +244,29 @@ function checkAssetPath(&$path)
     }
 }
 
+/**
+ * Validates the format of a block name string
+ *
+ * @param string $name
+ *
+ * @return void|string
+ */
+function validateBlockName($name) {
+    global $sage_error;
+
+    // A block name can only contain lowercase alphanumeric characters and dashes, and must begin with a letter.
+    // NOTE: this cannot check whether a block is valid and registered (since others may be registered after this),
+    // it just confirms the block name format is correct.
+    if (!preg_match('/^[a-z]+\/[a-z][a-z0-9-]+$/', $name)) {
+        $sage_error(__('Invalid parent block name format: ' . $name, 'sage'), __('Invalid parent block name', 'sage'));
+
+        // Return NULL for invalid block names.
+        return null;
+    }
+
+    return $name;
+}
+
 /**
  * Check if Sage 10 is used.
  *