Carry standalone form-control inputs as runtime islands (clears unsupported_input)

php-transformer/src/HtmlToBlocks/HtmlTransformer.php

@@ -2165,6 +2165,10 @@ private function convertElement(DOMElement $element, array &$fallbacks, bool $ca
             return $readableControlBlock;
         }
 
+        if ( $this->preserveStandaloneFormControlAsRuntimeIsland($element) ) {
+            return null;
+        }
+
         if ( $captureUnsupported ) {
             $fallback = array(
                 'type'            => 'unsupported_element',
@@ -5200,6 +5204,36 @@ private function readableFormControlBlockFromElement(DOMElement $element): ?arra
         return $this->createBlock('core/paragraph', array_merge($this->presentationAttributes($element), array( 'content' => $summary )), array(), $element);
     }
 
+    /**
+     * Preserve a standalone form control that has no faithful native block or
+     * readable static approximation as a bounded runtime island instead of an
+     * unsupported-element loss.
+     *
+     * Reached only after the readable-control and search paths decline, so the
+     * control is one whose behavior depends on a client runtime: file/hidden/
+     * color/date-style inputs core blocks cannot represent, or any control
+     * carrying inline event handlers. The source markup is carried in the
+     * island snippet so the behavior can be re-attached, and no misleading
+     * static text is emitted for controls (often hidden) that have no visual
+     * representation. This yields a `preserved_runtime_island` outcome rather
+     * than an `unsupported_element_loss`.
+     */
+    private function preserveStandaloneFormControlAsRuntimeIsland(DOMElement $element): bool
+    {
+        $tagName = strtolower($element->tagName);
+        if ( ! in_array($tagName, array( 'input', 'select', 'textarea' ), true) ) {
+            return false;
+        }
+
+        $this->recordRuntimeIsland($element, 'control', 'form_control_requires_runtime', 'client_form_control_runtime', array(
+            'control'          => $this->formControlMetadata($element),
+            'events'           => $this->eventMetadata($element),
+            'required_scripts' => $this->requiredScriptsForElement($element),
+        ));
+
+        return true;
+    }
+
     /**
      * @return array<string, mixed>|null
      */

php-transformer/tests/fixtures/parity/html-standalone-input-runtime-island-preserved.json

@@ -0,0 +1,37 @@
+{
+  "schema": "blocks-engine/php-transformer/parity-fixture/v1",
+  "name": "html-standalone-input-runtime-island-preserved",
+  "description": "Preserves a standalone non-readable form-control input (a hidden file picker) as a bounded runtime island with an acceptable runtime_island_preserved loss class instead of an unsupported_element_loss fallback.",
+  "source_reference": {
+    "repo": "php-transformer",
+    "path": "tests/fixtures/parity/html-standalone-input-runtime-island-preserved.json",
+    "notes": "Mirrors the corpus JSON-import file inputs in 58-infinite-whiteboard, 59-spreadsheet, 60-node-editor, 64-kanban-board, 67-dataviz-studio, and 68-drum-machine, which previously produced unsupported_input (html_unsupported_element) findings."
+  },
+  "legacy_comparison": {
+    "skip": true,
+    "reason": "This upstream primitive fixture has no downstream legacy comparison."
+  },
+  "operation": "html_transformer.transform",
+  "input": {
+    "content": "<input type=\"file\" id=\"import-file\" accept=\"application/json,.json\" hidden>"
+  },
+  "expected_blocks": [],
+  "expected_fallbacks": [],
+  "expect": [
+    { "path": "status", "assert": "equals", "value": "success" },
+    { "path": "blocks", "assert": "count", "count": 0 },
+    { "path": "fallbacks", "assert": "count", "count": 0 },
+    { "path": "source_reports.html.runtime_islands", "assert": "count", "count": 1 },
+    { "path": "source_reports.html.runtime_islands.0.kind", "assert": "equals", "value": "control" },
+    { "path": "source_reports.html.runtime_islands.0.tag", "assert": "equals", "value": "input" },
+    { "path": "source_reports.html.runtime_islands.0.selector", "assert": "equals", "value": "#import-file" },
+    { "path": "source_reports.html.runtime_islands.0.preservation_reason", "assert": "equals", "value": "form_control_requires_runtime" },
+    { "path": "source_reports.html.runtime_islands.0.source_snippet", "assert": "contains", "value": "<input type=\"file\" id=\"import-file\"" },
+    { "path": "diagnostics.1.code", "assert": "equals", "value": "preserved_runtime_island" },
+    { "path": "diagnostics.1.loss_class", "assert": "equals", "value": "runtime_island_preserved" },
+    { "path": "diagnostics.1.conversion_classification", "assert": "equals", "value": "runtime_island_preserved" },
+    { "path": "coverage.0.fallback_count", "assert": "equals", "value": 0 },
+    { "path": "serialized_blocks", "assert": "not_contains", "value": "<!-- wp:html" },
+    { "path": "serialized_blocks", "assert": "not_contains", "value": "<input" }
+  ]
+}