metadata: add example-request-only-empty recipe for empty-output testing

New cookbook recipe that copies fas_config/request_only_empty_metadata.json verbatim into example_metadata.json. Every recipe field (filename, title, description, ...) ends up as the empty string, so a mapping that wires one of these to an easydb target sees an empty value flow through the recipe path in fylr's internal/api/object/file_metadata.go.

Used by the ticket-79607 apitest in fylr to reproduce the production weblink-cleared bug without needing the ai-metadata plugin (which isn't part of the apitest CI). Registered in custom_produce.yml as metadata_request_only so it doesn't run on every upload.

see #79607

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: martinrode

fas_config/cookbook_metadata_example.yml

@@ -55,6 +55,46 @@ recipes:
               - "require('fs').createReadStream(process.argv[1]).pipe(process.stdout)"
               - "%_exec.pluginDir%/fas_config/recipe_dynamic_request_only.json"
 
+  # example-request-only-empty mirrors example-request-only but writes a
+  # metadata JSON where every field is an empty string. Used by ticket
+  # 79607's apitest to drive the "recipe ran but delivered no data" path
+  # without needing the ai-metadata plugin in CI: any mapping that targets
+  # a custom-data-type sub-field through this recipe will see an empty
+  # value flow through the recipe loop in file_metadata.go, which was
+  # silently clearing the existing CDT (e.g. weblink.url) before the fix.
+  example-request-only-empty:
+    class: _metadata
+    metadata:
+      - file: "example_metadata.json"
+    displayname:
+      de-DE: Beispiel Metadaten Mapping (empty)
+      en-US: Example Metadaten Mapping (empty)
+    execs:
+      - service: node
+        commands:
+          - prog: node
+            args:
+              - "-e"
+              # copy request_only_empty_metadata.json (arg 1) verbatim into example_metadata.json (arg 2)
+              - "require('fs').createReadStream(process.argv[1]).pipe(require('fs').createWriteStream(process.argv[2]));"
+              - "%_exec.pluginDir%/fas_config/request_only_empty_metadata.json"
+              - type: file_out
+                file:
+                  name: "example_metadata.json"
+    # dynamic.exec serves the field schema (filename/title/description/...);
+    # same shape as example-request-only so existing mapping field names work.
+    dynamic:
+      exec:
+        service: node
+        commands:
+          - prog: node
+            stdout:
+              type: body
+            args:
+              - "-e"
+              - "require('fs').createReadStream(process.argv[1]).pipe(process.stdout)"
+              - "%_exec.pluginDir%/fas_config/recipe_dynamic_request_only.json"
+
   example-request-only-with-error:
     class: _metadata
     metadata:

fas_config/custom_produce.yml

@@ -25,6 +25,15 @@ custommetadata:
     extensions:
       - png
       - jpg
+  - recipename: fylr_example:example_metadata:example-request-only-empty
+    includeversions: false
+    # request-only: the recipe runs lazily, only when a metadata mapping
+    # actually references it. Used by ticket 79607's apitest to drive the
+    # "recipe ran but delivered no data" path without the ai-metadata plugin.
+    metadata_request_only: true
+    extensions:
+      - png
+      - jpg
 
 classes:
   image:

fas_config/request_only_empty_metadata.json

@@ -0,0 +1,11 @@
+{
+    "plugin-example": {
+        "chat-gpt": {
+            "fields": {
+                "filename": "",
+                "description": "",
+                "title": ""
+            }
+        }
+    }
+}