🐛 [#4908] Revise how attachments are processed

There was a bug with the previous attachment processing, where attachments would get overwritten if multiple were uploaded. Now, an object will be returned with the 'file_name' and 'content' properties in case of a single file component (or 'None' if no file was uploaded). And in case of a multiple files component, it will be a list of these file objects (or an empty list if no file was uploaded). This keeps the data type consistent, and we can give guarantees that an object will always have the file_name and content keys.

src/openforms/registrations/contrib/json_dump/plugin.py

@@ -6,7 +6,12 @@
 
 from zgw_consumers.client import build_client
 
-from openforms.submissions.models import Submission
+from openforms.formio.typing import Component
+from openforms.submissions.models import (
+    Submission,
+    SubmissionFileAttachment,
+    SubmissionValueVariable,
+)
 from openforms.typing import JSONObject
 
 from ...base import BasePlugin  # openforms.registrations.base
@@ -34,15 +39,8 @@ def register_submission(
             if key in options["form_variables"]
         }
 
-        # Encode (base64) and add attachments to values dict if their form keys were specified in the
-        # form variables list
-        for attachment in submission.attachments:
-            if attachment.form_key not in options["form_variables"]:
-                continue
-            options["form_variables"].remove(attachment.form_key)
-            with attachment.content.open("rb") as f:
-                f.seek(0)
-                values[attachment.form_key] = base64.b64encode(f.read()).decode()
+        # Process attachments
+        self.process_variables(submission, values)
 
         # Generate schema
         # TODO: will be added in #4980. Hardcoded example for now.
@@ -77,3 +75,69 @@ def register_submission(
     def check_config(self) -> None:
         # Config checks are not really relevant for this plugin right now
         pass
+
+    @staticmethod
+    def process_variables(submission: Submission, values: JSONObject):
+        """Process variables.
+
+        File components need special treatment, as we send the content of the file
+        encoded with base64, instead of the output from the serializer.
+        """
+        state = submission.load_submission_value_variables_state()
+
+        for key in values.keys():
+            variable = state.variables.get(key)
+            if variable is None:
+                # None for static variables
+                continue
+
+            component = get_component(variable)
+            if component is None or component["type"] != "file":
+                continue
+
+            encoded_attachments = [
+                {
+                    "file_name": attachment.original_name,
+                    "content": encode_attachment(attachment),
+                }
+                for attachment in submission.attachments
+                if attachment.form_key == key
+            ]
+
+            match (
+                multiple := component.get("multiple", False),
+                n_attachments := len(encoded_attachments)
+            ):
+                case False, 0:
+                    values[key] = None
+                case False, 1:
+                    values[key] = encoded_attachments[0]
+                case True, _:
+                    values[key] = encoded_attachments
+                case _:
+                    raise ValueError(
+                        f"Combination of multiple ({multiple}) and number of "
+                        f"attachments ({n_attachments}) is not allowed."
+                    )
+
+def encode_attachment(attachment: SubmissionFileAttachment) -> str:
+    """Encode an attachment using base64
+
+    :param attachment: Attachment to encode
+    :returns: Encoded base64 data as a string
+    """
+    with attachment.content.open("rb") as f:
+        f.seek(0)
+        return base64.b64encode(f.read()).decode()
+
+
+def get_component(variable: SubmissionValueVariable) -> Component:
+    """Get the component from a submission value variable.
+
+    :param variable: SubmissionValueVariable
+    :return component: Component
+    """
+    config_wrapper = variable.form_variable.form_definition.configuration_wrapper
+    component = config_wrapper.component_map[variable.key]
+
+    return component

src/openforms/registrations/contrib/json_dump/tests/test_backend.py

@@ -116,3 +116,65 @@ def test_exception_raised_when_service_returns_unexpected_status_code(self):
 
         with self.assertRaises(RequestException):
             json_plugin.register_submission(submission, json_form_options)
+
+    def test_multiple_file_uploads(self):
+        submission = SubmissionFactory.from_components(
+            [{"key": "file", "type": "file", "multiple": True}],
+            completed=True,
+            submitted_data={
+                "file": [
+                    {
+                        "url": "some://url",
+                        "name": "file1.txt",
+                        "type": "application/text",
+                        "originalName": "file1.txt",
+                    },
+                    {
+                        "url": "some://url",
+                        "name": "file2.txt",
+                        "type": "application/text",
+                        "originalName": "file2.txt",
+                    }
+                ],
+            },
+        )
+
+        SubmissionFileAttachmentFactory.create(
+            form_key="file",
+            submission_step=submission.submissionstep_set.get(),
+            file_name="file1.txt",
+            content_type="application/text",
+            content__data=b"This is example content.",
+            _component_configuration_path="components.2",
+            _component_data_path="file",
+        )
+
+        SubmissionFileAttachmentFactory.create(
+            form_key="file",
+            submission_step=submission.submissionstep_set.get(),
+            file_name="file2.txt",
+            content_type="application/text",
+            content__data=b"Content example is this.",
+            _component_configuration_path="components.2",
+            _component_data_path="file",
+        )
+
+        json_form_options = dict(
+            service=(ServiceFactory(api_root="http://localhost:80/")),
+            relative_api_endpoint="json_plugin",
+            form_variables=["file"],
+        )
+        json_plugin = JSONDumpRegistration("json_registration_plugin")
+        set_submission_reference(submission)
+
+        expected_values = {
+            "file": {
+                "file1.txt": "VGhpcyBpcyBleGFtcGxlIGNvbnRlbnQu",  # This is example content.
+                "file2.txt": "Q29udGVudCBleGFtcGxlIGlzIHRoaXMu",  # Content example is this.
+            },
+        }
+
+        res = json_plugin.register_submission(submission, json_form_options)
+        res_json = res["api_response"]
+
+        self.assertEqual(res_json["data"]["values"], expected_values)