♻️ [#1068] -- refactor 'update for request' component processing pipe…

…line

Instead of using a fixed pipeline, the concerns are now moved to the component level
that can opt-in to request-specific component rewriting.

This should also lead to slightly more optimized code execution since we're looping
over a caching datastructure rather than looping over the entire component tree
over and over again.

src/openforms/formio/components/vanilla.py

@@ -4,6 +4,15 @@
 Custom component types (defined by us or third parties) need to be organized in the
 adjacent custom.py module.
 """
+from typing import Literal
+
+from rest_framework.request import Request
+from rest_framework.reverse import reverse
+
+from csp_post_processor import post_process_html
+from openforms.config.models import GlobalConfiguration
+from openforms.utils.urls import build_absolute_uri
+
 from ..formatters.formio import (
     CheckboxFormatter,
     CurrencyFormatter,
@@ -22,6 +31,7 @@
     TimeFormatter,
 )
 from ..registry import BasePlugin, register
+from ..typing import Component
 
 
 @register("default")
@@ -53,10 +63,28 @@ class PhoneNumber(BasePlugin):
     formatter = PhoneNumberFormatter
 
 
+class FileComponent(Component):
+    storage: Literal["url"]
+    url: str
+    useConfigFiletypes: bool
+    filePattern: str
+
+
 @register("file")
 class File(BasePlugin):
     formatter = FileFormatter
 
+    @staticmethod
+    def rewrite_for_request(component: FileComponent, request: Request):
+        # write the upload endpoint information
+        upload_endpoint = reverse("api:formio:temporary-file-upload")
+        component["url"] = build_absolute_uri(upload_endpoint, request=request)
+
+        # check if we need to apply "filePattern" modifications
+        if component.get("useConfigFiletypes", False):
+            config = GlobalConfiguration.get_solo()
+            component["filePattern"] = ",".join(config.form_upload_default_file_types)
+
 
 @register("textarea")
 class TextArea(BasePlugin):
@@ -101,3 +129,31 @@ class Radio(BasePlugin):
 @register("signature")
 class Signature(BasePlugin):
     formatter = SignatureFormatter
+
+
+class ContentComponent(Component):
+    html: str
+
+
+@register("content")
+class Content(BasePlugin):
+    """
+    Formio's WYSIWYG component.
+    """
+
+    # not really relevant as content components don't have values
+    formatter = DefaultFormatter
+
+    @staticmethod
+    def rewrite_for_request(component: ContentComponent, request: Request):
+        """
+        Ensure that the inline styles are made compatible with Content-Security-Policy.
+
+        .. note:: we apply Bleach and a CSS declaration allowlist as part of the
+           post-processor because content components are not purely "trusted" content
+           from form-designers, but can contain malicious user input if the form
+           designer uses variables inside the HTML. The form submission data is passed
+           as template context to these HTML blobs, posing a potential injection
+           security risk.
+        """
+        component["html"] = post_process_html(component["html"], request)

src/openforms/formio/dynamic_config/__init__.py

@@ -5,22 +5,44 @@
 """
 from typing import Optional
 
+from rest_framework.request import Request
+
 from openforms.typing import DataMapping
 
 from ..datastructures import FormioConfigurationWrapper
 from ..registry import register
 
-__all__ = ["apply_dynamic_configuration"]
+__all__ = ["rewrite_formio_components", "rewrite_formio_components_for_request"]
 
 
-def apply_dynamic_configuration(
+def rewrite_formio_components(
     configuration_wrapper: FormioConfigurationWrapper,
     data: Optional[DataMapping] = None,
 ) -> FormioConfigurationWrapper:
     """
     Loop over the formio configuration and mutate components in place.
+
+    :arg configuration_wrapper: Container object holding the Formio form configuration
+      to be updated (if applicable). The rewriting loops over all components one-by-one
+      and applies the changes.
+    :arg data: key-value mapping of variable name to variable value. If a submission
+      context is available, the variables of the submission are included here.
+    :arg request: The HTTP request received by the API view when rewriting is done as
+      part of an HTTP request-response cycle. This is ``None`` otherwise (e.g. in
+      background tasks).
     """
     data = data or {}  # normalize
     for component in configuration_wrapper:
         register.update_config(component, data=data)
     return configuration_wrapper
+
+
+def rewrite_formio_components_for_request(
+    configuration_wrapper: FormioConfigurationWrapper, request: Request
+) -> FormioConfigurationWrapper:
+    """
+    Loop over the formio configuration and inject request-specific configuration.
+    """
+    for component in configuration_wrapper:
+        register.update_config_for_request(component, request=request)
+    return configuration_wrapper

src/openforms/formio/registry.py

@@ -15,6 +15,8 @@
 
 from django.utils.translation import gettext as _
 
+from rest_framework.request import Request
+
 from openforms.plugins.plugin import AbstractBasePlugin
 from openforms.plugins.registry import BaseRegistry
 from openforms.typing import DataMapping
@@ -39,6 +41,11 @@ def __call__(self, component: Component, value: Any) -> Any:
         ...
 
 
+class RewriterForRequestProtocol(Protocol):
+    def __call__(self, component: Component, request: Request) -> None:
+        ...
+
+
 class BasePlugin(AbstractBasePlugin):
     """
     Base class for Formio component plugins.
@@ -57,6 +64,10 @@ class BasePlugin(AbstractBasePlugin):
     """
     Specify the normalizer callable to use for value normalization.
     """
+    rewrite_for_request: None | RewriterForRequestProtocol = None
+    """
+    Callback to invoke to rewrite plugin configuration for a given HTTP request.
+    """
 
     @property
     def verbose_name(self):
@@ -114,6 +125,21 @@ def update_config(
         plugin = self[component_type]
         plugin.mutate_config_dynamically(component, data)
 
+    def update_config_for_request(self, component: Component, request: Request) -> None:
+        """
+        Mutate the component in place for the given request context.
+        """
+        # if there is no plugin registered for the component, return the input
+        if (component_type := component["type"]) not in register:
+            return
+
+        # invoke plugin if exists
+        rewriter = self[component_type].rewrite_for_request
+        if rewriter is None:
+            return
+
+        rewriter(component, request)
+
     def handle_custom_types(
         self,
         configuration: FormioConfigurationWrapper,

src/openforms/formio/service.py

@@ -1,34 +1,42 @@
-from typing import Any, Optional
+"""
+Expose the public openforms.formio Python API.
+
+The service module exposes the functions/utilities that may be used by other Django
+apps/packages:
 
-from django.urls import reverse
+* Try to keep this module stable and avoid breaking changes - extensions may rely on this!
+* Keep it small! The actual implementation should be done in specialized subpackages or
+  submodules and only their 'public' API should be imported and used.
+"""
+from typing import Any, Optional
 
 import elasticapm
 from rest_framework.request import Request
 
-from csp_post_processor import post_process_html
 from openforms.forms.custom_field_types import handle_custom_types
 from openforms.prefill import inject_prefill
 from openforms.submissions.models import Submission
 from openforms.typing import DataMapping
 
 from .datastructures import FormioConfigurationWrapper
-from .dynamic_config import apply_dynamic_configuration
+from .dynamic_config import (
+    rewrite_formio_components,
+    rewrite_formio_components_for_request,
+)
 from .registry import register
 from .typing import Component
 from .utils import iter_components
 from .variables import inject_variables
 
 __all__ = [
     "get_dynamic_configuration",
-    "update_configuration_for_request",
     "normalize_value_for_component",
     "iter_components",
     "inject_variables",
     "format_value",
+    "rewrite_formio_components_for_request",
 ]
 
-from ..config.models import GlobalConfiguration
-
 
 def format_value(component: Component, value: Any, as_html: bool = False):
     return register.format(component, value, as_html=as_html)
@@ -42,8 +50,6 @@ def normalize_value_for_component(component: Component, value: Any) -> Any:
     return register.normalize(component, value)
 
 
-# TODO: it might be beneficial to memoize this function if it runs multiple times in
-# the context of the same request
 @elasticapm.capture_span(span_type="app.formio")
 def get_dynamic_configuration(
     config_wrapper: FormioConfigurationWrapper,
@@ -61,7 +67,8 @@ def get_dynamic_configuration(
         config_wrapper.configuration, request=request, submission=submission
     )
 
-    apply_dynamic_configuration(config_wrapper, data=data)
+    rewrite_formio_components(config_wrapper, data=data)
+
     # prefill is still 'special' even though it uses variables, as we specifically
     # set the `defaultValue` key to the resulting variable.
     # This *could* be refactored in the future by assigning a template expression to
@@ -70,46 +77,3 @@ def get_dynamic_configuration(
     # as checkboxes/dropdowns/radios/...
     inject_prefill(config_wrapper, submission)
     return config_wrapper
-
-
-def update_configuration_for_request(
-    config_wrapper: FormioConfigurationWrapper, request: Request
-) -> None:
-    """
-    Given a static Formio configuration, apply dynamic changes we always must do, like setting absolute urls.
-
-    The configuration is modified in the context of the provided :arg:`submission`.
-    """
-
-    # TODO move this to openforms.formio.dynamic_config
-    pipeline = (
-        update_urls_in_place,
-        update_default_file_types,
-        update_content_inline_csp,
-    )
-    for component in config_wrapper:
-        for function in pipeline:
-            function(component, request=request)
-
-
-def update_urls_in_place(component: Component, request: Request) -> None:
-    if component.get("type") == "file":
-        component["url"] = request.build_absolute_uri(
-            reverse("api:formio:temporary-file-upload")
-        )
-
-
-def update_default_file_types(component: Component, **kwargs) -> None:
-    if component.get("type") == "file" and component.get("useConfigFiletypes"):
-        config = GlobalConfiguration.get_solo()
-        component["filePattern"] = ",".join(config.form_upload_default_file_types)
-
-
-def update_content_inline_csp(component: Component, request: Request) -> None:
-    if component.get("type") == "content":
-        """
-        NOTE: we apply Bleach and a CSS declaration whitelist because content components are not purely "trusted" content from form-designers,
-        but can contain malicious user input if the form designer uses variables inside the HTML
-        (and the form submission data is passed as template context to those HTML blobs)
-        """
-        component["html"] = post_process_html(component["html"], request)

src/openforms/formio/tests/test_service.py

@@ -5,13 +5,13 @@
 
 from openforms.formio.service import (
     FormioConfigurationWrapper,
-    update_configuration_for_request,
+    rewrite_formio_components_for_request,
 )
 
 
 class ServiceTestCase(TestCase):
     @patch("csp_post_processor.processor.get_html_id", return_value="1234")
-    def test_update_configuration_for_request(self, m):
+    def test_rewrite_formio_components_for_request(self, m):
         request = RequestFactory().get("/", HTTP_X_CSP_NONCE="dGVzdA==")
 
         configuration = {
@@ -31,7 +31,7 @@ def test_update_configuration_for_request(self, m):
                 },
             ],
         }
-        update_configuration_for_request(
+        rewrite_formio_components_for_request(
             FormioConfigurationWrapper(configuration), request
         )
         with self.subTest("temporary file upload url"):

src/openforms/forms/api/serializers/form_definition.py

@@ -5,7 +5,7 @@
 from drf_spectacular.utils import extend_schema_field
 from rest_framework import serializers
 
-from openforms.formio.service import update_configuration_for_request
+from openforms.formio.service import rewrite_formio_components_for_request
 
 from ...models import Form, FormDefinition
 from ...validators import validate_form_definition_is_reusable
@@ -50,10 +50,15 @@ def get_admin_url(self, obj: Form) -> str:
 class FormDefinitionSerializer(serializers.HyperlinkedModelSerializer):
     def to_representation(self, instance):
         representation = super().to_representation(instance=instance)
-        # set upload urls etc
-        # TODO: move this to openforms.formio.dynamic_config
-        update_configuration_for_request(
-            instance.configuration_wrapper, request=self.context["request"]
+        # Finalize formio component configuration with dynamic parts that depend on the
+        # HTTP request. Note that this is invoked through:
+        # 1. the :class:`openforms.submissions.api.serializers.SubmissionStepSerializer`
+        #    for the dynamic formio configuration in the context of a submission.
+        # 2. The serializers/API endpoints of :module:`openforms.forms.api` for
+        #    'standalone' use/introspection.
+        rewrite_formio_components_for_request(
+            instance.configuration_wrapper,
+            request=self.context["request"],
         )
         representation["configuration"] = instance.configuration_wrapper.configuration
         return representation