Implement preserveSvg flag for srcSet() (#370)

Co-authored-by: Alex Morega <[email protected]>

docs/general-usage/graphql-types.rst

@@ -61,6 +61,7 @@ the root query type like so:
     srcSet(
         sizes: [Int]
         format: String
+        preserveSvg: Boolean
     ): String
     isSvg: Boolean!
 

grapple/types/images.py

@@ -59,6 +59,24 @@ def get_rendition_field_kwargs() -> dict[str, graphene.Scalar]:
     return kwargs
 
 
+def get_src_set_field_kwargs() -> dict[str, graphene.Scalar]:
+    """
+    Returns a list of kwargs for the srcSet field.
+    Extracted for convenience, to accommodate for the conditional logic needed for various Wagtail versions.
+    """
+    kwargs = {
+        "sizes": graphene.List(graphene.Int),
+        "format": graphene.String(),
+    }
+    if WAGTAIL_VERSION > (5, 0):
+        kwargs["preserve_svg"] = graphene.Boolean(
+            description="Prevents raster image operations (e.g. `format-webp`, `bgcolor`, etc.) being applied to SVGs. "
+            "More info: https://docs.wagtail.org/en/stable/topics/images.html#svg-images"
+        )
+
+    return kwargs
+
+
 def rendition_allowed(filter_specs: str) -> bool:
     """Checks a given rendition filter is allowed"""
     allowed_filters = grapple_settings.ALLOWED_IMAGE_FILTERS
@@ -110,9 +128,7 @@ class ImageObjectType(DjangoObjectType):
     collection = graphene.Field(lambda: CollectionObjectType, required=True)
     tags = graphene.List(graphene.NonNull(lambda: TagObjectType), required=True)
     rendition = graphene.Field(get_rendition_type, **get_rendition_field_kwargs())
-    src_set = graphene.String(
-        sizes=graphene.List(graphene.Int), format=graphene.String()
-    )
+    src_set = graphene.String(**get_src_set_field_kwargs())
     if WAGTAIL_VERSION > (5, 0):
         is_svg = graphene.Boolean(required=True)
 
@@ -181,6 +197,7 @@ def resolve_src_set(
         info: GraphQLResolveInfo,
         sizes: list[int],
         format: str | None = None,
+        preserve_svg: bool = False,
         **kwargs,
     ) -> str:
         """
@@ -191,7 +208,11 @@ def resolve_src_set(
         if instance.file.name is not None:
             rendition_list = [
                 ImageObjectType.resolve_rendition(
-                    instance, info, width=width, **format_kwarg
+                    instance,
+                    info,
+                    width=width,
+                    preserve_svg=preserve_svg,
+                    **format_kwarg,
                 )
                 for width in sizes
                 if rendition_allowed(f"width-{width}{filter_suffix}")

tests/test_image_types.py

@@ -230,9 +230,11 @@ def test_schema_for_svg_related_fields_and_arguments(self):
             field["name"]: field for field in results["data"]["__type"]["fields"]
         }
         rendition_args = {arg["name"]: arg for arg in mapping["rendition"]["args"]}
+        src_set_args = {arg["name"]: arg for arg in mapping["srcSet"]["args"]}
 
         self.assertNotIn("isSvg", mapping)
         self.assertNotIn("preserveSvg", rendition_args)
+        self.assertNotIn("preserveSvg", src_set_args)
 
 
 if WAGTAIL_VERSION >= (5, 0):
@@ -262,6 +264,7 @@ def test_schema_for_svg_related_fields_and_arguments(self):
                 field["name"]: field for field in results["data"]["__type"]["fields"]
             }
             rendition_args = {arg["name"]: arg for arg in mapping["rendition"]["args"]}
+            src_set_args = {arg["name"]: arg for arg in mapping["srcSet"]["args"]}
 
             self.assertIn("isSvg", mapping)
             self.assertEqual(mapping["isSvg"]["type"]["kind"], "NON_NULL")
@@ -271,6 +274,12 @@ def test_schema_for_svg_related_fields_and_arguments(self):
                 "Prevents raster image operations (e.g. `format-webp`, `bgcolor`, etc.) being applied to SVGs. "
                 "More info: https://docs.wagtail.org/en/stable/topics/images.html#svg-images",
             )
+            self.assertEqual(src_set_args["preserveSvg"]["type"]["name"], "Boolean")
+            self.assertEqual(
+                src_set_args["preserveSvg"]["description"],
+                "Prevents raster image operations (e.g. `format-webp`, `bgcolor`, etc.) being applied to SVGs. "
+                "More info: https://docs.wagtail.org/en/stable/topics/images.html#svg-images",
+            )
 
         def test_svg_rendition(self):
             query = """
@@ -310,6 +319,24 @@ def test_svg_rendition_with_raster_format_with_preserve_svg(self):
                 )
             )
 
+        def test_svg_src_set_with_raster_format_with_preserve_svg(self):
+            query = """
+            query ($id: ID!) {
+                image(id: $id) {
+                    srcSet(sizes: [100], format: "webp", preserveSvg: true)
+                }
+            }
+            """
+
+            results = self.client.execute(
+                query, variables={"id": self.example_svg_image.id}
+            )
+            self.assertTrue(
+                results["data"]["image"]["srcSet"]
+                .split()[0]
+                .endswith("test.width-100.svg")
+            )
+
         def test_svg_rendition_with_raster_format_without_preserve_svg(self):
             query = """
             query ($id: ID!) {
@@ -329,6 +356,23 @@ def test_svg_rendition_with_raster_format_without_preserve_svg(self):
                 "'SvgImage' object has no attribute 'save_as_webp'",
             )
 
+        def test_svg_src_set_with_raster_format_without_preserve_svg(self):
+            query = """
+            query ($id: ID!) {
+                image(id: $id) {
+                    srcSet(sizes: [100], format: "webp")
+                }
+            }
+            """
+
+            results = self.client.execute(
+                query, variables={"id": self.example_svg_image.id}
+            )
+            self.assertEqual(
+                results["errors"][0]["message"],
+                "'SvgImage' object has no attribute 'save_as_webp'",
+            )
+
         def test_svg_rendition_with_filters_passed_through_to_svg_safe_spec(self):
             # bgcolor is not one of the allowed filters, so we should end with an empty filter spec
             query = """