Automatically trim redundant mixins (#1399)

Co-authored-by: saschanaz <saschanaz@users.noreply.github.com>

Author: saschanaz

inputfiles/removedTypes.jsonc

@@ -51,25 +51,7 @@
                         "elementFromPoint": null,
                         "elementsFromPoint": null
                     }
-                },
-                "implements": ["GeometryUtils"]
-            },
-            "Element": {
-                "implements": ["GeometryUtils", "Region"]
-            },
-            "Navigator": {
-                "implements": [
-                    "NavigatorBadge",
-                    "NavigatorDeviceMemory",
-                    "NavigatorFonts",
-                    "NavigatorGPU",
-                    "NavigatorML",
-                    "NavigatorNetworkInformation",
-                    "NavigatorUA"
-                ]
-            },
-            "NetworkInformation": {
-                "implements": ["NetworkInformationSaveData"]
+                }
             },
             "Response": {
                 "methods": {
@@ -91,9 +73,6 @@
                     }
                 }
             },
-            "SVGElement": {
-                "implements": ["SVGElementInstance"]
-            },
             "SVGFEGaussianBlurElement": {
                 "constants": {
                     "constant": {
@@ -104,9 +83,6 @@
                     }
                 }
             },
-            "Text": {
-                "implements": ["GeometryUtils"]
-            },
             "WebGLBuffer": {
                 "extends": null
             },
@@ -142,17 +118,6 @@
             },
             "WebGLVertexArrayObjectOES": {
                 "extends": null
-            },
-            "WorkerNavigator": {
-                "implements": [
-                    "NavigatorBadge",
-                    "NavigatorDeviceMemory",
-                    "NavigatorFonts",
-                    "NavigatorGPU",
-                    "NavigatorML",
-                    "NavigatorNetworkInformation",
-                    "NavigatorUA"
-                ]
             }
         }
     },
@@ -576,6 +541,18 @@
             }
         }
     },
+    "mixins": {
+        "mixin":{
+            "NavigatorNetworkInformation": {
+                "properties": {
+                    "property": {
+                        // https://github.com/mdn/browser-compat-data/pull/17824
+                        "connection": null
+                    }
+                }
+            }
+        }
+    },
     "typedefs": {
         "typedef": [
             "ArrayBufferView"

src/build/bcd.ts

@@ -52,8 +52,9 @@ function isSuitable(
 
 export function getRemovalData(webidl: Browser.WebIdl): Browser.WebIdl {
   return mapToBcdCompat(webidl, ({ key, parentKey, compat, mixin }) => {
-    // Allow all mixins for now, but not their members
-    // Ultimately expose.ts should be updated to check empty mixins
+    // Allow all mixins here, but not their members.
+    // Empty mixins created by this will be managed by exposed.ts.
+    // (It's better to manage mixins there as mixins can also conditionally be empty by exposure settings)
     if (mixin && !parentKey) {
       return;
     }

src/build/expose.ts

@@ -8,6 +8,7 @@ import {
   mapToArray,
   arrayToMap,
 } from "./helpers.js";
+import { isEmptyRecord } from "./utils/record.js";
 
 class LoggedSet extends Set<string> {
   private unvisited: Set<string>;
@@ -52,6 +53,24 @@ export function getExposedTypes(
     );
   }
 
+  if (webidl.mixins) {
+    const allIncludes = Object.values(filtered.interfaces?.interface || {})
+      .map((i) => i.implements || [])
+      .flat();
+    const mixins = deepFilter(webidl.mixins.mixin, (o) => exposesTo(o, target));
+    filtered.mixins!.mixin = filterProperties(
+      mixins,
+      (m: Browser.Interface) => allIncludes.includes(m.name) && !isEmptyMixin(m)
+    );
+    for (const value of Object.values(filtered.interfaces!.interface || {})) {
+      if (value.implements) {
+        value.implements = value.implements.filter(
+          (i) => !!filtered.mixins!.mixin[i]
+        );
+      }
+    }
+  }
+
   const knownIDLTypes = new Set([
     ...followTypeReferences(webidl, filtered.interfaces!.interface),
     ...followTypeReferences(
@@ -92,10 +111,6 @@ export function getExposedTypes(
     );
   if (webidl.enums)
     filtered.enums!.enum = filterProperties(webidl.enums.enum, isKnownName);
-  if (webidl.mixins) {
-    const mixins = deepFilter(webidl.mixins.mixin, (o) => exposesTo(o, target));
-    filtered.mixins!.mixin = filterProperties(mixins, isKnownName);
-  }
 
   for (const unvisited of forceKnownTypesLogged.unvisitedValues()) {
     console.warn(`${unvisited} is redundant in knownTypes.json (${target})`);
@@ -264,3 +279,14 @@ function flattenType(type: Browser.Typed[]) {
   }
   throw new Error("Cannot process empty union type");
 }
+
+function isEmptyMixin(i?: Browser.Interface) {
+  return (
+    !!i?.mixin &&
+    isEmptyRecord(i.properties?.property) &&
+    isEmptyRecord(i.methods?.method) &&
+    isEmptyRecord(i.constants?.constant) &&
+    !i.anonymousMethods?.method.length &&
+    !i.events?.event.length
+  );
+}