using kstate with power levels should mix them

matrix/api.js

@@ -169,7 +169,7 @@ async function profileSetAvatarUrl(mxid, avatar_url) {
 async function setUserPower(roomID, mxid, power) {
 	assert(roomID[0] === "!")
 	assert(mxid[0] === "@")
-	// Yes it's this hard https://github.com/matrix-org/matrix-appservice-bridge/blob/2334b0bae28a285a767fe7244dad59f5a5963037/src/components/intent.ts#L352
+	// Yes there's no shortcut https://github.com/matrix-org/matrix-appservice-bridge/blob/2334b0bae28a285a767fe7244dad59f5a5963037/src/components/intent.ts#L352
 	const powerLevels = await getStateEvent(roomID, "m.room.power_levels", "")
 	const users = powerLevels.users || {}
 	if (power != null) {

matrix/kstate.js

@@ -1,6 +1,7 @@
 // @ts-check
 
-const assert = require("assert")
+const assert = require("assert").strict
+const mixin = require("mixin-deep")
 
 /** Mutates the input. */
 function kstateStripConditionals(kstate) {
@@ -43,18 +44,34 @@ function diffKState(actual, target) {
 	// go through each key that it should have
 	for (const key of Object.keys(target)) {
 		if (!key.includes("/")) throw new Error(`target kstate's key "${key}" does not contain a slash separator; if a blank state_key was intended, add a trailing slash to the kstate key.`)
-		if (key in actual) {
+
+		if (key === "m.room.power_levels/") {
+			// Special handling for power levels, we want to deep merge the actual and target into the final state.
+			console.log(actual[key])
+			const temp = mixin({}, actual[key], target[key])
+			console.log(actual[key])
+			console.log(temp)
+			try {
+				assert.deepEqual(actual[key], temp)
+			} catch (e) {
+				// they differ. use the newly prepared object as the diff.
+				diff[key] = temp
+			}
+
+		} else if (key in actual) {
 			// diff
 			try {
 				assert.deepEqual(actual[key], target[key])
 			} catch (e) {
-				// they differ. reassign the target
+				// they differ. use the target as the diff.
 				diff[key] = target[key]
 			}
+
 		} else {
 			// not present, needs to be added
 			diff[key] = target[key]
 		}
+
 		// keys that are missing in "actual" will not be deleted on "target" (no action)
 	}
 	return diff

matrix/kstate.test.js

@@ -92,3 +92,57 @@ test("diffKState: detects new properties", t => {
 		}
 	)
 })
+
+test("diffKState: power levels are mixed together", t => {
+	const original = {
+		"m.room.power_levels/": {
+			"ban": 50,
+			"events": {
+				"m.room.name": 100,
+				"m.room.power_levels": 100
+			},
+			"events_default": 0,
+			"invite": 50,
+			"kick": 50,
+			"notifications": {
+				"room": 20
+			},
+			"redact": 50,
+			"state_default": 50,
+			"users": {
+				"@example:localhost": 100
+			},
+			"users_default": 0
+		}
+	}
+	const result = diffKState(original, {
+		"m.room.power_levels/": {
+			"events": {
+				"m.room.avatar": 0
+			}
+		}
+	})
+	t.deepEqual(result, {
+		"m.room.power_levels/": {
+			"ban": 50,
+			"events": {
+				"m.room.name": 100,
+				"m.room.power_levels": 100,
+				"m.room.avatar": 0
+			},
+			"events_default": 0,
+			"invite": 50,
+			"kick": 50,
+			"notifications": {
+				"room": 20
+			},
+			"redact": 50,
+			"state_default": 50,
+			"users": {
+				"@example:localhost": 100
+			},
+			"users_default": 0
+		}
+	})
+	t.notDeepEqual(original, result)
+})