fix(#2): don't copy level 1 obj refs

Author: alexsasharegan

Diff for: src/index.ts

@@ -1,103 +1,113 @@
 import { VNodeData } from "vue"
 
-const keys = Object.keys
-
 function concat(...items: any[]): any[]
 function concat(...items: any[][]): any[]
 function concat() {
-  return Array.prototype.concat.apply([], arguments)
+	return Array.prototype.concat.apply([], arguments)
+}
+
+function cp(value: any): any {
+	if (typeof value != "object" || value == null) {
+		return value
+	}
+	if (Array.isArray(value)) {
+		return [...value]
+	}
+	return Object.assign({}, value)
 }
 
 /**
  * Intelligently merges data for createElement.
  * Merges arguments left to right, preferring the right argument.
  * Returns new VNodeData object.
  */
-function mergeData(...vNodeData: VNodeData[]): VNodeData
-function mergeData() {
-  // Start by copying the first arg into a fresh object
-  let mergeTarget = { ...arguments[0] }
+function mergeData(...vNodeData: VNodeData[]): VNodeData {
+	let mergeTarget: VNodeData & { [key: string]: any } = {}
+	let i: number = 0
+	let argLen: number = arguments.length
+	let prop: string
 
-  // Allow for variadic argument length.
-  // Skip first argument that was assigned to mergeTarget.
-  for (let i = 1; i < arguments.length; i++) {
-    // Iterate through the data properties and execute merge strategies
-    // Object.keys eliminates need for hasOwnProperty call
-    for (const prop of keys(arguments[i])) {
-      // If strictly undefined, simply assign value and continue
-      if (mergeTarget[prop] === undefined) {
-        mergeTarget[prop] = arguments[i][prop]
-        continue
-      }
+	// Allow for variadic argument length.
+	for (; i < argLen; i++) {
+		// Iterate through the data properties and execute merge strategies
+		// Object.keys eliminates need for hasOwnProperty call
+		for (prop of Object.keys(arguments[i])) {
+			// If strictly undefined, copy value and continue
+			if (mergeTarget[prop] === undefined) {
+				mergeTarget[prop] = cp(arguments[i][prop])
+				continue
+			}
 
-      switch (prop) {
-        // Array merge strategy (array concatenation)
-        case "class":
-        case "style":
-        case "directives":
-          // Repackaging in an array allows Vue runtime
-          // to merge class/style bindings regardless of type.
-          mergeTarget[prop] = concat(mergeTarget[prop], arguments[i][prop])
-          break
+			switch (prop) {
+				// Array merge strategy (array concatenation)
+				case "class":
+				case "style":
+				case "directives":
+					if (!Array.isArray(mergeTarget[prop])) {
+						mergeTarget[prop] = []
+					}
+					// Repackaging in an array allows Vue runtime
+					// to merge class/style bindings regardless of type.
+					mergeTarget[prop] = concat(mergeTarget[prop], arguments[i][prop])
+					break
 
-        // Space delimited string concatenation strategy
-        case "staticClass":
-          // If we get here,
-          // value !== undefined,
-          // but it could still be an empty string.
-          if (mergeTarget[prop]) {
-            // Not an empty string, so concatenate
-            mergeTarget[prop] = mergeTarget[prop].trim() + " "
-          }
-          mergeTarget[prop] += arguments[i][prop].trim()
-          break
+				// Space delimited string concatenation strategy
+				case "staticClass":
+					// undefined values are handled above.
+					if (mergeTarget[prop]) {
+						// Not an empty string, so concatenate
+						mergeTarget[prop] += " "
+					}
+					mergeTarget[prop] += arguments[i][prop].trim()
+					break
 
-        // Object, the properties of which to merge via array merge strategy (array concatenation).
-        // Callback merge strategy merges callbacks to the beginning of the array,
-        // so that the last defined callback will be invoked first.
-        // This is done since to mimic how Object.assign merging
-        // uses the last given value to assign.
-        case "on":
-        case "nativeOn":
-          // If we get here,
-          // value must be of type Object.
-          for (const event of keys(arguments[i][prop])) {
-            // Concat function to array of functions if callback present.
-            if (mergeTarget[prop][event]) {
-              // Insert current iteration data in beginning of merged array.
-              mergeTarget[prop][event] = concat(arguments[i][prop][event], mergeTarget[prop][event])
-            } else {
-              // Straight assign.
-              mergeTarget[prop][event] = arguments[i][prop][event]
-            }
-          }
-          break
+				// Object, the properties of which to merge via array merge strategy (array concatenation).
+				// Callback merge strategy merges callbacks to the beginning of the array,
+				// so that the last defined callback will be invoked first.
+				// This is done since to mimic how Object.assign merging
+				// uses the last given value to assign.
+				case "on":
+				case "nativeOn":
+					// If we get here,
+					// value must be of type Object.
+					for (const event of Object.keys(arguments[i][prop])) {
+						// Concat function to array of functions if callback present.
+						if (mergeTarget[prop][event]) {
+							// Insert current iteration data in beginning of merged array.
+							mergeTarget[prop][event] = concat(arguments[i][prop][event], mergeTarget[prop][event])
+						} else {
+							// Straight assign.
+							mergeTarget[prop][event] = arguments[i][prop][event]
+						}
+					}
+					break
 
-        // Object merge strategy
-        case "attrs":
-        case "props":
-        case "domProps":
-        case "scopedSlots":
-        case "staticStyle":
-        case "hook":
-        case "transition":
-          mergeTarget[prop] = { ...mergeTarget[prop], ...arguments[i][prop] }
-          break
+				// Object merge strategy
+				case "attrs":
+				case "props":
+				case "domProps":
+				case "scopedSlots":
+				case "staticStyle":
+				case "hook":
+				case "transition":
+					mergeTarget[prop] = { ...mergeTarget[prop], ...arguments[i][prop] }
+					break
 
-        // Reassignment strategy (no merge)
-        case "slot":
-        case "key":
-        case "ref":
-        case "tag":
-        case "show":
-        case "keepAlive":
-        default:
-          mergeTarget[prop] = arguments[i][prop]
-      }
-    }
-  }
+				// Reassignment strategy (no merge)
+				case "slot":
+				case "key":
+				case "ref":
+				case "tag":
+				case "show":
+				case "keepAlive":
+				default:
+					mergeTarget[prop] = arguments[i][prop]
+			}
+		}
+	}
 
-  return mergeTarget
+	return mergeTarget
 }
 
 export default mergeData
+export { mergeData }