[improvement] rename packages dir to src (#3659)

src/mixins/relation.js

@@ -0,0 +1,68 @@
+export function ChildrenMixin(parent, options = {}) {
+  const indexKey = options.indexKey || 'index';
+
+  return {
+    inject: {
+      [parent]: {
+        default: null
+      }
+    },
+
+    computed: {
+      parent() {
+        return this[parent];
+      },
+
+      [indexKey]() {
+        this.bindRelation();
+        return this.parent.children.indexOf(this);
+      }
+    },
+
+    created() {
+      this.bindRelation();
+    },
+
+    beforeDestroy() {
+      if (this.parent) {
+        this.parent.children = this.parent.children.filter(item => item !== this);
+      }
+    },
+
+    methods: {
+      bindRelation() {
+        if (!this.parent) {
+          return;
+        }
+
+        const { children } = this.parent;
+
+        if (children.indexOf(this) === -1) {
+          const vnodeIndex = this.parent.slots().indexOf(this.$vnode);
+
+          if (vnodeIndex === -1) {
+            children.push(this);
+          } else {
+            children.splice(vnodeIndex, 0, this);
+          }
+        }
+      }
+    }
+  };
+}
+
+export function ParentMixin(parent) {
+  return {
+    provide() {
+      return {
+        [parent]: this
+      };
+    },
+
+    data() {
+      return {
+        children: []
+      };
+    }
+  };
+}