Singleton List refactor

.changeset/wise-icons-shake.md

@@ -0,0 +1,5 @@
+---
+'@keystonejs/list-plugins': major
+---
+
+* Added `singleton` list plugin which prevents creating more items for a list or delete the only item in the list.

packages/list-plugins/README.md

@@ -52,7 +52,7 @@ const { createdAt, updatedAt } = require('@keystonejs/list-plugins');
 
 _Note_: The API is the same.
 
-## byTracking
+# byTracking
 
 Adds `createdBy` and `updatedBy` fields to a list. These fields are read-only by will be updated automatically when items are created or updated.
 
@@ -103,3 +103,20 @@ const { createdBy, updatedBy } = require('@keystonejs/list-plugins');
 ```
 
 _Note_: The API is the same.
+
+# singleton
+
+This plugin makes a list singleton by allowing only one item in the list. Useful for list which must contain only one items.
+
+## Usage
+
+```js
+const { singleton } = require('@keystonejs/list-plugins');
+
+keystone.createList('ListWithPlugin', {
+  fields: {...},
+  plugins: [
+    singleton(),
+  ],
+});
+```

packages/list-plugins/index.js

@@ -1,5 +1,6 @@
 const { atTracking, createdAt, updatedAt } = require('./lib/tracking/atTracking');
 const { byTracking, createdBy, updatedBy } = require('./lib/tracking/byTracking');
+const { singleton } = require('./lib/limiting/singleton');
 
 module.exports = {
   atTracking,
@@ -8,4 +9,5 @@ module.exports = {
   byTracking,
   createdBy,
   updatedBy,
+  singleton,
 };

packages/list-plugins/lib/limiting/singleton.js

@@ -0,0 +1,34 @@
+const { composeHook, composeAccess } = require('../utils');
+
+exports.singleton = () => (
+  { hooks = {}, access = {}, adminConfig = {}, ...rest },
+  { listKey, keystone }
+) => {
+  const newResolveInput = async ({ resolvedData, operation }) => {
+    if (operation === 'create') {
+      const list = keystone.getListByKey(listKey);
+      const query = `{${list.gqlNames.listQueryMetaName} { count }}`;
+      const {
+        data: { [list.gqlNames.listQueryMetaName]: listQuery } = {},
+        errors,
+      } = await keystone.executeQuery(query);
+      if (errors) {
+        throw errors;
+      }
+      if (listQuery && listQuery.count && listQuery.count > 0) {
+        throw new Error(`ItemLimit reached, This Singleton list can not add more item`);
+      }
+    }
+    return resolvedData;
+  };
+
+  const listAccess = composeAccess(access, { delete: false }, keystone.defaultAccess.list);
+  const originalResolveInput = hooks.resolveInput;
+  hooks.resolveInput = composeHook(originalResolveInput, newResolveInput);
+  return {
+    access: listAccess,
+    hooks,
+    adminConfig: { ...adminConfig, singleton: true },
+    ...rest,
+  };
+};

packages/list-plugins/lib/utils.js

@@ -5,3 +5,27 @@ exports.composeHook = (originalHook, newHook) => async params => {
   }
   return newHook({ ...params, resolvedData });
 };
+
+exports.composeAccess = (originalAccess, newAccess = {}) => {
+  if (typeof originalAccess === 'undefined') {
+    return {
+      ...newAccess,
+    };
+  }
+
+  const isShorthand = typeof originalAccess === 'boolean';
+  if (isShorthand) {
+    return {
+      create: originalAccess,
+      read: originalAccess,
+      update: originalAccess,
+      delete: originalAccess,
+      auth: originalAccess,
+      ...newAccess,
+    };
+  }
+  return {
+    ...originalAccess,
+    ...newAccess,
+  };
+};

packages/list-plugins/singleton.md

@@ -0,0 +1,21 @@
+<!--[meta]
+section: list-plugins
+title: singletoon
+[meta]-->
+
+# singleton Plugin
+
+This plugin makes a list singleton by allowing only one item in the list. Useful for list which must contain only one items.
+
+## Usage
+
+```js
+const { singleton } = require('@keystonejs/list-plugins');
+
+keystone.createList('ListWithPlugin', {
+  fields: {...},
+  plugins: [
+    singleton(),
+  ],
+});
+```