From c3ac2f8ae4f7721bd04c729947eda595e07f9d36 Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Mon, 27 Apr 2020 03:33:07 +0530
Subject: [PATCH 1/8] create singleton list plugin

---
 packages/list-plugins/index.js                |  2 ++
 .../list-plugins/lib/limiting/singleton.js    | 24 +++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 packages/list-plugins/lib/limiting/singleton.js

diff --git a/packages/list-plugins/index.js b/packages/list-plugins/index.js
index e81094640e8..576a059afa5 100644
--- a/packages/list-plugins/index.js
+++ b/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,
 };
diff --git a/packages/list-plugins/lib/limiting/singleton.js b/packages/list-plugins/lib/limiting/singleton.js
new file mode 100644
index 00000000000..16e8cd0c4db
--- /dev/null
+++ b/packages/list-plugins/lib/limiting/singleton.js
@@ -0,0 +1,24 @@
+const { composeHook } = require('../utils');
+
+exports.singleton = () => ({ hooks = {}, 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 originalResolveInput = hooks.resolveInput;
+  hooks.resolveInput = composeHook(originalResolveInput, newResolveInput);
+  return { hooks, adminConfig: { ...adminConfig, singleton: true }, ...rest };
+};

From 660866c8364554e09103b8fccbd54f2e9aaac66b Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Mon, 27 Apr 2020 04:17:14 +0530
Subject: [PATCH 2/8] prevent delete by setting access control.

---
 .../list-plugins/lib/limiting/singleton.js    | 16 ++++++++++---
 packages/list-plugins/lib/utils.js            | 24 +++++++++++++++++++
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/packages/list-plugins/lib/limiting/singleton.js b/packages/list-plugins/lib/limiting/singleton.js
index 16e8cd0c4db..52936143c2a 100644
--- a/packages/list-plugins/lib/limiting/singleton.js
+++ b/packages/list-plugins/lib/limiting/singleton.js
@@ -1,6 +1,9 @@
-const { composeHook } = require('../utils');
+const { composeHook, composeAccess } = require('../utils');
 
-exports.singleton = () => ({ hooks = {}, adminConfig = {}, ...rest }, { listKey, keystone }) => {
+exports.singleton = () => (
+  { hooks = {}, access = {}, adminConfig = {}, ...rest },
+  { listKey, keystone }
+) => {
   const newResolveInput = async ({ resolvedData, operation }) => {
     if (operation === 'create') {
       const list = keystone.getListByKey(listKey);
@@ -18,7 +21,14 @@ exports.singleton = () => ({ hooks = {}, adminConfig = {}, ...rest }, { listKey,
     }
     return resolvedData;
   };
+
+  const listAccess = composeAccess(access, { delete: false }, keystone.defaultAccess.list);
   const originalResolveInput = hooks.resolveInput;
   hooks.resolveInput = composeHook(originalResolveInput, newResolveInput);
-  return { hooks, adminConfig: { ...adminConfig, singleton: true }, ...rest };
+  return {
+    access: listAccess,
+    hooks,
+    adminConfig: { ...adminConfig, singleton: true },
+    ...rest,
+  };
 };
diff --git a/packages/list-plugins/lib/utils.js b/packages/list-plugins/lib/utils.js
index f27958d8f4a..47607052f19 100644
--- a/packages/list-plugins/lib/utils.js
+++ b/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,
+  };
+};

From e9c0dc06a4018c92c930c8b4ce7cda9b7fea707e Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Fri, 22 May 2020 02:51:58 +0530
Subject: [PATCH 3/8] update ui fr singleton list

---
 .../client/pages/Item/AddNewItem.js           |  7 +++--
 .../client/pages/Item/ItemTitle.js            | 26 +++++++++++--------
 .../app-admin-ui/client/pages/List/index.js   |  7 ++++-
 3 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/packages/app-admin-ui/client/pages/Item/AddNewItem.js b/packages/app-admin-ui/client/pages/Item/AddNewItem.js
index 95e16caea46..136f94ed86f 100644
--- a/packages/app-admin-ui/client/pages/Item/AddNewItem.js
+++ b/packages/app-admin-ui/client/pages/Item/AddNewItem.js
@@ -7,10 +7,13 @@ import { useList } from '../../providers/List';
 
 const AddNewItem = () => {
   let {
-    list: { access },
+    list: {
+      access,
+      adminConfig: { singleton = false },
+    },
     openCreateItemModal,
   } = useList();
-  if (!access.create) return null;
+  if (!access.create || singleton) return null;
   const cypressId = 'item-page-create-button';
   return (
     <Tooltip content="Create" hideOnMouseDown hideOnKeyDown>
diff --git a/packages/app-admin-ui/client/pages/Item/ItemTitle.js b/packages/app-admin-ui/client/pages/Item/ItemTitle.js
index 81b6a06efda..0fdfdc0d940 100644
--- a/packages/app-admin-ui/client/pages/Item/ItemTitle.js
+++ b/packages/app-admin-ui/client/pages/Item/ItemTitle.js
@@ -29,17 +29,21 @@ export const ItemTitle = memo(function ItemTitle({ titleText }) {
       <PageTitle>{titleText}</PageTitle>
       <ListDescription text={list.adminDoc} />
       <FlexGroup align="center" justify="space-between" css={{ marginBottom: '0.9rem' }}>
-        <div>
-          <IconButton
-            variant="subtle"
-            icon={ChevronLeftIcon}
-            to={list.getFullPersistentPath()}
-            css={{ marginLeft: -12 }}
-          >
-            {list.label}
-          </IconButton>
-          <Search list={list} />
-        </div>
+        {!list.adminConfig.singleton ? (
+          <div>
+            <IconButton
+              variant="subtle"
+              icon={ChevronLeftIcon}
+              to={list.getFullPersistentPath()}
+              css={{ marginLeft: -12 }}
+            >
+              {list.label}
+            </IconButton>
+            <Search list={list} />
+          </div>
+        ) : (
+          <div />
+        )}
         {itemHeaderActions ? (
           itemHeaderActions()
         ) : (
diff --git a/packages/app-admin-ui/client/pages/List/index.js b/packages/app-admin-ui/client/pages/List/index.js
index 7c1e9e64050..514571ef908 100644
--- a/packages/app-admin-ui/client/pages/List/index.js
+++ b/packages/app-admin-ui/client/pages/List/index.js
@@ -32,6 +32,7 @@ import Search from './Search';
 import Management, { ManageToolbar } from './Management';
 import { useListFilter, useListSelect, useListSort, useListUrlState } from './dataHooks';
 import { captureSuspensePromises } from '@keystonejs/utils';
+import { useAdminMeta } from '../../providers/AdminMeta';
 
 export function ListLayout(props) {
   const { items, itemCount, queryErrors, query } = props;
@@ -225,7 +226,7 @@ const ListPage = props => {
     queryErrorsParsed,
     query,
   } = useList();
-
+  const { adminPath } = useAdminMeta();
   const history = useHistory();
   const location = useLocation();
 
@@ -278,6 +279,10 @@ const ListPage = props => {
     );
   }
 
+  if (list.adminConfig.singleton && itemCount > 0) {
+    history.push(`${adminPath}/${list.path}/${items[0].id}`);
+  }
+
   // Success
   // ------------------------------
   return (

From c5dafe2fb39a1210be90b74b82a7677dd6f46001 Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Mon, 27 Apr 2020 04:33:10 +0530
Subject: [PATCH 4/8] add readme and changeset

---
 .changeset/wise-icons-shake.md     | 10 ++++++++++
 packages/list-plugins/README.md    | 19 ++++++++++++++++++-
 packages/list-plugins/singleton.md | 21 +++++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/wise-icons-shake.md
 create mode 100644 packages/list-plugins/singleton.md

diff --git a/.changeset/wise-icons-shake.md b/.changeset/wise-icons-shake.md
new file mode 100644
index 00000000000..0b2afa55b6d
--- /dev/null
+++ b/.changeset/wise-icons-shake.md
@@ -0,0 +1,10 @@
+---
+'@keystonejs/app-admin-ui': minor
+'@keystonejs/list-plugins': major
+---
+
+* Added `singleton` list plugin which prevents creating more items for a list or delete the only item in the list.
+
+* Updated `admin-ui` to 
+  - Redirect to the only item if there is an item in singleton list
+  - Hide `Search` field, `Back` and `AddNew` buttons on item details page
diff --git a/packages/list-plugins/README.md b/packages/list-plugins/README.md
index 99d9a447319..d32a30a3583 100644
--- a/packages/list-plugins/README.md
+++ b/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({...}),
+  ],
+});
+```
diff --git a/packages/list-plugins/singleton.md b/packages/list-plugins/singleton.md
new file mode 100644
index 00000000000..4cc44ea0fbc
--- /dev/null
+++ b/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({...}),
+  ],
+});
+```

From 097814a4af0db18ac9c00391c8ea9197a9248d31 Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Fri, 22 May 2020 08:24:08 +0530
Subject: [PATCH 5/8] review comment - use fullpath on list, move it to
 useEffect

---
 packages/app-admin-ui/client/pages/List/index.js | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/packages/app-admin-ui/client/pages/List/index.js b/packages/app-admin-ui/client/pages/List/index.js
index 514571ef908..7327e847769 100644
--- a/packages/app-admin-ui/client/pages/List/index.js
+++ b/packages/app-admin-ui/client/pages/List/index.js
@@ -226,7 +226,6 @@ const ListPage = props => {
     queryErrorsParsed,
     query,
   } = useList();
-  const { adminPath } = useAdminMeta();
   const history = useHistory();
   const location = useLocation();
 
@@ -248,6 +247,12 @@ const ListPage = props => {
     }
   }, []);
 
+  useEffect(() => {
+    if (list.adminConfig.singleton && itemCount > 0) {
+      history.replace(`${list.fullPath}/${items[0].id}`);
+    }
+  }, [itemCount]);
+
   // Error
   // ------------------------------
   // Only show error page if there is no data
@@ -279,10 +284,6 @@ const ListPage = props => {
     );
   }
 
-  if (list.adminConfig.singleton && itemCount > 0) {
-    history.push(`${adminPath}/${list.path}/${items[0].id}`);
-  }
-
   // Success
   // ------------------------------
   return (

From 85448f09405e39ba9387090dfe21e042d32e0783 Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Fri, 22 May 2020 08:38:23 +0530
Subject: [PATCH 6/8] update readme

---
 packages/list-plugins/README.md    | 2 +-
 packages/list-plugins/singleton.md | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/list-plugins/README.md b/packages/list-plugins/README.md
index d32a30a3583..183a224cb20 100644
--- a/packages/list-plugins/README.md
+++ b/packages/list-plugins/README.md
@@ -116,7 +116,7 @@ const { singleton } = require('@keystonejs/list-plugins');
 keystone.createList('ListWithPlugin', {
   fields: {...},
   plugins: [
-    singleton({...}),
+    singleton(),
   ],
 });
 ```
diff --git a/packages/list-plugins/singleton.md b/packages/list-plugins/singleton.md
index 4cc44ea0fbc..d947b608b34 100644
--- a/packages/list-plugins/singleton.md
+++ b/packages/list-plugins/singleton.md
@@ -15,7 +15,7 @@ const { singleton } = require('@keystonejs/list-plugins');
 keystone.createList('ListWithPlugin', {
   fields: {...},
   plugins: [
-    singleton({...}),
+    singleton(),
   ],
 });
 ```

From 643b02aa805d788ed3cc0d2753b778b9c89f39e0 Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Fri, 22 May 2020 09:52:46 +0530
Subject: [PATCH 7/8] lint error

---
 packages/app-admin-ui/client/pages/List/index.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/packages/app-admin-ui/client/pages/List/index.js b/packages/app-admin-ui/client/pages/List/index.js
index 7327e847769..5d6789374cd 100644
--- a/packages/app-admin-ui/client/pages/List/index.js
+++ b/packages/app-admin-ui/client/pages/List/index.js
@@ -32,7 +32,6 @@ import Search from './Search';
 import Management, { ManageToolbar } from './Management';
 import { useListFilter, useListSelect, useListSort, useListUrlState } from './dataHooks';
 import { captureSuspensePromises } from '@keystonejs/utils';
-import { useAdminMeta } from '../../providers/AdminMeta';
 
 export function ListLayout(props) {
   const { items, itemCount, queryErrors, query } = props;

From b3473831c5d3d0bdd0f3894a2b13c9f262b93e65 Mon Sep 17 00:00:00 2001
From: Gautam Singh <gautamsi@users.noreply.github.com>
Date: Fri, 22 May 2020 13:05:01 +0530
Subject: [PATCH 8/8] revert UI changes to make it as part of different PR.

---
 .changeset/wise-icons-shake.md                |  5 ----
 .../client/pages/Item/AddNewItem.js           |  7 ++---
 .../client/pages/Item/ItemTitle.js            | 26 ++++++++-----------
 .../app-admin-ui/client/pages/List/index.js   |  7 +----
 4 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/.changeset/wise-icons-shake.md b/.changeset/wise-icons-shake.md
index 0b2afa55b6d..0455f194bbc 100644
--- a/.changeset/wise-icons-shake.md
+++ b/.changeset/wise-icons-shake.md
@@ -1,10 +1,5 @@
 ---
-'@keystonejs/app-admin-ui': minor
 '@keystonejs/list-plugins': major
 ---
 
 * Added `singleton` list plugin which prevents creating more items for a list or delete the only item in the list.
-
-* Updated `admin-ui` to 
-  - Redirect to the only item if there is an item in singleton list
-  - Hide `Search` field, `Back` and `AddNew` buttons on item details page
diff --git a/packages/app-admin-ui/client/pages/Item/AddNewItem.js b/packages/app-admin-ui/client/pages/Item/AddNewItem.js
index 136f94ed86f..95e16caea46 100644
--- a/packages/app-admin-ui/client/pages/Item/AddNewItem.js
+++ b/packages/app-admin-ui/client/pages/Item/AddNewItem.js
@@ -7,13 +7,10 @@ import { useList } from '../../providers/List';
 
 const AddNewItem = () => {
   let {
-    list: {
-      access,
-      adminConfig: { singleton = false },
-    },
+    list: { access },
     openCreateItemModal,
   } = useList();
-  if (!access.create || singleton) return null;
+  if (!access.create) return null;
   const cypressId = 'item-page-create-button';
   return (
     <Tooltip content="Create" hideOnMouseDown hideOnKeyDown>
diff --git a/packages/app-admin-ui/client/pages/Item/ItemTitle.js b/packages/app-admin-ui/client/pages/Item/ItemTitle.js
index 0fdfdc0d940..81b6a06efda 100644
--- a/packages/app-admin-ui/client/pages/Item/ItemTitle.js
+++ b/packages/app-admin-ui/client/pages/Item/ItemTitle.js
@@ -29,21 +29,17 @@ export const ItemTitle = memo(function ItemTitle({ titleText }) {
       <PageTitle>{titleText}</PageTitle>
       <ListDescription text={list.adminDoc} />
       <FlexGroup align="center" justify="space-between" css={{ marginBottom: '0.9rem' }}>
-        {!list.adminConfig.singleton ? (
-          <div>
-            <IconButton
-              variant="subtle"
-              icon={ChevronLeftIcon}
-              to={list.getFullPersistentPath()}
-              css={{ marginLeft: -12 }}
-            >
-              {list.label}
-            </IconButton>
-            <Search list={list} />
-          </div>
-        ) : (
-          <div />
-        )}
+        <div>
+          <IconButton
+            variant="subtle"
+            icon={ChevronLeftIcon}
+            to={list.getFullPersistentPath()}
+            css={{ marginLeft: -12 }}
+          >
+            {list.label}
+          </IconButton>
+          <Search list={list} />
+        </div>
         {itemHeaderActions ? (
           itemHeaderActions()
         ) : (
diff --git a/packages/app-admin-ui/client/pages/List/index.js b/packages/app-admin-ui/client/pages/List/index.js
index 5d6789374cd..7c1e9e64050 100644
--- a/packages/app-admin-ui/client/pages/List/index.js
+++ b/packages/app-admin-ui/client/pages/List/index.js
@@ -225,6 +225,7 @@ const ListPage = props => {
     queryErrorsParsed,
     query,
   } = useList();
+
   const history = useHistory();
   const location = useLocation();
 
@@ -246,12 +247,6 @@ const ListPage = props => {
     }
   }, []);
 
-  useEffect(() => {
-    if (list.adminConfig.singleton && itemCount > 0) {
-      history.replace(`${list.fullPath}/${items[0].id}`);
-    }
-  }, [itemCount]);
-
   // Error
   // ------------------------------
   // Only show error page if there is no data