Move `Plugin` class to `@uppy/core` package.

Steps taken:

```bash
git mv src/core/Plugin.js packages/@uppy/core/src
vim packages/@uppy/core/src/index.test.js # Update require
sed -i 's/[./]*\/core\/Plugin/@uppy\/core\/lib\/Plugin/' src/**/*.js
vim test/mocks/* # manually update require() calls
vim website/src/docs/writing-plugins.md # manually update require() calls
```

packages/@uppy/core/package.json

@@ -21,12 +21,13 @@
     "url": "git+https://github.com/transloadit/uppy.git"
   },
   "dependencies": {
-    "@uppy/utils": "^0.25.5",
     "@uppy/store-default": "^0.25.5",
+    "@uppy/utils": "^0.25.5",
     "cuid": "^2.1.1",
     "lodash.throttle": "^4.1.1",
     "mime-match": "^1.0.2",
     "namespace-emitter": "^2.0.1",
+    "preact": "^8.2.9",
     "prettier-bytes": "^1.0.4"
   }
 }

packages/@uppy/core/src/index.test.js

@@ -1,7 +1,7 @@
 const fs = require('fs')
 const path = require('path')
 const Core = require('./index')
-const Plugin = require('../../../../src/core/Plugin')
+const Plugin = require('./Plugin')
 const AcquirerPlugin1 = require('../../../../test/mocks/acquirerPlugin1')
 const AcquirerPlugin2 = require('../../../../test/mocks/acquirerPlugin2')
 const InvalidPlugin = require('../../../../test/mocks/invalidPlugin')

src/index.js

@@ -7,7 +7,7 @@ const server = require('./server')
 const views = require('./views')
 
 // Parent
-const Plugin = require('./core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 // Acquirers
 const Dashboard = require('./plugins/Dashboard')

src/plugins/AwsS3/Multipart.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const RequestClient = require('../../server/RequestClient')
 const UppySocket = require('../../core/UppySocket')
 const emitSocketProgress = require('@uppy/utils/lib/emitSocketProgress')

src/plugins/AwsS3/index.js

@@ -1,5 +1,5 @@
 const resolveUrl = require('resolve-url')
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Translator = require('@uppy/utils/lib/Translator')
 const limitPromises = require('@uppy/utils/lib/limitPromises')
 const XHRUpload = require('../XHRUpload')

src/plugins/Dashboard/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Translator = require('@uppy/utils/lib/Translator')
 const dragDrop = require('drag-drop')
 const DashboardUI = require('./Dashboard')

src/plugins/DragDrop/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Translator = require('@uppy/utils/lib/Translator')
 const toArray = require('@uppy/utils/lib/toArray')
 const dragDrop = require('drag-drop')

src/plugins/Dropbox/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { Provider } = require('../../server')
 const { ProviderView } = require('../../views')
 const icons = require('./icons')

src/plugins/Dummy.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { h } = require('preact')
 
 /**

src/plugins/FileInput.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const toArray = require('@uppy/utils/lib/toArray')
 const Translator = require('@uppy/utils/lib/Translator')
 const { h } = require('preact')

src/plugins/Form.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const findDOMElement = require('@uppy/utils/lib/findDOMElement')
 // Rollup uses get-form-data's ES modules build, and rollup-plugin-commonjs automatically resolves `.default`.
 // So, if we are being built using rollup, this require() won't have a `.default` property.

src/plugins/GoldenRetriever/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const ServiceWorkerStore = require('./ServiceWorkerStore')
 const IndexedDBStore = require('./IndexedDBStore')
 const MetaDataStore = require('./MetaDataStore')

src/plugins/GoogleDrive/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { Provider } = require('../../server')
 const { ProviderView } = require('../../views')
 const { h } = require('preact')

src/plugins/Informer.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { h } = require('preact')
 
 /**

src/plugins/Instagram/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { Provider } = require('../../server')
 const { ProviderView } = require('../../views')
 const { h } = require('preact')

src/plugins/MagicLog.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 // import deepDiff from 'deep-diff'
 
 /**

src/plugins/ProgressBar.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { h } = require('preact')
 
 /**

src/plugins/ReduxDevTools.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 /**
  * Add Redux DevTools support to Uppy

src/plugins/StatusBar/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Translator = require('@uppy/utils/lib/Translator')
 const StatusBarUI = require('./StatusBar')
 const statusBarStates = require('./StatusBarStates')

src/plugins/ThumbnailGenerator/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const dataURItoBlob = require('@uppy/utils/lib/dataURItoBlob')
 const isPreviewSupported = require('@uppy/utils/lib/isPreviewSupported')
 

src/plugins/ThumbnailGenerator/index.test.js

@@ -1,5 +1,5 @@
 const ThumbnailGeneratorPlugin = require('./index')
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const emitter = require('namespace-emitter')
 
 const delay = duration => new Promise(resolve => setTimeout(resolve, duration))

src/plugins/Transloadit/index.js

@@ -1,5 +1,5 @@
 const Translator = require('@uppy/utils/lib/Translator')
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Tus = require('../Tus')
 const Client = require('./Client')
 const StatusSocket = require('./Socket')

src/plugins/Tus.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const tus = require('tus-js-client')
 const UppySocket = require('../core/UppySocket')
 const { Provider, RequestClient } = require('../server')

src/plugins/Url/index.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Translator = require('@uppy/utils/lib/Translator')
 const { h } = require('preact')
 const { RequestClient } = require('../../server')

src/plugins/Webcam/index.js

@@ -1,5 +1,5 @@
 const { h } = require('preact')
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const Translator = require('@uppy/utils/lib/Translator')
 const getFileTypeExtension = require('@uppy/utils/lib/getFileTypeExtension')
 const canvasToBlob = require('@uppy/utils/lib/canvasToBlob')

src/plugins/XHRUpload.js

@@ -1,4 +1,4 @@
-const Plugin = require('../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const cuid = require('cuid')
 const Translator = require('@uppy/utils/lib/Translator')
 const UppySocket = require('../core/UppySocket')

src/react/__mocks__/DashboardPlugin.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class Dashboard extends Plugin {
   constructor (uppy, opts) {

src/react/__mocks__/DragDropPlugin.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class DragDrop extends Plugin {
   constructor (uppy, opts) {

src/react/__mocks__/ProgressBarPlugin.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class ProgressBar extends Plugin {
   constructor (uppy, opts) {

src/react/__mocks__/StatusBarPlugin.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class StatusBar extends Plugin {
   constructor (uppy, opts) {

test/mocks/acquirerPlugin1.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../src/core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class TestSelector1 extends Plugin {
   constructor (uppy, opts) {

test/mocks/acquirerPlugin2.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../src/core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class TestSelector2 extends Plugin {
   constructor (uppy, opts) {

test/mocks/invalidPluginWithoutId.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../src/core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class InvalidPluginWithoutName extends Plugin {
   constructor (uppy, opts) {

test/mocks/invalidPluginWithoutType.js

@@ -1,4 +1,4 @@
-const Plugin = require('../../src/core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 
 module.exports = class InvalidPluginWithoutType extends Plugin {
   constructor (uppy, opts) {

website/src/docs/writing-plugins.md

@@ -18,7 +18,7 @@ Plugins are classes that extend from Uppy's `Plugin` class. Each plugin has an `
 The plugin constructor receives the Uppy instance in the first parameter, and any options passed to `uppy.use()` in the second parameter.
 
 ```js
-const Plugin = require('uppy/lib/plugins/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 module.exports = class MyPlugin extends Plugin {
   constructor (uppy, opts) {
     super(uppy, opts)
@@ -175,7 +175,7 @@ See the Preact [Getting Started Guide](https://preactjs.com/guide/getting-starte
 
 ```js
 /** @jsx h */
-const Plugin = require('uppy/lib/core/Plugin')
+const Plugin = require('@uppy/core/lib/Plugin')
 const { h } = require('preact')
 
 class NumFiles extends Plugin {