RFC: use LB3 models in an LB4 app [SPIKE - DO NOT MERGE]

lb3api.md

@@ -6,32 +6,36 @@ How to test code migrated from strong-remoting and loopback (v3)? Do we want to
 copy existing tests over? Migrate them to async/await style? Don't bother with
 testing at all, use few acceptance-level tests only?
 
-How to split 1k+ lines of new (migrated) code into smaller chunks that will be
+How to split 2k+ lines of new (migrated) code into smaller chunks that will be
 easier to review?
 
-TODO:
-
-1. expose remote methods via REST
-2. boot
+Should we register LB3 Models for dependency injection into LB4 code? Register
+them as repositories, models, services, or something else?
 
 ## Should have/next iterations:
 
 - PersistedModel - all CRUD APIs
-- register Models and DataSources for dependency injection?
-- allow LB3 models to be attached to LB4 dataSources?
 - pick up models/methods added after app start
 - hasUpdateOnlyProps (different request body schema for "create" method)
 - set options from HTTP context (`http: 'optionsFromRequest'`)
 - `{rest: {after: convertNullToNotFoundError}}`
 - mixins
 - case-insensitive URL paths (?) (/Todo is same as /todo)
+- model-sources and mixin-sources in model-config.json
+
+On aside
 
-## Model
+- https://github.com/Microsoft/TypeScript/issues/6480
+- extract the Booter contract into a standalone package so that v3compat does
+  not have to inherit entire boot
+
+### Model
 
 - beforeRemote/afterRemote/afterRemoteError
 - disableRemoteMethodByName(name)
 
-## HttpContext
+### HttpContext
+
 - method
 - req
 - res
@@ -40,13 +44,15 @@ TODO:
 - methodString
 - result
 
-## SharedMethod
+### SharedMethod
+
 - isMethodEnabled(sharedMethod)
 - resolve(resolver)
 - findMethodByName
 - disableMethodByName
 
 ### Application
+
 - app.connector(name, connector)
 - app.connectors.{name}
 
@@ -74,10 +80,12 @@ TODO:
 
 ### Remoting features
 
-- respond with a  Buffer, respond with a ReadableStream
+- respond with a Buffer, respond with a ReadableStream
 
-## Won't have
+## WILL NOT HAVE
 
+- allow LB3 models to be attached to LB4 dataSources. This won't work
+  because LB3 requires all datasources to share the same ModelBuilder
 - CLS-based context
 - global registry: loopback.createModel, loopback.findModel, etc.
 - Model.checkAccess(token, modelId, sharedMethod, ctx, cb)
@@ -102,6 +110,7 @@ TODO:
   - fillCustomChangeProperties
 
 built-in models
+
 - Access-token
 - Acl
 - Application
@@ -114,13 +123,16 @@ built-in models
 - User
 
 SharedClass
+
 - find: was already deprecated
 - disableMethod: was already deprecated
 
 SharedMethod
+
 - prototype.invoke(scope, args, remotingOptions, ctx, cb)
 
 HttpContext
+
 - ~~typeRegistry~~
 - ~~supportedTypes~~
 - invoke
@@ -134,6 +146,11 @@ HttpContext
 - (etc.)
 
 Remoting
+
 - XML
 - JSON API
 - piping retval of remote function into response
+
+Booting
+
+- datasources

packages/v3compat/fixtures/model-config.json

@@ -0,0 +1,6 @@
+{
+  "Todo": {
+    "dataSource": "db",
+    "public": true
+  }
+}

packages/v3compat/fixtures/models/todo.js

@@ -0,0 +1,11 @@
+// Copyright IBM Corp. 2018. All Rights Reserved.
+// Node module: @loopback/v3compat
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+module.exports = function(Todo) {
+  // A dummy custom method to verify that model JS file was correctly processed
+  Todo.findByTitle = function(title) {
+    return this.find({where: {title}});
+  };
+};

packages/v3compat/fixtures/models/todo.json

@@ -0,0 +1,11 @@
+{
+  "name": "Todo",
+  "base": "PersistedModel",
+  "strict": false,
+  "properties": {
+    "title": {
+      "type": "string",
+      "required": true
+    }
+  }
+}

packages/v3compat/package.json

@@ -29,7 +29,7 @@
     "url": "https://github.com/strongloop/loopback-next.git"
   },
   "dependencies": {
-    "@loopback/context": "^1.4.0",
+    "@loopback/boot": "^1.0.10",
     "@loopback/core": "^1.1.3",
     "@loopback/rest": "^1.5.3",
     "debug": "^4.1.1",

packages/v3compat/src/boot/README.md

@@ -0,0 +1,4 @@
+# v3compat/boot
+
+Source code migrated from
+[loopback-boot](https://github.com/strongloop/loopback-boot).

packages/v3compat/src/boot/index.ts

@@ -0,0 +1,6 @@
+// Copyright IBM Corp. 2018. All Rights Reserved.
+// Node module: @loopback/v3compat
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+export * from './lb3-model-booter';

packages/v3compat/src/boot/lb3-model-booter.ts

@@ -0,0 +1,121 @@
+// Copyright IBM Corp. 2018. All Rights Reserved.
+// Node module: @loopback/v3compat
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+import {BootBindings, Booter, discoverFiles} from '@loopback/boot';
+import {Application, CoreBindings, inject} from '@loopback/core';
+import * as debugFactory from 'debug';
+import * as fs from 'fs';
+import * as path from 'path';
+import {promisify} from 'util';
+import {Lb3Application} from '../core';
+
+const fileExists = promisify(fs.exists);
+
+const debug = debugFactory('loopback:v3compat:model-booter');
+
+const DefaultOptions = {
+  root: './legacy',
+};
+
+export class Lb3ModelBooter implements Booter {
+  options: Lb3ModelBooterOptions;
+
+  root: string;
+  modelDefinitionsGlob: string;
+  modelConfigFile: string;
+
+  discoveredDefinitionFiles: string[];
+
+  constructor(
+    @inject(CoreBindings.APPLICATION_INSTANCE)
+    public app: Application & {v3compat: Lb3Application},
+    @inject(BootBindings.PROJECT_ROOT)
+    public projectRoot: string,
+    @inject(`${BootBindings.BOOT_OPTIONS}#v3compat`)
+    options: Partial<Lb3ModelBooterOptions> = {},
+  ) {
+    this.options = Object.assign({}, DefaultOptions, options);
+  }
+
+  async configure?(): Promise<void> {
+    this.root = path.join(this.projectRoot, this.options.root);
+    this.modelDefinitionsGlob = '/models/*.json';
+    this.modelConfigFile = 'model-config.json';
+  }
+
+  async discover?(): Promise<void> {
+    debug(
+      'Discovering LB3 model definitions in %j using glob %j',
+      this.root,
+      this.modelDefinitionsGlob,
+    );
+
+    const allFiles = await discoverFiles(this.modelDefinitionsGlob, this.root);
+    this.discoveredDefinitionFiles = allFiles.filter(
+      f => f[0] !== '_' && path.extname(f) === '.json',
+    );
+    debug(' -> %j', allFiles);
+  }
+
+  async load?(): Promise<void> {
+    for (const f of this.discoveredDefinitionFiles) await this.loadModel(f);
+
+    await this.configureModels();
+  }
+
+  private async loadModel(jsonFile: string) {
+    const basename = path.basename(jsonFile, path.extname(jsonFile));
+    const sourceDir = path.dirname(jsonFile);
+    // TODO: support additional extensions like `.ts` and `.coffee`
+    const sourceFile = path.join(sourceDir, `${basename}.js`);
+    const sourceExists = await fileExists(sourceFile);
+
+    debug(
+      'Loading model from %j (%j)',
+      path.relative(this.projectRoot, jsonFile),
+      sourceExists
+        ? path.relative(this.projectRoot, sourceFile)
+        : '<no source code>',
+    );
+
+    const definition = require(jsonFile);
+    const script = sourceExists ? require(sourceFile) : undefined;
+
+    debug('  creating a new model %j', definition.name);
+    const modelCtor = this.app.v3compat.registry.createModel(definition);
+
+    if (typeof script === 'function') {
+      debug(
+        '  customizing model %j using %j',
+        definition.name,
+        path.relative(this.projectRoot, sourceFile),
+      );
+      script(modelCtor);
+    } else if (sourceExists) {
+      debug(
+        '  skipping model file %s - `module.exports` is not a function',
+        sourceFile,
+      );
+    }
+  }
+
+  private async configureModels() {
+    const configFile = path.join(this.root, this.modelConfigFile);
+    debug('Loading model-config from %j', configFile);
+
+    const config = require(configFile);
+    for (const modelName in config) {
+      if (modelName === '_meta') continue;
+      const modelConfig = config[modelName];
+      debug('  configuring %j with %j', modelName, modelConfig);
+      const modelCtor = this.app.v3compat.registry.getModel(modelName);
+      this.app.v3compat.model(modelCtor, modelConfig);
+    }
+  }
+}
+
+export interface Lb3ModelBooterOptions {
+  root: string;
+}

packages/v3compat/src/compat.component.ts

@@ -0,0 +1,11 @@
+// Copyright IBM Corp. 2018. All Rights Reserved.
+// Node module: @loopback/v3compat
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+import {Component} from '@loopback/core';
+import {Lb3ModelBooter} from './boot';
+
+export class CompatComponent implements Component {
+  booters = [Lb3ModelBooter];
+}

packages/v3compat/src/compat.mixin.ts

@@ -5,7 +5,8 @@
 
 import {Constructor} from '@loopback/context';
 import {Application} from '@loopback/core';
-import {Lb3Application} from './core/lb3-application';
+import {CompatComponent} from './compat.component';
+import {Lb3Application} from './core';
 
 /**
  * A mixin class for Application that adds `v3compat` property providing
@@ -39,6 +40,7 @@ export function CompatMixin<T extends Constructor<any>>(superClass: T) {
     constructor(...args: any[]) {
       super(...args);
       this.v3compat = new Lb3Application((this as unknown) as Application);
+      this.component(CompatComponent);
     }
   };
 }

packages/v3compat/src/core/lb3-application.ts

@@ -32,7 +32,7 @@ export class Lb3Application {
   }
 
   dataSource(name: string, config: DataSourceConfig): DataSource {
-    debug('registering datasource %s with config %j', name, config);
+    debug('Registering datasource %j with config %j', name, config);
     // TODO: use the implementation from LB3's lib/application.js
     const ds = this.registry.createDataSource(name, config);
     this.dataSources[name] = ds;
@@ -46,7 +46,7 @@ export class Lb3Application {
   }
 
   model(modelCtor: ModelClass, config: ModelConfig) {
-    debug('registering model %s with config %s', modelCtor.modelName, config);
+    debug('Registering model %j with config %j', modelCtor.modelName, config);
     // TODO: use the implementation from LB3's lib/application.js
     if (typeof config.dataSource === 'string') {
       const dataSource = this.dataSources[config.dataSource];
@@ -56,7 +56,7 @@ export class Lb3Application {
     this.models[modelCtor.modelName] = modelCtor;
     modelCtor.app = this;
 
-    // TODO: register Model schema
+    // TODO: register Model schema for OpenAPI spec
     this.restAdapter.registerSharedClass(modelCtor.sharedClass);
   }
 

packages/v3compat/src/core/lb3-model.ts

@@ -20,6 +20,14 @@ import {
 } from './lb3-types';
 import {PersistedModelClass} from './lb3-persisted-model';
 
+// A workaround for https://github.com/Microsoft/TypeScript/issues/6480
+// I was not able to find a way how to mix arbitrary static properties
+// while preserving constructor signature. We need to contribute this
+// feature to TypeScript ourselves.
+export interface AnyStaticMethods {
+  [methodName: string]: Function;
+}
+
 export type ModelClass = typeof Model;
 
 export declare class Model extends ModelBase {

packages/v3compat/src/core/lb3-persisted-model.ts

@@ -3,8 +3,9 @@
 // This file is licensed under the MIT License.
 // License text available at https://opensource.org/licenses/MIT
 
+import {Constructor} from '@loopback/core';
 import {RemoteMethodOptions} from '../remoting';
-import {Model} from './lb3-model';
+import {AnyStaticMethods, Model} from './lb3-model';
 import {Lb3Registry} from './lb3-registry';
 import {
   Callback,