feat(cli): add new command import-lb3-model (EXPERIMENTAL)

docs/site/Importing-LB3-models.md

@@ -0,0 +1,113 @@
+---
+lang: en
+title: 'Importing models from LoopBack 3 projects'
+keywords: LoopBack 4.0, Migration
+sidebar: lb4_sidebar
+permalink: /doc/en/lb4/Importing-LB3-models.html
+---
+
+## Synopsis
+
+To simplify migration from LoopBack 3, LoopBack 4 provides a CLI tool to import
+LoopBack 3 models into your LoopBack 4 project.
+
+{% include warning.html content="
+This command is experimental and not feature-complete yet.
+See the list of known limitations below.
+" %}
+
+## Overview
+
+Import one or more models from your LB 3.x application by running
+`lb4 import-lb3-models` command.
+
+### Arguments
+
+`lb3app`: Path to the directory containing your LoopBack 3.x application.
+
+{% include important.html content="
+The generator loads the application via `require()`, it does not
+support applications that are unable to boot (throw errors at startup).
+" %}
+
+### Options
+
+`outDir`: Directory where to write the generated source file. Default:
+`src/models`
+
+## Known limitations
+
+{% include note.html content="
+Please up-vote the tracking GitHub issue for scenarios that are important to
+your project. It will help us to better prioritize which limitations to remove
+first.
+" %}
+
+### Connector-specific metadata in property definitions is not imported
+
+_The tracking GitHub issue:
+[loopback-next#3810](https://github.com/strongloop/loopback-next/issues/3810)_
+
+Workaround: Add this metadata manually to the generated file.
+
+### Nested properties are not upgraded
+
+_The tracking GitHub issue:
+[loopback-next#3811](https://github.com/strongloop/loopback-next/issues/3811)_
+
+When a property is defined with a complex object type, the nested property
+definitions are not converted from LB3 to LB4 format.
+
+Workaround: Fix the generated definition manually.
+
+### Model relations are not imported
+
+_The tracking GitHub issue:
+[loopback-next#3812](https://github.com/strongloop/loopback-next/issues/3812)_
+
+Workaround: define relational metadata & navigational properties manually.
+
+### Models inheriting from custom base class
+
+_The tracking GitHub issue:
+[loopback-next#3813](https://github.com/strongloop/loopback-next/issues/3813)_
+
+Models inheriting from application-specific models (including LB3 built-in
+models like `User`) cannot be imported yet.
+
+Workaround:
+
+1. Modify your LB3 model to inherit from `Model`, `PersistedModel` or
+   `KeyValueModel`.
+
+2. Import the model to LB4
+
+3. Update the imported model to inherit for the desired application-specific
+   model.
+
+### MongoDB's `ObjectID` type
+
+The tracking GitHub issue:
+[loopback-next#3814](https://github.com/strongloop/loopback-next/issues/3814).
+
+For models attached to MongoDB datasource, the imported LB4 model contains
+incorrect definition of the primary key property of `ObjectID` type.
+
+As a workaround, you can change the property definition from:
+
+```ts
+@property({
+  type: ObjectID;
+})
+id: ObjectID;
+```
+
+to:
+
+```ts
+@property({
+  type: 'string',
+  mongodb: {dataType: 'ObjectID'}
+})
+id: string;
+```

docs/site/sidebars/lb4_sidebar.yml

@@ -384,6 +384,10 @@ children:
     url: DataSource-generator.html
     output: 'web, pdf'
 
+  - title: 'Import models from LoopBack 3'
+    url: Importing-LB3-models.html
+    output: 'web, pdf'
+
   - title: 'Model generator'
     url: Model-generator.html
     output: 'web, pdf'

docs/site/tables/lb4-artifact-commands.html

@@ -23,6 +23,11 @@
       <td><a href="DataSource-generator.html">DataSource generator</a></td>
     </tr>
 
+    <tr>
+      <td><code>lb4 import-lb3-models</code></td>
+      <td>Import one or more LoopBack 3 models to a LoopBack 4 application</td>
+      <td><a href="Importing-LB3-models.html">Importer for LoopBack 3 models</a></td>
+    </tr>
     <tr>
       <td><code>lb4 model</code></td>
       <td>Add a new model to a LoopBack 4 application</td>
@@ -70,7 +75,5 @@
       <td>Generate interceptors</td>
       <td><a href="Interceptor-generator.html">Global interceptor generator</a></td>
     </tr>
-
-
   </tbody>
 </table>

packages/cli/generators/import-lb3-models/index.js

@@ -0,0 +1,162 @@
+// Copyright IBM Corp. 2019. All Rights Reserved.
+// Node module: @loopback/cli
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+const chalk = require('chalk');
+const path = require('path');
+const BaseGenerator = require('../../lib/base-generator');
+const modelUtils = require('../../lib/model-discoverer');
+const debug = require('../../lib/debug')('import-lb3-models');
+const utils = require('../../lib/utils');
+const {loadLb3App} = require('./lb3app-loader');
+const {importLb3ModelDefinition} = require('./migrate-model');
+const {canImportModelName} = require('./model-names');
+
+module.exports = class Lb3ModelImporter extends BaseGenerator {
+  constructor(args, opts) {
+    super(args, opts);
+
+    this.argument('lb3app', {
+      type: String,
+      required: true,
+      description:
+        'Path to your LoopBack 3.x application. ' +
+        'This can be a project directory (e.g. "my-lb3-app") or ' +
+        'the server file (e.g. "my-lb3-app/server/server.js").',
+    });
+
+    this.option('outDir', {
+      type: String,
+      description: 'Directory where to write the generated source file',
+      default: 'src/models',
+    });
+  }
+
+  async processOptions() {
+    this.sourceAppDir = this.args[0];
+    this.artifactInfo.outDir = this.options.outDir;
+    this.artifactInfo.relPath = path.relative(
+      this.destinationPath(),
+      this.artifactInfo.outDir,
+    );
+    return super.setOptions();
+  }
+
+  async logExperimentalStatus() {
+    this.log(
+      chalk.red(`
+WARNING: This command is experimental and not feature-complete yet.
+Learn more at https://loopback.io/doc/en/lb4/Importing-LB3-models.html
+`),
+    );
+  }
+
+  /**
+   * Ensure CLI is being run in a LoopBack 4 project.
+   */
+  checkLoopBackProject() {
+    if (this.shouldExit()) return;
+    return super.checkLoopBackProject();
+  }
+
+  async loadTheApp() {
+    this.lb3app = await loadLb3App(this.sourceAppDir);
+    this.modelRegistry = this.lb3app.registry.modelBuilder.models;
+  }
+
+  async promptModels() {
+    const modelNames = Object.keys(this.modelRegistry).filter(
+      canImportModelName,
+    );
+
+    debug('Available LB3 models', modelNames);
+
+    const prompts = [
+      {
+        name: 'modelNames',
+        message: 'Select models to import:',
+        type: 'checkbox',
+        choices: modelNames,
+        validate: result => !!result.length,
+        // TODO: add a CLI flag to supply these names programmatically
+      },
+    ];
+
+    const answers = await this.prompt(prompts);
+    debug('Models chosen:', answers.modelNames);
+    this.modelNames = answers.modelNames;
+  }
+
+  async migrateSelectedModels() {
+    if (this.shouldExit()) return;
+    this.modelFiles = [];
+
+    try {
+      for (const name of this.modelNames) {
+        await this._migrateSingleModel(name);
+      }
+    } catch (err) {
+      if (err.exit) {
+        this.exit(err.message);
+      } else {
+        throw err;
+      }
+    }
+  }
+
+  async _migrateSingleModel(name) {
+    utils.logClassCreation('model', 'models', name, this.log.bind(this));
+    const modelCtor = this.modelRegistry[name];
+    if (typeof modelCtor !== 'function') {
+      const availableModels = Object.keys(this.modelRegistry)
+        .filter(canImportModelName)
+        .join(', ');
+
+      this.exit(
+        `Unknown model name ${name}. Available models: ${availableModels}.`,
+      );
+      return;
+    }
+
+    const templateData = importLb3ModelDefinition(
+      modelCtor,
+      this.log.bind(this),
+    );
+    debug('LB4 model data', templateData);
+
+    const fileName = utils.getModelFileName(name);
+    const fullTargetPath = path.resolve(this.artifactInfo.relPath, fileName);
+    debug('Model %s output file', name, fullTargetPath);
+
+    this.copyTemplatedFiles(
+      modelUtils.MODEL_TEMPLATE_PATH,
+      fullTargetPath,
+      templateData,
+    );
+
+    this.modelFiles.push(fileName);
+  }
+
+  /**
+   * Iterate through all the models we have discovered and scaffold
+   */
+  async scaffold() {
+    if (this.shouldExit()) return;
+  }
+
+  async end() {
+    if (this.shouldExit() || !this._isGenerationSuccessful()) {
+      await super.end();
+      return;
+    }
+
+    for (const f of this.modelFiles) {
+      await this._updateIndexFile(this.artifactInfo.outDir, f);
+    }
+
+    await super.end();
+  }
+};

packages/cli/generators/import-lb3-models/lb3app-loader.js

@@ -0,0 +1,31 @@
+// Copyright IBM Corp. 2019. All Rights Reserved.
+// Node module: @loopback/cli
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+const debug = require('../../lib/debug')('import-lb3-models');
+const path = require('path');
+const pEvent = require('p-event');
+
+module.exports = {
+  loadLb3App,
+};
+
+// TODO: do we want to share this code with `Lb3AppBooter.loadAndBootTheApp`?
+async function loadLb3App(dir) {
+  debug('Loading LB3 app from', dir);
+  const lb3App = require(path.resolve(dir));
+
+  debug(
+    'If your LB3 app does not boot correctly then make sure it is using loopback-boot version 3.2.1 or higher.',
+  );
+
+  if (lb3App.booting) {
+    debug('  waiting for boot process to finish');
+    // Wait until the legacy LB3 app boots
+    await pEvent(lb3App, 'booted');
+  }
+  return lb3App;
+}