feat(migrations): add support for initial migrations (#818)

If you want to start using migrations, and you already have the schema generated,
you can do so by creating so called initial migration:

> Initial migration can be created only if there are no migrations previously
> generated or executed.

```sh
npx mikro-orm migration:create --initial
```

This will create the initial migration, containing the schema dump from
`schema:create` command. The migration will be automatically marked as executed.

Closes #772

docs/docs/migrations.md

@@ -29,6 +29,26 @@ per migration basis by implementing the `isTransactional(): boolean` method.
 
 `Configuration` object and driver instance are available in the `Migration` class context.
 
+You can execute queries in the migration via `Migration.execute()` method, which 
+will run queries in the same transaction as the rest of the migration. The 
+`Migration.addSql()` method also accepts instances of knex. Knex instance can be 
+accessed via `Migration.getKnex()`; 
+
+## Initial migration
+
+If you want to start using migrations, and you already have the schema generated, 
+you can do so by creating so called initial migration:
+
+> Initial migration can be created only if there are no migrations previously
+> generated or executed. 
+
+```sh
+npx mikro-orm migration:create --initial
+```
+
+This will create the initial migration, containing the schema dump from 
+`schema:create` command. The migration will be automatically marked as executed. 
+
 ## Configuration
 
 ```typescript

packages/cli/src/commands/MigrationCommandFactory.ts

@@ -60,6 +60,11 @@ export class MigrationCommandFactory {
       type: 'boolean',
       desc: 'Create blank migration',
     });
+    args.option('i', {
+      alias: 'initial',
+      type: 'boolean',
+      desc: 'Create initial migration',
+    });
     args.option('d', {
       alias: 'dump',
       type: 'boolean',
@@ -122,7 +127,7 @@ export class MigrationCommandFactory {
   }
 
   private static async handleCreateCommand(migrator: Migrator, args: Arguments<Options>, config: Configuration): Promise<void> {
-    const ret = await migrator.createMigration(args.path, args.blank);
+    const ret = await migrator.createMigration(args.path, args.blank, args.initial);
 
     if (ret.diff.length === 0) {
       return CLIHelper.dump(c.green(`No changes required, schema is up-to-date`));
@@ -179,5 +184,5 @@ export class MigrationCommandFactory {
 
 type MigratorMethod = 'create' | 'up' | 'down' | 'list' | 'pending';
 type CliUpDownOptions = { to?: string | number; from?: string | number; only?: string };
-type GenerateOptions = { dump?: boolean; blank?: boolean; path?: string; disableFkChecks?: boolean };
+type GenerateOptions = { dump?: boolean; blank?: boolean; initial?: boolean; path?: string; disableFkChecks?: boolean };
 type Options = GenerateOptions & CliUpDownOptions;

packages/migrations/src/Migrator.ts

@@ -48,22 +48,39 @@ export class Migrator {
     });
   }
 
-  async createMigration(path?: string, blank = false): Promise<MigrationResult> {
-    const diff = blank ? ['select 1'] : await this.getSchemaDiff();
+  async createMigration(path?: string, blank = false, initial = false): Promise<MigrationResult> {
+    if (initial) {
+      await this.validateInitialMigration();
+    }
+
+    const diff = await this.getSchemaDiff(blank, initial);
 
     if (diff.length === 0) {
       return { fileName: '', code: '', diff };
     }
 
     const migration = await this.generator.generate(diff, path);
 
+    if (initial) {
+      await this.storage.logMigration(migration[1]);
+    }
+
     return {
       fileName: migration[1],
       code: migration[0],
       diff,
     };
   }
 
+  async validateInitialMigration() {
+    const executed = await this.getExecutedMigrations();
+    const pending = await this.getPendingMigrations();
+
+    if (executed.length > 0 || pending.length > 0) {
+      throw new Error('Initial migration cannot be created, as some migrations already exist');
+    }
+  }
+
   async getExecutedMigrations(): Promise<MigrationRow[]> {
     await this.storage.ensureTable();
     return this.storage.getExecutedMigrations();
@@ -82,6 +99,10 @@ export class Migrator {
     return this.runMigrations('down', options);
   }
 
+  getStorage(): MigrationStorage {
+    return this.storage;
+  }
+
   protected resolve(file: string) {
     // eslint-disable-next-line @typescript-eslint/no-var-requires
     const migration = require(file);
@@ -100,9 +121,18 @@ export class Migrator {
     };
   }
 
-  private async getSchemaDiff(): Promise<string[]> {
-    const dump = await this.schemaGenerator.getUpdateSchemaSQL(false, this.options.safe, this.options.dropTables);
-    const lines = dump.split('\n');
+  private async getSchemaDiff(blank: boolean, initial: boolean): Promise<string[]> {
+    const lines: string[] = [];
+
+    if (blank) {
+      lines.push('select 1');
+    } else if (initial) {
+      const dump = await this.schemaGenerator.getCreateSchemaSQL(false);
+      lines.push(...dump.split('\n'));
+    } else {
+      const dump = await this.schemaGenerator.getUpdateSchemaSQL(false, this.options.safe, this.options.dropTables);
+      lines.push(...dump.split('\n'));
+    }
 
     for (let i = lines.length - 1; i > 0; i--) {
       if (lines[i]) {

tests/Migrator.test.ts

@@ -1,7 +1,7 @@
 (global as any).process.env.FORCE_COLOR = 0;
 import umzug from 'umzug';
 import { Logger, MikroORM } from '@mikro-orm/core';
-import { Migration, Migrator } from '@mikro-orm/migrations';
+import { Migration, MigrationStorage, Migrator } from '@mikro-orm/migrations';
 import { MySqlDriver } from '@mikro-orm/mysql';
 import { remove, writeFile } from 'fs-extra';
 import { initORMMySql } from './bootstrap';
@@ -76,6 +76,30 @@ describe('Migrator', () => {
     await remove(process.cwd() + '/temp/migrations/' + migration.fileName);
   });
 
+  test('generate initial migration', async () => {
+    const getExecutedMigrationsMock = jest.spyOn<any, any>(Migrator.prototype, 'getExecutedMigrations');
+    getExecutedMigrationsMock.mockResolvedValueOnce(['test.ts']);
+    const migrator = new Migrator(orm.em);
+    const err = 'Initial migration cannot be created, as some migrations already exist';
+    await expect(migrator.createMigration(undefined, false, true)).rejects.toThrowError(err);
+
+    getExecutedMigrationsMock.mockResolvedValueOnce([]);
+    const logMigrationMock = jest.spyOn<any, any>(MigrationStorage.prototype, 'logMigration');
+    logMigrationMock.mockImplementationOnce(i => i);
+    const dateMock = jest.spyOn(Date.prototype, 'toISOString');
+    dateMock.mockReturnValue('2019-10-13T21:48:13.382Z');
+
+    const migration = await migrator.createMigration(undefined, false, true);
+    expect(logMigrationMock).toBeCalledWith('Migration20191013214813.ts');
+    expect(migration).toMatchSnapshot('initial-migration-dump');
+    await remove(process.cwd() + '/temp/migrations/' + migration.fileName);
+  });
+
+  test('migration storage getter', async () => {
+    const migrator = new Migrator(orm.em);
+    expect(migrator.getStorage()).toBeInstanceOf(MigrationStorage);
+  });
+
   test('migration is skipped when no diff', async () => {
     const migrator = new Migrator(orm.em);
     const getSchemaDiffMock = jest.spyOn<any, any>(Migrator.prototype, 'getSchemaDiff');