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Sequelize Migration Generator

Overview

This package simplifies the generation of Sequelize migration files from models. It processes models written in either sequelize.define format or class-based format, as outlined in Sequelize's official documentation. The generated migrations are compatible with Sequelize CLI commands.

Features

  • Input: Reads Sequelize models in both sequelize.define and class-based formats.
  • Output: Generates CLI-compatible migration files.
  • Support: Automatically extracts schema, including references (with limitations).

Installation

  1. Install the package using npm:

    npm install sequelize-migration-builder

  2. Ensure you have Sequelize installed in your project:

    npm install sequelize

Supported Model Formats

This tool supports the following formats for Sequelize models:

  1. Using sequelize.define:

    module.exports = (sequelize, DataTypes) => {
  const User = sequelize.define("User", {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true,
      primaryKey: true,
    },
    name: {
      type: DataTypes.STRING,
      allowNull: false,
    },
    role_id: {
      type: DataTypes.INTEGER,
      references: {
        model: "Roles", // Must be a string, not an imported reference
        key: "id",
      },
    },
  });
  return User;
};

  2. Using Class-Based Format:

    const { Model, DataTypes } = require("sequelize");

module.exports = (sequelize) => {
  class User extends Model {}

  User.init(
    {
      id: {
        type: DataTypes.INTEGER,
        autoIncrement: true,
        primaryKey: true,
      },
      name: {
        type: DataTypes.STRING,
        allowNull: false,
      },
      role_id: {
        type: DataTypes.INTEGER,
        references: {
          model: "Roles", // Use string instead of imported reference
          key: "id",
        },
      },
    },
    {
      sequelize,
      modelName: "User",
    }
  );

  return User;
};

For more information about defining models, refer to the official Sequelize documentation:
https://sequelize.org/docs/v6/core-concepts/model-basics/

Usage

There are two ways to use this package: as a CLI tool and as a module in your code.

1. CLI Usage

  1. Prepare Models:

    • Models must follow sequelize.define or class-based format.
    • Ensure that foreign key references use string-based models.

  2. Run the Generator:

    npx migrator-plugin create-migration --models ./models --template ./migration-template.ejs
    • --models: Path to the folder containing Sequelize models.
    • --template: (Optional) Path to a custom migration template. If not provided, the default template will be used.

  3. Generated Migrations:

    • Migrations will be created in a migrations directory in your project's root.

2. Programmatic Usage

  1. Import the Package:

    const { exec } = require('child_process');
const path = require('path');

  2. Generate Migrations:

    const modelsPath = path.resolve(__dirname, "models/mysql");

exec(`npx migrator-plugin create-migration --models ${modelsPath}`, (err, stdout, stderr) => {
  if (err) {
    console.error("Error executing CLI:", err);
    return;
  }

  // Output the stdout and stderr (if any)
  if (stdout) {
    console.log("stdout:", stdout);
  }
  if (stderr) {
    console.error("stderr:", stderr);
  }
});

Default Template Example

The default migration template (migration.ejs) is as follows. If no custom template is provided, this one will be used.

module.exports = {
  up: async (queryInterface, Sequelize) => {
    await queryInterface.createTable('<%= model.name %>', {
      <% Object.entries(model.schema).forEach(([key, value], index, array) => { %>
        <%- key %>: {
          <% Object.entries(value).forEach((propKey, propValue, i, propsArray) => { %>
            <% if (propValue !== undefined) { %>
              <% if (propKey === 'references') { %>
                references: {
                  model: '<%- propValue.model %>',
                  key: '<%- propValue.key %>',
                }
              <% } else { %>
                <%- propKey %>: <%- typeof propValue === 'string' ? propValue : JSON.stringify(propValue) %>
              <% } %>
            <% } %>
          <% }); %>
        }<%- index < array.length - 1 ? ',' : '' %>
      <% }); %>
    });
  },

  down: async (queryInterface) => {
    await queryInterface.dropTable('<%= model.name %>');
  },
};

This template will be used if no custom template is specified. It generates Sequelize migrations for creating tables with columns, including foreign key references.

Known Limitations

  1. Imported References:

    • Do not use imported references for foreign keys (e.g., model: SomeImportedModel).
    • Use string values for the model property in references instead: 
      references: {
  model: "Roles",
  key: "id",
}

  2. Default Values:

    • While the tool attempts to preserve default values, some complex objects may not render correctly.

  3. Ignore Certain Files:

    • The tool ignores errors caused by files like index.js that are often used for setting up the database in the models directory (where the database is initialized). These files are not processed as part of the migration generation and any errors for such files, please ignore those in the CLI.

  4. Incomplete Features:

    • The package is under development and may have limitations or bugs. Contributions are welcome!

Contributing

  1. Fork the repository.
  2. Create a new branch for your changes.
  3. Submit a pull request describing the updates.

For more detailed instructions on contributing, check out the CONTRIBUTING.md file.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Thank You!

We hope this tool simplifies your workflow. If you encounter any issues or have suggestions, feel free to open an issue or contribute to the repository. 🎉