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tessl/npm-babel-plugin-transform-inline-environment-variables

Babel plugin that transforms process.env references into inline string literals at build time.

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babel-plugin-transform-inline-environment-variables

A Babel plugin that transforms process.env references into inline string literals at build time. This enables compile-time environment variable inlining, which helps with dead code elimination and optimization by replacing environment variable references with their actual values during the build process.

Package Information

  • Package Name: babel-plugin-transform-inline-environment-variables
  • Package Type: npm
  • Language: JavaScript
  • Installation: npm install babel-plugin-transform-inline-environment-variables --save-dev

Core Imports

This plugin is configured through Babel configuration files rather than imported directly in code:

.babelrc:

{
  "plugins": ["transform-inline-environment-variables"]
}

Node API:

const babel = require("@babel/core");

babel.transform("code", {
  plugins: ["transform-inline-environment-variables"]
});

Basic Usage

The plugin automatically transforms process.env references during Babel compilation:

Input code:

// Assuming process.env.NODE_ENV is "production"
if (process.env.NODE_ENV === "development") {
  console.log("Debug mode");
}
const apiUrl = process.env.API_URL;

Output after transformation:

if ("production" === "development") {
  console.log("Debug mode");
}
const apiUrl = "https://api.production.com";

Capabilities

Plugin Factory Function

The main export is a Babel plugin factory function that creates a plugin with environment variable inlining behavior.

/**
 * Creates a Babel plugin that transforms process.env references into inline literals
 * @param {Object} babel - Babel core object with types
 * @param {Object} babel.types - Babel types utilities (t)
 * @returns {BabelPlugin} Babel plugin object with name and visitor
 */
function pluginFactory({ types: t }) {
  return {
    name: "transform-inline-environment-variables",
    visitor: {
      MemberExpression(path, { opts: { include, exclude } = {} }) {
        // Implementation: transforms process.env.X to string literals
      }
    }
  };
}

/**
 * Plugin object structure returned by the factory
 */
interface BabelPlugin {
  name: string;
  visitor: {
    MemberExpression(path: NodePath, state: PluginState): void;
  };
}

interface PluginState {
  opts: PluginOptions;
}

interface NodePath {
  get(key: string): NodePath;
  matchesPattern(pattern: string): boolean;
  toComputedKey(): Node;
  parent: Node;
  node: Node;
  replaceWith(node: Node): void;
}

interface Node {
  value?: any;
}

Plugin Options

The plugin accepts configuration options to control which environment variables are processed:

interface PluginOptions {
  /** Array of environment variable names to include (whitelist) */
  include?: string[];
  /** Array of environment variable names to exclude (blacklist) */
  exclude?: string[];
}

Usage with options:

{
  "plugins": [
    ["transform-inline-environment-variables", {
      "include": ["NODE_ENV", "API_URL"],
      "exclude": ["SECRET_KEY"]
    }]
  ]
}

Transformation Behavior

The plugin transforms the following patterns:

Dot Notation Access

// Input
process.env.VARIABLE_NAME

// Output (if VARIABLE_NAME = "value")
"value"

Bracket Notation Access

// Input  
process.env["VARIABLE_NAME"]

// Output (if VARIABLE_NAME = "value")
"value"

Assignment Protection

The plugin does not transform assignments to prevent unintended side effects:

// Input (remains unchanged)
process.env.NODE_ENV = "development";

// Output (no transformation)
process.env.NODE_ENV = "development";

Configuration Examples

Include specific variables only:

{
  "plugins": [
    ["transform-inline-environment-variables", {
      "include": ["NODE_ENV", "DEBUG", "API_VERSION"]
    }]
  ]
}

Exclude sensitive variables:

{
  "plugins": [
    ["transform-inline-environment-variables", {
      "exclude": ["SECRET_KEY", "DATABASE_PASSWORD", "JWT_SECRET"]
    }]
  ]
}

Via CLI:

babel --plugins transform-inline-environment-variables script.js

Via Node.js API:

const babel = require("@babel/core");

const result = babel.transform(sourceCode, {
  plugins: [
    ["transform-inline-environment-variables", {
      include: ["NODE_ENV"]
    }]
  ]
});

Limitations

  • Only processes string literal property access (process.env.VAR or process.env["VAR"])
  • Does not transform computed property access with variables (process.env[varName])
  • Does not transform assignment expressions (process.env.VAR = "value")
  • Requires environment variables to be available at build time
  • Transforms are based on the build environment, not runtime environment

docs

index.md

tile.json