ifndef

$$ifndef is a compile-time macro that keeps code when a define key is missing or falsy.

IMPORTANT

To get macro autocomplete in TypeScript, add @remotex-labs/xBuild to types in tsconfig.json.

{
  "compilerOptions": {
    "types": [
      "node",
      "@remotex-labs/xBuild"
    ]
  }
}

Syntax

$$ifndef('DEFINE_NAME', valueOrCallback)

Arguments

Argument	Type	Required	Notes
defineName	string literal	Yes	Must be a string literal, ex: 'PROD'
valueOrCallback	unknown	Yes	Function, expression, or literal

Define Evaluation

$$ifndef is enabled when the key is missing from define or its value is falsy.

define: {
  DEBUG: true,        // disabled
  PROD: false,        // enabled
  LOG_LEVEL: 'info',  // disabled
  RETRIES: 0          // enabled
}

NOTE

To inspect real macro replacements, run build with --verbose or -v.

Examples

Variable macro (function transform)

Source:

const $$devOnly = $$ifndef('PROD', () => console.log('dev mode'));

Output when enabled:

function $$devOnly() { return console.log('dev mode'); }

Output when disabled:

undefined

Immediate-call shape (IIFE expression)

Source:

const $$value = $$ifndef('PROD', (name: string) => {
  return name + ' dev';
})('test');

Output when enabled:

const $$value = ((name: string) => {
  return name + ' dev';
})('test');

Output when disabled:

// The macro call expression is removed (empty replacement).
// Avoid this shape when the define may be truthy.

Standalone expression

Source:

function initDevTools(): void {
  console.log('init dev tools');
}

$$ifndef('PROD', initDevTools());

Output when enabled:

function initDevTools(): void {
  console.log('init dev tools');
}

(() => { return initDevTools(); })();

Output when disabled:

function initDevTools(): void {
  console.log('init dev tools');
}

Exported typed function (complex example)

Source:

export const $$complexFunction = $$ifndef('PROD', (value: string, key: number) => {
  return `${value}-${key}`;
});

$$complexFunction('test', 42);

Output when enabled:

export function $$complexFunction(value: string, key: number) {
  return `${value}-${key}`;
}

$$complexFunction('test', 42);

Output when disabled:

undefined('test', 42);

5. Exported literals

Source:

export const $$feature = $$ifndef('PROD', true);
export const $$someValue = $$ifndef('PROD', 40);

Output when enabled:

export const $$feature = true;
export const $$someValue = 40;

Validation Rules

• $$ifndef requires exactly 2 arguments.
• The first argument must be a string literal.
• Invalid arg count throws a build error.
• Non-string first argument is not transformed.

Related

• ifdef: inverse behavior (keeps code when key exists and is truthy).