Enum EsModuleFlag 

pub enum EsModuleFlag {
    Always,
    Never,
    IfDefaultProp,
}

This configuration determines how the bundler should handle the synthetic __esModule property in the CJS and IIFE format. It is rollup-capable, and the rollup default is IfDefaultProp. You may find rollup explanation here.

Whether to add a __esModule: true property when generating exports for non-ES formats. This property signifies that the exported value is the namespace of an ES module and that the default export of this module corresponds to the .default property of the exported object.

From rollupjs.org

Variants

Always

Always generate Object.defineProperty(exports, "__esModule", { value: true }); in the CJS and IIFE format. It is similar to other bundlers’ behavior.

Never

Never generate the synthetic __esModule property in the CJS and IIFE format.

IfDefaultProp

Generate the synthetic __esModule property in the CJS and IIFE format only if the module has a default export.

It will only add the property when using named exports mode and there also is a default export. The subtle difference is that if there is no default export, consumers of the CommonJS version of your library will get all named exports as default export instead of an error or undefined. We chose to make this the default value as the __esModule property is not a standard followed by any JavaScript runtime and leads to many interop issues, so we want to limit its use to the cases where it is really needed.

From rollupjs.org

For example, rolldown will define the __esModule property in the following entry code:

export default function() {}
export const a = 1; // For this module, rolldown will automatically regard it as the `named` export mode.

And rolldown won’t generate the __esModule property in the following entry code:

export const a = 1;

Trait Implementations

impl Clone for EsModuleFlag

fn clone(&self) -> EsModuleFlag

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for EsModuleFlag

impl Debug for EsModuleFlag

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for EsModuleFlag

fn default() -> EsModuleFlag

Returns the “default value” for a type.

impl From<String> for EsModuleFlag

fn from(value: String) -> EsModuleFlag

Converts to this type from the input type.

impl From<bool> for EsModuleFlag

fn from(value: bool) -> EsModuleFlag

Converts to this type from the input type.