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const { kebabCase } = require( 'lodash' );
function importChunk( t, name ) {
const chunkName = 'async-load-' + kebabCase( name );
const argumentWithMagicComments = t.addComment(
t.stringLiteral( name ),
'leading',
`webpackChunkName: "${ chunkName }"`,
false
);
return t.callExpression( t.import(), [ argumentWithMagicComments ] );
}
function importError( t, name ) {
const chunkName = 'async-load-' + kebabCase( name );
return t.newExpression( t.identifier( 'Error' ), [
t.stringLiteral( 'ignoring load of: ' + chunkName ),
] );
}
module.exports = ( { types: t } ) => {
/**
* Nested visitor for `require` function expression hoisting. This is
* assigned here as a shared reference for optimized path traversal.
* @see https://github.com/thejameskyle/babel-handbook/blob/HEAD/translations/en/plugin-handbook.md#optimizing-nested-visitors
* @type {Object}
*/
const asyncAttributeVisitor = {
ArrowFunctionExpression( path ) {
// Hoist using the parent JSXAttribute's scope, since the scopes
// from AST parse stage are not valid for replacement expression
path.hoist( this.scope );
},
};
return {
visitor: {
JSXAttribute( path, state ) {
// We only transform the require prop on AsyncLoad components.
// The component could have been imported under a different
// name, but tracking the identifier to the import would add
// complexity to the parsing. In other words, I'm lazy.
const parent = path.parentPath.parent;
if ( 'AsyncLoad' !== parent.openingElement.name.name ) {
return;
}
const name = path.node.name;
if ( 'JSXIdentifier' !== name.type || 'require' !== name.name ) {
return;
}
const value = path.node.value;
if ( 'StringLiteral' !== value.type ) {
return;
}
const body = state.opts.ignore
? t.blockStatement( [ t.throwStatement( importError( t, value.value ) ) ] )
: importChunk( t, value.value );
path.replaceWith(
t.jSXAttribute( name, t.jSXExpressionContainer( t.arrowFunctionExpression( [], body ) ) )
);
// Traverse replacement attribute to hoist function expression
path.traverse( asyncAttributeVisitor, { scope: path.scope } );
},
CallExpression( path, state ) {
if ( 'asyncRequire' !== path.node.callee.name ) {
return;
}
const argument = path.node.arguments[ 0 ];
if ( ! argument || 'StringLiteral' !== argument.type ) {
return;
}
const expr = state.opts.ignore
? t.callExpression(
t.memberExpression( t.identifier( 'Promise' ), t.identifier( 'reject' ) ),
[ importError( t, argument.value ) ]
)
: importChunk( t, argument.value );
path.replaceWith( expr );
},
},
};
};
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