Package Exports

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (babel-import-util) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

babel-import-util

Makes it easier for a babel plugin to emit imported names. Key benefits:

the output composes correctly with subsequent babel plugins, because we update Babel's understanding of the bindings
redundant imports will be deduplicated automatically
written in TypeScript

Usage by example:

If you want to rewrite:

myTarget('hello world');

To:

import { theMethod } from 'my-implementation';
theMethod('hello world');

Your plugin would look like this:

function testTransform(babel) {
  return {
    visitor: {
      Program: {
        enter(path, state) {
          // Always instantiate the ImportUtil instance at the Program scope
          state.importUtil = new ImportUtil(babel, path);
        },
      },
      CallExpression(path, state) {
        let callee = path.get('callee');
        if (callee.isIdentifier() && callee.node.name === 'myTarget') {
          state.importUtil.replaceWith(callee, (i) =>
            i.import(callee, 'my-implementation', 'theMethod')
          );
        }
      },
    },
  };
}

API

import type { NodePath } from '@babel/traverse';
import type * as t from '@babel/types';

class ImportUtil {
  /*
   Replace `target` with the new node produced by your callback. Your
   callback can use `i.import` to gain access to imported identifiers.

   Example:

   util.replaceWith(path, (i) =>
     t.callExpression(i.import('my-library', 'someFunction'), [])
   );
  */
  replaceWith<T extends t.Node, R extends t.Node>(
    target: NodePath<T>,
    fn: (i: Importer) => R
  ): NodePath<R>;

  /*
    Similar to `replaceWith` above, except instead of replacing the target 
    we will insert the new Node before or after it.
  */
  insertAfter<T extends t.Node, R extends t.Node>(
    target: NodePath<T>,
    fn: (i: Importer) => R
  ): NodePath<R>;
  insertBefore<T extends t.Node, R extends t.Node>(
    target: NodePath<T>,
    fn: (i: Importer) => R
  ): NodePath<R>;

  // If needed, adds a bare import like:
  //    import "your-module";
  importForSideEffect(moduleSpecifier: string): void;

  // Remove an import specifier. If the removed specifier is
  // the last one on the whole import statement, the whole
  // statement is also removed.
  //
  // You can use "default" and "*" as exportedName to handle
  // those special cases.
  removeImport(moduleSpecifier: string, exportedName: string): void;

  // Remove all imports from the given moduleSpecifier. Unlike
  // removeImport(), this can also remove "bare" import statements
  //  that were purely for side effect.
  removeAllImports(moduleSpecifier: string): void;

  // Import the given value (if needed) and return an Identifier representing
  // it.
  // CAUTION: this is a lower-level API that leaves some of the reference
  // safety up to you. It's better to use replaceWith, insertAfter, insertBefore,
  // or mutate. But this can still be helpful in contexts where you're already
  // planning to manage babel's scopes anyawy.
  import(
    // the spot at which you will insert the Identifier we return to you
    target: NodePath<t.Node>,

    // the path to the module you're importing from
    moduleSpecifier: string,

    // the name you're importing from that module. Use "default" for the default
    // export. Use "*" for the namespace.
    exportedName: string,

    // Optional hint for helping us pick a name for the imported binding
    nameHint?: string
  ): t.Identifier;
}