Add a promise version of each of Babel's transform functions.

packages/babel-core/src/index.js

@@ -17,10 +17,18 @@ export { createConfigItem } from "./config/item";
 
 export { loadPartialConfig, loadOptions } from "./config";
 
-export { transform, transformSync } from "./transform";
-export { transformFile, transformFileSync } from "./transform-file";
-export { transformFromAst, transformFromAstSync } from "./transform-ast";
-export { parse, parseSync } from "./parse";
+export { transform, transformSync, transformAsync } from "./transform";
+export {
+  transformFile,
+  transformFileSync,
+  transformFileAsync,
+} from "./transform-file";
+export {
+  transformFromAst,
+  transformFromAstSync,
+  transformFromAstAsync,
+} from "./transform-ast";
+export { parse, parseSync, parseAsync } from "./parse";
 
 /**
  * Recommended set of compilable extensions. Not used in @babel/core directly, but meant as

packages/babel-core/src/parse.js

@@ -70,3 +70,15 @@ export function parseSync(
 
   return normalizeFile(config.passes, normalizeOptions(config), code).ast;
 }
+
+export function parseAsync(
+  code: string,
+  opts?: InputOptions,
+): Promise<ParseResult | null> {
+  return new Promise((res, rej) => {
+    parse(code, opts, (err, result) => {
+      if (err == null) res(result);
+      else rej(err);
+    });
+  });
+}

packages/babel-core/src/transform-ast.js

@@ -71,3 +71,16 @@ export function transformFromAstSync(
 
   return runSync(config, code, ast);
 }
+
+export function transformFromAstAsync(
+  ast: AstRoot,
+  code: string,
+  opts: ?InputOptions,
+): Promise<FileResult | null> {
+  return new Promise((res, rej) => {
+    transformFromAst(ast, code, opts, (err, result) => {
+      if (err == null) res(result);
+      else rej(err);
+    });
+  });
+}

packages/babel-core/src/transform-file.js

@@ -73,3 +73,15 @@ export function transformFileSync(
 
   return runSync(config, fs.readFileSync(filename, "utf8"));
 }
+
+export function transformFileAsync(
+  filename: string,
+  opts: ?InputOptions,
+): Promise<FileResult | null> {
+  return new Promise((res, rej) => {
+    transformFile(filename, opts, (err, result) => {
+      if (err == null) res(result);
+      else rej(err);
+    });
+  });
+}

packages/babel-core/src/transform.js

@@ -53,3 +53,15 @@ export function transformSync(
 
   return runSync(config, code);
 }
+
+export function transformAsync(
+  code: string,
+  opts: ?InputOptions,
+): Promise<FileResult | null> {
+  return new Promise((res, rej) => {
+    transform(code, opts, (err, result) => {
+      if (err == null) res(result);
+      else rej(err);
+    });
+  });
+}