From 25fa8562ae110ca3b558893470568699fe14aa1d Mon Sep 17 00:00:00 2001
From: Yen-Chi Chen <gruenen@gmail.com>
Date: Sun, 3 May 2020 11:36:17 +0200
Subject: [PATCH] async version of transform()

---
 .../jest-transform/src/ScriptTransformer.ts   | 82 +++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/packages/jest-transform/src/ScriptTransformer.ts b/packages/jest-transform/src/ScriptTransformer.ts
index 6241b4255f73..57f573d9a601 100644
--- a/packages/jest-transform/src/ScriptTransformer.ts
+++ b/packages/jest-transform/src/ScriptTransformer.ts
@@ -630,6 +630,54 @@ export default class ScriptTransformer {
 
   }
 
+  private async _transformAndBuildScriptAsync(
+    filename: Config.Path,
+    options: Options,
+    instrument: boolean,
+    fileSource?: string,
+  ): Promise<TransformResult> {
+    const {
+      isCoreModule,
+      isInternalModule,
+      supportsDynamicImport,
+      supportsStaticESM,
+    } = options;
+    const content = stripShebang(
+      fileSource || fs.readFileSync(filename, 'utf8'),
+    );
+
+    let code = content;
+    let sourceMapPath: string | null = null;
+
+    const willTransform =
+      !isInternalModule &&
+      !isCoreModule &&
+      (this.shouldTransform(filename) || instrument);
+
+    try {
+      if (willTransform) {
+        const transformedSource = await this.transformSourceAsync(
+          filename,
+          content,
+          instrument,
+          supportsDynamicImport,
+          supportsStaticESM,
+        );
+
+        code = transformedSource.code;
+        sourceMapPath = transformedSource.sourceMapPath;
+      }
+
+      return {
+        code,
+        originalCode: content,
+        sourceMapPath,
+      };
+    } catch (e) {
+      throw handlePotentialSyntaxError(e);
+    }
+  }
+
   private _transformAndBuildScript(
     filename: Config.Path,
     options: Options,
@@ -678,6 +726,40 @@ export default class ScriptTransformer {
     }
   }
 
+
+  async transformAsync(
+    filename: Config.Path,
+    options: Options,
+    fileSource?: string,
+  ): Promise<TransformResult> {
+    let scriptCacheKey = undefined;
+    let instrument = false;
+
+    if (!options.isCoreModule) {
+      instrument =
+        options.coverageProvider === 'babel' &&
+        shouldInstrument(filename, options, this._config);
+      scriptCacheKey = getScriptCacheKey(filename, instrument);
+      const result = this._cache.transformedFiles.get(scriptCacheKey);
+      if (result) {
+        return result;
+      }
+    }
+
+    const result = await this._transformAndBuildScriptAsync(
+      filename,
+      options,
+      instrument,
+      fileSource,
+    );
+
+    if (scriptCacheKey) {
+      this._cache.transformedFiles.set(scriptCacheKey, result);
+    }
+
+    return result;
+  }
+
   transform(
     filename: Config.Path,
     options: Options,