metro-bundler: ModuleGraph: add support for require.async() when collecting dependencies

Summary: This is the last step remaining before enabling the `import()` syntax to use `require.async()` (for now that function is just doing a simple `require()` in behind).

Reviewed By: davidaurelio

Differential Revision: D6147030

fbshipit-source-id: 5cd8ee6cc550816ae3cdea0b457dc2419c99e7a7

packages/metro-bundler/src/ModuleGraph/worker/__tests__/collect-dependencies-test.js

@@ -37,6 +37,20 @@ describe('dependency collection from ASTs:', () => {
     ]);
   });
 
+  it('collects asynchronous dependencies', () => {
+    const ast = astFromCode(`
+      const a = require('b/lib/a');
+      if (!something) {
+        require.async("some/async/module").then(foo => {});
+      }
+    `);
+
+    expect(collectDependencies(ast).dependencies).toEqual([
+      'b/lib/a',
+      'some/async/module',
+    ]);
+  });
+
   it('supports template literals as arguments', () => {
     const ast = astFromCode('require(`left-pad`)');
 
@@ -101,11 +115,12 @@ describe('Dependency collection from optimized ASTs:', () => {
     ast = astFromCode(`
       const a = require(${dependencyMapName}[0], 'b/lib/a');
       exports.do = () => require(${dependencyMapName}[1], "do");
+      require.async(${dependencyMapName}[2], 'some/async/module').then(foo => {});
       if (!something) {
-        require(${dependencyMapName}[2], "setup/something");
+        require(${dependencyMapName}[3], "setup/something");
       }
     `);
-    names = ['b/lib/a', 'do', 'setup/something'];
+    names = ['b/lib/a', 'do', 'some/async/module', 'setup/something'];
   });
 
   it('passes the `dependencyMapName` through', () => {
@@ -130,8 +145,9 @@ describe('Dependency collection from optimized ASTs:', () => {
       comparableCode(`
       const a = require(${dependencyMapName}[0]);
       exports.do = () => require(${dependencyMapName}[1]);
+      require.async(${dependencyMapName}[2]).then(foo => {});
       if (!something) {
-        require(${dependencyMapName}[2]);
+        require(${dependencyMapName}[3]);
       }
     `),
     );

packages/metro-bundler/src/ModuleGraph/worker/collect-dependencies.js

@@ -132,6 +132,16 @@ function createMapLookup(dependencyMapIdentifier, propertyIdentifier) {
 function collectDependencies(ast, replacement, dependencyMapIdentifier) {
   const visited = new WeakSet();
   const traversalState = {dependencyMapIdentifier};
+  function processRequireCall(node, state, isAsync) {
+    const arg = replacement.getRequireCallArg(node);
+    const index = replacement.getIndex(arg);
+    node.arguments = replacement.makeArgs(
+      types.numericLiteral(index),
+      arg,
+      state.dependencyMapIdentifier,
+    );
+    visited.add(node);
+  }
   traverse(
     ast,
     {
@@ -148,14 +158,9 @@ function collectDependencies(ast, replacement, dependencyMapIdentifier) {
           return;
         }
         if (isRequireCall(node.callee)) {
-          const arg = replacement.getRequireCallArg(node);
-          const index = replacement.getIndex(arg);
-          node.arguments = replacement.makeArgs(
-            types.numericLiteral(index),
-            arg,
-            state.dependencyMapIdentifier,
-          );
-          visited.add(node);
+          processRequireCall(node, state, false);
+        } else if (isAsyncRequireCall(node.callee)) {
+          processRequireCall(node, state, true);
         }
       },
     },
@@ -180,6 +185,15 @@ function isRequireCall(callee) {
   return callee.type === 'Identifier' && callee.name === 'require';
 }
 
+function isAsyncRequireCall(callee) {
+  return (
+    callee.type === 'MemberExpression' &&
+    !callee.computed &&
+    callee.property.name === 'async' &&
+    isRequireCall(callee.object)
+  );
+}
+
 class InvalidRequireCallError extends Error {
   constructor(message) {
     super(message);