From d0f1f4e129926316edab8e75768d640649ad4313 Mon Sep 17 00:00:00 2001
From: "Robert Hurst (Dialpad)"
 <43556103+rhurstdialpad@users.noreply.github.com>
Date: Mon, 25 Feb 2019 10:44:14 -0800
Subject: [PATCH] Prevent circular deps from causing a stack overflow in HMR
 runtime (#2660)

---
 packages/core/integration-tests/test/hmr.js   | 31 +++++++++++++++++++
 .../test/integration/hmr-circular/index.js    |  9 ++++++
 .../test/integration/hmr-circular/local.js    |  4 +++
 .../src/builtins/hmr-runtime.js               |  8 +++++
 4 files changed, 52 insertions(+)
 create mode 100644 packages/core/integration-tests/test/integration/hmr-circular/index.js
 create mode 100644 packages/core/integration-tests/test/integration/hmr-circular/local.js

diff --git a/packages/core/integration-tests/test/hmr.js b/packages/core/integration-tests/test/hmr.js
index e06276c6e30..4766bac154b 100644
--- a/packages/core/integration-tests/test/hmr.js
+++ b/packages/core/integration-tests/test/hmr.js
@@ -287,6 +287,37 @@ describe('hmr', function() {
     assert.deepEqual(outputs, [3, 10]);
   });
 
+  it('should work with circular dependencies', async function() {
+    await ncp(
+      path.join(__dirname, '/integration/hmr-circular'),
+      path.join(__dirname, '/input')
+    );
+
+    b = bundler(path.join(__dirname, '/input/index.js'), {
+      watch: true,
+      hmr: true
+    });
+    let bundle = await b.bundle();
+    let outputs = [];
+
+    await run(bundle, {
+      output(o) {
+        outputs.push(o);
+      }
+    });
+
+    assert.deepEqual(outputs, [3]);
+
+    await sleep(100);
+    fs.writeFile(
+      path.join(__dirname, '/input/local.js'),
+      "var other = require('./index.js'); exports.a = 5; exports.b = 5;"
+    );
+
+    await nextEvent(b, 'bundled');
+    assert.deepEqual(outputs, [3, 10]);
+  });
+
   it('should call dispose and accept callbacks', async function() {
     await ncp(
       path.join(__dirname, '/integration/hmr-callbacks'),
diff --git a/packages/core/integration-tests/test/integration/hmr-circular/index.js b/packages/core/integration-tests/test/integration/hmr-circular/index.js
new file mode 100644
index 00000000000..72533c84aa2
--- /dev/null
+++ b/packages/core/integration-tests/test/integration/hmr-circular/index.js
@@ -0,0 +1,9 @@
+var local = require('./local');
+
+function run() {
+  output(local.a + local.b);
+}
+
+run();
+
+module.exports = 'value';
diff --git a/packages/core/integration-tests/test/integration/hmr-circular/local.js b/packages/core/integration-tests/test/integration/hmr-circular/local.js
new file mode 100644
index 00000000000..3bb6f4669b5
--- /dev/null
+++ b/packages/core/integration-tests/test/integration/hmr-circular/local.js
@@ -0,0 +1,4 @@
+var other = require('./index.js');
+
+exports.a = 1;
+exports.b = 2;
diff --git a/packages/core/parcel-bundler/src/builtins/hmr-runtime.js b/packages/core/parcel-bundler/src/builtins/hmr-runtime.js
index 74efb86d4d6..766bb1592ee 100644
--- a/packages/core/parcel-bundler/src/builtins/hmr-runtime.js
+++ b/packages/core/parcel-bundler/src/builtins/hmr-runtime.js
@@ -20,6 +20,7 @@ function Module(moduleName) {
 }
 
 module.bundle.Module = Module;
+var updatedAssets;
 
 var parent = module.bundle.parent;
 if ((!parent || !parent.isParcelRequire) && typeof WebSocket !== 'undefined') {
@@ -27,6 +28,8 @@ if ((!parent || !parent.isParcelRequire) && typeof WebSocket !== 'undefined') {
   var protocol = location.protocol === 'https:' ? 'wss' : 'ws';
   var ws = new WebSocket(protocol + '://' + hostname + ':' + process.env.HMR_PORT + '/');
   ws.onmessage = function(event) {
+    updatedAssets = {};
+    
     var data = JSON.parse(event.data);
 
     if (data.type === 'update') {
@@ -147,6 +150,11 @@ function hmrAccept(bundle, id) {
     return hmrAccept(bundle.parent, id);
   }
 
+  if (updatedAssets[id]) {
+    return;
+  }
+  updatedAssets[id] = true;
+
   var cached = bundle.cache[id];
   bundle.hotData = {};
   if (cached) {