process: add flag for uncaught exception abort

Introduce `process.shouldAbortOnUncaughtException` to control
`--abort-on-uncaught-exception` behaviour, and implement
some of the domains functionality on top of it.

PR-URL: https://github.com/nodejs/node/pull/17159
Refs: https://github.com/nodejs/node/issues/17143
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>

1 files changed, 73 insertions, 11 deletions

diff --git a/lib/domain.js b/lib/domain.js
index dc3c550866..6c85ca2b17 100644
--- a/lib/domain.js
+++ b/lib/domain.js
@@ -28,6 +28,7 @@
 
 const util = require('util');
 const EventEmitter = require('events');
+const errors = require('internal/errors');
 const { createHook } = require('async_hooks');
 
 // communicate with events module, but don't require that
@@ -81,19 +82,77 @@ const asyncHook = createHook({
   }
 });
 
+// When domains are in use, they claim full ownership of the
+// uncaught exception capture callback.
+if (process.hasUncaughtExceptionCaptureCallback()) {
+  throw new errors.Error('ERR_DOMAIN_CALLBACK_NOT_AVAILABLE');
+}
+
+// Get the stack trace at the point where `domain` was required.
+const domainRequireStack = new Error('require(`domain`) at this point').stack;
+
+const { setUncaughtExceptionCaptureCallback } = process;
+process.setUncaughtExceptionCaptureCallback = function(fn) {
+  const err =
+      new errors.Error('ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE');
+  err.stack = err.stack + '\n' + '-'.repeat(40) + '\n' + domainRequireStack;
+  throw err;
+};
+
 // It's possible to enter one domain while already inside
 // another one. The stack is each entered domain.
 const stack = [];
 exports._stack = stack;
-process._setupDomainUse(stack);
+process._setupDomainUse();
 
-class Domain extends EventEmitter {
+function updateExceptionCapture() {
+  if (stack.every((domain) => domain.listenerCount('error') === 0)) {
+    setUncaughtExceptionCaptureCallback(null);
+  } else {
+    setUncaughtExceptionCaptureCallback(null);
+    setUncaughtExceptionCaptureCallback((er) => {
+      return process.domain._errorHandler(er);
+    });
+  }
+}
+
+
+process.on('newListener', (name, listener) => {
+  if (name === 'uncaughtException' &&
+      listener !== domainUncaughtExceptionClear) {
+    // Make sure the first listener for `uncaughtException` always clears
+    // the domain stack.
+    process.removeListener(name, domainUncaughtExceptionClear);
+    process.prependListener(name, domainUncaughtExceptionClear);
+  }
+});
+
+process.on('removeListener', (name, listener) => {
+  if (name === 'uncaughtException' &&
+      listener !== domainUncaughtExceptionClear) {
+    // If the domain listener would be the only remaining one, remove it.
+    const listeners = process.listeners('uncaughtException');
+    if (listeners.length === 1 && listeners[0] === domainUncaughtExceptionClear)
+      process.removeListener(name, domainUncaughtExceptionClear);
+  }
+});
 
+function domainUncaughtExceptionClear() {
+  stack.length = 0;
+  exports.active = process.domain = null;
+  updateExceptionCapture();
+}
+
+
+class Domain extends EventEmitter {
   constructor() {
     super();
 
     this.members = [];
     asyncHook.enable();
+
+    this.on('removeListener', updateExceptionCapture);
+    this.on('newListener', updateExceptionCapture);
   }
 }
 
@@ -131,14 +190,14 @@ Domain.prototype._errorHandler = function _errorHandler(er) {
     // prevent the process 'uncaughtException' event from being emitted
     // if a listener is set.
     if (EventEmitter.listenerCount(this, 'error') > 0) {
+      // Clear the uncaughtExceptionCaptureCallback so that we know that, even
+      // if technically the top-level domain is still active, it would
+      // be ok to abort on an uncaught exception at this point
+      setUncaughtExceptionCaptureCallback(null);
       try {
-        // Set the _emittingTopLevelDomainError so that we know that, even
-        // if technically the top-level domain is still active, it would
-        // be ok to abort on an uncaught exception at this point
-        process._emittingTopLevelDomainError = true;
         caught = this.emit('error', er);
       } finally {
-        process._emittingTopLevelDomainError = false;
+        updateExceptionCapture();
       }
     }
   } else {
@@ -161,11 +220,13 @@ Domain.prototype._errorHandler = function _errorHandler(er) {
       if (this === exports.active) {
         stack.pop();
       }
+      updateExceptionCapture();
       if (stack.length) {
         exports.active = process.domain = stack[stack.length - 1];
-        caught = process._fatalException(er2);
+        caught = process.domain._errorHandler(er2);
       } else {
-        caught = false;
+        // Pass on to the next exception handler.
+        throw er2;
       }
     }
   }
@@ -173,8 +234,7 @@ Domain.prototype._errorHandler = function _errorHandler(er) {
   // Exit all domains on the stack.  Uncaught exceptions end the
   // current tick and no domains should be left on the stack
   // between ticks.
-  stack.length = 0;
-  exports.active = process.domain = null;
+  domainUncaughtExceptionClear();
 
   return caught;
 };
@@ -185,6 +245,7 @@ Domain.prototype.enter = function() {
   // to push it onto the stack so that we can pop it later.
   exports.active = process.domain = this;
   stack.push(this);
+  updateExceptionCapture();
 };
 
 
@@ -198,6 +259,7 @@ Domain.prototype.exit = function() {
 
   exports.active = stack[stack.length - 1];
   process.domain = exports.active;
+  updateExceptionCapture();
 };