v8::MaybeLocal::ToLocalChecked() will abort on an empty handle.
AsyncWrap::MakeCallback returns an empty handle if the domain is
disposed, but this should not cause the process to abort. So instead
return v8::Undefined() and allow the error to be handled normally.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Reword several of the comments to be more descriptive.
* Rename functions to better indicate what they are doing.
* Change AsyncHooks::uid_fields_ to be a fixed array instead of a
  pointer.
* Define regex early so line ends before 80 columns.
* Remove obsolete comments.
* Rename AsyncHooks::InitScope::uid_fields_ to uid_fields_ptr_ because
  using the same name as AsyncHooks::uid_fields_ was confusing.
* Place variables that are used to store the new set of hooks if another
  hook is enabled/disabled during hook execution into an object to act
  as a namespace.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Because Emit{Before,After}() will always exit the process if there's
  an exception there's no need to check a return value. This simplifies
  the conditions and makes {Pre,Post}CallbackExecution() unnecessary.
  They have been removed and relevant code has been moved to the
  respective call sites. Which are:
  * PromiseHook() never needs to run domains, and without a return value
    to check place the calls to Emit{Before,After}() on location.
  * The logic in MakeCallback() is simplified by moving the single calls
    to Emit{Before,After}() then doing a simpler conditional to check if
    the domain has been disposed.
* Change Domain{Enter,Exit}() to return true if the instance has been
  disposed. Makes the conditional check in MakeCallback() simpler to
  reason about.
* Add UNREACHABLE() after FatalException() to make sure all error
  handlers have been cleared and the process really does exit.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* id values of -1 are allowed. They indicate that the id was never
  correctly assigned to the async resource. These will appear in any
  call graph, and will only be apparent to those using the async_hooks
  module, then reported in an issue.
* ids < -1 are still not allowed and will cause the application to
  exit the process; because there is no scenario where this should ever
  happen.
* Add asyncId range checks to emitAfterScript().
* Fix emitBeforeScript() range checks which should have been || not &&.
* Replace errors with entries in internal/errors.
* Fix async_hooks tests that check for exceptions to match new
  internal/errors entries.

NOTE: emit{Before,After,Destroy}() must continue to exit the process
because in the case of an exception during hook execution the state of
the application is unknowable. For example, an exception could cause a
memory leak:

    const id_map = new Map();

    before(id) {
      id_map.set(id, /* data object or similar */);
    },
    after(id) {
      throw new Error('id never dies!');
      id_map.delete(id);
    }

Allowing a recoverable exception may also cause an abort because of a
stack check in Environment::AsyncHooks::pop_ids() that verifies the
async id and pop'd ids match. This case would be more difficult to debug
than if fatalError() (lib/async_hooks.js) was called immediately.

    try {
      async_hooks.emitBefore(null, NaN);
    } catch (e) { }
    // do something
    async_hooks.emitAfter(5);

It also allows an edge case where emitBefore() could be called twice and
not have the pop_ids() CHECK fail:

    try {
      async_hooks.emitBefore(5, NaN);
    } catch (e) { }
    async_hooks.emitBefore(5);
    // do something
    async_hooks.emitAfter(5);

There is the option of allowing mismatches in the stack and ignoring the
check if no async hooks are enabled, but I don't believe going this far
is necessary.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

v8::MaybeLocal::ToLocalChecked() will abort on an empty handle.
AsyncWrap::MakeCallback returns an empty handle if the domain is
disposed, but this should not cause the process to abort. So instead
return v8::Undefined() and allow the error to be handled normally.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Reword several of the comments to be more descriptive.
* Rename functions to better indicate what they are doing.
* Change AsyncHooks::uid_fields_ to be a fixed array instead of a
  pointer.
* Define regex early so line ends before 80 columns.
* Remove obsolete comments.
* Rename AsyncHooks::InitScope::uid_fields_ to uid_fields_ptr_ because
  using the same name as AsyncHooks::uid_fields_ was confusing.
* Place variables that are used to store the new set of hooks if another
  hook is enabled/disabled during hook execution into an object to act
  as a namespace.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Because Emit{Before,After}() will always exit the process if there's
  an exception there's no need to check a return value. This simplifies
  the conditions and makes {Pre,Post}CallbackExecution() unnecessary.
  They have been removed and relevant code has been moved to the
  respective call sites. Which are:
  * PromiseHook() never needs to run domains, and without a return value
    to check place the calls to Emit{Before,After}() on location.
  * The logic in MakeCallback() is simplified by moving the single calls
    to Emit{Before,After}() then doing a simpler conditional to check if
    the domain has been disposed.
* Change Domain{Enter,Exit}() to return true if the instance has been
  disposed. Makes the conditional check in MakeCallback() simpler to
  reason about.
* Add UNREACHABLE() after FatalException() to make sure all error
  handlers have been cleared and the process really does exit.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* id values of -1 are allowed. They indicate that the id was never
  correctly assigned to the async resource. These will appear in any
  call graph, and will only be apparent to those using the async_hooks
  module, then reported in an issue.
* ids < -1 are still not allowed and will cause the application to
  exit the process; because there is no scenario where this should ever
  happen.
* Add asyncId range checks to emitAfterScript().
* Fix emitBeforeScript() range checks which should have been || not &&.
* Replace errors with entries in internal/errors.
* Fix async_hooks tests that check for exceptions to match new
  internal/errors entries.

NOTE: emit{Before,After,Destroy}() must continue to exit the process
because in the case of an exception during hook execution the state of
the application is unknowable. For example, an exception could cause a
memory leak:

    const id_map = new Map();

    before(id) {
      id_map.set(id, /* data object or similar */);
    },
    after(id) {
      throw new Error('id never dies!');
      id_map.delete(id);
    }

Allowing a recoverable exception may also cause an abort because of a
stack check in Environment::AsyncHooks::pop_ids() that verifies the
async id and pop'd ids match. This case would be more difficult to debug
than if fatalError() (lib/async_hooks.js) was called immediately.

    try {
      async_hooks.emitBefore(null, NaN);
    } catch (e) { }
    // do something
    async_hooks.emitAfter(5);

It also allows an edge case where emitBefore() could be called twice and
not have the pop_ids() CHECK fail:

    try {
      async_hooks.emitBefore(5, NaN);
    } catch (e) { }
    async_hooks.emitBefore(5);
    // do something
    async_hooks.emitAfter(5);

There is the option of allowing mismatches in the stack and ignoring the
check if no async hooks are enabled, but I don't believe going this far
is necessary.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

v8::MaybeLocal::ToLocalChecked() will abort on an empty handle.
AsyncWrap::MakeCallback returns an empty handle if the domain is
disposed, but this should not cause the process to abort. So instead
return v8::Undefined() and allow the error to be handled normally.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Reword several of the comments to be more descriptive.
* Rename functions to better indicate what they are doing.
* Change AsyncHooks::uid_fields_ to be a fixed array instead of a
  pointer.
* Define regex early so line ends before 80 columns.
* Remove obsolete comments.
* Rename AsyncHooks::InitScope::uid_fields_ to uid_fields_ptr_ because
  using the same name as AsyncHooks::uid_fields_ was confusing.
* Place variables that are used to store the new set of hooks if another
  hook is enabled/disabled during hook execution into an object to act
  as a namespace.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Because Emit{Before,After}() will always exit the process if there's
  an exception there's no need to check a return value. This simplifies
  the conditions and makes {Pre,Post}CallbackExecution() unnecessary.
  They have been removed and relevant code has been moved to the
  respective call sites. Which are:
  * PromiseHook() never needs to run domains, and without a return value
    to check place the calls to Emit{Before,After}() on location.
  * The logic in MakeCallback() is simplified by moving the single calls
    to Emit{Before,After}() then doing a simpler conditional to check if
    the domain has been disposed.
* Change Domain{Enter,Exit}() to return true if the instance has been
  disposed. Makes the conditional check in MakeCallback() simpler to
  reason about.
* Add UNREACHABLE() after FatalException() to make sure all error
  handlers have been cleared and the process really does exit.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* id values of -1 are allowed. They indicate that the id was never
  correctly assigned to the async resource. These will appear in any
  call graph, and will only be apparent to those using the async_hooks
  module, then reported in an issue.
* ids < -1 are still not allowed and will cause the application to
  exit the process; because there is no scenario where this should ever
  happen.
* Add asyncId range checks to emitAfterScript().
* Fix emitBeforeScript() range checks which should have been || not &&.
* Replace errors with entries in internal/errors.
* Fix async_hooks tests that check for exceptions to match new
  internal/errors entries.

NOTE: emit{Before,After,Destroy}() must continue to exit the process
because in the case of an exception during hook execution the state of
the application is unknowable. For example, an exception could cause a
memory leak:

    const id_map = new Map();

    before(id) {
      id_map.set(id, /* data object or similar */);
    },
    after(id) {
      throw new Error('id never dies!');
      id_map.delete(id);
    }

Allowing a recoverable exception may also cause an abort because of a
stack check in Environment::AsyncHooks::pop_ids() that verifies the
async id and pop'd ids match. This case would be more difficult to debug
than if fatalError() (lib/async_hooks.js) was called immediately.

    try {
      async_hooks.emitBefore(null, NaN);
    } catch (e) { }
    // do something
    async_hooks.emitAfter(5);

It also allows an edge case where emitBefore() could be called twice and
not have the pop_ids() CHECK fail:

    try {
      async_hooks.emitBefore(5, NaN);
    } catch (e) { }
    async_hooks.emitBefore(5);
    // do something
    async_hooks.emitAfter(5);

There is the option of allowing mismatches in the stack and ignoring the
check if no async hooks are enabled, but I don't believe going this far
is necessary.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

v8::MaybeLocal::ToLocalChecked() will abort on an empty handle.
AsyncWrap::MakeCallback returns an empty handle if the domain is
disposed, but this should not cause the process to abort. So instead
return v8::Undefined() and allow the error to be handled normally.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Reword several of the comments to be more descriptive.
* Rename functions to better indicate what they are doing.
* Change AsyncHooks::uid_fields_ to be a fixed array instead of a
  pointer.
* Define regex early so line ends before 80 columns.
* Remove obsolete comments.
* Rename AsyncHooks::InitScope::uid_fields_ to uid_fields_ptr_ because
  using the same name as AsyncHooks::uid_fields_ was confusing.
* Place variables that are used to store the new set of hooks if another
  hook is enabled/disabled during hook execution into an object to act
  as a namespace.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* Because Emit{Before,After}() will always exit the process if there's
  an exception there's no need to check a return value. This simplifies
  the conditions and makes {Pre,Post}CallbackExecution() unnecessary.
  They have been removed and relevant code has been moved to the
  respective call sites. Which are:
  * PromiseHook() never needs to run domains, and without a return value
    to check place the calls to Emit{Before,After}() on location.
  * The logic in MakeCallback() is simplified by moving the single calls
    to Emit{Before,After}() then doing a simpler conditional to check if
    the domain has been disposed.
* Change Domain{Enter,Exit}() to return true if the instance has been
  disposed. Makes the conditional check in MakeCallback() simpler to
  reason about.
* Add UNREACHABLE() after FatalException() to make sure all error
  handlers have been cleared and the process really does exit.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

* id values of -1 are allowed. They indicate that the id was never
  correctly assigned to the async resource. These will appear in any
  call graph, and will only be apparent to those using the async_hooks
  module, then reported in an issue.
* ids < -1 are still not allowed and will cause the application to
  exit the process; because there is no scenario where this should ever
  happen.
* Add asyncId range checks to emitAfterScript().
* Fix emitBeforeScript() range checks which should have been || not &&.
* Replace errors with entries in internal/errors.
* Fix async_hooks tests that check for exceptions to match new
  internal/errors entries.

NOTE: emit{Before,After,Destroy}() must continue to exit the process
because in the case of an exception during hook execution the state of
the application is unknowable. For example, an exception could cause a
memory leak:

    const id_map = new Map();

    before(id) {
      id_map.set(id, /* data object or similar */);
    },
    after(id) {
      throw new Error('id never dies!');
      id_map.delete(id);
    }

Allowing a recoverable exception may also cause an abort because of a
stack check in Environment::AsyncHooks::pop_ids() that verifies the
async id and pop'd ids match. This case would be more difficult to debug
than if fatalError() (lib/async_hooks.js) was called immediately.

    try {
      async_hooks.emitBefore(null, NaN);
    } catch (e) { }
    // do something
    async_hooks.emitAfter(5);

It also allows an edge case where emitBefore() could be called twice and
not have the pop_ids() CHECK fail:

    try {
      async_hooks.emitBefore(5, NaN);
    } catch (e) { }
    async_hooks.emitBefore(5);
    // do something
    async_hooks.emitAfter(5);

There is the option of allowing mismatches in the stack and ignoring the
check if no async hooks are enabled, but I don't believe going this far
is necessary.

PR-URL: #14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

PR-URL: #15454
Ref: #14387
Ref: #14722
Ref: #14717
Ref: #15448
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>