src: print exceptions from PromiseRejectCallback

[addaleax]

Previously, leaving the exception lying around would leave the JS
engine in an invalid state, as it was not expecting exceptions to
be thrown from the C++ PromiseRejectCallback, and lead to hard
crashes under some conditions (e.g. with coverage enabled).

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[benjamingr]

I am confused, when would our PromiseRejectCallback ever throw? I am probably tired but:

• we export setPromiseRejectCallback
• We call it with handlePromiseRejections
• promiseRejectHandler adds the rejection to the weakmap here and calls setHasRejectionToWarn which sets kHasRejectionToWarn to true on the tickinfo.
• That gets processed in processTicksAndRejections which is always at a later point.

I am not sure how/why handlePromiseRejections would throw. I might be completely misunderstanding things :]

---

Actual technical changes LGTM, I am not ✅ing simply because I did not checkout the code and reproduce what this fixed because I am not sure how to make it throw.

[addaleax]

@benjamingr If you look at test/parallel/test-ttywrap-stack.js, you’ll see that it generates unhandled rejections near the stack limit. In that case, the PromiseRejectCallback may also throw an exception, namely a stack depth exceeded exception, when it tries to run JS code. Currently, when running the test with NODE_V8_COVERAGE set, that makes the test crash hard, because the exception isn’t used anywhere and the inspector’s console.log() code in V8 doesn’t expect to be run while there is a scheduled/pending exception.

(I’m not sure but it’s probably also possible to make the callback crash by overriding internals enough, e.g. WeakMap.prototype.set.)

[benjamingr]

Thanks for explaining how to test this Anna :]

Changes LGTM

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25437/

[Trott]

Some minor JS lint errors to fix:

/home/travis/build/nodejs/node/test/parallel/test-promise-reject-callback-exception.js
   2:7  error  'common' is assigned a value but never used   no-unused-vars
  25:1  error  Expected indentation of 9 spaces but found 6  indent
  28:1  error  Expected indentation of 9 spaces but found 6  indent

[addaleax]

Thanks, CI should be fixed now – also updated another test to account for the changes here.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25456/

[Trott]

Documenting here so people don't do futile "Resume Build" runs: At least some CI failures appear to be relevant edge cases. One example:

https://ci.nodejs.org/job/node-test-commit-linux-containered/14774/nodes=ubuntu1604_sharedlibs_withoutintl_x64/console

test-digitalocean-ubuntu1604_sharedlibs_container-x64-10

13:09:28 not ok 1630 parallel/test-promise-reject-callback-exception
13:09:28   ---
13:09:28   duration_ms: 0.266
13:09:28   severity: fail
13:09:28   exitcode: 1
13:09:28   stack: |-
13:09:28     assert.js:373
13:09:28         throw err;
13:09:28         ^
13:09:28     
13:09:28     AssertionError [ERR_ASSERTION]: stdout: <>
13:09:28         at Object.<anonymous> (/home/iojs/build/workspace/node-test-commit-linux-containered/test/parallel/test-promise-reject-callback-exception.js:23:3)
13:09:28         at Module._compile (internal/modules/cjs/loader.js:936:30)
13:09:28         at Object.Module._extensions..js (internal/modules/cjs/loader.js:947:10)
13:09:28         at Module.load (internal/modules/cjs/loader.js:789:32)
13:09:28         at Function.Module._load (internal/modules/cjs/loader.js:702:12)
13:09:28         at Function.Module.runMain (internal/modules/cjs/loader.js:999:10)
13:09:28         at internal/main/run_main_module.js:17:11 {
13:09:28       generatedMessage: false,
13:09:28       code: 'ERR_ASSERTION',
13:09:28       actual: false,
13:09:28       expected: true,
13:09:28       operator: '=='
13:09:28     }
13:09:28   ...

[addaleax]

@Trott Thanks, I’ve opened #29542 to track that, and added a workaround to the test for now.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25471/

[danbev]

Landed in e095e64.

[gengjiawen]

Just want to say thank you from 2020 😭