repl: handle unexpected error objects #12400

cjihrig · 2017-04-13T15:58:22Z

This commit allows the repl's domain error handler to process
unexpected error formats, such as primitives.

Fixes: #12373

Checklist

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

Affected core subsystem(s)

repl

aqrln · 2017-04-13T16:29:21Z

lib/repl.js

    }
-    top.outputStream.write((e.stack || e) + '\n');
+
+    top.outputStream.write(out + '\n');


It will fail if e is a Symbol, won't it?

refack · 2017-04-13T16:01:48Z

lib/repl.js

@@ -282,17 +282,24 @@ function REPLServer(prompt,
  self._domain.on('error', function debugDomainError(e) {
    debug('domain error');
    const top = replMap.get(self);
+    var out;


We haven't moved over to let completely yet.

refack · 2017-04-13T16:18:30Z

lib/repl.js

+
+    if (!((e instanceof Error) && typeof e.stack === 'string')) {
+      out = e;
+    } else if (e instanceof SyntaxError) {


if there a chance e.stack != true || !('replace' in e.stack)?
Maybe a custom error:

function MySillyError(a, b, c) { console.log(a) } MySillyError.prototype = SyntaxError

I don't think we need to jump through hoops for extreme edge cases like this. As long as they don't crash.

Cool, just tested, no crash just TypeError: Function.prototype.toString is not generic

refack · 2017-04-13T16:30:40Z

lib/repl.js

    }
-    top.outputStream.write((e.stack || e) + '\n');
+
+    top.outputStream.write(out + '\n');


how about if delete e.toString?

refack · 2017-04-13T16:32:18Z

test/parallel/test-repl.js

+      client: client_unix,
+      send: 'var e = new Error(\'test error\'); delete e.stack; throw e;',
+      expect: /^Error: test error/
+    },


add this monstrosity:

send: 'function MySillyError() {}; MySillyError.prototype = SyntaxError; var e = new MySillyError(); throw e', expect: /^TypeError: Function.prototype.toString is not generic/

No crash, but INHO it's a good test
also @aqrln's

send: 'throw Symbol.for', expect: /^function for() { [native code] }/

refack · 2017-04-13T16:34:33Z

@cjihrig you're not a first time contributor 😁 kudos on the commitment...

I added some horrible code to try and crash your cases...

cjihrig · 2017-04-13T17:17:21Z

lib/repl.js

-    if (e instanceof SyntaxError && e.stack) {
+
+    if (!((e instanceof Error) && typeof e.stack === 'string')) {
+      out = e;


Symbols and other bad inputs are taken care of here if I move to out = util.inspect(e);. However, it causes test-repl-sigint.js and test-repl-sigint-nested-eval.js to fail. @addaleax any idea why that would be?

that’s odd… I’ll have a look

@addaleax I just pushed up the changes that include that and more tests, if you want to take a look.

@cjihrig I think this might be the missing puzzle piece. ;)

Anyway I would "de-morgan" it to:

(!(e instanceof Error) || typeof e.stack !== 'string')

then add the original ~~gourd🎃~~ guard

(typeof e === 'undefined' || !(e instanceof Error) || typeof e.stack !== 'string')

Thanks @addaleax. The special snowflake that is the REPL. I added a length check for stack, so errors with empty stacks will print with util.inspect().

refack · 2017-04-13T17:28:49Z

mo' tests less trouble?!

refack · 2017-04-13T17:31:07Z

You could add the extreme edge cases as tests

send: 'function MySillyError() {}; MySillyError.prototype = SyntaxError; var e = new MySillyError(); throw e',
expect: /^TypeError: Function.prototype.toString is not generic/

also @aqrln's

send: 'throw Symbol.for',
expect: /^function for() { [native code] }/

benjamingr

Changes LGTM and improve current status quo.

This commit allows the repl's domain error handler to process unexpected error formats, such as primitives.

refack · 2017-04-14T00:41:17Z

test/parallel/test-repl.js

+    // Throws Object with bad toString() method and prints out
+    {
+      client: client_unix,
+      send: 'var e = { toString() { throw new Error(\'test\'); } }; throw e;',


Even smarter! 👍

TimothyGu · 2017-04-14T06:35:35Z

lib/repl.js

-    if (e instanceof SyntaxError && e.stack) {
+
+    if (!((e instanceof Error) && typeof e.stack === 'string' &&
+        e.stack.length > 0)) {


Not sure how robust you want this code to be, but the typeof e.stack will crash with

function FakeError() {} FakeError.prototype = Object.create(Error.prototype, { stack: { get() { throw new Error(); } } }); var e = new FakeError();

I don't know how others feel, but I'm OK with it, at least in the context of this PR. It seems like any Node application can be crashed with a well crafted getter.

One thing that I would (personally) prefer is either using V8’s IsNativeError over instanceof Error or going full 🦆 here. Both would increase robustness in different ways :)

Just noting that whatever is done here would need to factor in compatibility with internal/errors.js

Refs: nodejs#12400 PR-URL: nodejs#12546 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>

Refs: #12400 PR-URL: #12546 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>

addaleax · 2017-05-26T19:29:27Z

@cjihrig Did you mean to close this?

cjihrig · 2017-06-06T17:21:17Z

Sorry @addaleax. Yes, I did. The move to internal/errors.js is going to prevent IsNativeError() from working correctly, and I didn't want to go full on duck typing.

TimothyGu · 2017-06-17T16:03:16Z

@cjihrig

The move to internal/errors.js is going to prevent IsNativeError() from working correctly

Can you elaborate? The Node.js error classes all extend from the native error classes, and generally V8's methods recognize subclasses.

cjihrig · 2017-06-19T00:15:14Z

Hm, good question. I tested this before, but maybe I did something wrong. process.binding('util').isNativeError() does appear to work with internal/errors.

nodejs-github-bot added the repl Issues and PRs related to the REPL subsystem. label Apr 13, 2017

aqrln reviewed Apr 13, 2017

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cjihrig commented Apr 13, 2017

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refack approved these changes Apr 13, 2017

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cjihrig force-pushed the repl branch from 6052da6 to 9828645 Compare April 13, 2017 17:23

princejwesley approved these changes Apr 13, 2017

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benjamingr approved these changes Apr 13, 2017

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cjihrig force-pushed the repl branch from 9828645 to 5262d6d Compare April 14, 2017 00:37

repl: handle unexpected error objects

9a8dec0

This commit allows the repl's domain error handler to process unexpected error formats, such as primitives.

cjihrig force-pushed the repl branch from 5262d6d to 9a8dec0 Compare April 14, 2017 00:39

refack reviewed Apr 14, 2017

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refack approved these changes Apr 14, 2017

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cjihrig added the semver-major PRs that contain breaking changes and should be released in the next major version. label Apr 14, 2017

refack force-pushed the master branch from 16073c0 to fbe946b Compare April 14, 2017 04:12

aqrln approved these changes Apr 14, 2017

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TimothyGu reviewed Apr 14, 2017

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cjihrig mentioned this pull request Apr 20, 2017

src: expose V8's IsNativeError() in util bindings #12546

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cjihrig closed this May 17, 2017

bnoordhuis mentioned this pull request Jun 16, 2017

setTimeout(function(){throw null},0) crashes toplevel #12373

Closed

TimothyGu mentioned this pull request Jul 18, 2017

repl: handle null thrown #14306

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cjihrig commented Apr 13, 2017

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repl: handle unexpected error objects #12400

repl: handle unexpected error objects #12400

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cjihrig commented Apr 13, 2017

Checklist

Affected core subsystem(s)

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addaleax commented May 26, 2017

cjihrig commented Jun 6, 2017

TimothyGu commented Jun 17, 2017

cjihrig commented Jun 19, 2017

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