Errors from Result will now contain the caller stack trace

[legraphista]

Consider the following code:

const fn_a = cb => fn_b(cb);
const fn_b = cb => fn_c(cb);
const fn_c = cb => session.run('RETURN 1/0 AS x').catch(cb).then(_ => cb(void 0, _));

Before, when the execution had an error, we would get the following stack track:

Neo4jError: / by zero
    at new Neo4jError (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/error.js:76:132)
    at newError (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/error.js:66:10)
    at Connection._handleMessage (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/connector.js:356:56)
    at Dechunker.Connection._dechunker.onmessage (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/connector.js:287:12)
    at Dechunker._onHeader (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/chunking.js:246:14)
    at Dechunker.AWAITING_CHUNK (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/chunking.js:199:21)
    at Dechunker.write (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/chunking.js:257:28)
    at NodeChannel.self._ch.onmessage (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/connector.js:260:27)
    at TLSSocket.<anonymous> (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/ch-node.js:308:16)
    at emitOne (events.js:115:13)

In this case is easy to pinpoint the issue, but in a broader environment where there are a lot of queries, like for example in an API endpoint, It's hard find the bad one, even harder if the error doesn't contain any cypher at all for you to try to match against.

This change stores the current calling stack trace in this._stack in the constructor of Result and concatenates it with the original stack trace of Result in cases when Result throws an error.

Neo4jError: / by zero
    at new Neo4jError (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/error.js:76:132)
    at newError (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/error.js:66:10)
    at Connection._handleMessage (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/connector.js:356:56)
    at Dechunker.Connection._dechunker.onmessage (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/connector.js:287:12)
    at Dechunker._onHeader (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/chunking.js:246:14)
    at Dechunker.AWAITING_CHUNK (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/chunking.js:199:21)
    at Dechunker.write (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/chunking.js:257:28)
    at NodeChannel.self._ch.onmessage (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/connector.js:260:27)
    at TLSSocket.<anonymous> (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/internal/ch-node.js:308:16)
    at emitOne (events.js:115:13)
    at new Result (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/result.js:73:19)
    at Session._run (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/session.js:122:14)
    at Session.run (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/session.js:101:19)
    at fn_c (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:18:39)
    at fn_b (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:12:23)
    at fn_a (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:11:23)
    at __dirname (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:30:9)
    at Object.<anonymous> (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:31:3)
    at Module._compile (module.js:624:30)
    at Object.Module._extensions..js (module.js:635:10)

With the new stack trace, the location of the issue is immediately available to the developer to look at and fix.

...
    at fn_c (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:18:39)
    at fn_b (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:12:23)
    at fn_a (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:11:23)
    at __dirname (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:30:9)
    at Object.<anonymous> (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:31:3)
...

Also included test for it and all the other test are passing.

[eek]

Definitely useful! 👍

[lutovich]

Hi @legraphista,

Thanks for this PR. I definitely agree that having "real" stacktrace is valuable.
However, I think that concatenated stacktraces look weird. What do you think about just replacing the original stacktrace with Result._stack?

[legraphista]

Hey @lutovich,

That was my first approach, but then you'd loose backwards compatibility with anything that was dependent on that stack trace. But if you'd like, I can update the branch to replace the original stack trace.

[lutovich]

@legraphista do you think there might be some code out there that depends on the stacktrace?
I do not really know if it is common to parse stacktraces in real JS applications.

[legraphista]

Yes @lutovich, it's uncommon to parse the stack traces, I was thinking more from a logging side of things. But I think you're right, the old stack traces don't offer you much in terms of locating the issue, might as well just fully replace them.

[legraphista]

I've pushed the change, new stack trace example looks like:

Neo4jError: / by zero
    at new Result (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/result.js:73:19)
    at Session._run (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/session.js:122:14)
    at Session.run (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/lib/v1/session.js:101:19)
    at c (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:18:39)
    at b (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:12:23)
    at a (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:11:23)
    at __dirname (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:30:9)
    at Object.<anonymous> (/Users/Stefan/Desktop/GitHub/neo4j-javascript-driver/test.js:31:3)
    at Module._compile (module.js:624:30)
    at Object.Module._extensions..js (module.js:635:10)

[lutovich]

@legraphista thanks, change looks good to me.
@oskarhane could you please take a look as well?

[lutovich]

@legraphista merged, thanks again!
I think we'll release 1.5.1 version with this fix in a week or two.