Also log any extra data attached to an error #46
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lib/logger.js
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| pick(['message', 'name', 'stack']) | ||
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| const flattenProps = | ||
| converge(merge, [ identity, clean ]) |
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😕 I don't follow. Are we picking the props off of an object & then merging them back into the same object?
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Javascript errors are super weird. The { message, name, stack } properties are not "own" properties. Instead they are built-in getters. Consequently:
JSON.stringify(new Error('my message')) === '{}'Which is not at all what we want. In the past we've resolved this with a pick, which reads the specified props whether they are "own" or not.
With the code in this PR, if we've attached new "own" properties to an error, it will pick off the special { message, name, stack } props, and then merge them with the extra "own" props, flattening them into a serializable object.
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Oooh... okay. A comment may be in order.
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Maybe "own" is the wrong word. I may be thinking of "enumerable". Those three props are not "enumerable", which is why a JSON.stringify won't pick them up when serializing.
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I want to fix this problem in Datadog. But currently we clean errors before logging them, and just log the
{ message, name, stack }. Any injected trace ids would be scrubbed, and errors would not be attached to the corresponding traces.This PR fixes that, by continuing to log at least the
{ message, name, stack }for errors, but also any other data that is attached to the error.