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encoding/json: UnmarshalTypeError should tell you what key you were unmarshaling #8254

kbloom opened this issue Jun 20, 2014 · 5 comments


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kbloom commented Jun 20, 2014

As seen at,
it would make it easier to debug JSON decoding errors, if UnmarshalTypeError would tell
you which key you were unmarshaling when you encountered the type error.
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Comment 1:

Labels changed: added repo-main, release-go1.4.

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Comment 2:

CL mentions this issue.

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rsc commented Sep 15, 2014

Comment 3:

Some kind of better reporting would be nice but I don't think this is the right answer.

Labels changed: added release-none, removed release-go1.4.

Status changed to Accepted.

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I think it would be helpful here for json.UnmarshalTypeError to have a reference to the full set of bytes that were being unmarshalled, and the character location where the decoding failed. It could even print context lines with an extra line with a ^ character pointing to the problem character:

json: cannot unmarshal #/Person/properties/job/description into Go value of type string.
Failed on line 42 at character 33:
  40     "properties": {
  41         "job": {
  42             "description": 7,
  43             "salary": 100000
  45         },

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@petemoore it's already in master by #9693. Using an offset you can then write your own tool for visualization.

@bradfitz bradfitz closed this as completed Feb 2, 2015
@golang golang locked and limited conversation to collaborators Jun 25, 2016
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7 participants