Re: [Json] Go JSON parser ignores the case of member names

"Manger, James" <James.H.Manger@team.telstra.com> Thu, 10 March 2016 04:56 UTC

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From: "Manger, James" <James.H.Manger@team.telstra.com>
To: John Cowan <cowan@mercury.ccil.org>, Rob Sayre <sayrer@gmail.com>
Date: Thu, 10 Mar 2016 15:55:47 +1100
Thread-Topic: [Json] Go JSON parser ignores the case of member names
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Subject: Re: [Json] Go JSON parser ignores the case of member names
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>> I understand the situation. I guess I don't agree there's a 
>> conformance problem here, since there are plenty of other APIs in the 
>> standard package that don't do this transformation, and even the API 
>> in question doesn't do this transformation for all arguments. They're 
>> right below the section James quoted.

> Ah.  I didn't know that.

I am fairly new to Go so there is heaps I don't know. However, I don't think the case-insensitive transformation is quite as optional as Rob suggests.

"encoding/json" looks like THE standard JSON package in Go.
It can parse (Unmarshall) a JSON object into a Go map or struct.
Parsing to a map (useful for handling unknown or arbitrary JSON) preserves the case of the object members.
Parsing to a struct (ie object-mapping) ignores case - always.

I cannot see any option NOT to ignore case when parsing to a struct. There is no equivalent of MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES.

Object-mapping is a great developer convenience. However, it looks like the Go implementation is an "attractive nuisance" < https://en.wikipedia.org/wiki/Attractive_nuisance_doctrine>gt;. Parsing to a struct is front and centre in the doco, yet comes with this risky case-ignoring transformation that cannot be disabled.

>> BTW, here's how to get a similar effect using the widely-used Java library Jackson[0]:
>> 
>> ObjectMapper objectMapper = new ObjectMapper(); 
>> objectMapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);

> Sure, but this is a feature you have to enable specifically, not the default.  But from what you are saying, the Go case mapping is not the default either.

> It's perfectly reasonable, given how much ill-formed or incorrect JSON there is, to have relaxed modes.  It's just that the main mode should be strict.

Go supports tags on struct fields (eg Algorithm string `json:"alg,omitempty"`). Supporting, say, an "ignorecase" option in the tag might have been a reasonable design.


P.S. Another interesting feature of the standard JSON package in Go is that it ALWAYS escapes "<" as "\u003c" - as a safety feature, in case the JSON is used within HTML. This safety decision seems such a contrast to the decision to ALWAYS ignore case when parsing to a struct.

--
James Manger