From: Tom Lane <tgl@sss.pgh.pa.us>
To: Erwin Brandstetter <brsaweda@gmail.com>
cc: "David G. Johnston" <david.g.johnston@gmail.com>,
        pgsql-docs <pgsql-docs@postgresql.org>
Subject: Re: json_strip_nulls()
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Comments: In-reply-to Erwin Brandstetter <brsaweda@gmail.com>
	message dated "Sat, 22 Jan 2022 21:20:21 +0100"
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Date: Sat, 22 Jan 2022 16:00:39 -0500
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Erwin Brandstetter <brsaweda@gmail.com> writes:
> On Sat, 22 Jan 2022 at 20:31, David G. Johnston <david.g.johnston@gmail.com>
> wrote:
>> json_strip_nulls doesn't make any promise regarding its output json other
>> than that it is valid.  Since we are munging the json we are arguably
>> within our rights to output whatever transformed version we want.  The
>> format should not be documented.

> Within our rights, maybe. The manual makes related promises[1]:
>> Because the json type stores an exact copy of the input text, it will
>> preserve semantically-insignificant white space between tokens
> And[2]:
>> As previously stated, when a JSON value is input and then printed without
>> any additional processing, json outputs the same text that was input,

"Without any additional processing" is the key restriction there.

> Not strictly contradicting, but the current behavior of json_strip_nulls()
> is still surprising. Either the input should be preserved as far as
> possible or, failing that, the actual behavior documented.

It is documented --- you just quoted the text that does so.

I don't have a lot of sympathy for "JSON-reading" code that fails to
conform to the JSON RFC, so I'm disinclined to work harder than that.

			regards, tom lane