code review 100430043: encoding/json: document what unmarshal of `null` into n...

encoding/json: document what unmarshal of `null` into non-reference type does

Originally it was an error, which made perfect sense, but in issue 2540
I got talked out of this sensible behavior. I'm not thrilled with the "new"
behavior but it's been there since Go 1.1 so we're stuck with it now.

Fixes issue 6724.

[rsc, 2014-05-13 03:30:11]

Hello golang-codereviews@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go/

[bradfitz, 2014-05-13 03:31:56]

LGTM
 On May 12, 2014 8:30 PM, <rsc@golang.org> wrote:

> Reviewers: golang-codereviews,
>
> Message:
> Hello golang-codereviews@googlegroups.com,
>
> I'd like you to review this change to
> https://code.google.com/p/go/
>
>
> Description:
> encoding/json: document what unmarshal of `null` into non-reference type
> does
>
> Originally it was an error, which made perfect sense, but in issue 2540
> I got talked out of this sensible behavior. I'm not thrilled with the
> "new"
> behavior but it's been there since Go 1.1 so we're stuck with it now.
>
> Fixes issue 6724.
>
> Please review this at https://codereview.appspot.com/100430043/
>
> Affected files (+5, -0 lines):
>   M src/pkg/encoding/json/decode.go
>
>
> Index: src/pkg/encoding/json/decode.go
> ===================================================================
> --- a/src/pkg/encoding/json/decode.go
> +++ b/src/pkg/encoding/json/decode.go
> @@ -54,6 +54,11 @@
>  // If no more serious errors are encountered, Unmarshal returns
>  // an UnmarshalTypeError describing the earliest such error.
>  //
> +// The JSON null value unmarshals into an interface, map, pointer, or
> slice
> +// by setting that Go value to nil. Because null is often used in JSON to
> mean
> +// ``not present,'' unmarshaling a JSON null into any other Go type has
> no effect
> +// on the value and produces no error.
> +//
>  // When unmarshaling quoted strings, invalid UTF-8 or
>  // invalid UTF-16 surrogate pairs are not treated as an error.
>  // Instead, they are replaced by the Unicode replacement
>
>
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[rsc, 2014-05-13 03:38:27]

*** Submitted as https://code.google.com/p/go/source/detail?r=d17b1b44d2cb ***

encoding/json: document what unmarshal of `null` into non-reference type does

Originally it was an error, which made perfect sense, but in issue 2540
I got talked out of this sensible behavior. I'm not thrilled with the "new"
behavior but it's been there since Go 1.1 so we're stuck with it now.

Fixes issue 6724.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://codereview.appspot.com/100430043