encoding/xml: Encoder encodes double quotes incorrectly.

[dragonfax]

xml.Encoder encodes a double quote in a text node into the entity ". Technically this a valid entity. But the standard is to encode a double quote into " instead. This is the standard when not using a DTD. https://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references#Predefined_entities_in_XML

I only noticed this because it sends riak-cs haywire when used with the aws-sdk-go client (an AWS s3 client written in go).

Here is an example.
https://gist.github.com/dragonfax/ca3ee45a0acf97820f58

[nodirt]

Same applies to ' https://play.golang.org/p/tIu_6xahLG
I'd like to work on this

[nodirt]

Except, this may be considered backwards incompatible. @adg?

[nodirt]

Apparently, this is behavior is intended because " and ' are shorter than " and ' respectively

go/src/encoding/xml/xml.go

Lines 1833 to 1834 in bf21643

	esc_quot = []byte(""") // shorter than """
	esc_apos = []byte("'") // shorter than "'"

@adg (or another core gopher) to make the final decision (I can't close bugs)

[adg]

I don't see anywhere in the spec that says " must be used and not ". In fact, all I could find was this sentence which suggests that it's fine to use the numeric entity instead:

Entity and character references may both be used to escape the left angle bracket, ampersand, and other delimiters. A set of general entities (amp, lt, gt, apos, quot) is specified for this purpose. Numeric character references may also be used; they are expanded immediately when recognized and must be treated as character data, so the numeric character references " < " and " & " may be used to escape < and & when they occur in character data.

I'd be inclined not to change the existing behavior because—as @nodirt says—this may break (or at least unexpectedly change) existing programs.

[rakyll]

" is just a predefined ". Given the fact that " is intentional, there is no reason we should fix this bug if there are no other major practical reasons.