encoding/xml, encoding/json: package docs don't mention encoding.TextMarshaler and encoding.TextUnmarshaler

[songgao]

version: Go 1.2

What is the expected output?
`encoding/xml` and `encoding/json` should document the behavior that it will check
encoding.TextMarshaler and encoding.TextUnmarshaler.

[dsymonds]

Comment 1:

Labels changed: added priority-soon, documentation, size-s, removed priority-triage.

Owner changed to @rsc.

Status changed to Accepted.

[rsc]

Comment 2:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 3:

Labels changed: added repo-main.

[AlekSi]

I wanted some text format for for my struct so I implemented TextMarshaler and TextUnmarshaler like this:

func (t *T) MarshalText() ([]byte, error) {
    return xml.MarshalIndent(m, "", "  ")
}

func (t *T) UnmarshalText(b []byte) error {
    return xml.Unmarshal(b, m)
}

Then I spent an hour debugging why simplest code like t.UnmarshalText(bytes) fails with io.EOF.

Please document this behaviour.

[gopherbot]

Change https://golang.org/cl/76350 mentions this issue: encoding/xml,encoding/json: docs and examples using custom marshalers

[leighmcculloch]

CL 76350 contains:

• Examples for both encoding/json and encoding/xml that demonstrate using the encoding.TextMarshaler and encoding.TextUnmarshaler interfaces.
• An example for encoding/xml that demonstrates custom marshaling using MarshalXML and UnmarshalXML.
• Docs for encoding/xml that are mirrored off encoding/json.

All new examples are modeled off the existing custom marshal example in encoding/json.