encoding/xml: cannot mark parent of nested element omitempty

[stbenjam]

What version of Go are you using (go version)?

$ go version
go version go1.19.5 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/stbenjam/.cache/go-build"
GOENV="/home/stbenjam/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/stbenjam/.gvm/pkgsets/go1.19.5/global/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/stbenjam/.gvm/pkgsets/go1.19.5/global"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/stbenjam/.gvm/gos/go1.19.5"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/stbenjam/.gvm/gos/go1.19.5/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.19.5"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/stbenjam/git/ci-tools/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2862434727=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Trying to marshal/unmarshal junit XML testsuites. I cannot get omitempty to work on the parent of a potentially nested field.

For this example XML:

<testsuite>
  <properties>
    <property name="go.version" value="go1.17.5 linux/amd64"/>
  </properties>
</testsuite>

If there is no properties element, like this:

<testsuite>
</testsuite>

I would like properties to NOT be marshalled.

Example: https://go.dev/play/p/iYsJBSIKAQl

I tried to put omitempty in two different ways:

	Properties []*Property `xml:"properties>property,omitempty"`

and

	Properties []*Property `xml:"properties,omitempty>property,omitempty"`

The former does not work for properties, the latter is invalid because > is split after splitting on , (https://cs.opensource.google/go/go/+/refs/tags/go1.19.5:src/encoding/xml/typeinfo.go;l=113)

What did you expect to see?

I expected <properties></properties> to not be in the marshalled output when specifying omitempty

What did you see instead?

It was included.

[seankhliao]

Duplicate of #7233

[deltamualpha]

Might it be worth adding some clarity to the documentation that modifiers like omitempty or any are only allowed at the end of a struct tag, not interwoven with nested tags in the XML case?