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lwabish opened this issue Feb 27, 2025 · 1 comment
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encoding/json: []string was left with redunt element after a fail unmarshal #71997

lwabish opened this issue Feb 27, 2025 · 1 comment
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BugReport Issues describing a possible bug in the Go implementation.

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@lwabish
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lwabish commented Feb 27, 2025

Go version

go version go1.23.4 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE='on'
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/xxx/Library/Caches/go-build'
GOENV='/Users/xxx/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/xxx/go/pkg/mod'
GONOPROXY='xxx/*'
GONOSUMDB='xxx/*'
GOOS='darwin'
GOPATH='/Users/xxx/go'
GOPRIVATE='xxx/*'
GOPROXY='https://goproxy.cn,direct'
GOROOT='/opt/homebrew/opt/go/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/opt/homebrew/opt/go/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.23.4'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/xxx/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/Users/xxx/Desktop/go-tmp/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/69/cq904fld4v1gzx12qwwn01k00000gn/T/go-build4189542584=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

This is the code to reproduce my issue

func TestUnmarshalStringArray(t *testing.T) {
	var a []string
	if err := json.Unmarshal([]byte(`[1,2,3]`), &a); err != nil {
		t.Logf("unmarshal error: %v", err)
	}
	t.Logf("result: %v", a[0])
	t.Logf("len: %d", len(a))
}

What did you see happen?

The code tries to unmarshal wrong type of json into a variable and returns an error as expected.
But after that, the variable of []string was filled with 3 elements of empty string, which is unexpected.

What did you expect to see?

If error occurred during unmarshal , the target variable should be recoverd to original states indead of filled with unexpected emements
@gabyhelp
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(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)

@gabyhelp gabyhelp added the BugReport Issues describing a possible bug in the Go implementation. label Feb 27, 2025
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@lwabish @seankhliao @gabyhelp