encoding/json: empty fields in json.UnmarshalTypeError

[Elojah]

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

go version go1.11 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/hdezier/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/hdezier/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.11/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.11/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/tq/qnrqmrr14jvb912sj71lc24w0000gp/T/go-build337010521=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Unmarshaling an invalid json data field int into a string with json.NewDecoder(data).Decode(&f)
https://play.golang.org/p/0ChwR84YV_v

What did you expect to see?

In go 1.10.3 (current goplayground), e.Struct and e.Field are correctly set

What did you see instead?

In go 1.11 those values are empty

[agnivade]

/cc @dsnet

[gopherbot]

Change https://golang.org/cl/131675 mentions this issue: encoding/json: add missing struct field context to an error

[cirla]

It appears that some paths are not calling addErrorContext:

In unmarshal the error returned from value (which never calls error (which called addErrorContext) after this commit) is also returned without ever adding the context.

[mvdan]

Already being fixed by https://go-review.googlesource.com/c/go/+/126897, which was a fix for the similar #26444. Not a duplicate, though.

[gopherbot]

Change https://golang.org/cl/126897 mentions this issue: encoding/json: fix UnmarshalTypeError without field and struct values

[edaniels]

Can this be made to be go 1.11.1 https://github.com/golang/go/milestone/80? This prevents us from an upgrade to go 1.11 in production.

[mvdan]

Perhaps so - it is a regression, and the CL is small, so it seems doable to me. cc @bradfitz @dsnet @rsc for a decision on that.

[bradfitz]

@gopherbot, please backport to Go 1.11.