x/tools/analysis/composite: Add InternalFuzzTarget to unkeyed literals allowlist

[abhinav]

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

% go version
go version go1.18rc1 linux/amd64

Does this issue reproduce with the latest release?

With the latest RC, yes. Not with the latest stable.

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

Linux, amd64, inside Bazel with rules_go v0.30.0.

go env Output

% go env
GO111MODULE="off"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/user/.cache/go-build"
GOENV="/home/user/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/user/go-code/cache/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/user/go-code/main"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/user/.cache/bazel/_bazel_user/a048389d619430c68eb2be362fdff40d/external/go_sdk_linux_amd64"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/user/.cache/bazel/_bazel_user/a048389d619430c68eb2be362fdff40d/external/go_sdk_linux_amd64/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18rc1"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2439313169=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I wrote a minimal fuzz test using the example from the official docs and ran bazel build.

FuzzHex

package fuzzing

import (
        "bytes"
        "encoding/hex"
        "testing"
)

func FuzzHex(f *testing.F) {
        for _, seed := range [][]byte{{}, {0}, {9}, {0xa}, {0xf}, {1, 2, 3, 4}} {
                f.Add(seed)
        }
        f.Fuzz(func(t *testing.T, in []byte) {
                enc := hex.EncodeToString(in)
                out, err := hex.DecodeString(enc)
                if err != nil {
                        t.Fatalf("%v: decode: %v", in, err)
                }
                if !bytes.Equal(in, out) {
                        t.Fatalf("%v: not equal after round trip: %v", in, out)
                }
        })
}

I then ran bazel build on the target:

% bazel build :go_default_test

What did you expect to see?

A successful build.

What did you see instead?

The following error:

[...]/go_default_test_/testmain.go:43:3: testing.InternalFuzzTarget composite literal uses unkeyed fields (composites)

Notes

Sorry, just to clarify: This is not a request to support fuzzing in rules_go. I'm aware that this is not the place to request that.

This is a request to add testing.InternalFuzzTarget to the allowlist in go/analysis/passes/composite, without which tests that use fuzzing do not pass the lint check—at least in Bazel (I was not able to get the same error with vanilla go test -vet=composites). I've verified that adding InternalFuzzTarget to the list resolves this issue in Bazel.

[gopherbot]

Change https://go.dev/cl/391875 mentions this issue: go/analysis/passes/composite: allow InternalFuzzTarget

[findleyr]

@bcmills @matloob do you have any sense for why this would affect bazel, but not go test? I suppose we do not run go vet on the generated test targets.

In any case, the associated CL looks reasonable to me.

[findleyr]

@abhinav even if we merge now it seems unlikely that this will be fixed for 1.18, due to the imminence of the release. Can you explain further if/how this impacts your workflow?

[abhinav]

@findleyr, oh this is not a blocker for us to upgrade in any way. I've patched our copy of x/tools with the change. Thanks!

[bcmills]

I suppose we do not run go vet on the generated test targets.

I suspect that's exactly it.

[rysteboe]

Are there plans to release this as part of a future 1.18.x version?