cmd/fix, x/tools/go/analysis: fix can print "applied 8 of 10 fixes; 2 files updated" and fail without actually applying any fixes

[dmitshur]

Go version

go version go1.26rc3 darwin/arm64

Output of go env in your module/workspace:

$ go env -changed | wc -l
       0

Details

AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/gopher/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/gopher/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/s_/5sjqzr0j6xggz_xtzmq_8r4m00jwcj/T/go-build3613773867=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/gopher/go/src/golang.org/x/build/go.mod'
GOMODCACHE='/Users/gopher/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/gopher/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='on'
GOTELEMETRYDIR='/Users/gopher/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.26rc3'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

Change directory into a checkout of the x/build module at its latest commit (golang/build@0556110), and try to run go fix on the golang.org/x/build/dashboard package. (I tried it on all x/build packages, and dashboard was the only one that ran into a problem.)

What did you see happen?

$ go fix ./dashboard
# golang.org/x/build/dashboard
# [golang.org/x/build/dashboard]
fix: applied 8 of 10 fixes; 2 files updated. (Re-run the command to apply more.)
$ echo $?
1
$ git status        
On branch main
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

Notably, go fix claimed it updated 2 files, but it didn't, at least nothing in the x/build module itself. Re-running it produces the same outcome. It's completely reproducible in my environment, but only on this particular package. There doesn't seem to be anything unusual about file permissions.

Details

dashboard $ ls -l  
total 288
-rw-r--r--  1 gopher  primarygroup   35547 Feb  6 11:05 builders_test.go
-rw-r--r--  1 gopher  primarygroup  105307 Feb  6 11:05 builders.go
-rw-r--r--  1 gopher  primarygroup     816 Feb 17  2024 README.md

(That said, it worked fine on all other packages in the module, so this seems like a rare edge case.)

What did you expect to see?

I expected it to update the two builders.go builders_test.go files in package dashboard with 8 of 10 fixes, allowing me to re-run it to apply the remaining 2 out of 10 fixes. I'd also probably expect exit status 0 (i.e., "the work done was partial, but there weren't unexpected errors"), but maybe exiting with status 1 was deemed better to indicate that the work was incomplete.

CC @adonovan, @golang/tools-team.

[gabyhelp]

Related Issues

• x/tools/go/analysis: The first time singlechecker -fix parameter is executed, it does not fix the problem in the _test.go file #54740 (closed)
• x/tools/gopls: `//go:fix inline` is very slow to compute fixes (excessive scans of Info.Uses and re-formatting/parsing of whole file) #75773 (closed)
• x/tools/gopls/internal/cmd: TestFix failures #64765 (closed)
• x/tools/go/analysis/internal/checker: TestApplyFixes broken at head #34265 (closed)
• x/tools/go/analysis/analysistest: output and golden file differ, but RunWithSuggestedFixes does not report failure #47118 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[dmitshur]

In case it helps, noting here that I found breaking out a single analyzer run to happen first in the dashboard package is a viable workaround:

go fix -stringsseq ./dashboard  # workaround for go.dev/issue/77482
go fix ./...

(See go.dev/cl/743500 for more context.)

[gopherbot]

Change https://go.dev/cl/743500 mentions this issue: -- dividing line after reaching go fix zero diff --

[kevinburke]

I did some more investigation before I found this issue report
When two analyzers (slicescontains and stringsseq) produce conflicting
fixes for the same code, go fix discards all fixes in the package — even
non-conflicting fixes in other files — and exits 1. The message misleadingly
says fixes were "applied" and files were "updated," but no files are actually
modified. Re-running produces the same output indefinitely.

Steps to reproduce

$ go version
go version go1.27-devel_f3755d9eba Thu Feb 19 20:07:04 2026 -0800 darwin/arm64

Two bugs

1. Conflicting analyzers discard all fixes, including non-conflicting ones

conflict.go has a loop over strings.Fields that both slicescontains
and stringsseq want to fix. These conflict.

other.go has an if/else that minmax wants to replace with min().
This fix has no conflict with anything.

Expected: go fix applies the non-conflicting minmax fix to other.go
and the winning fix (e.g. slicescontains) to conflict.go, skipping only
the losing stringsseq fix.

Running individual analyzers works fine:

$ go fix -minmax ./...     # correctly modifies other.go
$ go fix -slicescontains ./...  # correctly modifies conflict.go

2. "applied N fixes; K files updated" message is misleading

The message says fixes were applied and files were updated, but no files are
actually written to disk. This makes it look like progress is being made when
nothing is happening.

Workaround

Run conflicting analyzers individually:

$ go fix -slicescontains ./...
$ go fix -minmax ./...

here's conflict.go:

package main

import "strings"

// hasClass triggers conflicting fixes from slicescontains and stringsseq.
func hasClass(classes string, target string) bool {
	for _, class := range strings.Fields(classes) {
		if class == target {
			return true
		}
	}
	return false
}

and other.go:

package main

// smaller triggers the minmax analyzer, which has no conflict.
func smaller(a, b int) int {
	x := a
	if b < a {
		x = b
	}
	return x
}