cmd/go: build constraint of 'ignore' is special for modules? #29598

myitcv · 2019-01-07T19:38:33Z

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

> go version
[stdout]
go version go1.12beta1 linux/amd64

Does this issue reproduce with the latest release?

Yes; testing with the beta ahead of the 1.12 release.

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

go env Output

> go env
[stdout]
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/myitcv/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="$WORK/gopath"
GOPROXY="http://127.0.0.1:40043/mod"
GORACE=""
GOROOT="/home/myitcv/gos"
GOTMPDIR=""
GOTOOLDIR="/home/myitcv/gos/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="$WORK/go.mod"
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=$WORK/tmp/go-build168896432=/tmp/go-build -gno-record-gcc-switches"

What did you do?

# no build constraint
go list
go mod tidy
grep 'fruit.com v1.0.0' go.mod

# build constraint of other
cp mod.go.other mod.go
go mod tidy
grep 'fruit.com v1.0.0' go.mod

# build constraint of ignore
cp mod.go.ignore mod.go
go mod tidy
grep 'fruit.com v1.0.0' go.mod


-- go.mod --
module mod

-- mod.go --
package mod

import _ "fruit.com/fruit"

-- mod.go.ignore --
// +build ignore

package mod

import _ "fruit.com/fruit"

-- mod.go.other --
// +build other

package mod

import _ "fruit.com/fruit"

using the following module definition:

# mod/fruit.com_v1.0.0.txt 
-- .mod --
module fruit.com

-- .info --
{"Version":"v1.0.0","Time":"2018-10-22T18:45:39Z"}

-- go.mod --
module fruit.com

-- fruit/fruit.go --
package fruit

What did you expect to see?

A passing test.

What did you see instead?

--- FAIL: TestScripts (0.04s)
    --- FAIL: TestScripts/script (0.23s)
        testscript.go:193:
            # no build constraint (0.107s)
            # build constraint of other (0.021s)
            # build constraint of ignore (0.032s)
            > cp mod.go.ignore mod.go
            > go mod tidy
            > grep 'fruit.com v1.0.0' go.mod
            [go.mod]
            module mod

            go 1.12

            FAIL: testdata/script.txt:17: no match for `fruit.com v1.0.0` found in go.mod

I wasn't aware that the ignore build constraint was special but judging from the above it appears to be.

ignore is described as being conventional, but not that it carries any special semantics.

The cmd/go docs also don't appear to make mention of this special case.

Assuming this is the intended behaviour, I think it would be worth updating the docs to call this out. I just spent a good few mins trying to track down a go mod tidy bug that in fact turned out to be an instance of a file with a // +build ignore constraint.

cc @bcmills

FYI @mvdan @rogpeppe

The text was updated successfully, but these errors were encountered:

gopherbot · 2019-03-13T19:16:50Z

Change https://golang.org/cl/167159 mentions this issue: all: add go.mod

Commands run: sed -i 's;// +build OMIT;// +build ignore,OMIT;' $(grep -l OMIT -r) go mod init go mod edit -go=1.11 go mod tidy go list -m all go test ./... Updates golang/go#30228 Updates golang/go#29598 Change-Id: I3d0a4787c1158572bed8dd3785ff02e16d1cc1f3 Reviewed-on: https://go-review.googlesource.com/c/talks/+/167159 Run-TryBot: Bryan C. Mills <bcmills@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

…ps-update will not ignore it and properly vendor in code-generator. But using the build tag will cause the build to not generate a binary for this file. // +build ignore is special apparently golang/go#29598 Signed-off-by: Alexander Wels <awels@redhat.com>

make deps-update will not ignore it and properly vendor in code-generator. Buy using the +build tag will cause the build to not include this code during a build unless the codegen tag is used. // +build ignore is special apparently golang/go#29598 Signed-off-by: Alexander Wels <awels@redhat.com>

make deps-update will not ignore it and properly vendor in k8s.io/code-generator. By using the +build tag will cause the build to not include this code during a build unless the codegen tag is used. // +build ignore is special apparently golang/go#29598 Signed-off-by: Alexander Wels <awels@redhat.com>

AlekSi · 2021-07-31T10:26:42Z

https://golang.org/ref/mod#go-mod-tidy now says this:

There is one exception: the ignore build tag is not enabled, so a file with the build constraint // +build ignore will not be considered.

jayconrod · 2021-08-04T15:29:02Z

Since this is now documented in https://golang.org/ref/mod#go-mod-tidy, let's close this.

We'll need to be careful to document this for other commands that load the full import graph the way that go mod tidy does. For now, that's only https://golang.org/ref/mod#go-mod-vendor, which does mention this.

bcmills added Documentation modules NeedsFix The path to resolution is known, but the work has not been done. labels Jan 7, 2019

bcmills added this to the Go1.13 milestone Jan 7, 2019

johanbrandhorst mentioned this issue Feb 23, 2019

Dep should ignore packages only imported in files with tools build tag golang/dep#2112

Closed

myitcv mentioned this issue Mar 25, 2019

cmd/go: clarify best practice for tool dependencies #25922

Closed

bcmills mentioned this issue Mar 27, 2019

cmd/go: skip files tagged ignore in go mod vendor #31088

Closed

andybons modified the milestones: Go1.13, Go1.14 Jul 8, 2019

rsc modified the milestones: Go1.14, Backlog Oct 9, 2019

bcmills mentioned this issue Mar 25, 2020

cmd/go: tidy and vendor do not record dependencies of '// +build ignore' go:generate sources #38061

Closed

bendrucker mentioned this issue Jun 21, 2020

awsrules: add tags package with generator terraform-linters/tflint#803

Merged

segevfiner mentioned this issue Jul 22, 2020

"ignore" build tag is special in module mode shurcooL/vfsgen#83

Open

dmitshur added the GoCommand cmd/go label Jul 22, 2020

awels mentioned this issue Aug 13, 2020

Change +build ignore tag in tools.go to +build codegen kubevirt/containerized-data-importer#1339

Merged

johanneswuerbach mentioned this issue Nov 9, 2020

Fix golang build tag and make change detection kubernetes-sigs/custom-metrics-apiserver#77

Merged

jayconrod closed this as completed Aug 4, 2021

golang locked and limited conversation to collaborators Aug 4, 2022

gopherbot added the FrozenDueToAge label Aug 4, 2022

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cmd/go: build constraint of 'ignore' is special for modules? #29598

cmd/go: build constraint of 'ignore' is special for modules? #29598

myitcv commented Jan 7, 2019

gopherbot commented Mar 13, 2019

AlekSi commented Jul 31, 2021

jayconrod commented Aug 4, 2021

cmd/go: build constraint of 'ignore' is special for modules? #29598

cmd/go: build constraint of 'ignore' is special for modules? #29598

Comments

myitcv commented Jan 7, 2019

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

Does this issue reproduce with the latest release?

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

What did you do?

What did you expect to see?

What did you see instead?

gopherbot commented Mar 13, 2019

AlekSi commented Jul 31, 2021

jayconrod commented Aug 4, 2021

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

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