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

$ go version 1.15

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

$ go env
amd64
darwin

What did you do?

As an example, a build tag like // +build unit, !integration, !component will produce unexpected results when running tests. Running go vet does not warn about this type of ill-formed build constraint.

Example

// +build unit, !component, !integration

package test

import "fmt"

func init() {
	fmt.Println("unit test")
}

// +build component, !unit, !integration

package test

import "fmt"

func init() {
	fmt.Println("component test")
}

// +build integration, !unit, !component

package test

import "fmt"

func init() {
	fmt.Println("integration")
}

Running go test ./... -tags unit -v produces:

component test
integration
unit test

While running go test ./... -tags component -v produces:

component test
unit test

And running go test ./... -tags integration -v produces:

integration test

What did you expect to see?

While this conditional syntax is incorrect, the produced output is confusing and running go vet should warn about combining AND immediately followed by OR (i.e. , ). Updating build tags to // +build unit,!integration,!component leads to expected behavior but it would be helpful for go vet to catch and warn about using commas followed by a space in build tags.

What did you see instead?

Running go vet doesn't indicate any issues.