empty: report special message for len and string-cast cases

[ldez]

package sandbox

import (
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestName(t *testing.T) {
	assert.NotEmptyf(t, len([]string{"e"}), "text: %s", "a")
	assert.NotEmptyf(t, []string{"e"}, "text: %s", "a")
}

$ ./golangci-lint run --enable-only testifylint
main_test.go:10:2: empty: use assert.NotEmptyf (testifylint)
        assert.NotEmptyf(t, len([]string{"e"}), "text: %s", "a")
        ^

I used a version of golangci-lint that uses testifylint v1.4.3.

[ldez]

I think you already know that but it's the same for NotEmpty, Emptyf, Empty.

I have not tested all the assertions.

package sandbox

import (
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestName(t *testing.T) {
	assert.NotEmptyf(t, len([]string{"e"}), "text: %s", "a")
	assert.NotEmptyf(t, []string{"e"}, "text: %s", "a")

	assert.NotEmpty(t, len([]string{"e"}))
	assert.NotEmpty(t, []string{"e"})

	assert.Emptyf(t, len([]string{"e"}), "text: %s", "a")
	assert.Emptyf(t, []string{"e"}, "text: %s", "a")

	assert.Empty(t, len([]string{"e"}))
	assert.Empty(t, []string{"e"})
}

$ ./golangci-lint run --enable-only testifylint
main_test.go:10:2: empty: use assert.NotEmptyf (testifylint)
        assert.NotEmptyf(t, len([]string{"e"}), "text: %s", "a")
        ^
main_test.go:13:2: empty: use assert.NotEmpty (testifylint)
        assert.NotEmpty(t, len([]string{"e"}))
        ^
main_test.go:16:2: empty: use assert.Emptyf (testifylint)
        assert.Emptyf(t, len([]string{"e"}), "text: %s", "a")
        ^
main_test.go:19:2: empty: use assert.Empty (testifylint)
        assert.Empty(t, len([]string{"e"}))
        ^

[ccoVeille]

Good catch, the way it reports now could let people think it's a false negative, while it's not, testifylint suggests to simplify.

So I agree with you the message needs to be adapted

[Antonboom]

After fix:

$ testifylint --disable-all --enable=empty ./...                                                                        
/tmp/sandbox/main_test.go:10:2: empty: remove unnecessary len
/tmp/sandbox/main_test.go:13:2: empty: remove unnecessary len
/tmp/sandbox/main_test.go:16:2: empty: remove unnecessary len
/tmp/sandbox/main_test.go:19:2: empty: remove unnecessary len