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check_test.go
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check_test.go
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package gochecksumtype
import (
"testing"
"github.com/alecthomas/assert/v2"
)
// TestMissingOne tests that we detect a single missing variant.
func TestMissingOne(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T interface { sealed() }
type A struct {}
func (a *A) sealed() {}
type B struct {}
func (b *B) sealed() {}
func main() {
switch T(nil).(type) {
case *A:
}
}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 1, len(errs))
assert.Equal(t, []string{"B"}, missingNames(t, errs[0]))
}
// TestMissingTwo tests that we detect a two missing variants.
func TestMissingTwo(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T interface { sealed() }
type A struct {}
func (a *A) sealed() {}
type B struct {}
func (b *B) sealed() {}
type C struct {}
func (c *C) sealed() {}
func main() {
switch T(nil).(type) {
case *A:
}
}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 1, len(errs))
assert.Equal(t, []string{"B", "C"}, missingNames(t, errs[0]))
}
// TestMissingOneWithPanic tests that we detect a single missing variant even
// if we have a trivial default case that panics.
func TestMissingOneWithPanic(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T interface { sealed() }
type A struct {}
func (a *A) sealed() {}
type B struct {}
func (b *B) sealed() {}
func main() {
switch T(nil).(type) {
case *A:
default:
panic("unreachable")
}
}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 1, len(errs))
assert.Equal(t, []string{"B"}, missingNames(t, errs[0]))
}
// TestNoMissing tests that we correctly detect exhaustive case analysis.
func TestNoMissing(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T interface { sealed() }
type A struct {}
func (a *A) sealed() {}
type B struct {}
func (b *B) sealed() {}
type C struct {}
func (c *C) sealed() {}
func main() {
switch T(nil).(type) {
case *A, *B, *C:
}
}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 0, len(errs))
}
// TestNoMissingDefault tests that even if we have a missing variant, a default
// case should thwart exhaustiveness checking.
func TestNoMissingDefault(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T interface { sealed() }
type A struct {}
func (a *A) sealed() {}
type B struct {}
func (b *B) sealed() {}
func main() {
switch T(nil).(type) {
case *A:
default:
println("legit catch all goes here")
}
}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 0, len(errs))
}
// TestNotSealed tests that we report an error if one tries to declare a sum
// type with an unsealed interface.
func TestNotSealed(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T interface {}
func main() {}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 1, len(errs))
assert.Equal(t, "T", errs[0].(unsealedError).Decl.TypeName)
}
// TestNotInterface tests that we report an error if one tries to declare a sum
// type that doesn't correspond to an interface.
func TestNotInterface(t *testing.T) {
code := `
package gochecksumtype
//sumtype:decl
type T struct {}
func main() {}
`
tmpdir, pkgs := setupPackages(t, code)
defer teardownPackage(t, tmpdir)
errs := Run(pkgs)
assert.Equal(t, 1, len(errs))
assert.Equal(t, "T", errs[0].(notInterfaceError).Decl.TypeName)
}
func missingNames(t *testing.T, err error) []string {
t.Helper()
ierr, ok := err.(inexhaustiveError)
assert.True(t, ok, "error was not inexhaustiveError: %T", err)
return ierr.Names()
}