store semver parsing error

environ/semver.go

@@ -14,12 +14,15 @@ import (
 // helper function returns a list of environment variables
 // that represent the semantic version.
 func versions(s string) map[string]string {
+	env := map[string]string{}
+
 	s = strings.TrimPrefix(s, "v")
 	version, err := semver.NewVersion(s)
 	if err != nil {
-		return nil
+		env["DRONE_SEMVER_ERROR"] = err.Error()
+		return env
 	}
-	env := map[string]string{}
+
 	env["DRONE_SEMVER"] = version.String()
 	env["DRONE_SEMVER_MAJOR"] = fmt.Sprint(version.Major)
 	env["DRONE_SEMVER_MINOR"] = fmt.Sprint(version.Minor)

environ/semver_test.go

@@ -11,9 +11,11 @@ import (
 )
 
 func TestInvalidSemver(t *testing.T) {
-	v := versions("this is an invalid version")
-	if v != nil {
-		t.Errorf("Expect nil variables when invalid semver string")
+	a := versions("this is an invalid version")
+	b := map[string]string{"DRONE_SEMVER_ERROR": "this is an invalid version is not in dotted-tri format"}
+	if diff := cmp.Diff(a, b); diff != "" {
+		t.Errorf("Unexpected semver variables")
+		t.Log(diff)
 	}
 }