add unittests for canParse

1 files changed, 64 insertions, 0 deletions

diff --git a/reflect.go b/reflect.go
new file mode 100644
index 0000000..32efe04
--- /dev/null
+++ b/reflect.go
@@ -0,0 +1,64 @@
+package arg
+
+import (
+	"encoding"
+	"reflect"
+
+	scalar "github.com/alexflint/go-scalar"
+)
+
+var textUnmarshalerType = reflect.TypeOf([]encoding.TextUnmarshaler{}).Elem()
+
+// This file contains miscellaneous reflection utilities
+
+// canParse returns true if the type can be parsed from a string
+func canParse(t reflect.Type) (parseable, boolean, multiple bool) {
+	parseable = scalar.CanParse(t)
+	boolean = isBoolean(t)
+	if parseable {
+		return
+	}
+
+	// Look inside pointer types
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	// Look inside slice types
+	if t.Kind() == reflect.Slice {
+		multiple = true
+		t = t.Elem()
+	}
+
+	parseable = scalar.CanParse(t)
+	boolean = isBoolean(t)
+	if parseable {
+		return
+	}
+
+	// Look inside pointer types (again, in case of []*Type)
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+
+	parseable = scalar.CanParse(t)
+	boolean = isBoolean(t)
+	if parseable {
+		return
+	}
+
+	return false, false, false
+}
+
+// isBoolean returns true if the type can be parsed from a single string
+func isBoolean(t reflect.Type) bool {
+	switch {
+	case t.Implements(textUnmarshalerType):
+		return false
+	case t.Kind() == reflect.Bool:
+		return true
+	case t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Bool:
+		return true
+	default:
+		return false
+	}
+}