lang: Unnested the core package from the functions dir

The core package could contain non-functions, so we might as well move
it upwards.

lang/core/panic_func.go

@@ -0,0 +1,60 @@
+// Mgmt
+// Copyright (C) 2013-2024+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package core
+
+import (
+	"fmt"
+
+	"github.com/purpleidea/mgmt/lang/funcs/simplepoly"
+	"github.com/purpleidea/mgmt/lang/types"
+)
+
+func init() {
+	simplepoly.Register("panic", []*types.FuncValue{
+		{
+			T: types.NewType("func(x bool) bool"),
+			V: Panic,
+		},
+		{
+			T: types.NewType("func(x str) bool"),
+			V: Panic,
+		},
+	})
+}
+
+// Panic returns an error when it receives a non-empty string or a true boolean.
+// The error should cause the function engine to shutdown. If there's no error,
+// it returns false.
+func Panic(input []types.Value) (types.Value, error) {
+	switch k := input[0].Type().Kind; k {
+	case types.KindBool:
+		if input[0].Bool() {
+			return nil, fmt.Errorf("bool panic occurred")
+		}
+	case types.KindStr:
+		if s := input[0].Str(); s != "" {
+			return nil, fmt.Errorf("str panic occurred: %s", s)
+		}
+	default:
+		return nil, fmt.Errorf("unsupported kind: %+v", k)
+	}
+
+	return &types.BoolValue{
+		V: false,
+	}, nil
+}