diff --git a/lang/core/strings/join_nonempty.go b/lang/core/strings/join_nonempty.go new file mode 100644 index 00000000..7d3e36cc --- /dev/null +++ b/lang/core/strings/join_nonempty.go @@ -0,0 +1,70 @@ +// Mgmt +// Copyright (C) 2013-2024+ James Shubin and the project contributors +// Written by James Shubin 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 . +// +// Additional permission under GNU GPL version 3 section 7 +// +// If you modify this program, or any covered work, by linking or combining it +// with embedded mcl code and modules (and that the embedded mcl code and +// modules which link with this program, contain a copy of their source code in +// the authoritative form) containing parts covered by the terms of any other +// license, the licensors of this program grant you additional permission to +// convey the resulting work. Furthermore, the licensors of this program grant +// the original author, James Shubin, additional permission to update this +// additional permission if he deems it necessary to achieve the goals of this +// additional permission. + +package corestrings + +import ( + "context" + "strings" + + "github.com/purpleidea/mgmt/lang/funcs/simple" + "github.com/purpleidea/mgmt/lang/types" +) + +func init() { + simple.ModuleRegister(ModuleName, "join_nonempty", &simple.Scaffold{ + T: types.NewType("func(s []str, sep str) str"), + F: JoinNonempty, + }) +} + +// JoinNonempty behaves exactly like the regular string join, except it filters +// out empty elements first. Since this behaviour is commonly useful when +// writing scripts, we include it as a built-in primitive, since it is also +// cheaper than running the graph changing, filter function. +// TODO: compiler optimization: find patterns where someone used the filter +// function as previously described, and replace it with this implementation. +func JoinNonempty(ctx context.Context, input []types.Value) (types.Value, error) { + return &types.StrValue{ + V: joinNonempty(types.ValueToListStr(input[0]), input[1].Str()), + }, nil +} + +// joinNonempty is the actual implementation. +func joinNonempty(elems []string, sep string) string { + l := []string{} + for _, x := range elems { + if x == "" { + continue + } + l = append(l, x) + } + + return strings.Join(l, sep) +} diff --git a/lang/types/util.go b/lang/types/util.go index 802a20b4..5ce8f27b 100644 --- a/lang/types/util.go +++ b/lang/types/util.go @@ -229,3 +229,15 @@ func ListStrToValue(input []string) Value { } return l } + +// ValueToListStr is a simple helper function to convert from a list of strings +// in our type system to the equivalent in golang. This panics if the input is +// not of the correct type. +func ValueToListStr(input Value) []string { + l := []string{} + for _, x := range input.List() { + s := x.Str() + l = append(l, s) + } + return l +}