go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/flag/stringlistflag/stringlistflag.go (about)

     1  // Copyright 2016 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package stringlistflag provides a flag.Value implementation which resolves
    16  // multiple args into a []string.
    17  package stringlistflag
    18  
    19  import (
    20  	"flag"
    21  	"fmt"
    22  	"strings"
    23  )
    24  
    25  // Flag is a flag.Value implementation which represents an ordered set of
    26  // strings.
    27  //
    28  // For example, this allows you to construct a flag that would behave like:
    29  //
    30  //	-myflag Foo
    31  //	-myflag Bar
    32  //	-myflag Bar
    33  //
    34  // And then myflag would be []string{"Foo", "Bar", "Bar"}
    35  type Flag []string
    36  
    37  var _ flag.Value = (*Flag)(nil)
    38  
    39  func (f Flag) String() string {
    40  	return strings.Join(f, ", ")
    41  }
    42  
    43  // Set implements flag.Value's Set function.
    44  func (f *Flag) Set(val string) error {
    45  	if val == "" {
    46  		return fmt.Errorf("must have an argument value")
    47  	}
    48  
    49  	*f = append(*f, val)
    50  	return nil
    51  }