go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/flag/stringsetflag/stringsetflag.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 stringsetflag provides a flag.Value implementation which resolves
    16  // multiple args into a stringset.
    17  package stringsetflag
    18  
    19  import (
    20  	"flag"
    21  	"fmt"
    22  	"sort"
    23  	"strings"
    24  
    25  	"go.chromium.org/luci/common/data/stringset"
    26  )
    27  
    28  // Flag is a flag.Value implementation which represents an unordered set of
    29  // strings.
    30  //
    31  // For example, this allows you to construct a flag that would behave like:
    32  //
    33  //	-myflag Foo
    34  //	-myflag Bar
    35  //	-myflag Bar
    36  //
    37  // And then myflag.Data.Has("Bar") would be true.
    38  type Flag struct{ Data stringset.Set }
    39  
    40  var _ flag.Value = (*Flag)(nil)
    41  
    42  func (f Flag) String() string {
    43  	if f.Data == nil {
    44  		return ""
    45  	}
    46  	slc := f.Data.ToSlice()
    47  	sort.Strings(slc)
    48  	return strings.Join(slc, ",")
    49  }
    50  
    51  // Set implements flag.Value's Set function.
    52  func (f *Flag) Set(val string) error {
    53  	if val == "" {
    54  		return fmt.Errorf("must have an argument value")
    55  	}
    56  
    57  	if f.Data == nil {
    58  		f.Data = stringset.NewFromSlice(val)
    59  	} else {
    60  		f.Data.Add(val)
    61  	}
    62  	return nil
    63  }