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

     1  // Copyright 2019 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 flag
    16  
    17  import (
    18  	"encoding/json"
    19  	"flag"
    20  
    21  	"go.chromium.org/luci/common/errors"
    22  )
    23  
    24  type jsonMap map[string]string
    25  
    26  // JSONMap returns a flag.Value that can be passed to flag.Var to
    27  // parse a JSON string into a map.
    28  func JSONMap(m *map[string]string) flag.Value {
    29  	return (*jsonMap)(m)
    30  }
    31  
    32  func (m *jsonMap) String() string {
    33  	if m == nil {
    34  		return "null"
    35  	}
    36  	d, err := json.Marshal(*m)
    37  	if err != nil {
    38  		// Marshaling a map[string]string shouldn't error.
    39  		panic(err)
    40  	}
    41  	return string(d)
    42  }
    43  
    44  func (m *jsonMap) Set(s string) error {
    45  	if m == nil {
    46  		return errors.Reason("JSONMap pointer is nil").Err()
    47  	}
    48  	d := []byte(s)
    49  	return json.Unmarshal(d, m)
    50  }