Implement json encoder/decoder for regexp (#15383)

* implement json encoder/decoder for regexp

---------

Signed-off-by: Ben Ye <benye@amazon.com>

model/relabel/relabel.go

@@ -16,6 +16,7 @@ package relabel
 import (
 	"crypto/md5"
 	"encoding/binary"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"strconv"
@@ -84,20 +85,20 @@ func (a *Action) UnmarshalYAML(unmarshal func(interface{}) error) error {
 type Config struct {
 	// A list of labels from which values are taken and concatenated
 	// with the configured separator in order.
-	SourceLabels model.LabelNames `yaml:"source_labels,flow,omitempty"`
+	SourceLabels model.LabelNames `yaml:"source_labels,flow,omitempty" json:"sourceLabels,omitempty"`
 	// Separator is the string between concatenated values from the source labels.
-	Separator string `yaml:"separator,omitempty"`
+	Separator string `yaml:"separator,omitempty" json:"separator,omitempty"`
 	// Regex against which the concatenation is matched.
-	Regex Regexp `yaml:"regex,omitempty"`
+	Regex Regexp `yaml:"regex,omitempty" json:"regex,omitempty"`
 	// Modulus to take of the hash of concatenated values from the source labels.
-	Modulus uint64 `yaml:"modulus,omitempty"`
+	Modulus uint64 `yaml:"modulus,omitempty" json:"modulus,omitempty"`
 	// TargetLabel is the label to which the resulting string is written in a replacement.
 	// Regexp interpolation is allowed for the replace action.
-	TargetLabel string `yaml:"target_label,omitempty"`
+	TargetLabel string `yaml:"target_label,omitempty" json:"targetLabel,omitempty"`
 	// Replacement is the regex replacement pattern to be used.
-	Replacement string `yaml:"replacement,omitempty"`
+	Replacement string `yaml:"replacement,omitempty" json:"replacement,omitempty"`
 	// Action is the action to be performed for the relabeling.
-	Action Action `yaml:"action,omitempty"`
+	Action Action `yaml:"action,omitempty" json:"action,omitempty"`
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.
@@ -207,6 +208,25 @@ func (re Regexp) MarshalYAML() (interface{}, error) {
 	return nil, nil
 }
 
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (re *Regexp) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	r, err := NewRegexp(s)
+	if err != nil {
+		return err
+	}
+	*re = r
+	return nil
+}
+
+// MarshalJSON implements the json.Marshaler interface.
+func (re Regexp) MarshalJSON() ([]byte, error) {
+	return json.Marshal(re.String())
+}
+
 // IsZero implements the yaml.IsZeroer interface.
 func (re Regexp) IsZero() bool {
 	return re.Regexp == DefaultRelabelConfig.Regex.Regexp

model/relabel/relabel_test.go

@@ -14,6 +14,7 @@
 package relabel
 
 import (
+	"encoding/json"
 	"strconv"
 	"testing"
 
@@ -964,3 +965,35 @@ func TestRegexp_ShouldMarshalAndUnmarshalZeroValue(t *testing.T) {
 	require.NoError(t, err)
 	require.Nil(t, unmarshalled.Regexp)
 }
+
+func TestRegexp_JSONUnmarshalThenMarshal(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+	}{
+		{
+			name:  "Empty regex",
+			input: `{"regex":""}`,
+		},
+		{
+			name:  "string literal",
+			input: `{"regex":"foo"}`,
+		},
+		{
+			name:  "regex",
+			input: `{"regex":".*foo.*"}`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var unmarshalled Config
+			err := json.Unmarshal([]byte(test.input), &unmarshalled)
+			require.NoError(t, err)
+
+			marshalled, err := json.Marshal(&unmarshalled)
+			require.NoError(t, err)
+
+			require.Equal(t, test.input, string(marshalled))
+		})
+	}
+}