make environment variable interpolation preprocessor optional (#1715)

config/reader/json/json.go

@@ -66,7 +66,7 @@ func (j *jsonReader) Values(ch *source.ChangeSet) (reader.Values, error) {
 	if ch.Format != "json" {
 		return nil, errors.New("unsupported format")
 	}
-	return newValues(ch)
+	return newValues(ch, j.opts)
 }
 
 func (j *jsonReader) String() string {

config/reader/json/json_test.go

@@ -3,6 +3,7 @@ package json
 import (
 	"testing"
 
+	"github.com/micro/go-micro/v2/config/reader"
 	"github.com/micro/go-micro/v2/config/source"
 )
 
@@ -23,7 +24,46 @@ func TestReader(t *testing.T) {
 		},
 	}
 
-	r := NewReader()
+	values := newTestValues(t, data)
+
+	for _, test := range testData {
+		if v := values.Get(test.path...).String(""); v != test.value {
+			t.Fatalf("Expected %s got %s for path %v", test.value, v, test.path)
+		}
+	}
+}
+
+func TestDisableReplaceEnvVars(t *testing.T) {
+	data := []byte(`{"foo": "bar", "baz": {"bar": "test/${test}"}}`)
+
+	tests := []struct {
+		path  []string
+		value string
+		opts  []reader.Option
+	}{
+		{
+			[]string{"baz", "bar"},
+			"test/",
+			nil,
+		},
+		{
+			[]string{"baz", "bar"},
+			"test/${test}",
+			[]reader.Option{reader.WithDisableReplaceEnvVars()},
+		},
+	}
+
+	for _, test := range tests {
+		values := newTestValues(t, data, test.opts...)
+
+		if v := values.Get(test.path...).String(""); v != test.value {
+			t.Fatalf("Expected %s got %s for path %v", test.value, v, test.path)
+		}
+	}
+}
+
+func newTestValues(t *testing.T, data []byte, opts ...reader.Option) reader.Values {
+	r := NewReader(opts...)
 
 	c, err := r.Merge(&source.ChangeSet{Data: data}, &source.ChangeSet{})
 	if err != nil {
@@ -35,9 +75,5 @@ func TestReader(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	for _, test := range testData {
-		if v := values.Get(test.path...).String(""); v != test.value {
-			t.Fatalf("Expected %s got %s for path %v", test.value, v, test.path)
-		}
-	}
+	return values
 }

config/reader/json/values.go

@@ -21,9 +21,14 @@ type jsonValue struct {
 	*simple.Json
 }
 
-func newValues(ch *source.ChangeSet) (reader.Values, error) {
+func newValues(ch *source.ChangeSet, opts reader.Options) (reader.Values, error) {
 	sj := simple.New()
-	data, _ := reader.ReplaceEnvVars(ch.Data)
+	data := ch.Data
+
+	if !opts.DisableReplaceEnvVars {
+		data, _ = reader.ReplaceEnvVars(ch.Data)
+	}
+
 	if err := sj.UnmarshalJSON(data); err != nil {
 		sj.SetPath(nil, string(ch.Data))
 	}

config/reader/json/values_test.go

@@ -4,6 +4,7 @@ import (
 	"reflect"
 	"testing"
 
+	"github.com/micro/go-micro/v2/config/reader"
 	"github.com/micro/go-micro/v2/config/source"
 )
 
@@ -32,7 +33,7 @@ func TestValues(t *testing.T) {
 	for idx, test := range testData {
 		values, err := newValues(&source.ChangeSet{
 			Data: test.csdata,
-		})
+		}, reader.Options{})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -69,7 +70,7 @@ func TestStructArray(t *testing.T) {
 	for idx, test := range testData {
 		values, err := newValues(&source.ChangeSet{
 			Data: test.csdata,
-		})
+		}, reader.Options{})
 		if err != nil {
 			t.Fatal(err)
 		}

config/reader/options.go

@@ -11,6 +11,7 @@ import (
 
 type Options struct {
 	Encoding              map[string]encoder.Encoder
+	DisableReplaceEnvVars bool
 }
 
 type Option func(o *Options)
@@ -40,3 +41,10 @@ func WithEncoder(e encoder.Encoder) Option {
 		o.Encoding[e.String()] = e
 	}
 }
+
+// WithDisableReplaceEnvVars disables the environment variable interpolation preprocessor
+func WithDisableReplaceEnvVars() Option {
+	return func(o *Options) {
+		o.DisableReplaceEnvVars = true
+	}
+}