From b5cd1162191a8163b7d2b0fbc28c7a91b05b9264 Mon Sep 17 00:00:00 2001
From: Timo Vetter <timo.vetter@blackforestbytes.de>
Date: Thu, 5 Oct 2023 10:45:09 +0200
Subject: [PATCH] DYN-166 add jsonfilter to json library

---
 gojson/encode.go      | 52 ++++++++++++++++++++++++++++++++-----------
 gojson/encode_test.go |  8 ++++++-
 gojson/gionic.go      |  3 ++-
 3 files changed, 48 insertions(+), 15 deletions(-)

diff --git a/gojson/encode.go b/gojson/encode.go
index 9f521e1..765e30e 100644
--- a/gojson/encode.go
+++ b/gojson/encode.go
@@ -174,9 +174,9 @@ type IndentOpt struct {
 
 // MarshalSafeCollections is like Marshal except it will marshal nil maps and
 // slices as '{}' and '[]' respectfully instead of 'null'
-func MarshalSafeCollections(v interface{}, nilSafeSlices bool, nilSafeMaps bool, indent *IndentOpt) ([]byte, error) {
+func MarshalSafeCollections(v interface{}, nilSafeSlices bool, nilSafeMaps bool, indent *IndentOpt, filter *string) ([]byte, error) {
 	e := &encodeState{}
-	err := e.marshal(v, encOpts{escapeHTML: true, nilSafeSlices: nilSafeSlices, nilSafeMaps: nilSafeMaps})
+	err := e.marshal(v, encOpts{escapeHTML: true, nilSafeSlices: nilSafeSlices, nilSafeMaps: nilSafeMaps, filter: filter})
 	if err != nil {
 		return nil, err
 	}
@@ -393,6 +393,9 @@ type encOpts struct {
 	nilSafeSlices bool
 	// nilSafeMaps marshals a nil maps '{}' instead of 'null'
 	nilSafeMaps bool
+	// filter matches jsonfilter tag of struct
+	// marshals if no jsonfilter is set or otherwise if jsonfilter has the filter value
+	filter *string
 }
 
 type encoderFunc func(e *encodeState, v reflect.Value, opts encOpts)
@@ -777,6 +780,8 @@ FieldLoop:
 
 		if f.omitEmpty && isEmptyValue(fv) {
 			continue
+		} else if opts.filter != nil && len(f.jsonfilter) > 0 && !f.jsonfilter.Contains(*opts.filter) {
+			continue
 		}
 		e.WriteByte(next)
 		next = ','
@@ -1220,15 +1225,28 @@ type field struct {
 	nameNonEsc  string // `"` + name + `":`
 	nameEscHTML string // `"` + HTMLEscape(name) + `":`
 
-	tag       bool
-	index     []int
-	typ       reflect.Type
-	omitEmpty bool
-	quoted    bool
+	tag        bool
+	index      []int
+	typ        reflect.Type
+	omitEmpty  bool
+	jsonfilter jsonfilter
+	quoted     bool
 
 	encoder encoderFunc
 }
 
+// jsonfilter stores the value of the jsonfilter struct tag
+type jsonfilter []string
+
+func (j jsonfilter) Contains(t string) bool {
+	for _, tag := range j {
+		if t == tag {
+			return true
+		}
+	}
+	return false
+}
+
 // byIndex sorts field by index sequence.
 type byIndex []field
 
@@ -1304,6 +1322,13 @@ func typeFields(t reflect.Type) structFields {
 				if !isValidTag(name) {
 					name = ""
 				}
+
+				var jsonfilter []string
+				jsonfilterTag := sf.Tag.Get("jsonfilter")
+				if isValidTag(jsonfilterTag) {
+					jsonfilter = strings.Split(jsonfilterTag, ",")
+				}
+
 				index := make([]int, len(f.index)+1)
 				copy(index, f.index)
 				index[len(f.index)] = i
@@ -1334,12 +1359,13 @@ func typeFields(t reflect.Type) structFields {
 						name = sf.Name
 					}
 					field := field{
-						name:      name,
-						tag:       tagged,
-						index:     index,
-						typ:       ft,
-						omitEmpty: opts.Contains("omitempty"),
-						quoted:    quoted,
+						name:       name,
+						tag:        tagged,
+						index:      index,
+						typ:        ft,
+						omitEmpty:  opts.Contains("omitempty"),
+						jsonfilter: jsonfilter,
+						quoted:     quoted,
 					}
 					field.nameBytes = []byte(field.name)
 					field.equalFold = foldFunc(field.nameBytes)
diff --git a/gojson/encode_test.go b/gojson/encode_test.go
index e3f35c6..104a78f 100644
--- a/gojson/encode_test.go
+++ b/gojson/encode_test.go
@@ -1253,6 +1253,10 @@ func TestMarshalSafeCollections(t *testing.T) {
 		nilMapStruct struct {
 			NilMap map[string]interface{} `json:"nil_map"`
 		}
+		testWithFilter struct {
+			Test1 string `json:"test1" jsonfilter:"FILTERONE"`
+			Test2 string `json:"test2" jsonfilter:"FILTERTWO"`
+		}
 	)
 
 	tests := []struct {
@@ -1271,10 +1275,12 @@ func TestMarshalSafeCollections(t *testing.T) {
 		{map[string]interface{}{"1": 1, "2": 2, "3": 3}, "{\"1\":1,\"2\":2,\"3\":3}"},
 		{pNilMap, "null"},
 		{nilMapStruct{}, "{\"nil_map\":{}}"},
+		{testWithFilter{}, "{\"test1\":\"\"}"},
 	}
 
+	filter := "FILTERONE"
 	for i, tt := range tests {
-		b, err := MarshalSafeCollections(tt.in, true, true, nil)
+		b, err := MarshalSafeCollections(tt.in, true, true, nil, &filter)
 		if err != nil {
 			t.Errorf("test %d, unexpected failure: %v", i, err)
 		}
diff --git a/gojson/gionic.go b/gojson/gionic.go
index 2bd18f9..005218c 100644
--- a/gojson/gionic.go
+++ b/gojson/gionic.go
@@ -17,6 +17,7 @@ type GoJsonRender struct {
 	NilSafeSlices bool
 	NilSafeMaps   bool
 	Indent        *IndentOpt
+	Filter        *string
 }
 
 func (r GoJsonRender) Render(w http.ResponseWriter) error {
@@ -25,7 +26,7 @@ func (r GoJsonRender) Render(w http.ResponseWriter) error {
 		header["Content-Type"] = []string{"application/json; charset=utf-8"}
 	}
 
-	jsonBytes, err := MarshalSafeCollections(r.Data, r.NilSafeSlices, r.NilSafeMaps, r.Indent)
+	jsonBytes, err := MarshalSafeCollections(r.Data, r.NilSafeSlices, r.NilSafeMaps, r.Indent, r.Filter)
 	if err != nil {
 		panic(err)
 	}