commit 6883f03201546121013b6d67674a7451f87fe639
Author: Dmitri Shuralyov <[email protected]>
Date:   Sat Mar 4 22:26:16 2017 -0500

    WIP: tests/fields: Fix #576.
    
    TODO: Decide on the high-level approach, clean up, finish.

diff --git a/tests/fields/fields.go b/tests/fields/fields.go
index bd1463e..bc6d417 100644
--- a/tests/fields/fields.go
+++ b/tests/fields/fields.go
@@ -59,12 +59,13 @@ func main() {
 		typ interface{}
 	}{
 		//{"rate_limit", &github.RateLimits{}},
-		{"users/octocat", &github.User{}},
-		{"user", &github.User{}},
-		{"users/willnorris/keys", &[]github.Key{}},
-		{"orgs/google-test", &github.Organization{}},
-		{"repos/google/go-github", &github.Repository{}},
-		{"/gists/9257657", &github.Gist{}},
+		//{"users/octocat", &github.User{}},
+		//{"user", &github.User{}},
+		//{"users/willnorris/keys", &[]github.Key{}},
+		//{"orgs/google-test", &github.Organization{}},
+		//{"repos/google/go-github", &github.Repository{}},
+		{"repos/google/go-github/issues/1", &github.Issue{}},
+		//{"/gists/9257657", &github.Gist{}},
 	} {
 		err := testType(tt.url, tt.typ)
 		if err != nil {
@@ -106,31 +107,25 @@ func testType(urlStr string, typ interface{}) error {
 		}
 	}
 
-	// unmarshal to typ first, then re-marshal and unmarshal to a map
-	err = json.Unmarshal(*raw, typ)
-	if err != nil {
-		return err
-	}
-
-	var byt []byte
-	if slice {
-		// use first item in slice
+	// Populate m2 with all fields from typ,
+	// using encoding/json rules for mapping struct fields to JSON key names.
+	var m2 = make(map[string]struct{})
+	{
 		v := reflect.Indirect(reflect.ValueOf(typ))
-		byt, err = json.Marshal(v.Index(0).Interface())
-		if err != nil {
-			return err
+		if slice {
+			v = v.Index(0)
 		}
-	} else {
-		byt, err = json.Marshal(typ)
-		if err != nil {
-			return err
+		t := v.Type()
+		if t.Kind() != reflect.Struct {
+			return fmt.Errorf("typ is %v (%T), expected a struct", typ, typ)
+		}
+		for i := 0; i < t.NumField(); i++ {
+			name, ok := structFieldToJSONKeyName(t.Field(i))
+			if !ok {
+				continue
+			}
+			m2[name] = struct{}{}
 		}
-	}
-
-	var m2 map[string]interface{}
-	err = json.Unmarshal(byt, &m2)
-	if err != nil {
-		return err
 	}
 
 	// now compare the two maps
@@ -145,3 +140,29 @@ func testType(urlStr string, typ interface{}) error {
 
 	return nil
 }
+
+// structFieldToJSONKeyName returns JSON key name that the struct field maps to, if any,
+// according to encoding/json rules.
+// TODO: This doesn't fully include embedded structs...
+// TODO: This also doesn't fully implement all encoding/json rules. For example,
+//       there's no valid tag check (isValidTag), etc. If encoding/json rules change,
+//       this code will be out of date, since it duplicates its private functionality.
+//       However, this might be sufficient (good enough) for the limited purposes of this tool.
+func structFieldToJSONKeyName(field reflect.StructField) (string, bool) {
+	if field.PkgPath != "" && !field.Anonymous { // unexported
+		// json.Unmarshal will only set exported fields of the struct.
+		return "", false
+	}
+	tag, ok := field.Tag.Lookup("json")
+	if !ok {
+		return field.Name, true
+	}
+	if tag == "-" {
+		return "", false
+	}
+	name := strings.Split(tag, ",")[0]
+	if name == "" {
+		return "", false
+	}
+	return name, true
+}