feat(test): improve anoonation code and add unit tests to cover proce…

…ssStruct()

tools/logger/generating.md

@@ -27,7 +27,7 @@ type OrgInfo struct
 
 ```
 
-With the addition of the annotation (which matches the [standard
+With the addition of the log tags `ie. log:"xyz"` for fields (xyz matches the [standard
 attributes](https://app.datadoghq.com/logs/pipelines/standard-attributes)),
 we can use
 [logger](https://github.com/getoutreach/gobox/tree/master/tools/logger)
@@ -51,6 +51,41 @@ func (s *OrgInfo) MarshalLog(addField func(key string, value interface{})) {
 }
 ```
 
+### Annotations:
+These tags for fields also have limited support for annotations: `ie. log:"xyz,annotation"`.
+
+Supported annotations:
+
+- **omitempty**: makes the field optional.
+
+    `omitempty` annotation is available for simple built-in types or
+    custom types with underlying type being built-in or pointers of any type.
+    
+    Example:
+    ```go
+    type OrgInfo struct
+        Org  string `log:"or.org.shortname,omitempty"`
+        Guid *Custom `log:"or.org.guid,omitempty"`
+    }
+    ```
+
+    Generated code:
+    
+    ```go
+    func (s *OrgInfo) MarshalLog(addField func(key string, value interface{})) {
+        if s == nil {
+            return
+        }
+        if s.Org != "" {
+            addField("or.org.shortname", s.Org)
+        }
+        if s.Guid != nil {
+            addField("or.org.guid", s.Guid)
+        }
+    }
+    ```
+
+
 ## Using go generate
 
 Go `generate` is the standard way to generate pre-build artifacts

tools/logger/logger.go

@@ -46,6 +46,10 @@ func (s *{{ .name }}) MarshalLog(addField func(key string, value interface{})) {
 addField("{{.key}}", s.{{.name}}.UTC().Format(time.RFC3339Nano))`
 	simpleFieldFormat = `
 addField("{{.key}}", s.{{.name}})`
+	simpleOptionalFieldFormat = `
+if s.{{.name}} != %s {
+	addField("{{.key}}", s.{{.name}})
+}`
 	nestedMarshalerFormat = `
 s.{{.name}}.MarshalLog(addField)`
 	nestedNilableMarshalerFormat = `
@@ -55,7 +59,7 @@ if s.{{.name}} != nil {
 )
 
 const (
-	tagOmitEmpty = ",omitempty"
+	annotationOmitEmpty = "omitempty"
 )
 
 func main() {
@@ -136,6 +140,12 @@ func processStruct(w io.Writer, s *types.Struct, name string) {
 	write(w, functionHeaderFormat, map[string]string{"name": name})
 	for kk := 0; kk < s.NumFields(); kk++ {
 		if field, ok := reflect.StructTag(s.Tag(kk)).Lookup("log"); ok {
+			var annotations string
+			fieldParts := strings.SplitN(field, ",", 2)
+			field = fieldParts[0]
+			if len(fieldParts) > 1 {
+				annotations = fieldParts[1]
+			}
 			args := map[string]string{"key": field, "name": s.Field(kk).Name()}
 			switch {
 			case s.Field(kk).Type().String() == "time.Time":
@@ -144,8 +154,7 @@ func processStruct(w io.Writer, s *types.Struct, name string) {
 				write(w, nestedNilableMarshalerFormat, args)
 			case field == ".":
 				write(w, nestedMarshalerFormat, args)
-			case strings.HasSuffix(field, tagOmitEmpty):
-				args["key"] = strings.TrimSuffix(field, tagOmitEmpty)
+			case strings.Contains(annotations, annotationOmitEmpty):
 				write(w, getSimpleOptionalFieldFormat(s.Field(kk).Type()), args)
 			default:
 				write(w, simpleFieldFormat, args)
@@ -192,8 +201,5 @@ func getSimpleOptionalFieldFormat(p types.Type) string {
 		defaultValue = "nil"
 	}
 
-	return fmt.Sprintf(`
-if s.{{.name}} != %s {
-	addField("{{.key}}", s.{{.name}})
-}`, defaultValue)
+	return fmt.Sprintf(simpleOptionalFieldFormat, defaultValue)
 }

tools/logger/logger_test.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"bytes"
 	"go/types"
+	"gotest.tools/v3/assert"
 	"testing"
 )
 
@@ -80,3 +82,121 @@ func TestGetSimpleOptionalFieldFormat(t *testing.T) {
 		})
 	}
 }
+
+func TestProcessStruct(t *testing.T) {
+	tests := []struct {
+		name     string
+		setup    func() (*types.Struct, string)
+		expected string
+	}{
+		{
+			name: "basic fields",
+			setup: func() (*types.Struct, string) {
+				fields := []*types.Var{
+					types.NewField(0, nil, "Name", types.Typ[types.String], false),
+					types.NewField(0, nil, "Age", types.Typ[types.Int], false),
+				}
+				tags := []string{
+					`log:"name"`,
+					`log:"age"`,
+				}
+				return types.NewStruct(fields, tags), "BasicStruct"
+			},
+			expected: `
+func (s *BasicStruct) MarshalLog(addField func(key string, value interface{})) {
+	if s == nil {
+		return
+	}
+
+addField("name", s.Name)
+addField("age", s.Age)
+}
+`,
+		},
+		{
+			name: "time field",
+			setup: func() (*types.Struct, string) {
+				pkg := types.NewPackage("time", "time")
+				timeType := types.NewNamed(types.NewTypeName(0, pkg, "Time", nil), &types.Struct{}, nil)
+
+				fields := []*types.Var{
+					types.NewField(0, nil, "CreatedAt", timeType, false),
+				}
+				tags := []string{`log:"created_at"`}
+				return types.NewStruct(fields, tags), "TimeStruct"
+			},
+			expected: `
+func (s *TimeStruct) MarshalLog(addField func(key string, value interface{})) {
+	if s == nil {
+		return
+	}
+
+addField("created_at", s.CreatedAt.UTC().Format(time.RFC3339Nano))
+}
+`,
+		},
+		{
+			name: "omitempty fields",
+			setup: func() (*types.Struct, string) {
+				fields := []*types.Var{
+					types.NewField(0, nil, "Name", types.Typ[types.String], false),
+					types.NewField(0, nil, "AgeP", types.NewPointer(types.Typ[types.Int]), false),
+				}
+				tags := []string{
+					`log:"name,omitempty"`,
+					`log:"ageP,omitempty"`,
+				}
+				return types.NewStruct(fields, tags), "OmitStruct"
+			},
+			expected: `
+func (s *OmitStruct) MarshalLog(addField func(key string, value interface{})) {
+	if s == nil {
+		return
+	}
+
+if s.Name != "" {
+	addField("name", s.Name)
+}
+if s.AgeP != nil {
+	addField("ageP", s.AgeP)
+}
+}
+`,
+		},
+		{
+			name: "nested marshaler",
+			setup: func() (*types.Struct, string) {
+				nestedType := types.NewPointer(types.NewNamed(
+					types.NewTypeName(0, nil, "NestedStruct", nil),
+					&types.Struct{},
+					nil,
+				))
+				fields := []*types.Var{
+					types.NewField(0, nil, "Nested", nestedType, false),
+				}
+				tags := []string{`log:"."`}
+				return types.NewStruct(fields, tags), "ParentStruct"
+			},
+			expected: `
+func (s *ParentStruct) MarshalLog(addField func(key string, value interface{})) {
+	if s == nil {
+		return
+	}
+
+if s.Nested != nil {
+	s.Nested.MarshalLog(addField)
+}
+}
+`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s, name := tt.setup()
+			buf := &bytes.Buffer{}
+			processStruct(buf, s, name)
+			assert.Equal(t, tt.expected, buf.String())
+		})
+	}
+}