From f07a47a1bf491f715e8d4674b2dc3e7d790a3ee7 Mon Sep 17 00:00:00 2001
From: "Sarthak S. Waghmare" <sarthakw7@gmail.com>
Date: Sat, 16 Aug 2025 01:00:40 +0530
Subject: [PATCH] feature: support spanner struct tag in struct-tag rule
 (#1479)

---
 RULES_DESCRIPTIONS.md               |  2 +-
 rule/struct_tag.go                  | 16 +++++++++++++++-
 test/struct_tag_test.go             |  1 +
 testdata/struct_tag.go              | 14 ++++++++++++++
 testdata/struct_tag_user_options.go |  5 +++++
 5 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/RULES_DESCRIPTIONS.md b/RULES_DESCRIPTIONS.md
index 2463f86..e916ca9 100644
--- a/RULES_DESCRIPTIONS.md
+++ b/RULES_DESCRIPTIONS.md
@@ -1104,7 +1104,7 @@ _Configuration_: N/A
 
 _Description_: Struct tags are not checked at compile time.
 This rule spots errors in struct tags of the following types:
-asn1, bson, datastore, default, json, mapstructure, properties, protobuf, required, toml, url, validate, xml, yaml.
+asn1, bson, datastore, default, json, mapstructure, properties, protobuf, required, spanner, toml, url, validate, xml, yaml.
 
 _Configuration_: (optional) list of user defined options.
 
diff --git a/rule/struct_tag.go b/rule/struct_tag.go
index a4cfec7..396ffbb 100644
--- a/rule/struct_tag.go
+++ b/rule/struct_tag.go
@@ -30,6 +30,7 @@ const (
 	keyProperties   tagKey = "properties"
 	keyProtobuf     tagKey = "protobuf"
 	keyRequired     tagKey = "required"
+	keySpanner      tagKey = "spanner"
 	keyTOML         tagKey = "toml"
 	keyURL          tagKey = "url"
 	keyValidate     tagKey = "validate"
@@ -49,6 +50,7 @@ var tagCheckers = map[tagKey]tagChecker{
 	keyProperties:   checkPropertiesTag,
 	keyProtobuf:     checkProtobufTag,
 	keyRequired:     checkRequiredTag,
+	keySpanner:      checkSpannerTag,
 	keyTOML:         checkTOMLTag,
 	keyURL:          checkURLTag,
 	keyValidate:     checkValidateTag,
@@ -198,7 +200,7 @@ func (w lintStructTagRule) checkTagNameIfNeed(checkCtx *checkContext, tag *struc
 
 	key := tagKey(tag.Key)
 	switch key {
-	case keyBSON, keyJSON, keyXML, keyYAML, keyProtobuf:
+	case keyBSON, keyJSON, keyXML, keyYAML, keyProtobuf, keySpanner:
 	default:
 		return "", true
 	}
@@ -558,6 +560,18 @@ func checkYAMLTag(checkCtx *checkContext, tag *structtag.Tag, _ ast.Expr) (messa
 	return "", true
 }
 
+func checkSpannerTag(checkCtx *checkContext, tag *structtag.Tag, _ ast.Expr) (message string, succeeded bool) {
+	if tag.Name == "-" {
+		return "", true
+	}
+	for _, opt := range tag.Options {
+		if !checkCtx.isUserDefined(keySpanner, opt) {
+			return fmt.Sprintf(msgUnknownOption, opt), false
+		}
+	}
+	return "", true
+}
+
 func checkValidateOptionsAlternatives(checkCtx *checkContext, alternatives []string) (message string, succeeded bool) {
 	for _, alternative := range alternatives {
 		alternative := strings.TrimSpace(alternative)
diff --git a/test/struct_tag_test.go b/test/struct_tag_test.go
index 389f0a8..40cc8a8 100644
--- a/test/struct_tag_test.go
+++ b/test/struct_tag_test.go
@@ -21,6 +21,7 @@ func TestStructTagWithUserOptions(t *testing.T) {
 			"mapstructure,myMapstructureOption",
 			"validate,displayName",
 			"toml,unknown",
+			"spanner,mySpannerOption",
 		},
 	})
 }
diff --git a/testdata/struct_tag.go b/testdata/struct_tag.go
index e9d9933..2382008 100644
--- a/testdata/struct_tag.go
+++ b/testdata/struct_tag.go
@@ -88,6 +88,12 @@ type TestDuplicatedProtobufTags struct {
 	C int `protobuf:"varint,name=c"` // MATCH /duplicated tag name "c" in protobuf tag/
 }
 
+type SpannerDuplicatedTags struct {
+	A int `spanner:"field_a"`
+	B int `spanner:"field_a"` // MATCH /duplicated tag name "field_a" in spanner tag/
+	C int `spanner:"field_c"`
+}
+
 // test case from
 // sigs.k8s.io/kustomize/api/types/helmchartargs.go
 
@@ -182,3 +188,11 @@ type PropertiesTags struct {
 	Field []string          `properties:",default=a;b;c"`
 	Field map[string]string `properties:"myName,omitempty"` // MATCH /unknown or malformed option "omitempty" in properties tag/
 }
+
+type SpannerUser struct {
+	ID        int       `spanner:"user_id"`
+	Name      string    `spanner:"full_name"`
+	Email     string    `spanner:"-"`                    // Valid: ignore field
+	CreatedAt time.Time `spanner:"created_at"`
+	UpdatedAt time.Time `spanner:"updated_at,unknown"`   // MATCH /unknown option "unknown" in spanner tag/
+}
\ No newline at end of file
diff --git a/testdata/struct_tag_user_options.go b/testdata/struct_tag_user_options.go
index f2a925b..7ec12e2 100644
--- a/testdata/struct_tag_user_options.go
+++ b/testdata/struct_tag_user_options.go
@@ -46,3 +46,8 @@ type TomlUser struct {
 	Username string `toml:"username,omitempty"`
 	Location string `toml:"location,unknown"`
 }
+
+type SpannerUserOptions struct {
+	ID        int    `spanner:"user_id,mySpannerOption"`
+	Name      string `spanner:"full_name,unknownOption"` // MATCH /unknown option "unknownOption" in spanner tag/
+}
\ No newline at end of file