contrib/gin-gonic/gin: refactor Option, deprecate OptionFn

Refactor Options handling.
Deprecate OptionFn which was an implementation detail that is not needed
anymore.

This change is fully source compatible with existing client code. Also,
as implementation details are now hidden behind the private 'option'
type, the API is more future-proof.

Full rationale for this change: #3612

Note: golangci-lint 2.1.6 reports lint error "unexported-return: exported func
WithAnalytics returns unexported type gin.Option, which can be annoying to use (revive)"
However this is false positive that I have reported in
mgechev/revive#1406.

Author: dolmen

contrib/gin-gonic/gin/gintrace.go

@@ -32,7 +32,7 @@ func init() {
 func Middleware(service string, opts ...Option) gin.HandlerFunc {
 	cfg := newConfig(service)
 	for _, opt := range opts {
-		opt.apply(cfg)
+		opt(cfg)
 	}
 	instr.Logger().Debug("contrib/gin-gonic/gin: Configuring Middleware: Service: %s, %#v", cfg.serviceName, cfg)
 	spanOpts := []tracer.StartSpanOption{

contrib/gin-gonic/gin/option.go

@@ -36,20 +36,19 @@ func newConfig(serviceName string) *config {
 	}
 }
 
-// Option describes options for the Gin integration.
-type Option interface {
-	apply(*config)
-}
+// Option describes an option for the Gin integration.
+type Option = option
 
-// OptionFn represents options applicable to Middleware.
-type OptionFn func(*config)
+// option is the hidden concrete implementation of [Option] using the functional options pattern.
+type option func(*config)
 
-func (fn OptionFn) apply(cfg *config) {
-	fn(cfg)
-}
+// OptionFn is an implementation detail of [Option].
+//
+// Deprecated: use [Option].
+type OptionFn = Option
 
 // WithAnalytics enables Trace Analytics for all started spans.
-func WithAnalytics(on bool) OptionFn {
+func WithAnalytics(on bool) Option {
 	return func(cfg *config) {
 		if on {
 			cfg.analyticsRate = 1.0
@@ -61,7 +60,7 @@ func WithAnalytics(on bool) OptionFn {
 
 // WithAnalyticsRate sets the sampling rate for Trace Analytics events
 // correlated to started spans.
-func WithAnalyticsRate(rate float64) OptionFn {
+func WithAnalyticsRate(rate float64) Option {
 	return func(cfg *config) {
 		if rate >= 0.0 && rate <= 1.0 {
 			cfg.analyticsRate = rate
@@ -73,7 +72,7 @@ func WithAnalyticsRate(rate float64) OptionFn {
 
 // WithResourceNamer specifies a function which will be used to obtain a resource name for a given
 // gin request, using the request's context.
-func WithResourceNamer(namer func(c *gin.Context) string) OptionFn {
+func WithResourceNamer(namer func(c *gin.Context) string) Option {
 	return func(cfg *config) {
 		cfg.resourceNamer = namer
 	}
@@ -83,15 +82,15 @@ func WithResourceNamer(namer func(c *gin.Context) string) OptionFn {
 // Warning:
 // Using this feature can risk exposing sensitive data such as authorization tokens to Datadog.
 // Special headers can not be sub-selected. E.g., an entire Cookie header would be transmitted, without the ability to choose specific Cookies.
-func WithHeaderTags(headers []string) OptionFn {
+func WithHeaderTags(headers []string) Option {
 	return func(cfg *config) {
 		cfg.headerTags = instrumentation.NewHeaderTags(headers)
 	}
 }
 
 // WithIgnoreRequest specifies a function to use for determining if the
 // incoming HTTP request tracing should be skipped.
-func WithIgnoreRequest(f func(c *gin.Context) bool) OptionFn {
+func WithIgnoreRequest(f func(c *gin.Context) bool) Option {
 	return func(cfg *config) {
 		cfg.ignoreRequest = f
 	}