Gin support (rs#51)

* Impl gin.HandlerFunc wrappers for Cors handler
* Provide an example for Gin
* Update TravisCI matrix from Go 1.8 to Go 1.9 + 1.10

.travis.yml

@@ -1,6 +1,7 @@
 language: go
 go:
-- 1.8
+- 1.9
+- "1.10"
 - tip
 matrix:
   allow_failures:

README.md

@@ -59,6 +59,7 @@ The server now runs on `localhost:8080`:
 * [HttpRouter](https://github.com/julienschmidt/httprouter): [examples/httprouter/server.go](https://github.com/rs/cors/blob/master/examples/httprouter/server.go)
 * [Gorilla](http://www.gorillatoolkit.org/pkg/mux): [examples/gorilla/server.go](https://github.com/rs/cors/blob/master/examples/gorilla/server.go)
 * [Buffalo](https://gobuffalo.io): [examples/buffalo/server.go](https://github.com/rs/cors/blob/master/examples/buffalo/server.go)
+* [Gin](https://gin-gonic.github.io/gin): [examples/gin/server.go](https://github.com/rs/cors/blob/master/examples/gin/server.go)
 
 ## Parameters
 

examples/gin/server.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	cors "github.com/rs/cors/wrapper/gin"
+)
+
+func main() {
+	router := gin.Default()
+
+	router.Use(cors.Default())
+	router.GET("/", func(context *gin.Context) {
+		context.JSON(http.StatusOK, gin.H{"hello": "world"})
+	})
+
+	router.Run(":8080")
+}

wrapper/gin/gin.go

@@ -0,0 +1,50 @@
+// Package cors/wrapper/gin provides gin.HandlerFunc to handle CORS related
+// requests as a wrapper of github.com/rs/cors handler.
+package gin
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/rs/cors"
+)
+
+// Options is a configuration container to setup the CORS middleware.
+type Options = cors.Options
+
+// corsWrapper is a wrapper of cors.Cors handler which preserves information
+// about configured 'optionPassthrough' option.
+type corsWrapper struct {
+	*cors.Cors
+	optionPassthrough bool
+}
+
+// build transforms wrapped cors.Cors handler into Gin middleware.
+func (c corsWrapper) build() gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		c.HandlerFunc(ctx.Writer, ctx.Request)
+		if !c.optionPassthrough &&
+			ctx.Request.Method == http.MethodOptions &&
+			ctx.GetHeader("Access-Control-Request-Method") != "" {
+			// Abort processing next Gin middlewares.
+			ctx.AbortWithStatus(http.StatusOK)
+		}
+	}
+}
+
+// AllowAll creates a new CORS Gin middleware with permissive configuration
+// allowing all origins with all standard methods with any header and
+// credentials.
+func AllowAll() gin.HandlerFunc {
+	return corsWrapper{Cors: cors.AllowAll()}.build()
+}
+
+// Default creates a new CORS Gin middleware with default options.
+func Default() gin.HandlerFunc {
+	return corsWrapper{Cors: cors.Default()}.build()
+}
+
+// New creates a new CORS Gin middleware with the provided options.
+func New(options Options) gin.HandlerFunc {
+	return corsWrapper{cors.New(options), options.OptionsPassthrough}.build()
+}

wrapper/gin/gin_test.go

@@ -0,0 +1,76 @@
+package gin
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/rs/cors"
+)
+
+func init() {
+	gin.SetMode(gin.ReleaseMode)
+}
+
+func TestAllowAllNotNil(t *testing.T) {
+	handler := AllowAll()
+	if handler == nil {
+		t.Error("Should not return nil Gin handler")
+	}
+}
+
+func TestDefaultNotNil(t *testing.T) {
+	handler := Default()
+	if handler == nil {
+		t.Error("Should not return nil Gin handler")
+	}
+}
+
+func TestNewNotNil(t *testing.T) {
+	handler := New(Options{})
+	if handler == nil {
+		t.Error("Should not return nil Gin handler")
+	}
+}
+
+func TestCorsWrapper_buildAbortsWhenPreflight(t *testing.T) {
+	res := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(res)
+	ctx.Request, _ = http.NewRequest("OPTIONS", "http://example.com/foo", nil)
+	ctx.Request.Header.Add("Origin", "http://example.com/")
+	ctx.Request.Header.Add("Access-Control-Request-Method", "POST")
+	ctx.Status(http.StatusAccepted)
+	res.Code = http.StatusAccepted
+
+	handler := corsWrapper{Cors: cors.New(Options{
+		// Intentionally left blank.
+	})}.build()
+
+	handler(ctx)
+
+	if !ctx.IsAborted() {
+		t.Error("Should abort on preflight requests")
+	}
+	if res.Code != http.StatusOK {
+		t.Error("Should abort with 200 OK status")
+	}
+}
+
+func TestCorsWrapper_buildNotAbortsWhenPassthrough(t *testing.T) {
+	res := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(res)
+	ctx.Request, _ = http.NewRequest("OPTIONS", "http://example.com/foo", nil)
+	ctx.Request.Header.Add("Origin", "http://example.com/")
+	ctx.Request.Header.Add("Access-Control-Request-Method", "POST")
+
+	handler := corsWrapper{cors.New(Options{
+		OptionsPassthrough: true,
+	}), true}.build()
+
+	handler(ctx)
+
+	if ctx.IsAborted() {
+		t.Error("Should not abort when OPTIONS passthrough enabled")
+	}
+}