feat: rest.WithChain to replace builtin middlewares (#2033)
* feat: rest.WithChain to replace builtin middlewares * chore: add comments * chore: refine codemaster
Kevin Wan
2 years ago
committed by
GitHub
parent
50f16e2892
commit
47c49de94e
@ -0,0 +1,109 @@
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package chain
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// This is a modified version of https://github.com/justinas/alice
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// The original code is licensed under the MIT license.
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// It's modified for couple reasons:
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// - Added the Chain interface
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// - Added support for the Chain.Prepend(...) method
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import "net/http"
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type (
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// Chain defines a chain of middleware.
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Chain interface {
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Append(middlewares ...Middleware) Chain
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Prepend(middlewares ...Middleware) Chain
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Then(h http.Handler) http.Handler
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ThenFunc(fn http.HandlerFunc) http.Handler
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}
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// Middleware is an HTTP middleware.
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Middleware func(http.Handler) http.Handler
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// chain acts as a list of http.Handler middlewares.
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// chain is effectively immutable:
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// once created, it will always hold
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// the same set of middlewares in the same order.
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chain struct {
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middlewares []Middleware
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}
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)
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// New creates a new Chain, memorizing the given list of middleware middlewares.
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// New serves no other function, middlewares are only called upon a call to Then() or ThenFunc().
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func New(middlewares ...Middleware) Chain {
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return chain{middlewares: append(([]Middleware)(nil), middlewares...)}
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}
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// Append extends a chain, adding the specified middlewares as the last ones in the request flow.
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//
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// c := chain.New(m1, m2)
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// c.Append(m3, m4)
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// // requests in c go m1 -> m2 -> m3 -> m4
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func (c chain) Append(middlewares ...Middleware) Chain {
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return chain{middlewares: join(c.middlewares, middlewares)}
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}
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// Prepend extends a chain by adding the specified chain as the first one in the request flow.
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//
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// c := chain.New(m3, m4)
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// c1 := chain.New(m1, m2)
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// c.Prepend(c1)
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// // requests in c go m1 -> m2 -> m3 -> m4
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func (c chain) Prepend(middlewares ...Middleware) Chain {
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return chain{middlewares: join(middlewares, c.middlewares)}
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}
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// Then chains the middleware and returns the final http.Handler.
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// New(m1, m2, m3).Then(h)
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// is equivalent to:
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// m1(m2(m3(h)))
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// When the request comes in, it will be passed to m1, then m2, then m3
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// and finally, the given handler
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// (assuming every middleware calls the following one).
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//
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// A chain can be safely reused by calling Then() several times.
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// stdStack := chain.New(ratelimitHandler, csrfHandler)
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// indexPipe = stdStack.Then(indexHandler)
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// authPipe = stdStack.Then(authHandler)
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// Note that middlewares are called on every call to Then() or ThenFunc()
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// and thus several instances of the same middleware will be created
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// when a chain is reused in this way.
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// For proper middleware, this should cause no problems.
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//
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// Then() treats nil as http.DefaultServeMux.
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func (c chain) Then(h http.Handler) http.Handler {
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if h == nil {
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h = http.DefaultServeMux
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}
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for i := range c.middlewares {
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h = c.middlewares[len(c.middlewares)-1-i](h)
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}
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return h
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}
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// ThenFunc works identically to Then, but takes
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// a HandlerFunc instead of a Handler.
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//
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// The following two statements are equivalent:
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// c.Then(http.HandlerFunc(fn))
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// c.ThenFunc(fn)
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//
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// ThenFunc provides all the guarantees of Then.
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func (c chain) ThenFunc(fn http.HandlerFunc) http.Handler {
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// This nil check cannot be removed due to the "nil is not nil" common mistake in Go.
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// Required due to: https://stackoverflow.com/questions/33426977/how-to-golang-check-a-variable-is-nil
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if fn == nil {
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return c.Then(nil)
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}
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return c.Then(fn)
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}
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func join(a, b []Middleware) []Middleware {
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mids := make([]Middleware, 0, len(a)+len(b))
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mids = append(mids, a...)
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mids = append(mids, b...)
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return mids
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}
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@ -0,0 +1,126 @@
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package chain
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import (
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"net/http"
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"net/http/httptest"
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"reflect"
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"testing"
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"github.com/stretchr/testify/assert"
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)
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// A constructor for middleware
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// that writes its own "tag" into the RW and does nothing else.
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// Useful in checking if a chain is behaving in the right order.
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func tagMiddleware(tag string) Middleware {
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return func(h http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte(tag))
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h.ServeHTTP(w, r)
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})
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}
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}
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// Not recommended (https://golang.org/pkg/reflect/#Value.Pointer),
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// but the best we can do.
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func funcsEqual(f1, f2 interface{}) bool {
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val1 := reflect.ValueOf(f1)
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val2 := reflect.ValueOf(f2)
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return val1.Pointer() == val2.Pointer()
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}
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var testApp = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte("app\n"))
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})
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func TestNew(t *testing.T) {
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c1 := func(h http.Handler) http.Handler {
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return nil
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}
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c2 := func(h http.Handler) http.Handler {
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return http.StripPrefix("potato", nil)
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}
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slice := []Middleware{c1, c2}
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c := New(slice...)
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for k := range slice {
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assert.True(t, funcsEqual(c.(chain).middlewares[k], slice[k]),
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"New does not add constructors correctly")
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}
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}
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func TestThenWorksWithNoMiddleware(t *testing.T) {
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assert.True(t, funcsEqual(New().Then(testApp), testApp),
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"Then does not work with no middleware")
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}
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func TestThenTreatsNilAsDefaultServeMux(t *testing.T) {
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assert.Equal(t, http.DefaultServeMux, New().Then(nil),
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"Then does not treat nil as DefaultServeMux")
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}
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func TestThenFuncTreatsNilAsDefaultServeMux(t *testing.T) {
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assert.Equal(t, http.DefaultServeMux, New().ThenFunc(nil),
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"ThenFunc does not treat nil as DefaultServeMux")
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}
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func TestThenFuncConstructsHandlerFunc(t *testing.T) {
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fn := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.WriteHeader(200)
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})
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chained := New().ThenFunc(fn)
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rec := httptest.NewRecorder()
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chained.ServeHTTP(rec, (*http.Request)(nil))
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assert.Equal(t, reflect.TypeOf((http.HandlerFunc)(nil)), reflect.TypeOf(chained),
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"ThenFunc does not construct HandlerFunc")
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}
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func TestThenOrdersHandlersCorrectly(t *testing.T) {
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t1 := tagMiddleware("t1\n")
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t2 := tagMiddleware("t2\n")
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t3 := tagMiddleware("t3\n")
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chained := New(t1, t2, t3).Then(testApp)
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w := httptest.NewRecorder()
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r, err := http.NewRequest("GET", "/", nil)
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if err != nil {
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t.Fatal(err)
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}
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chained.ServeHTTP(w, r)
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assert.Equal(t, "t1\nt2\nt3\napp\n", w.Body.String(),
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"Then does not order handlers correctly")
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}
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func TestAppendAddsHandlersCorrectly(t *testing.T) {
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c := New(tagMiddleware("t1\n"), tagMiddleware("t2\n"))
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c = c.Append(tagMiddleware("t3\n"), tagMiddleware("t4\n"))
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h := c.Then(testApp)
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w := httptest.NewRecorder()
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r, err := http.NewRequest("GET", "/", nil)
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assert.Nil(t, err)
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h.ServeHTTP(w, r)
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assert.Equal(t, "t1\nt2\nt3\nt4\napp\n", w.Body.String(),
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"Append does not add handlers correctly")
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}
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func TestExtendAddsHandlersCorrectly(t *testing.T) {
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c := New(tagMiddleware("t3\n"), tagMiddleware("t4\n"))
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c = c.Prepend(tagMiddleware("t1\n"), tagMiddleware("t2\n"))
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h := c.Then(testApp)
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w := httptest.NewRecorder()
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r, err := http.NewRequest("GET", "/", nil)
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assert.Nil(t, err)
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h.ServeHTTP(w, r)
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assert.Equal(t, "t1\nt2\nt3\nt4\napp\n", w.Body.String(),
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"Extend does not add handlers in correctly")
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}
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