chore(coderd/httpmw): extract HTTPRoute middleware (#21498)

Extracts part of the prometheus middleware that stores the route
information in the request context into its own middleware. Also adds
request method information to context.

Relates to https://github.com/coder/internal/issues/1214

coderd/httpmw/httproute_test.go

@@ -0,0 +1,104 @@
+package httpmw_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/coder/coder/v2/coderd/httpmw"
+	"github.com/coder/coder/v2/testutil"
+)
+
+func TestHTTPRoute(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range []struct {
+		name           string
+		reqFn          func() *http.Request
+		registerRoutes map[string]string
+		mws            []func(http.Handler) http.Handler
+		expectedRoute  string
+		expectedMethod string
+	}{
+		{
+			name: "without middleware",
+			reqFn: func() *http.Request {
+				return httptest.NewRequest(http.MethodGet, "/", nil)
+			},
+			registerRoutes: map[string]string{http.MethodGet: "/"},
+			mws:            []func(http.Handler) http.Handler{},
+			expectedRoute:  "",
+			expectedMethod: "",
+		},
+		{
+			name: "root",
+			reqFn: func() *http.Request {
+				return httptest.NewRequest(http.MethodGet, "/", nil)
+			},
+			registerRoutes: map[string]string{http.MethodGet: "/"},
+			mws:            []func(http.Handler) http.Handler{httpmw.HTTPRoute},
+			expectedRoute:  "/",
+			expectedMethod: http.MethodGet,
+		},
+		{
+			name: "parameterized route",
+			reqFn: func() *http.Request {
+				return httptest.NewRequest(http.MethodPut, "/users/123", nil)
+			},
+			registerRoutes: map[string]string{http.MethodPut: "/users/{id}"},
+			mws:            []func(http.Handler) http.Handler{httpmw.HTTPRoute},
+			expectedRoute:  "/users/{id}",
+			expectedMethod: http.MethodPut,
+		},
+		{
+			name: "unknown",
+			reqFn: func() *http.Request {
+				return httptest.NewRequest(http.MethodGet, "/api/a", nil)
+			},
+			registerRoutes: map[string]string{http.MethodGet: "/api/b"},
+			mws:            []func(http.Handler) http.Handler{httpmw.HTTPRoute},
+			expectedRoute:  "UNKNOWN",
+			expectedMethod: http.MethodGet,
+		},
+		{
+			name: "static",
+			reqFn: func() *http.Request {
+				return httptest.NewRequest(http.MethodGet, "/some/static/file.png", nil)
+			},
+			registerRoutes: map[string]string{http.MethodGet: "/"},
+			mws:            []func(http.Handler) http.Handler{httpmw.HTTPRoute},
+			expectedRoute:  "STATIC",
+			expectedMethod: http.MethodGet,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx := testutil.Context(t, testutil.WaitShort)
+			r := chi.NewRouter()
+			done := make(chan string)
+			for _, mw := range tc.mws {
+				r.Use(mw)
+			}
+			r.Use(func(next http.Handler) http.Handler {
+				return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					defer close(done)
+					method := httpmw.ExtractHTTPMethod(r.Context())
+					route := httpmw.ExtractHTTPRoute(r.Context())
+					assert.Equal(t, tc.expectedMethod, method, "expected method mismatch")
+					assert.Equal(t, tc.expectedRoute, route, "expected route mismatch")
+					next.ServeHTTP(w, r)
+				})
+			})
+			for method, route := range tc.registerRoutes {
+				r.MethodFunc(method, route, func(w http.ResponseWriter, r *http.Request) {})
+			}
+			req := tc.reqFn()
+			r.ServeHTTP(httptest.NewRecorder(), req)
+			_ = testutil.TryReceive(ctx, t, done)
+		})
+	}
+}