feat: serve files using embed.FS (#4847)

rest/internal/fileserver/filehandler.go

@@ -2,6 +2,7 @@ package fileserver
 
 import (
 	"net/http"
+	pathpkg "path"
 	"strings"
 	"sync"
 )
@@ -29,6 +30,18 @@ func createFileChecker(fs http.FileSystem) func(string) bool {
 	fileChecker := make(map[string]bool)
 
 	return func(path string) bool {
+		// Emulate http.Dir.Open’s path normalization for embed.FS.Open.
+		// http.FileServer redirects any request ending in "/index.html"
+		// to the same path without the final "index.html".
+		// So the path here may be empty or end with a "/".
+		// http.Dir.Open uses this logic to clean the path,
+		// correctly handling those two cases.
+		// embed.FS doesn’t perform this normalization, so we apply the same logic here.
+		path = pathpkg.Clean("/" + path)[1:]
+		if path == "" {
+			path = "."
+		}
+
 		lock.RLock()
 		exist, ok := fileChecker[path]
 		lock.RUnlock()

rest/internal/fileserver/filehandler_test.go

@@ -1,6 +1,8 @@
 package fileserver
 
 import (
+	"embed"
+	"io/fs"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -61,6 +63,46 @@ func TestMiddleware(t *testing.T) {
 			requestPath:    "/ws",
 			expectedStatus: http.StatusAlreadyReported,
 		},
+
+		// http.FileServer redirects any request ending in "/index.html"
+		// to the same path, without the final "index.html".
+		{
+			name:           "Serve index.html",
+			path:           "/static",
+			dir:            "testdata",
+			requestPath:    "/static/index.html",
+			expectedStatus: http.StatusMovedPermanently,
+		},
+		{
+			name:           "Serve index.html with path with trailing slash",
+			path:           "/static/",
+			dir:            "testdata",
+			requestPath:    "/static/index.html",
+			expectedStatus: http.StatusMovedPermanently,
+		},
+		{
+			name:           "Serve index.html in a nested directory",
+			path:           "/static",
+			dir:            "testdata",
+			requestPath:    "/static/nested/index.html",
+			expectedStatus: http.StatusMovedPermanently,
+		},
+		{
+			name:            "Request index.html indirectly",
+			path:            "/static",
+			dir:             "testdata",
+			requestPath:     "/static/",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "hello",
+		},
+		{
+			name:            "Request index.html in a nested directory indirectly",
+			path:            "/static",
+			dir:             "testdata",
+			requestPath:     "/static/nested/",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "hello",
+		},
 	}
 
 	for _, tt := range tests {
@@ -87,6 +129,128 @@ func TestMiddleware(t *testing.T) {
 	}
 }
 
+var (
+	//go:embed testdata
+	testdataFS embed.FS
+)
+
+func TestMiddleware_embedFS(t *testing.T) {
+	tests := []struct {
+		name            string
+		path            string
+		requestPath     string
+		expectedStatus  int
+		expectedContent string
+	}{
+		{
+			name:            "Serve static file",
+			path:            "/static",
+			requestPath:     "/static/example.txt",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "1",
+		},
+		{
+			name:            "Path with trailing slash",
+			path:            "/static/",
+			requestPath:     "/static/example.txt",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "1",
+		},
+		{
+			name:            "Root path",
+			path:            "/",
+			requestPath:     "/example.txt",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "1",
+		},
+		{
+			name:           "Pass through non-matching path",
+			path:           "/static/",
+			requestPath:    "/other/path",
+			expectedStatus: http.StatusAlreadyReported,
+		},
+		{
+			name:           "Not exist file",
+			path:           "/assets",
+			requestPath:    "/assets/not-exist.txt",
+			expectedStatus: http.StatusAlreadyReported,
+		},
+		{
+			name:           "Not exist file in root",
+			path:           "/",
+			requestPath:    "/not-exist.txt",
+			expectedStatus: http.StatusAlreadyReported,
+		},
+		{
+			name:           "websocket request",
+			path:           "/",
+			requestPath:    "/ws",
+			expectedStatus: http.StatusAlreadyReported,
+		},
+
+		// http.FileServer redirects any request ending in "/index.html"
+		// to the same path, without the final "index.html".
+		{
+			name:           "Serve index.html",
+			path:           "/static",
+			requestPath:    "/static/index.html",
+			expectedStatus: http.StatusMovedPermanently,
+		},
+		{
+			name:           "Serve index.html with path with trailing slash",
+			path:           "/static/",
+			requestPath:    "/static/index.html",
+			expectedStatus: http.StatusMovedPermanently,
+		},
+		{
+			name:           "Serve index.html in a nested directory",
+			path:           "/static",
+			requestPath:    "/static/nested/index.html",
+			expectedStatus: http.StatusMovedPermanently,
+		},
+		{
+			name:            "Request index.html indirectly",
+			path:            "/static",
+			requestPath:     "/static/",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "hello",
+		},
+		{
+			name:            "Request index.html in a nested directory indirectly",
+			path:            "/static",
+			requestPath:     "/static/nested/",
+			expectedStatus:  http.StatusOK,
+			expectedContent: "hello",
+		},
+	}
+
+	subFS, err := fs.Sub(testdataFS, "testdata")
+	assert.Nil(t, err)
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			middleware := Middleware(tt.path, http.FS(subFS))
+			nextHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusAlreadyReported)
+			})
+
+			handlerToTest := middleware(nextHandler)
+
+			for i := 0; i < 2; i++ {
+				req := httptest.NewRequest(http.MethodGet, tt.requestPath, nil)
+				rr := httptest.NewRecorder()
+
+				handlerToTest.ServeHTTP(rr, req)
+
+				assert.Equal(t, tt.expectedStatus, rr.Code)
+				if len(tt.expectedContent) > 0 {
+					assert.Equal(t, tt.expectedContent, rr.Body.String())
+				}
+			}
+		})
+	}
+}
+
 func TestEnsureTrailingSlash(t *testing.T) {
 	tests := []struct {
 		input    string

rest/internal/fileserver/testdata/index.html

@@ -0,0 +1 @@
+hello

rest/internal/fileserver/testdata/nested/index.html

@@ -0,0 +1 @@
+hello