net/http: add tests covering non-GET methods for file serving

ServeFile and FileServer will respond to methods such as DELETE by
serving the file contents. This is surprising, but we don't want to
change it without some consideration.

Add tests covering the current behavior.

For #59470

Change-Id: Ib6a2594c5b2b7f380149fc1628f7204b308161e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/482876
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/net/http/fs_test.go

@@ -87,15 +87,39 @@ func testServeFile(t *testing.T, mode testMode) {
 	if req.URL, err = url.Parse(ts.URL); err != nil {
 		t.Fatal("ParseURL:", err)
 	}
-	req.Method = "GET"
 
-	// straight GET
-	_, body := getBody(t, "straight get", req, c)
-	if !bytes.Equal(body, file) {
-		t.Fatalf("body mismatch: got %q, want %q", body, file)
+	// Get contents via various methods.
+	//
+	// See https://go.dev/issue/59471 for a proposal to limit the set of methods handled.
+	// For now, test the historical behavior.
+	for _, method := range []string{
+		MethodGet,
+		MethodPost,
+		MethodPut,
+		MethodPatch,
+		MethodDelete,
+		MethodOptions,
+		MethodTrace,
+	} {
+		req.Method = method
+		_, body := getBody(t, method, req, c)
+		if !bytes.Equal(body, file) {
+			t.Fatalf("body mismatch for %v request: got %q, want %q", method, body, file)
+		}
+	}
+
+	// HEAD request.
+	req.Method = MethodHead
+	resp, body := getBody(t, "HEAD", req, c)
+	if len(body) != 0 {
+		t.Fatalf("body mismatch for HEAD request: got %q, want empty", body)
+	}
+	if got, want := resp.Header.Get("Content-Length"), fmt.Sprint(len(file)); got != want {
+		t.Fatalf("Content-Length mismatch for HEAD request: got %v, want %v", got, want)
 	}
 
 	// Range tests
+	req.Method = MethodGet
 Cases:
 	for _, rt := range ServeFileRangeTests {
 		if rt.r != "" {
@@ -1521,3 +1545,52 @@ func testServeFileRejectsInvalidSuffixLengths(t *testing.T, mode testMode) {
 		})
 	}
 }
+
+func TestFileServerMethods(t *testing.T) {
+	run(t, testFileServerMethods)
+}
+func testFileServerMethods(t *testing.T, mode testMode) {
+	ts := newClientServerTest(t, mode, FileServer(Dir("testdata"))).ts
+
+	file, err := os.ReadFile(testFile)
+	if err != nil {
+		t.Fatal("reading file:", err)
+	}
+
+	// Get contents via various methods.
+	//
+	// See https://go.dev/issue/59471 for a proposal to limit the set of methods handled.
+	// For now, test the historical behavior.
+	for _, method := range []string{
+		MethodGet,
+		MethodHead,
+		MethodPost,
+		MethodPut,
+		MethodPatch,
+		MethodDelete,
+		MethodOptions,
+		MethodTrace,
+	} {
+		req, _ := NewRequest(method, ts.URL+"/file", nil)
+		t.Log(req.URL)
+		res, err := ts.Client().Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		body, err := io.ReadAll(res.Body)
+		res.Body.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+		wantBody := file
+		if method == MethodHead {
+			wantBody = nil
+		}
+		if !bytes.Equal(body, wantBody) {
+			t.Fatalf("%v: got body %q, want %q", method, body, wantBody)
+		}
+		if got, want := res.Header.Get("Content-Length"), fmt.Sprint(len(file)); got != want {
+			t.Fatalf("%v: got Content-Length %q, want %q", method, got, want)
+		}
+	}
+}