Add support for HEAD operations (#19520)

* Add header operation to sdk/logical

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

* Add support for routing HEAD operations

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

* Add changelog entry

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

---------

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

changelog/19520.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+http: Support responding to HEAD operation from plugins
+```

http/logical.go

@@ -183,8 +183,10 @@ func buildLogicalRequestNoAuth(perfStandby bool, w http.ResponseWriter, r *http.
 		}
 
 		data = parseQuery(r.URL.Query())
-
-	case "OPTIONS", "HEAD":
+	case "HEAD":
+		op = logical.HeaderOperation
+		data = parseQuery(r.URL.Query())
+	case "OPTIONS":
 	default:
 		return nil, nil, http.StatusMethodNotAllowed, nil
 	}

sdk/logical/request.go

@@ -369,6 +369,7 @@ const (
 	HelpOperation                     = "help"
 	AliasLookaheadOperation           = "alias-lookahead"
 	ResolveRoleOperation              = "resolve-role"
+	HeaderOperation                   = "header"
 
 	// The operations below are called globally, the path is less relevant.
 	RevokeOperation   Operation = "revoke"

sdk/logical/response_util.go

@@ -20,7 +20,7 @@ import (
 func RespondErrorCommon(req *Request, resp *Response, err error) (int, error) {
 	if err == nil && (resp == nil || !resp.IsError()) {
 		switch {
-		case req.Operation == ReadOperation:
+		case req.Operation == ReadOperation || req.Operation == HeaderOperation:
 			if resp == nil {
 				return http.StatusNotFound, nil
 			}

sdk/logical/response_util_test.go

@@ -42,6 +42,14 @@ func TestResponseUtil_RespondErrorCommon_basic(t *testing.T) {
 			respErr:        nil,
 			expectedStatus: 404,
 		},
+		{
+			title: "Header not found",
+			req: &Request{
+				Operation: HeaderOperation,
+			},
+			respErr:        nil,
+			expectedStatus: 404,
+		},
 		{
 			title: "List with response and no keys",
 			req: &Request{