Fix HEAD method in resources.GetRemote

Fixes #10604

resources/resource_factories/create/remote.go

@@ -45,7 +45,29 @@ type HTTPError struct {
 	Body       string
 }
 
-func toHTTPError(err error, res *http.Response) *HTTPError {
+func responseToData(res *http.Response, readBody bool) map[string]any {
+	var body []byte
+	if readBody {
+		body, _ = ioutil.ReadAll(res.Body)
+	}
+
+	m := map[string]any{
+		"StatusCode":       res.StatusCode,
+		"Status":           res.Status,
+		"TransferEncoding": res.TransferEncoding,
+		"ContentLength":    res.ContentLength,
+		"ContentType":      res.Header.Get("Content-Type"),
+	}
+
+	if readBody {
+		m["Body"] = string(body)
+	}
+
+	return m
+
+}
+
+func toHTTPError(err error, res *http.Response, readBody bool) *HTTPError {
 	if err == nil {
 		panic("err is nil")
 	}
@@ -56,19 +78,9 @@ func toHTTPError(err error, res *http.Response) *HTTPError {
 		}
 	}
 
-	var body []byte
-	body, _ = ioutil.ReadAll(res.Body)
-
 	return &HTTPError{
 		error: err,
-		Data: map[string]any{
-			"StatusCode":       res.StatusCode,
-			"Status":           res.Status,
-			"Body":             string(body),
-			"TransferEncoding": res.TransferEncoding,
-			"ContentLength":    res.ContentLength,
-			"ContentType":      res.Header.Get("Content-Type"),
-		},
+		Data:  responseToData(res, readBody),
 	}
 }
 
@@ -80,6 +92,12 @@ func (c *Client) FromRemote(uri string, optionsm map[string]any) (resource.Resou
 		return nil, fmt.Errorf("failed to parse URL for resource %s: %w", uri, err)
 	}
 
+	method := "GET"
+	if s, ok := maps.LookupEqualFold(optionsm, "method"); ok {
+		method = strings.ToUpper(s.(string))
+	}
+	isHeadMethod := method == "HEAD"
+
 	resourceID := calculateResourceID(uri, optionsm)
 
 	_, httpResponse, err := c.cacheGetResource.GetOrCreate(resourceID, func() (io.ReadCloser, error) {
@@ -100,15 +118,16 @@ func (c *Client) FromRemote(uri string, optionsm map[string]any) (resource.Resou
 		if err != nil {
 			return nil, err
 		}
+		defer res.Body.Close()
 
 		httpResponse, err := httputil.DumpResponse(res, true)
 		if err != nil {
-			return nil, toHTTPError(err, res)
+			return nil, toHTTPError(err, res, !isHeadMethod)
 		}
 
 		if res.StatusCode != http.StatusNotFound {
 			if res.StatusCode < 200 || res.StatusCode > 299 {
-				return nil, toHTTPError(fmt.Errorf("failed to fetch remote resource: %s", http.StatusText(res.StatusCode)), res)
+				return nil, toHTTPError(fmt.Errorf("failed to fetch remote resource: %s", http.StatusText(res.StatusCode)), res, !isHeadMethod)
 
 			}
 		}
@@ -124,15 +143,24 @@ func (c *Client) FromRemote(uri string, optionsm map[string]any) (resource.Resou
 	if err != nil {
 		return nil, err
 	}
+	defer res.Body.Close()
 
 	if res.StatusCode == http.StatusNotFound {
 		// Not found. This matches how looksup for local resources work.
 		return nil, nil
 	}
 
-	body, err := ioutil.ReadAll(res.Body)
-	if err != nil {
-		return nil, fmt.Errorf("failed to read remote resource %q: %w", uri, err)
+	var (
+		body      []byte
+		mediaType media.Type
+	)
+	// A response to a HEAD method should not have a body. If it has one anyway, that body must be ignored.
+	// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/HEAD
+	if !isHeadMethod && res.Body != nil {
+		body, err = ioutil.ReadAll(res.Body)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read remote resource %q: %w", uri, err)
+		}
 	}
 
 	filename := path.Base(rURL.Path)
@@ -142,30 +170,38 @@ func (c *Client) FromRemote(uri string, optionsm map[string]any) (resource.Resou
 		}
 	}
 
-	var extensionHints []string
-
 	contentType := res.Header.Get("Content-Type")
 
-	// mime.ExtensionsByType gives a long list of extensions for text/plain,
-	// just use ".txt".
-	if strings.HasPrefix(contentType, "text/plain") {
-		extensionHints = []string{".txt"}
+	if isHeadMethod {
+		// We have no body to work with, so we need to use the Content-Type header.
+		mediaType, _ = media.FromString(contentType)
 	} else {
-		exts, _ := mime.ExtensionsByType(contentType)
-		if exts != nil {
-			extensionHints = exts
+
+		var extensionHints []string
+
+		// mime.ExtensionsByType gives a long list of extensions for text/plain,
+		// just use ".txt".
+		if strings.HasPrefix(contentType, "text/plain") {
+			extensionHints = []string{".txt"}
+		} else {
+			exts, _ := mime.ExtensionsByType(contentType)
+			if exts != nil {
+				extensionHints = exts
+			}
 		}
+
+		// Look for a file extension. If it's .txt, look for a more specific.
+		if extensionHints == nil || extensionHints[0] == ".txt" {
+			if ext := path.Ext(filename); ext != "" {
+				extensionHints = []string{ext}
+			}
+		}
+
+		// Now resolve the media type primarily using the content.
+		mediaType = media.FromContent(c.rs.MediaTypes, extensionHints, body)
+
 	}
 
-	// Look for a file extension. If it's .txt, look for a more specific.
-	if extensionHints == nil || extensionHints[0] == ".txt" {
-		if ext := path.Ext(filename); ext != "" {
-			extensionHints = []string{ext}
-		}
-	}
-
-	// Now resolve the media type primarily using the content.
-	mediaType := media.FromContent(c.rs.MediaTypes, extensionHints, body)
 	if mediaType.IsZero() {
 		return nil, fmt.Errorf("failed to resolve media type for remote resource %q", uri)
 	}