Tempo: Correctly escape/unescape tag when looking for tag values (#114275)

* Correctly escape/unescape tag

Signed-off-by: Joe Elliott <number101010@gmail.com>

* changelog

Signed-off-by: Joe Elliott <number101010@gmail.com>

* Revert "changelog"

This reverts commit e0cde18994c67fbdd601514d2f930798b0ae76c6.

---------

Signed-off-by: Joe Elliott <number101010@gmail.com>

pkg/tsdb/tempo/tempo.go

@@ -280,7 +280,15 @@ func (s *Service) handleTagValues(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	tempoPath := fmt.Sprintf("api/v2/search/tag/%s/values", encodedTag)
+	// escape tag
+	tag, err := url.PathUnescape(encodedTag)
+	if err != nil {
+		s.logger.Error("Failed to unescape", "error", err, "tag", encodedTag)
+		http.Error(rw, "Invalid 'tag' parameter", http.StatusBadRequest)
+		return
+	}
+
+	tempoPath := fmt.Sprintf("api/v2/search/tag/%s/values", tag)
 	s.proxyToTempo(rw, req, tempoPath)
 }
 

public/app/plugins/datasource/tempo/language_provider.ts

@@ -190,9 +190,7 @@ export default class TempoLanguageProvider extends LanguageProvider {
    * @returns the encoded tag
    */
   private encodeTag = (tag: string): string => {
-    // If we call `encodeURIComponent` only once, we still get an error when issuing a request to the backend
-    // Reference: https://stackoverflow.com/a/37456192
-    return encodeURIComponent(encodeURIComponent(tag));
+    return encodeURIComponent(tag);
   };
 
   generateQueryFromFilters({