Log volume: Fix functionality if query has multiple comments (#61306)

* Log volume: Fix functionality if query has comments

* Add additional test

public/app/plugins/datasource/loki/modifyQuery.test.ts

@@ -152,6 +152,8 @@ describe('removeCommentsFromQuery', () => {
     ${'{job="grafana"}#hello'}                                                        | ${'{job="grafana"}'}
     ${'{job="grafana"} | logfmt #hello'}                                              | ${'{job="grafana"} | logfmt '}
     ${'{job="grafana", bar="baz"} |="test" | logfmt | label_format level=lvl #hello'} | ${'{job="grafana", bar="baz"} |="test" | logfmt | label_format level=lvl '}
+    ${`#sum(rate(\n{host="containers"}\n#[1m]))`}                                     | ${`\n{host="containers"}\n`}
+    ${`#sum(rate(\n{host="containers"}\n#| logfmt\n#[1m]))`}                          | ${`\n{host="containers"}\n\n`}
   `('strips comments in log query:  {$query}', ({ query, expectedResult }) => {
     expect(removeCommentsFromQuery(query)).toBe(expectedResult);
   });

public/app/plugins/datasource/loki/modifyQuery.ts

@@ -128,10 +128,7 @@ export function removeCommentsFromQuery(query: string): string {
   let prev = 0;
 
   for (let lineCommentPosition of lineCommentPositions) {
-    const beforeComment = query.substring(prev, lineCommentPosition.from);
-    const afterComment = query.substring(lineCommentPosition.to);
-
-    newQuery += beforeComment + afterComment;
+    newQuery = newQuery + query.substring(prev, lineCommentPosition.from);
     prev = lineCommentPosition.to;
   }
   return newQuery;