[v9.3.x] Loki: Fix wrongly escaped label values when using LabelFilter (

grafana#59876)

Loki: Fix wrongly escaped label values when using LabelFilter (grafana#59812)

* change backticks to quotes

* add unescaping to `addFilterAsLabelFilter`

* fix removal of wrong quotes

* change unescape order

(cherry picked from commit 932349b)

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

@@ -1,4 +1,4 @@
-import { isBytesString } from './languageUtils';
+import { escapeLabelValueInExactSelector, isBytesString, unescapeLabelValue } from './languageUtils';
 
 describe('isBytesString', () => {
   it('correctly matches bytes string with integers', () => {
@@ -18,3 +18,27 @@ describe('isBytesString', () => {
     expect(isBytesString('1.234')).toBe(false);
   });
 });
+
+describe('escapeLabelValueInExactSelector', () => {
+  it.each`
+    value                      | escapedValue
+    ${'nothing to escape'}     | ${'nothing to escape'}
+    ${'escape quote: "'}       | ${'escape quote: \\"'}
+    ${'escape newline: \nend'} | ${'escape newline: \\nend'}
+    ${'escape slash: \\'}      | ${'escape slash: \\\\'}
+  `('when called with $value', ({ value, escapedValue }) => {
+    expect(escapeLabelValueInExactSelector(value)).toEqual(escapedValue);
+  });
+});
+
+describe('unescapeLabelValueInExactSelector', () => {
+  it.each`
+    value                       | unescapedValue
+    ${'nothing to unescape'}    | ${'nothing to unescape'}
+    ${'escape quote: \\"'}      | ${'escape quote: "'}
+    ${'escape newline: \\nend'} | ${'escape newline: \nend'}
+    ${'escape slash: \\\\'}     | ${'escape slash: \\'}
+  `('when called with $value', ({ value, unescapedValue }) => {
+    expect(unescapeLabelValue(value)).toEqual(unescapedValue);
+  });
+});

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

@@ -35,6 +35,10 @@ export function escapeLabelValueInExactSelector(labelValue: string): string {
   return labelValue.replace(/\\/g, '\\\\').replace(/\n/g, '\\n').replace(/"/g, '\\"');
 }
 
+export function unescapeLabelValue(labelValue: string): string {
+  return labelValue.replace(/\\n/g, '\n').replace(/\\"/g, '"').replace(/\\\\/g, '\\');
+}
+
 export function escapeLabelValueInRegexSelector(labelValue: string): string {
   return escapeLabelValueInExactSelector(escapeLokiRegexp(labelValue));
 }