From 0ed766d9a19761f403b11dbb1edc22be5e2e50b4 Mon Sep 17 00:00:00 2001
From: "grafana-delivery-bot[bot]"
 <132647405+grafana-delivery-bot[bot]@users.noreply.github.com>
Date: Fri, 19 Apr 2024 09:41:40 -0500
Subject: [PATCH] [v10.4.x] Prometheus: Do not throw error for label_join
 function (#86609)

---
 .../src/querybuilder/operations.ts            | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/packages/grafana-prometheus/src/querybuilder/operations.ts b/packages/grafana-prometheus/src/querybuilder/operations.ts
index 3b445efa37e..752bd564eda 100644
--- a/packages/grafana-prometheus/src/querybuilder/operations.ts
+++ b/packages/grafana-prometheus/src/querybuilder/operations.ts
@@ -201,6 +201,7 @@ export function getOperationDefinitions(): QueryBuilderOperationDef[] {
       ],
       defaultParams: ['', ',', ''],
       renderer: labelJoinRenderer,
+      explainHandler: labelJoinExplainHandler,
       addOperationHandler: labelJoinAddOperationHandler,
     }),
     createFunction({ id: PromOperationId.Log10 }),
@@ -356,11 +357,21 @@ function addNestedQueryHandler(def: QueryBuilderOperationDef, query: PromVisualQ
 }
 
 function labelJoinRenderer(model: QueryBuilderOperation, def: QueryBuilderOperationDef, innerExpr: string) {
-  if (typeof model.params[1] !== 'string') {
-    throw 'The separator must be a string';
+  const paramZero = model.params[0] ?? '';
+  const paramOne = model.params[1] ?? '';
+
+  const separator = `"${paramOne}"`;
+  return `${model.id}(${innerExpr}, "${paramZero}", ${separator}, "${model.params.slice(2).join(separator)}")`;
+}
+
+function labelJoinExplainHandler(op: QueryBuilderOperation, def?: QueryBuilderOperationDef): string {
+  let explainMessage = def?.documentation ?? 'no docs';
+
+  if (typeof op.params[1] !== 'string') {
+    explainMessage += ' 🚨🚨🚨 The `separator` must be a string.';
   }
-  const separator = `"${model.params[1]}"`;
-  return `${model.id}(${innerExpr}, "${model.params[0]}", ${separator}, "${model.params.slice(2).join(separator)}")`;
+
+  return explainMessage;
 }
 
 function labelJoinAddOperationHandler<T extends QueryWithOperations>(def: QueryBuilderOperationDef, query: T) {