From fb9468ffb7ef9509c9bac93585ddc2871404c2eb Mon Sep 17 00:00:00 2001
From: Miki <miki@amazon.com>
Date: Tue, 21 Mar 2023 11:20:27 -0700
Subject: [PATCH] Omit adding the `osd-version` header when the Fetch request
 was explicitly asked to not prepend the `basePath`

Fixes #3277

Signed-off-by: Miki <miki@amazon.com>
---
 src/core/public/http/fetch.ts | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/core/public/http/fetch.ts b/src/core/public/http/fetch.ts
index cefaa353f7fa..3fde5c542d18 100644
--- a/src/core/public/http/fetch.ts
+++ b/src/core/public/http/fetch.ts
@@ -31,6 +31,7 @@
 import { omitBy } from 'lodash';
 import { format } from 'url';
 import { BehaviorSubject } from 'rxjs';
+import { isRelativeUrl } from '@osd/std';
 
 import {
   IBasePath,
@@ -144,7 +145,6 @@ export class Fetch {
       headers: removedUndefined({
         'Content-Type': 'application/json',
         ...options.headers,
-        'osd-version': this.params.opensearchDashboardsVersion,
       }),
     };
 
@@ -158,6 +158,16 @@ export class Fetch {
       fetchOptions.headers['osd-system-request'] = 'true';
     }
 
+    /* `osd-version` is used on the server-side to make sure that an incoming request originated from a front-end
+     * of the same version; see core/server/http/lifecycle_handlers.ts
+     *
+     * If url equals `basePath,  starts with `basePath` + '/', or is relative, add `osd-version` header.
+     */
+    const basePath = this.params.basePath.get();
+    if (isRelativeUrl(url) || url === basePath || url.startsWith(`${basePath}/`)) {
+      fetchOptions.headers['osd-version'] = this.params.opensearchDashboardsVersion;
+    }
+
     return new Request(url, fetchOptions as RequestInit);
   }