From b44ba7216dab9382f96412a62efab54789acf004 Mon Sep 17 00:00:00 2001
From: Kristiyan Kostadinov <crisbeto@abv.bg>
Date: Sun, 1 Jun 2025 09:35:46 +0200
Subject: [PATCH] fix(material/schematics): avoid overwriting files that didn't
 change

Fixes that the v20 update migration was overwriting all files, even if they didn't change.

Fixes #31259.
---
 src/material/schematics/ng-update/index.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/material/schematics/ng-update/index.ts b/src/material/schematics/ng-update/index.ts
index 18644fe90a00..b76c9f98966b 100644
--- a/src/material/schematics/ng-update/index.ts
+++ b/src/material/schematics/ng-update/index.ts
@@ -59,7 +59,9 @@ function renameMdcTokens(): Rule {
       if (shouldRenameTokens(path)) {
         const content = tree.readText(path);
         const updatedContent = content.replace('--mdc-', '--mat-');
-        tree.overwrite(path, updatedContent);
+        if (content !== updatedContent) {
+          tree.overwrite(path, updatedContent);
+        }
       }
     });
   };