Fix validation again. (#5399)

Author: iclanton

common/changes/@microsoft/rush/fix-extensions-hash_2025-10-03-20-27.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Fix an issue with validation of the `pnpm-lock.yaml` `packageExtensionsChecksum` field in pnpm v10.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@microsoft/rush"
+}

common/config/rush/version-policies.json

@@ -103,7 +103,7 @@
     "policyName": "rush",
     "definitionName": "lockStepVersion",
     "version": "5.160.0",
-    "nextBump": "minor",
+    "nextBump": "patch",
     "mainProject": "@microsoft/rush"
   }
 ]

libraries/rush-lib/src/logic/installManager/WorkspaceInstallManager.ts

@@ -406,7 +406,7 @@ export class WorkspaceInstallManager extends BaseInstallManager {
       let packageExtensionsChecksumAlgorithm: string | undefined;
       if (existingPackageExtensionsChecksum) {
         const dashIndex: number = existingPackageExtensionsChecksum.indexOf('-');
-        if (dashIndex === -1) {
+        if (dashIndex !== -1) {
           packageExtensionsChecksumAlgorithm = existingPackageExtensionsChecksum.substring(0, dashIndex);
         }