test: warn on substr() usage (#35499)

* test: warn on substr() usage

Don't allow any new substr() usage after #35421

Signed-off-by: Tobias Speicher <rootcommander@gmail.com>

* Apply suggestions from code review

* Use slice in router-utils

Co-authored-by: Steven <steven@ceriously.com>

.eslintrc.json

@@ -203,7 +203,14 @@
     "no-octal-escape": "warn",
     "no-redeclare": ["warn", { "builtinGlobals": false }],
     "no-regex-spaces": "warn",
-    "no-restricted-syntax": ["warn", "WithStatement"],
+    "no-restricted-syntax": [
+      "warn",
+      "WithStatement",
+      {
+        "message": "substr() is deprecated, use slice() or substring() instead",
+        "selector": "MemberExpression > Identifier[name='substr']"
+      }
+    ],
     "no-script-url": "warn",
     "no-self-assign": "warn",
     "no-self-compare": "warn",

packages/next/server/router-utils.ts

@@ -3,7 +3,7 @@ export function replaceBasePath(pathname: string, basePath: string): string {
   // and doesn't contain extra chars e.g. basePath /docs
   // should replace for /docs, /docs/, /docs/a but not /docsss
   if (hasBasePath(pathname, basePath)) {
-    pathname = pathname.substr(basePath.length)
+    pathname = pathname.slice(basePath.length)
     if (!pathname.startsWith('/')) pathname = `/${pathname}`
   }
   return pathname