fix(setup): read MCPorter's XDG folder in the client configuration-root owner (#11193)

src/application/ClientConfigRoots.test.ts

@@ -5,6 +5,7 @@ import { expect, it } from "vitest";
 
 import {
   absoluteXdgConfigHome,
+  mcporterXdgConfigHome,
   xdgConfigHomeOrDefault,
 } from "./ClientConfigRoots.js";
 
@@ -24,6 +25,20 @@ it.each([
   },
 );
 
+it.each([
+  [undefined, undefined],
+  ["", undefined],
+  ["relative", undefined],
+  [" ~/xdg ", "/home/user/xdg"],
+  ["~", "/home/user"],
+  [" /custom ", "/custom"],
+])("reads XDG_CONFIG_HOME=%j as MCPorter's folder %j", (value, expected) => {
+  const env = value === undefined ? {} : { XDG_CONFIG_HOME: value };
+  expect(mcporterXdgConfigHome({ home, platform: "linux", env })).toBe(
+    expected,
+  );
+});
+
 // Client root semantics differ per reader, so they are derived only here.
 it("keeps client configuration-root variables in one owner", async () => {
   const directory = fileURLToPath(new URL(".", import.meta.url));

src/application/ClientConfigRoots.ts

@@ -43,6 +43,31 @@ export const absoluteXdgConfigHome = ({
     : join(home, ".config");
 };
 
+/** MCPorter's expandHome: a leading `~` path segment names the home folder. */
+export const mcporterExpandHome = (value: string, home: string): string =>
+  value === "~"
+    ? home
+    : value.startsWith("~/") || value.startsWith("~\\")
+      ? join(home, value.slice(2))
+      : value;
+
+/**
+ * MCPorter's XDG folder (`mcporterConfigCandidates`): `XDG_CONFIG_HOME` is
+ * trimmed and `~`-expanded, and only an absolute result counts. Otherwise
+ * MCPorter uses its legacy `~/.mcporter` folder rather than `~/.config`, so
+ * there is no XDG folder and this returns `undefined`.
+ */
+export const mcporterXdgConfigHome = ({
+  home,
+  platform,
+  env,
+}: ClientRootContext): string | undefined => {
+  const value = mcporterExpandHome(env.XDG_CONFIG_HOME?.trim() ?? "", home);
+  return (platform === "win32" ? win32 : posix).isAbsolute(value)
+    ? value
+    : undefined;
+};
+
 /**
  * Code-OSS's `getUserDataPath` for one product's data folder (`Code` for VS
  * Code; `Cursor`, `Windsurf`, `VSCodium` or `Code - Insiders` for builds that

src/application/SupportedClients.ts

@@ -25,6 +25,8 @@ import {
   clientPathDependence,
   absoluteXdgConfigHome,
   type ClientRootFailure,
+  mcporterExpandHome,
+  mcporterXdgConfigHome,
   vscodeUserDirectory,
   xdgConfigHomeOrDefault,
 } from "./ClientConfigRoots.js";
@@ -744,14 +746,6 @@ const zedLocation = ({
       });
 };
 
-/** MCPorter's expandHome: a leading `~` path segment names the home folder. */
-const mcporterExpandHome = (value: string, home: string): string =>
-  value === "~"
-    ? home
-    : value.startsWith("~/") || value.startsWith("~\\")
-      ? join(home, value.slice(2))
-      : value;
-
 const regularPathPresent = (
   path: string,
 ): Result<boolean, ClientPathFailure> => {
@@ -801,13 +795,8 @@ const mcporterLocation = ({
         })
       : absolute;
   }
-  const configHome = mcporterExpandHome(
-    env.XDG_CONFIG_HOME?.trim() ?? "",
-    home,
-  );
-  const base = pathApi.isAbsolute(configHome)
-    ? join(configHome, "mcporter")
-    : legacy;
+  const configHome = mcporterXdgConfigHome({ home, platform, env });
+  const base = configHome === undefined ? legacy : join(configHome, "mcporter");
   const candidates = [base, ...(base === legacy ? [] : [legacy])].flatMap(
     (directory) => [
       join(directory, "mcporter.json"),