fix(install): guard link-mode conflicts

scripts/install.mjs

@@ -178,6 +178,20 @@ function atomicWriteJson(path, content) {
 function installLink() {
   const dryRun = values["dry-run"];
   mkdirSync(target, { recursive: true });
+  function prepareLinkDestination(dest) {
+    let st;
+    try {
+      st = lstatSync(dest);
+    } catch (err) {
+      if (err?.code === "ENOENT") return;
+      throw err;
+    }
+    if (!st.isSymbolicLink() && !values.force) {
+      throw new UserError(`Refusing to replace existing non-symlink path during --link install: ${dest}
+Use --force to replace it.`);
+    }
+    if (!dryRun) rmSync(dest, { recursive: true, force: true });
+  }
   for (const dir of COMPONENT_DIRS) {
     const from = join(root, dir);
     if (!existsSync(from)) continue;
@@ -188,8 +202,10 @@ function installLink() {
         const dest = join(target, "plugins", name);
         if (!dryRun) {
           mkdirSync(dirname(dest), { recursive: true });
-          rmSync(dest, { recursive: true, force: true });
+          prepareLinkDestination(dest);
           symlinkSync(src, dest);
+        } else {
+          prepareLinkDestination(dest);
         }
         console.log(`${dryRun ? "Would link" : "Linked"} ${dest} -> ${src}`);
       }
@@ -200,8 +216,10 @@ function installLink() {
       const dest = join(target, dir, rel);
       if (!dryRun) {
         mkdirSync(dirname(dest), { recursive: true });
-        rmSync(dest, { force: true });
+        prepareLinkDestination(dest);
         symlinkSync(src, dest);
+      } else {
+        prepareLinkDestination(dest);
       }
       console.log(`${dryRun ? "Would link" : "Linked"} ${dest} -> ${src}`);
     }
@@ -343,4 +361,4 @@ try {
   if (DEBUG) throw err;
   console.error(err instanceof UserError ? `Error: ${err.message}` : `Error: ${err?.message || err}`);
   process.exit(1);
-}
+}

tests/install.test.mjs

@@ -1,7 +1,7 @@
 import { describe, it } from "node:test";
 import assert from "node:assert/strict";
 import { spawnSync } from "node:child_process";
-import { mkdtempSync, existsSync } from "node:fs";
+import { mkdtempSync, existsSync, lstatSync, mkdirSync, readlinkSync, symlinkSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
 import { fileURLToPath } from "node:url";
@@ -24,4 +24,55 @@ describe("install.mjs", () => {
     assert.ok(existsSync(join(target, "agents", "goal.md")));
     assert.ok(existsSync(join(target, ".goal-mode-manifest.json")));
   });
-});
+
+  it("link install refuses to delete existing non-symlink plugin paths", () => {
+    const target = join(mkdtempSync(join(tmpdir(), "goal-mode-link-conflict-")), "cfg");
+    const localPluginDir = join(target, "plugins", "goal-mode");
+    mkdirSync(localPluginDir, { recursive: true });
+    writeFileSync(join(localPluginDir, "keep.txt"), "user-data", "utf8");
+
+    const r = spawnSync(process.execPath, ["scripts/install.mjs", "--target", target, "--link"], {
+      cwd: root,
+      encoding: "utf8",
+    });
+
+    assert.equal(r.status, 1);
+    assert.match(r.stderr, /Refusing to replace existing non-symlink path/);
+    assert.ok(existsSync(join(localPluginDir, "keep.txt")));
+  });
+
+  it("link install replaces existing non-symlink paths only with force", () => {
+    const target = join(mkdtempSync(join(tmpdir(), "goal-mode-link-force-")), "cfg");
+    const localPluginDir = join(target, "plugins", "goal-mode");
+    mkdirSync(localPluginDir, { recursive: true });
+    writeFileSync(join(localPluginDir, "keep.txt"), "user-data", "utf8");
+
+    const r = spawnSync(process.execPath, ["scripts/install.mjs", "--target", target, "--link", "--force"], {
+      cwd: root,
+      encoding: "utf8",
+    });
+
+    assert.equal(r.status, 0, r.stderr || r.stdout);
+    assert.equal(lstatSync(localPluginDir).isSymbolicLink(), true);
+    assert.equal(existsSync(join(localPluginDir, "keep.txt")), false);
+  });
+
+  it("link install with force replaces dangling symlink plugin paths", () => {
+    const target = join(mkdtempSync(join(tmpdir(), "goal-mode-link-dangling-")), "cfg");
+    const pluginsDir = join(target, "plugins");
+    const localPluginDir = join(pluginsDir, "goal-mode");
+    mkdirSync(pluginsDir, { recursive: true });
+    symlinkSync(join(target, "missing-plugin-dir"), localPluginDir, "dir");
+    assert.equal(existsSync(localPluginDir), false);
+    assert.equal(lstatSync(localPluginDir).isSymbolicLink(), true);
+
+    const r = spawnSync(process.execPath, ["scripts/install.mjs", "--target", target, "--link", "--force"], {
+      cwd: root,
+      encoding: "utf8",
+    });
+
+    assert.equal(r.status, 0, r.stderr || r.stdout);
+    assert.equal(lstatSync(localPluginDir).isSymbolicLink(), true);
+    assert.equal(readlinkSync(localPluginDir), join(root, "plugins", "goal-mode"));
+  });
+});