electron: port mergeShellEnv logic from tauri (#20192)

packages/desktop-electron/src/main/shell-env.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, test } from "bun:test"
+
+import { isNushell, mergeShellEnv, parseShellEnv } from "./shell-env"
+
+describe("shell env", () => {
+  test("parseShellEnv supports null-delimited pairs", () => {
+    const env = parseShellEnv(Buffer.from("PATH=/usr/bin:/bin\0FOO=bar=baz\0\0"))
+
+    expect(env.PATH).toBe("/usr/bin:/bin")
+    expect(env.FOO).toBe("bar=baz")
+  })
+
+  test("parseShellEnv ignores invalid entries", () => {
+    const env = parseShellEnv(Buffer.from("INVALID\0=empty\0OK=1\0"))
+
+    expect(Object.keys(env).length).toBe(1)
+    expect(env.OK).toBe("1")
+  })
+
+  test("mergeShellEnv keeps explicit overrides", () => {
+    const env = mergeShellEnv(
+      {
+        PATH: "/shell/path",
+        HOME: "/tmp/home",
+      },
+      {
+        PATH: "/desktop/path",
+        OPENCODE_CLIENT: "desktop",
+      },
+    )
+
+    expect(env.PATH).toBe("/desktop/path")
+    expect(env.HOME).toBe("/tmp/home")
+    expect(env.OPENCODE_CLIENT).toBe("desktop")
+  })
+
+  test("isNushell handles path and binary name", () => {
+    expect(isNushell("nu")).toBe(true)
+    expect(isNushell("/opt/homebrew/bin/nu")).toBe(true)
+    expect(isNushell("C:\\Program Files\\nu.exe")).toBe(true)
+    expect(isNushell("/bin/zsh")).toBe(false)
+  })
+})