fix(nextjs): match standalone server copy patterns to build output la…

[imanmalekian31]

Fix nextjs_standalone_server producing a js_binary that fails at runtime because server.js is never copied into the assembled standalone directory.

Symptom

An OCI image (or bazel run) built from nextjs_standalone_build + nextjs_standalone_server fails to start:

FATAL: aspect_rules_js[js_binary]: the entry_point
'.../next_server.runfiles/_main/<pkg>/next_server/standalone/<pkg>/server.js' not found

The build succeeds — the failure only appears at runtime, because the server's js_binary entry point points at a server.js that was never assembled into the standalone output.

Root cause

nextjs_standalone_server's internal copy_to_directory uses include_srcs_patterns / replace_prefixes prefixed with .next/:

include_srcs_patterns = [
    "public/**",
    "{}/static/**".format(_next_build_out),     # ".next/static/**"
    "{}/standalone/**".format(_next_build_out),  # ".next/standalone/**"
],

But the app tree (the nextjs_standalone_build output) does not expose its files under a .next/ prefix. nextjs_standalone_build runs next build (which writes to .next) and then copies that tree into a directory named after the build target via _copy_exec_to_bin — it cannot reuse .next, since that path is already owned by the build action. So a build target :foo yields paths like foo/standalone/... and foo/static/....

Since copy_to_directory matches paths relative to the package (default root_paths = ["."]), the .next/-prefixed patterns match nothing — only public/** is copied. server.js and .next/static never make it into the standalone directory, and the binary dies at runtime.

Empirically confirmed (build target named next, package displayads/panel/frontend):

• .next/standalone/** → matches nothing
• standalone/** → matches nothing
• next/standalone/** → matches (the prefix is the build target's directory name)

This is a regression from #2879, which flattened the .next wrapper in nextjs_standalone_build's output layout without updating nextjs_standalone_server's patterns to match.

Fix

Derive the prefix from the app label (app.split(":")[-1].split("/")[-1]) and use it in include_srcs_patterns / replace_prefixes instead of the hardcoded .next, matching the actual flattened layout. This mirrors the existing label-parsing the macro already does for the config basename, and is independent of the Next.js version.

Reproduction

1. nextjs_standalone_build(name = "next", ...) then nextjs_standalone_server(name = "next_server", app = ":next").
2. bazel build //path:_next_server.standalone.
3. Inspect the output: only public/ is present; no server.js, no .next/static.
4. Running the resulting js_binary → entry_point ... server.js not found.

---

Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: no
• Breaking change (forces users to change their own code or config): no
• Suggested release notes appear below: yes

nextjs_standalone_server: fix the assembled standalone directory missing server.js and .next/static, which caused the server js_binary to fail at runtime with "entry_point ... server.js not found". Regression from #2879.

Test plan

• Manual testing; to reproduce:
  1. nextjs_standalone_build(name = "next", ...) + nextjs_standalone_server(name = "next_server", app = ":next").
  2. bazel build //path:_next_server.standalone and inspect the output — standalone/<pkg>/server.js and standalone/<pkg>/.next/static are now present.
  3. bazel run //path:next_server starts successfully instead of failing with the missing-entry-point error.

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[acozzette]

@imanmalekian31 Thank you for this fix and the detailed description! Would you be ok with signing the CLA?

[imanmalekian31]

@acozzette Thanks, I've signed it.