Fix race condition when collecting operations during parallel compilation

[ChrisLoer]

Summary

Fixes intermittent missing entries in channel_schema.json (e.g., sources:create would sometimes be missing after clean compiles).

The Fix

Change Code.ensure_compiled(module) to Code.ensure_compiled!(module) (add the bang).

From the Elixir 1.18.4 Code documentation:

If you are using Code.ensure_compiled/1, you are implying you may continue without the module and therefore Elixir may return {:error, :unavailable} for cases where the module is not yet available (but may be available later on).

For those reasons, developers must typically use Code.ensure_compiled!/1. In particular, do not do this:

case Code.ensure_compiled(module) do
  {:module, _} -> module
  {:error, _} -> raise ...
end

And from ensure_compiled!/1:

If the module was not compiled yet, ensure_compiled!/1 halts the compilation of the caller until the module given to ensure_compiled!/1 becomes available

The original code used ensure_compiled/1 (non-bang) but then expected the module to be available for function_exported? checks. When ensure_compiled/1 returned {:error, :unavailable}, the code silently skipped the module. The bang version properly blocks until the module is ready.

Why the Original Commit Worked

The original PR accidentally changed ensure_compiled to ensure_compiled! (with bang) while also adding module_info/0 calls. The ensure_compiled! change was the actual fix - the module_info/0 calls were unnecessary. The explanation about __before_compile__ timing was incorrect.

Verification

Tested in the Felt codebase by modifying deps/channel_spec/lib/channel_spec/socket.ex:

Without fix (Code.ensure_compiled):

$ for i in 1 2 3 4 5; do rm -rf _build/dev/lib/felt_server _build/dev/lib/channel_spec; mix compile; grep -c '"sources:create"' ../../shared/json-schemas/channel_schema.json; done
0
0
0
0
0

With fix (Code.ensure_compiled!):

$ for i in 1 2 3 4 5; do rm -rf _build/dev/lib/felt_server _build/dev/lib/channel_spec; mix compile; grep -c '"sources:create"' ../../shared/json-schemas/channel_schema.json; done
1
1
1
1
1

All 5 clean compiles consistently show sources:create present with the fix.

[axelson]

I tested this on the main repo with {:channel_spec, git: "https://github.com/felt/channel_spec.git", branch: "fix/ensure-module-fully-loaded-before-checking-exports"}

and ran mix clean and partial compiles and the json was successfully regenerated! Thanks for looking into this!

We'll want to follow this up with a version bump