Prevent rails specific code from being loaded by zeitwerk automatically #59
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OriPekelman
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trevorturk
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Nov 2, 2025
## Problem
Applications using ruby_llm crash during eager loading (production boot):
```
uninitialized constant RubyLLM::Rails (NameError)
class Railtie < Rails::Railtie
^^^^^
```
This occurs when:
- `config.eager_load = true` (standard in production)
- Zeitwerk eager loads all files including railtie.rb
- railtie.rb references `Rails::Railtie` unconditionally
- Rails isn't loaded yet or app doesn't use Rails
##Root Cause
PR crmne#59 added conditional require (`require 'ruby_llm/railtie' if defined?(Rails::Railtie)`),
but this is insufficient because Zeitwerk's eager loading happens BEFORE that
conditional check runs.
When Zeitwerk eager loads, it loads railtie.rb and expects `RubyLLM::Railtie`
to be defined, but the class definition fails because `Rails::Railtie` doesn't exist.
## Solution
Two complementary fixes (both required):
**1. Wrap class definition** in `if defined?(Rails::Railtie)` (railtie.rb)
- Prevents error when file is loaded without Rails
- Pattern used by github/secure_headers gem
**2. Ignore from Zeitwerk** with `loader.ignore()` (ruby_llm.rb)
- Prevents Zeitwerk from expecting a constant from this file
- Per Zeitwerk docs: "files not following conventions" should be ignored
## Evidence
**Zeitwerk maintainer guidance** (issue crmne#143):
> "have the strategy defined in `lib`, perform a `require` in the initializer"
**Zeitwerk docs**:
> Use `loader.ignore()` for "files not following conventions"
**Real-world precedent** (github/secure_headers):
```ruby
if defined?(Rails::Railtie)
module SecureHeaders
class Railtie < Rails::Railtie
# ...
end
end
end
```
## Testing
Before (ruby_llm 1.8.2):
```bash
$ bundle exec ruby -e "require 'swarm_sdk'; Zeitwerk::Loader.eager_load_all"
NameError: uninitialized constant RubyLLM::Rails
```
After (with both fixes):
```bash
$ bundle exec ruby -e "require 'swarm_sdk'; Zeitwerk::Loader.eager_load_all"
✓ SUCCESS
```
## Related
- PR crmne#59 - Partial fix (conditional require only)
- Zeitwerk issue crmne#143 - Guidance on conditional loading
- github/secure_headers - Real-world example of pattern
crmne
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Nov 4, 2025
## Summary Completes the fix from PR #59 to prevent crashes during eager loading in non-Rails contexts. ## Problem ``` uninitialized constant RubyLLM::Rails (NameError) class Railtie < Rails::Railtie ``` Occurs when Zeitwerk eager loads (e.g., in gems that depend on ruby_llm but don't use Rails). ## Root Cause **PR #59** added conditional require: `require 'ruby_llm/railtie' if defined?(Rails::Railtie)` This is insufficient because Zeitwerk's eager loading happens *before* that check runs. When Zeitwerk loads `railtie.rb`, the class definition fails because `Rails::Railtie` doesn't exist. ## Solution Two complementary fixes (both required per Zeitwerk documentation): **1. Wrap class definition** in `if defined?(Rails::Railtie)`: ```ruby if defined?(Rails::Railtie) module RubyLLM class Railtie < Rails::Railtie # ... end end end ``` **2. Ignore from Zeitwerk**: ```ruby loader.ignore("#{__dir__}/ruby_llm/railtie.rb") ``` ## Evidence - **Zeitwerk issue #143**: Maintainer confirms conditional loading pattern - **Zeitwerk docs**: Use `loader.ignore()` for "files not following conventions" - **Real-world example**: github/secure_headers uses same pattern ## Testing **Before**: `Zeitwerk::Loader.eager_load_all` → ❌ NameError **After**: `Zeitwerk::Loader.eager_load_all` → ✅ Success Thank you for reviewing! Co-authored-by: Carmine Paolino <[email protected]>
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Ignore rails specifics in zeitwerk configuration