Add Stylua Support for Lua Formatting

[GowayLee]

This PR adds full Stylua support to reform.nvim, replacing the previous Python formatter fallback for Lua files.

Changes

• Created new Stylua formatter module (lua/reform/formatters/stylua.lua)
• Updated formatter registry to use Stylua for Lua files
• Updated configuration defaults to include Stylua for Lua
• Updated documentation with Stylua requirements and usage

Benefits

• Proper Lua code formatting using dedicated formatter
• Maintains existing functionality and API
• Follows established patterns in the codebase

Fixes #4

---

🤖 Generated with Claude Code

[claude]

Claude finished @GowayLee's task —— View job

---

I'll analyze this and get back to you.

[GowayLee]

Code Review: Stylua Support Implementation

Overview The PR successfully adds Stylua support for Lua formatting, replacing the Python formatter fallback. The implementation follows existing patterns and maintains backward compatibility.

Detailed Review

1. Stylua Formatter Implementation (lua/reform/formatters/stylua.lua)
   ✅ Strengths:

Follows established patterns: Inherits from BaseFormatter correctly
Type annotations: Good use of Lua type annotations
Availability caching: Implements smart caching for is_available() checks
Error handling: Proper error handling and fallback behavior
⚠️ Areas for Improvement:

a) Security concern - Command injection vulnerability:

-- Current implementation (stylua.lua:50)
local cmd = "stylua -"
local result = vim.fn.system(cmd, text)
Issue: Direct shell command execution without proper escaping. While Stylua is a trusted formatter, this could be problematic if extended later.

b) Missing Stylua configuration support:

No way to pass Stylua configuration options
No support for .stylua.toml detection or custom configuration paths
c) Insufficient error reporting:

When formatting fails, the original text is returned silently
Users won't know why formatting didn't work
2. Formatter Registration (lua/reform/formatters.lua)
✅ Good:

Clean registration of Stylua for Lua files
Maintains lazy loading pattern
No breaking changes to existing API
⚠️ Issue:

Inconsistent formatter mapping: Lines 18-22 still map Java, JavaScript, JSON, ActionScript, and Ruby to Python formatter. This seems like a legacy mapping that might need review.
3. Configuration Updates (lua/reform/config.lua)
✅ Good:

Clean addition of Stylua to default formatters
Maintains existing configuration structure
4. Documentation (README.md)
✅ Good:

Clear requirements section updated with Stylua
Configuration examples updated
Maintains consistency with existing docs
Security Analysis
Low risk: Code appears non-malicious
Minor concern: Shell command execution via vim.fn.system() could be hardened
No secrets or credentials exposed
Performance Considerations
Good: Caching in is_available() prevents repeated PATH lookups
Good: Lazy loading maintains <1ms startup time
Potential: Large Lua files might block on system calls (no async formatting)
Test Coverage
Missing: No test files found for the new formatter
Recommendation: Add tests for:
Stylua availability detection
Formatting behavior with various Lua code samples
Error handling when Stylua fails
Caching behavior verification
Specific Recommendations
High Priority:
Fix security issue in command execution:
-- Safer implementation
local cmd = {"stylua", "-"}
local result = vim.fn.system(cmd, text)
Improve error handling:
function StyluaFormatter:format(text, filetype)
if text == "" then
return text
end

local cmd = {"stylua", "-"}
local result = vim.fn.system(cmd, text)

if vim.v.shell_error ~= 0 then
vim.notify("Reform: Stylua formatting failed", vim.log.levels.WARN)
return text
end

return vim.trim(result)
end
Add Stylua configuration support:
function StyluaFormatter:format(text, filetype)
if text == "" then
return text
end

-- Look for .stylua.toml in project root
local config_path = vim.fn.findfile(".stylua.toml", ".;")
local cmd = config_path ~= "" and {"stylua", "--config-path", config_path, "-"}
or {"stylua", "-"}

local result = vim.fn.system(cmd, text)
-- ... rest of implementation
end
Medium Priority:
Add comprehensive tests for the formatter
Document Stylua-specific configuration options
Consider async formatting for large files
Low Priority:
Review legacy formatter mappings for non-Lua languages
Add debug logging for troubleshooting
Overall Assessment
The implementation is solid and follows established patterns. The security concern is minor but should be addressed. The formatter will work correctly as-is, but the suggested improvements would make it more robust and user-friendly.

Approval Recommendation: ✅ Approve with minor fixes - The security issue should be addressed before merging, but this is a good addition to the codebase.

Great! @claude Help me improve the code based on this review.

[claude]

Claude finished @GowayLee's task —— View job

---

I'll analyze this and get back to you.

[GowayLee]

Good job