feat: add exclude config to skip directories during type generation

[enki]

Summary

Adds an exclude configuration field to sst.config.ts that allows users to specify directory patterns to skip during type generation. This prevents SST from generating sst-env.d.ts, sst.pyi, and lib/sst.rb files in unwanted locations.

Problem

SST recursively scans the entire project tree to generate type files with no way to exclude directories. This causes issues in monorepos with:

• Git submodules in external/ or vendor/ directories
• Test fixtures containing nested projects
• Large dependency trees users want to ignore

Real-world example: A monorepo with submodules generates 913+ sst-env.d.ts files in ignored directories, creating noise in git status.

Solution

Add an exclude field that accepts glob patterns:

export default $config({
  app(input) {
    return {
      name: "my-app",
      exclude: ["external/**", "vendor/**", "test-*"],
    };
  },
});

Implementation

Changes Made

1. Core Filesystem Logic (internal/fs/fs.go)

   • Added FindDownWithExcludes() with glob pattern support via filepath.Match()
   • Backward compatible: FindDown() delegates to new function with empty exclude list
   • Preserves existing node_modules and dotfile exclusions

2. Configuration (pkg/project/project.go)

   • Added Exclude []string field to App struct

3. Type Generation Pipeline

   • Updated all 3 generators (TypeScript, Python, Rails) to use FindDownWithExcludes()
   • Threaded exclude patterns from config through entire pipeline

4. Comprehensive Tests (internal/fs/fs_test.go - NEW, 170 lines)

   • 8 test cases covering single/multiple patterns, globs, nested dirs
   • TDD approach: tests written first, implementation followed
   • Follows SST conventions with table-driven tests and testify/assert

Test Results

=== RUN   TestFindDown_WithExcludePatterns
--- PASS: TestFindDown_WithExcludePatterns (0.01s)
    --- PASS: TestFindDown_WithExcludePatterns/basic_-_no_excludes
    --- PASS: TestFindDown_WithExcludePatterns/exclude_node_modules
    --- PASS: TestFindDown_WithExcludePatterns/exclude_external_directory
    --- PASS: TestFindDown_WithExcludePatterns/exclude_multiple_patterns
    --- PASS: TestFindDown_WithExcludePatterns/exclude_with_glob_pattern
    --- PASS: TestFindDown_WithExcludePatterns/exclude_nested_directories
    --- PASS: TestFindDown_WithExcludePatterns/existing_node_modules_still_excluded_by_default
    --- PASS: TestFindDown_WithExcludePatterns/existing_dotfiles_still_excluded_by_default
PASS
ok      github.com/sst/sst/v3/internal/fs       0.212s

Stats

• 8 files changed: 210 insertions(+), 11 deletions(-)
• Fully backward compatible: No breaking changes
• Zero new dependencies: Uses standard library filepath.Match()

Why This Matters

• Monorepos: Essential for projects with submodules or vendor directories
• Clean git status: No more untracked type files in ignored directories
• Performance: Skip large dependency trees during generation
• Industry standard: Matches patterns like .gitignore, tsconfig.exclude, Jest's testPathIgnorePatterns

Notes

This is the first test file for the internal/fs package, establishing testing patterns for filesystem operations. All existing tests continue to pass.