cell/docs/shop.md

title, description, weight, type

title	description	weight	type
Shop Architecture	How the shop resolves, compiles, caches, and loads modules	35	docs

The shop is the module resolution and loading engine behind use(). It handles finding modules, compiling them, caching the results, and loading C extensions. The shop lives in internal/shop.cm.

Startup Pipeline

When pit runs a program, three layers bootstrap in sequence:

bootstrap.cm → engine.cm → shop.cm → user program

bootstrap.cm loads the compiler toolchain (tokenize, parse, fold, mcode, streamline) from pre-compiled bytecode. It defines analyze() (source to AST) and compile_to_blob() (AST to binary blob). It then loads engine.cm.

engine.cm creates the actor runtime ($_), defines use_core() for loading core modules, and populates the environment that shop receives. It then loads shop.cm via use_core('internal/shop').

shop.cm receives its dependencies through the module environment — analyze, run_ast_fn, use_cache, shop_path, runtime_env, content_hash, cache_path, and others. It defines Shop.use(), which is the function behind every use() call in user code.

Module Resolution

When use('path') is called from a package context, the shop resolves the module through a multi-layer search. Both the .cm script file and C symbol are resolved independently, and the one with the narrowest scope wins.

Resolution Order

For a call like use('sprite') from package myapp:

1. Own package — ~/.pit/packages/myapp/sprite.cm and C symbol js_myapp_sprite_use
2. Aliased dependencies — if myapp/pit.toml has renderer = "gitea.pockle.world/john/renderer", checks renderer/sprite.cm and its C symbols
3. Core — built-in core modules and internal C symbols

For calls without a package context (from core modules), only core is searched.

Private Modules

Paths starting with internal/ are private to their package:

use('internal/helpers')  // OK from within the same package
// Cannot be accessed from other packages

Explicit Package Imports

Paths containing a dot in the first component are treated as explicit package references:

use('gitea.pockle.world/john/renderer/sprite')
// Resolves directly to the renderer package's sprite.cm

Compilation and Caching

Every module goes through a content-addressed caching pipeline. The cache key is the BLAKE2 hash of the source content, so changing the source automatically invalidates the cache.

Cache Hierarchy

When loading a module, the shop checks (in order):

1. In-memory cache — use_cache[key], checked first on every use() call
2. Installed dylib — per-file .dylib in ~/.pit/lib/<pkg>/<stem>.dylib
3. Internal symbols — statically linked into the pit binary (fat builds)
4. Installed mach — pre-compiled bytecode in ~/.pit/lib/<pkg>/<stem>.mach
5. Cached bytecode — content-addressed in ~/.pit/build/<hash> (no extension)
6. Cached .mcode IR — JSON IR in ~/.pit/build/<hash>.mcode
7. Adjacent .mach/.mcode — files alongside the source (e.g., sprite.mach)
8. Source compilation — full pipeline: analyze, mcode, streamline, serialize

When both a .dylib and .mach exist for the same module in lib/, the dylib is selected. Dylib resolution also wins over internal symbols, so a dylib in lib/ can hot-patch a fat binary. Delete the dylib to fall back to mach or static.

Results from steps 6-8 are cached back to the content-addressed store for future loads.

Content-Addressed Store

The build cache at ~/.pit/build/ stores ephemeral artifacts named by the BLAKE2 hash of their inputs:

~/.pit/build/
├── a1b2c3d4...          # cached bytecode blob (no extension)
├── c9d0e1f2...mcode     # cached JSON IR
└── f3a4b5c6...          # compiled dylib (checked before copying to lib/)

This scheme provides automatic cache invalidation: when source changes, its hash changes, and the old cache entry is simply never looked up again. When building a dylib, the build cache is checked first — if a matching hash exists, it is copied to lib/ without recompiling.

Core Module Caching

Core modules loaded via use_core() in engine.cm follow the same pattern. On first startup after a fresh install, core modules are compiled from .cm.mcode JSON IR and cached as .mach blobs. Subsequent startups load from cache, skipping the JSON parse and compile steps entirely.

User scripts (.ce files) are also cached. The first run compiles and caches; subsequent runs with unchanged source load from cache.

C Extension Resolution

C extensions are resolved alongside script modules. A C module is identified by a symbol name derived from the package and file name:

package: gitea.pockle.world/john/prosperon
file:    sprite.c
symbol:  js_gitea_pockle_world_john_prosperon_sprite_use

C Resolution Sources

1. Installed dylibs — per-file dylibs in ~/.pit/lib/<pkg>/<stem>.dylib (deterministic paths, no manifests)
2. Internal symbols — statically linked into the pit binary (fat builds)

Dylibs are checked first at each resolution scope, so an installed dylib always wins over a statically linked symbol. This enables hot-patching fat binaries by placing a dylib in lib/.

Name Collisions

Having both a .cm script and a .c file with the same stem at the same scope is a build error. For example, render.cm and render.c in the same directory will fail. Use distinct names — e.g., render.c for the C implementation and render_utils.cm for the script wrapper.

Environment Injection

When a module is loaded, the shop builds an env object that becomes the module's set of free variables. This includes:

• Runtime functions — logical, some, every, starts_with, ends_with, is_actor, log, send, fallback, parallel, race, sequence
• Capability injections — actor intrinsics like $self, $delay, $start, $receiver, $fd, etc.
• use function — scoped to the module's package context

The set of injected capabilities is controlled by script_inject_for(), which can be tuned per package or file.

Shop Directory Layout

~/.pit/
├── packages/         # installed packages (directories and symlinks)
│   └── core -> ...   # symlink to the ƿit core
├── lib/              # INSTALLED per-file artifacts (persistent, human-readable)
│   ├── core/
│   │   ├── fd.dylib
│   │   ├── time.mach
│   │   ├── time.dylib
│   │   └── internal/
│   │       └── os.dylib
│   └── gitea_pockle_world_john_prosperon/
│       ├── sprite.dylib
│       └── render.dylib
├── build/            # EPHEMERAL cache (safe to delete anytime)
│   ├── <hash>        # cached bytecode or dylib blobs (no extension)
│   └── <hash>.mcode  # cached JSON IR
├── cache/            # downloaded package zip archives
├── lock.toml         # installed package versions and commit hashes
└── link.toml         # local development link overrides

Key Files

File	Role
internal/bootstrap.cm	Loads compiler, defines analyze() and compile_to_blob()
internal/engine.cm	Actor runtime, use_core(), environment setup
internal/shop.cm	Module resolution, compilation, caching, C extension loading
internal/os.c	OS intrinsics: dylib ops, internal symbol lookup, embedded modules
package.cm	Package directory detection, alias resolution, file listing
link.cm	Development link management (link.toml read/write)