jolt/docs/building-and-deps.md

# Building and dependencies

How to build Jolt from source and how to pull Clojure libraries into a project.

## Building

```bash
git clone https://github.com/jolt-lang/jolt.git
cd jolt
git submodule update --init   # vendor/sci (used by the SCI bootstrap tests)
jpm build
```

This produces `build/jolt` — one binary that is both the runtime (REPL,
file/expr runner, nREPL server) and the dependency front-end (`deps.edn`
resolution, see below). The whole `.clj` standard library
(`clojure.string`/`set`/`walk`/`edn`/`zip`, `jolt.http`/`interop`/`shell`/
`nrepl`) is baked in at build time, so it loads from any directory — the artifact
is self-contained. (`clojure.core` is built into the runtime in Janet and
auto-referred, so it's always available.)

The runtime **core** stays deps-agnostic: it only reads source roots from
`JOLT_PATH`. Dependency resolution lives in a separate CLI front-end module
(`src/jolt/deps.janet`) that the `jolt` entry point calls *before* running your
code, and that lazily loads `jpm` (for git fetch + cache) only when it actually
resolves. So a run with no `deps.edn` never touches the resolver, and an app
baked from its own entry — which imports `jolt/api`, not the CLI — never links
it at all. (`build/` also contains a `jolt-deps` shim that just forwards to
`jolt` so old scripts keep working; prefer calling `jolt` directly.)

Needs `jpm` and a recent Janet — developed and CI-tested against **1.41**. The
futures and core.async layers use Janet's threaded `ev/` channels (`ev/thread`,
`ev/thread-chan`), so older Janets may not run the full suite.

`jpm build` doesn't always notice source changes; run `jpm clean && jpm build`
after editing `src/` to be sure the binaries are current. `jpm test` runs against
the source directly, so it never goes stale.

## How namespaces are found

`(require ...)` resolves a namespace to a file by searching an ordered list of
source roots — the stdlib first, then any extra roots — trying `<ns>.clj` then
`<ns>.cljc` (dots become directories, dashes become underscores). Extra roots
come from:

- `JOLT_PATH` — a colon-separated list of directories (like a classpath), applied
  at runtime;
- the `:paths` option to `init` when embedding Jolt as a library.

If a namespace isn't found on any root, the loader falls back to the stdlib baked
into the binary — that's how `clojure.string` and friends resolve when you run
the binary outside the source tree.

So you can point Jolt at a directory of Clojure source with no deps machinery at
all:

```bash
JOLT_PATH=/path/to/lib/src build/jolt myfile.clj
```

## Dependencies via deps.edn

`jolt` reads a `deps.edn` in the current directory, fetches its dependencies,
and puts the resolved source directories on `JOLT_PATH` for the run. A `deps.edn`
in the working dir is **auto-resolved** for the runnable commands (`repl`, `-m`,
`-e`, `nrepl-server`, a `FILE`); the explicit subcommands below also work
anywhere:

```bash
jolt -M:test [args]   # run the :test alias's :main-opts (the usual entry)
jolt -A:dev repl      # run a command with the :dev alias's extra paths/deps
jolt run FILE [args]  # resolve, then run FILE
jolt path             # print the resolved roots (':'-joined)
jolt tasks            # list :tasks from deps.edn
jolt task NAME [args] # run a task
```

So, for example, to start an nREPL server that loads a project and its deps,
add `:aliases {:nrepl {:main-opts ["nrepl-server"]}}` to `deps.edn` and run
`jolt -M:nrepl` (or just `jolt nrepl-server`, which auto-resolves the `deps.edn`).

Example `deps.edn`:

```clojure
{:paths ["src"]
 :deps {weavejester/medley {:git/url "https://github.com/weavejester/medley"
                            :git/tag "1.0.0"}
        my/helpers          {:local/root "../helpers"}}}
```

```bash
jolt run -m myapp.main
```

### What's supported

- **git deps** — `{:git/url … :git/tag …}` or `{:git/url … :git/sha …}` (use a
  full SHA; `git fetch` can't resolve a short one). Transitive deps from each
  dependency's own `deps.edn` are resolved too.
- **local deps** — `{:local/root "../path"}`.
- The project's own `:paths` (default `["src"]`) are included.
- **aliases** — `:aliases {:dev {:extra-paths ["dev"] :extra-deps {…}
  :main-opts ["-e" "…"]}}`, selected with `-A:dev` (or several: `-A:dev:test`).
  `:extra-paths`/`:extra-deps` accumulate across selected aliases;
  `:main-opts` is last-wins and runs via `-M:alias`.
- **user config** — a `deps.edn` under `$JOLT_CONFIG` (else
  `$XDG_CONFIG_HOME/jolt`, else `~/.jolt`) merges beneath the project's, the
  way `~/.clojure/deps.edn` does: `:deps`/`:aliases`/`:tasks` merge per key
  with the project winning.
- **tasks** — `:tasks {clean "rm -rf target" test {:doc "run the suite"
  :main-opts ["-e" "(run-tests)"]}}`. A string task is a shell command; a map
  task runs jolt with its `:main-opts`. `jolt tasks` lists, `jolt task NAME`
  runs.

Conflicts resolve the tools.deps way: resolution is breadth-first, so a
top-level coordinate always beats a transitive one for the same lib, and
conflicting coordinates print a warning naming both.

Git clones land in a global, sha-immutable cache shared across projects —
`$JOLT_GITLIBS`, else `<config-dir>/gitlibs` (the `~/.gitlibs` model). The
resolved roots are cached per project in `.cpcache/jolt-deps.jdn`, keyed on a
hash of the project `deps.edn` + the user `deps.edn` + the selected aliases.

### What's not

- **No Maven.** `:mvn/version` deps are ignored — git and local only.
- **Pure `clj`/`cljc` only.** A library that needs the JVM (Java interop, host
  classes) or a `clojure.core` feature Jolt doesn't implement will fail to load
  or fail at a call. Coverage is per-function: a namespace can load with most
  functions working and a few not.

### Bundling into one file

`jolt uberscript OUT.clj -m NS` bundles `NS` and every namespace it requires —
your code plus its dependencies — into a single `.clj` in dependency order,
ending with a call to `NS/-main`. Run it from a project dir and the `deps.edn`
is resolved first, so dependency namespaces are on the path to bundle. The
result runs on a plain `jolt` with no `JOLT_PATH`, no deps fetched, and no jpm:

```bash
jolt uberscript app.clj -m myapp.main
jolt app.clj arg1 arg2
```

See [`tools-deps.md`](tools-deps.md) for the design rationale.