jolt/docs/tools-deps.md

deps.edn support — design notes

How Jolt loads pure-Clojure libraries from a deps.edn, and why it's built the way it is. For how to use it, see building-and-deps.md.

Scope, decided up front:

• git + local deps only — no Maven/~/.m2 resolution.
• pure clj/cljc — anything needing the JVM won't load or run; expected.
• no classpath abstraction — require just needs to find a dep's namespaces; "the classpath" is an ordered list of source directories.
• own resolver, own reader — deps.edn is read by jolt's own reader, and git fetch/cache is a thin shell-out to git; no external package manager.
• deps-agnostic runtime core — resolution is a CLI front-end concern, not a runtime one. The runtime knows nothing about deps.edn; it only consumes a list of source roots. The CLI resolves a deps.edn into those roots before running.

How resolution works

jolt.deps (jolt-core/jolt/deps.clj) reads deps.edn (jolt's own reader parses the EDN), then walks :deps:

• :git/url + :git/sha (+ optional :deps/root) → clone the sha into the git cache and contribute the checkout (or its :deps/root subdir);
• :local/root → the path as-is;
• :mvn/* → skipped with a warning;
• anything else → ignored.

git resolution shells out to git through jolt.host/sh — git init + remote add + fetch + reset at the requested sha. Clones land in a global, sha-immutable cache ($JOLT_GITLIBS, else ~/.jolt/gitlibs) shared across projects, the tools.gitlibs ~/.gitlibs model.

Each resolved dependency contributes its own :paths (default ["src"]) as source roots; the walk is breadth-first so every top-level coordinate registers before any transitive one — a top-level pin always wins, matching tools.deps. The result is a de-duplicated, ordered list of directories.

Two tools.deps features are mirrored in reduced form. Aliases: :aliases entries supply :extra-paths/:extra-deps (accumulate across the aliases selected with -A:a:b) and :main-opts (last-wins, run with -M:alias). Tasks: the honest subset of babashka's — a string task is a shell command, a map task is {:main-opts […]}; bare Clojure expressions aren't a separate task form.

How the CLI ties it together

jolt.main (jolt-core/jolt/main.clj) is the CLI dispatch. Driven by cli.ss, it resolves the project (jolt.deps/resolve-project), prepends the resolved roots, and de-sugars the argv into a run:

• run -m NS args → load NS, call its -main;
• run FILE → load the file;
• -M:alias → run the alias's :main-opts;
• -A:alias → add the alias's paths/deps, then run the rest;
• repl → a line REPL;
• path → print the resolved roots;
• <task> → run a deps.edn :tasks entry.

The resolver lives in the overlay alongside the runtime, but the runtime's only dependency interface is the list of source roots it's handed.

Limitations

• Pure clj/cljc only — JVM interop, host classes, and unimplemented clojure.core corners fail. Coverage is per-function: a namespace can load with most functions working and a few not.
• Source only; compiled .class files in a git dep are ignored.
• git :git/sha must be a full SHA (git fetch can't resolve a short one).

Conformance

The known-working libraries (see libraries.md) and the examples exercise real pure-cljc git libraries end to end — resolving them from git, loading their namespaces, and running sample calls. A library fails when it relies on something Jolt doesn't provide — JVM interop, or a regex feature like Unicode property classes (\p{…}).