d724aa7069
read-char read the char name with symbol-char?, so a literal whose char isn't a
symbol char (\{, \(, \), \,, \%, …) came back as an empty name and errored
'Unsupported character'. Now a single non-symbol char after \ is taken as a
one-character literal of that char. Surfaced by funcool/cuerdas (uses \{), which
now loads. Spec cases added.
96 lines
5 KiB
Markdown
96 lines
5 KiB
Markdown
# deps.edn support — design notes
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How Jolt loads pure-Clojure libraries from a `deps.edn`, and why it's built the
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way it is. For how to *use* it, see [building-and-deps.md](building-and-deps.md).
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Scope, decided up front:
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- **git + local deps only** — no Maven/`~/.m2` resolution.
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- **pure `clj`/`cljc`** — anything needing the JVM won't load or run; expected.
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- **no classpath abstraction** — `require` just needs to find a dep's namespaces;
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"the classpath" is an ordered list of source directories.
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- **piggyback on jpm** — reuse jpm's git fetch + cache; don't write a package
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manager.
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- **separate tool** — resolution lives in `jolt-deps`, beside the runtime, the
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way `jpm` sits beside `janet`. The `jolt` runtime knows nothing about deps.edn.
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## How jpm handles dependencies
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jpm's package code (`jpm/pm.janet`) splits into a fetch half and a build half,
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and we use only the first:
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- **`resolve-bundle`** normalizes a dep spec to `{:url :tag :type :shallow}`,
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accepting `:url`/`:repo` + `:tag`/`:sha`/`:commit`/`:ref`. A deps.edn
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`{:git/url … :git/sha …}` maps straight onto it.
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- **`download-bundle url :git tag shallow`** clones into a content-addressed cache
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(`<modpath>/.cache/git_<tag>_<sanitized-url>`) and returns the path —
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`git init` + `remote add` + fetch + reset, plus submodules. No build step.
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- **`bundle-install`** is the half we skip: it then runs `project.janet` build
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rules, which a Clojure lib doesn't have. It's cleanly separable from the clone.
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So jpm gives us git resolution and a cache for free; calling `download-bundle`
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needs `jpm/config/load-default` first (it sets `gitpath` and the cache dyns).
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## How it works
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`src/jolt/deps.janet` reads `deps.edn` (Janet parses it directly — EDN and Janet
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syntax overlap for the `:deps`/`:paths` subset), then walks `:deps`:
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- `:git/url` (+ `:git/sha` or `:git/tag`) → `resolve-bundle` + `download-bundle`
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into `jpm_tree/.cache`;
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- `:local/root` → the path as-is;
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- `:mvn/*` and anything else → ignored.
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Each resolved dependency contributes its own `:paths` (default `["src"]`) as
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source roots, and we recurse into its `deps.edn` for transitive deps. The result
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is a de-duplicated, ordered list of directories. `resolve-deps-cached` memoizes
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that list in the tree keyed on a hash of `deps.edn`, so an unchanged file doesn't
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re-fetch. jpm is loaded lazily (`require`, not `import`) so it's pulled in only
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when resolving — never embedded in a built binary.
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The loader (`evaluator.janet/find-ns-file`) resolves a namespace by searching the
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context's `:source-paths` in order (the stdlib `src/jolt` first), trying `<ns>.clj`
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then `<ns>.cljc`. Extra roots come from `JOLT_PATH` or `init`'s `:paths` option.
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`jolt-deps` (`src/jolt/deps_cli.janet`, its own `declare-executable`) ties it
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together: it resolves the roots and runs the `jolt` binary with them on
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`JOLT_PATH`. The runtime's only dependency interface is that env var.
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Gotcha worth remembering: the `jolt` CLI's context is built into its image at
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build time, so `JOLT_PATH` is applied at runtime in `main`, not in `init` (whose
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env read would be frozen at build).
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## Limitations
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- Pure `clj`/`cljc` only — JVM interop, host classes, and unimplemented
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`clojure.core` corners fail. Coverage is per-function: a namespace can load with
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most functions working and a few not.
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- Source only; compiled `.class` files in a git dep are ignored.
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- git `:git/sha` must be a full SHA (`git fetch` can't resolve a short one).
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## Status
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- **Loader source roots** — done. `find-ns-file` + `:source-paths`, `.clj`/`.cljc`,
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`JOLT_PATH`/`:paths`. Test: `test/integration/deps-loader-test.janet`.
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- **Resolve git/local deps via jpm** — done. `deps.janet` + the `jolt-deps` tool.
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Test: `test/integration/deps-resolve-test.janet`.
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- **Bundling (uberscript)** — done. `jolt uberscript OUT -m NS` requires `NS`,
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records the load order the loader emits (a dependency finishes loading before
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the file that required it, so it's topological), and concatenates the source
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into one `.clj` that runs on a plain `jolt` — no deps, no jpm. `jolt-deps
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uberscript` resolves first. Test: `test/integration/uberscript-test.janet`.
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(This is the practical form of "compile the used namespaces into the build";
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embedding into a custom binary image is a heavier variant we haven't needed.)
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- **Conformance** — harness in place:
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`test/integration/deps-conformance-test.janet` resolves real pure-`cljc` git
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libs and reports load/run status (network-gated behind `JOLT_CONFORMANCE=1`, so
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CI stays offline). First run:
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- `medley` — loads and runs.
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- `cuerdas` — now loads (it used `\{`, a one-char literal the reader rejected;
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fixed). A function (`kebab`) still hits a separate runtime gap — a smaller,
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per-function issue rather than a whole-namespace failure.
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- `stuartsierra/dependency` — `Long/MAX_VALUE`: JVM interop, so out of scope
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(it isn't actually pure-`cljc`).
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The loop from here is the same as the clojure-test-suite battery: add libs,
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see what breaks, fix interpreter/reader gaps.
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