test/core: cover ns form + :use; fix use-impl spec parsing

Checking test coverage for the namespace tiers surfaced a real bug nothing
exercised: use-impl checked (array? s) to find a spec's ns symbol, but a
vector spec like [src.x] is a pvec/tuple, not a Janet array — so (:use ...)
and standalone (use ...) errored. Fixed to coerce (pvec->array) then take the
head when the spec is indexed (matching require-impl).

Added coverage that was missing:
- conformance (x3 modes): the (ns …) form itself + :use refers.
- namespaces-spec: (ns …) form, :use, standalone use.

The :use/(use …) path had ZERO tests before, which is why the bug slipped
through earlier tiers.

EBNF needs no change — it's a reader/syntax grammar with no special-forms
enumeration; ns/require/protocol syntax is unchanged (the destructuring note
was already updated in jolt-f79).

Gate green: conformance 269x3, fallback-zero 38/4, self-host, sci-bootstrap,
bootstrap-fixpoint, staged-bootstrap, clojure-test-suite >=4034/67, namespace,
all unit + spec (namespaces 27/27).

jolt-core/clojure/core/00-syntax.clj

@@ -36,6 +36,31 @@
     nil
     `(if ~(first clauses) ~(nth clauses 1) (cond ~@(drop 2 clauses)))))
 
+;; ns is sugar over the namespace-op fns (in-ns/require/use/import/refer-clojure,
+;; all ctx-capturing clojure.core fns) — matching Clojure, where require is a fn and
+;; the ns macro expands its clauses into require calls. Each spec is quoted
+;; individually and passed as data; non-list clauses (docstring, attr-map,
+;; :gen-class, …) are ignored. So ns compiles to a plain (do …) of invokes.
+;; MUST live in this first tier: the self-hosted analyzer build (triggered while
+;; 10-seq loads) processes jolt.analyzer's own (ns …) form, so ns has to exist by
+;; then. Its body resolves fn/map/reduce/cond at EXPANSION time, by which point all
+;; of 00-syntax has loaded, so using them here is fine.
+(defmacro ns [nm & clauses]
+  (let [calls (reduce
+                (fn [acc clause]
+                  (if (seq? clause)
+                    (let [head (first clause) args (rest clause)]
+                      (cond
+                        (= head :require) (conj acc `(require ~@(map (fn [s] `(quote ~s)) args)))
+                        (= head :use)     (conj acc `(use ~@(map (fn [s] `(quote ~s)) args)))
+                        (= head :import)  (conj acc `(import ~@(map (fn [s] `(quote ~s)) args)))
+                        (= head :refer-clojure)
+                          (conj acc `(refer-clojure ~@(map (fn [s] `(quote ~s)) args)))
+                        :else acc))
+                    acc))
+                [] clauses)]
+    `(do (in-ns (quote ~nm)) ~@calls)))
+
 ;; Threading: a list form threads x in as the first (->) or last (->>) arg; a bare
 ;; symbol becomes (form x). Recursive; the expand-once cache makes that free.
 (defmacro -> [x & forms]

src/jolt/compiler.janet

@@ -159,7 +159,7 @@
              "defmethod" "prefer-method" "remove-method" "remove-all-methods"
              "get-method" "methods"
              "satisfies?" "instance?" "set!" "var" "var-get"
-             "var-set" "var?" "ns" "create-ns" "remove-ns"
+             "var-set" "var?" "ns" "in-ns" "require" "create-ns" "remove-ns"
              "find-ns" "all-ns" "the-ns" "find-var" "intern" "resolve"
              "ns-resolve" "ns-aliases" "ns-imports" "ns-interns"
              "alter-var-root" "alter-meta!" "reset-meta!" "locking" "new"

src/jolt/evaluator.janet

@@ -772,6 +772,50 @@
   (ctx-set-current-ns ctx ns-name)
   nil)
 
+(defn use-impl
+  "(use '[ns ...] ...) — refer ALL public vars of each used ns into the CURRENT ns.
+  A fn; quoted specs arrive evaluated. Each spec is a ns symbol or a [ns & opts]
+  vector (a pvec/tuple, not a Janet array — coerce, then take the head as the ns)."
+  [ctx & specs]
+  (def target-ns (ctx-find-ns ctx (ctx-current-ns ctx)))
+  (each s specs
+    (let [spec (if (pvec? s) (pv->array s) s)
+          ns-sym (if (indexed? spec) (in spec 0) spec)
+          src-name (sym-name-str ns-sym)]
+      (maybe-require-ns ctx src-name)
+      (let [source-ns (ctx-find-ns ctx src-name)]
+        (loop [[sym v] :pairs (source-ns :mappings)]
+          (let [nv (ns-intern target-ns sym (var-get v))]
+            (when (get v :macro) (put nv :macro true)))))))
+  nil)
+
+(defn import-impl
+  "(import 'pkg.Class ...) — register the short class name as an alias of the fully
+  qualified name in the current ns. A fn; quoted class symbols arrive evaluated."
+  [ctx & class-specs]
+  (def ns (ctx-find-ns ctx (ctx-current-ns ctx)))
+  (each class-spec class-specs
+    (let [class-name (if (and (struct? class-spec) (= :symbol (class-spec :jolt/type)))
+                       (class-spec :name) (string class-spec))
+          last-dot (do (var idx -1) (var pos 0)
+                     (while (< pos (length class-name))
+                       (when (= (class-name pos) 46) (set idx pos)) (++ pos))
+                     idx)
+          short-name (if (>= last-dot 0) (string/slice class-name (+ last-dot 1)) class-name)]
+      (ns-import ns short-name class-name)))
+  nil)
+
+(defn refer-clojure-impl
+  "(refer-clojure :exclude [a b]) — currently only :exclude is honored: unmap the
+  excluded names from the current ns. A fn; quoted args arrive evaluated."
+  [ctx & args]
+  (when (and (>= (length args) 2) (= (in args 0) :exclude))
+    (let [ns (ctx-find-ns ctx (ctx-current-ns ctx))
+          excl (in args 1)]
+      (each sym excl
+        (ns-unmap ns (if (and (struct? sym) (= :symbol (sym :jolt/type))) (sym :name) (string sym))))))
+  nil)
+
 (defn install-stateful-fns!
   "Intern ctx-capturing closures for the stateful primitives into clojure.core, so
   both the interpreter and the compiler reach them as ordinary fns. Called by
@@ -789,6 +833,9 @@
     (fn [proto-name methods-map] (make-reified-impl ctx proto-name methods-map)))
   (ns-intern core "require" (fn [& specs] (require-impl ctx ;specs)))
   (ns-intern core "in-ns" (fn [sym] (in-ns-impl ctx sym)))
+  (ns-intern core "use" (fn [& specs] (use-impl ctx ;specs)))
+  (ns-intern core "import" (fn [& specs] (import-impl ctx ;specs)))
+  (ns-intern core "refer-clojure" (fn [& args] (refer-clojure-impl ctx ;args)))
   core)
 
 # Dispatch a special form by its string name.
@@ -932,69 +979,9 @@
                    # A (re)defined macro invalidates any cached expansions.
                    (table/clear macro-cache)
                    (var-get v)))
-    "ns" (let [raw-name (in form 1)
-               name-sym (unwrap-meta-name raw-name)
-               ns-name (sym-name-str name-sym)
-               clauses (tuple/slice form 2)]
-           (ctx-set-current-ns ctx ns-name)
-           (ctx-find-ns ctx ns-name)
-            (var result nil)
-            (var i 0)
-            (let [clen (length clauses)]
-              (while (< i clen)
-                (let [clause (in clauses i)
-                      head (if (and (array? clause) (> (length clause) 0)) (first clause) nil)]
-                  (if (nil? head)
-                    (do (set result clause) (++ i))
-                    (match head
-                      :require (let [specs (tuple/slice clause 1)
-                                     slen (length specs)]
-                                 (var j 0)
-                                 (while (< j slen)
-                                   (let [s (in specs j)]
-                                     (when s (eval-require ctx s)))
-                                   (++ j))
-                                 (set i (+ i 1)))
-                      :use (let [specs (tuple/slice clause 1)
-                                 slen (length specs)]
-                             (var j 0)
-                             (while (< j slen)
-                               (let [s (in specs j)
-                                     ns-sym (if (array? s) (in s 0) s)
-                                     ns-name (sym-name-str ns-sym)
-                                     source-ns (ctx-find-ns ctx ns-name)
-                                     target-ns (ctx-find-ns ctx ns-name)]
-                                 (loop [[sym v] :pairs (source-ns :mappings)]
-                                   (ns-intern target-ns sym (var-get v))))
-                               (++ j))
-                             (set i (+ i 1)))
-                      :refer-clojure (let [spec (in clause 1)]
-                                       (when (and (array? spec) (= (first spec) :exclude))
-                                         (let [ns (ctx-find-ns ctx ns-name)]
-                                           (each sym (tuple/slice spec 1)
-                                             (ns-unmap ns (if (struct? sym) (sym :name) sym)))))
-                                       (set i (+ i 1)))
-                      :import (let [specs (tuple/slice clause 1)
-                                    slen (length specs)]
-                                (var j 0)
-                                (while (< j slen)
-                                  (let [class-spec (in specs j)
-                                        class-name (if (struct? class-spec) (class-spec :name) (string class-spec))
-                                        last-dot (do
-                                                  (var idx -1)
-                                                  (var pos 0)
-                                                  (while (< pos (length class-name))
-                                                    (if (= (class-name pos) 46) (set idx pos))
-                                                    (++ pos))
-                                                  idx)
-                                        short-name (if (>= last-dot 0)
-                                                    (string/slice class-name (+ last-dot 1))
-                                                    class-name)]
-                                    (ns-import (ctx-find-ns ctx ns-name) short-name class-name))
-                                  (++ j))
-                                (set i (+ i 1)))
-                      (do (set result clause) (++ i)))))))
-           result)
+    # ns is now a macro (clojure.core, 30-macros) expanding to in-ns + require/use/
+    # import/refer-clojure calls — all ctx-capturing fns — so it compiles. No
+    # special-form arm; an (ns ...) head falls through to the macro-expansion path.
     # require / in-ns are now ordinary clojure.core fns (install-stateful-fns!) —
     # no special-form arm; they compile + interpret as plain invokes.
     "all-ns" (all-ns ctx)

src/jolt/host_iface.janet

@@ -82,9 +82,10 @@
              # ns-management forms dispatched by the interpreter (not core vars)
              "create-ns" "remove-ns" "find-ns" "all-ns" "the-ns" "resolve"
              "ns-resolve" "ns-aliases" "ns-imports" "ns-interns"
-             # require/in-ns are now clojure.core fns (compile as plain invokes).
-             "read-string" "macroexpand-1" "defonce" "ns"
-             "import" "use" "refer" "defrecord"
+             # ns/require/in-ns/use/import/refer-clojure are now clojure.core
+             # fns/macros (compile as plain invokes / expand to them).
+             "read-string" "macroexpand-1" "defonce"
+             "refer" "defrecord"
              # defprotocol/extend-type/extend-protocol/reify now expand to plain
              # def + protocol-dispatch/register-method/make-reified invokes.
              "gen-class"

src/jolt/loader.janet

@@ -13,7 +13,7 @@
 # host-coupled set (Stage 2 jolt-eaa): forms move off this list as they gain a
 # compile path; syntax-quote already compiles via the analyzer's `handled` set.
 (defn- stateful-head? [head-name]
-  (or (= head-name "defmacro") (= head-name "ns")
+  (or (= head-name "defmacro")
       (= head-name "deftype") (= head-name "defmulti") (= head-name "defmethod")
       (= head-name "set!")
       (= head-name ".") (= head-name "new")

test/integration/conformance-test.janet

@@ -135,6 +135,8 @@
 
    ### ---- HIGH: aliased namespace calls ----
    ["require :as alias"  "\"1,2,3\"" "(do (require (quote [clojure.string :as s])) (s/join \",\" [1 2 3]))"]
+   ["ns form + alias"    "\"HI\""  "(do (ns my.a (:require [clojure.string :as s])) (s/upper-case \"hi\"))"]
+   ["ns :use refers"     "42"      "(do (ns src.u) (def helper 42) (ns dst.u (:use [src.u])) helper)"]
 
    ### ---- MED: missing core fns ----
    ["peek vec"        "3"             "(peek [1 2 3])"]

test/integration/fallback-zero-test.janet

@@ -47,6 +47,7 @@
    # compiles over an INTERNED var; the built-in dynamic vars aren't interned yet,
    # so it's exercised end-to-end in the state spec instead.)
    "(require (quote [clojure.string :as s]))" "(in-ns (quote foo.bar))"
+   "(ns foo.bar (:require [clojure.string :as s]))"
    "(defprotocol P (m [x]))" "(extend-type Long P (m [x] x))"
    "(reify P (m [this] 1))" "(var map)"])
 
@@ -55,7 +56,7 @@
 # (require/in-ns/protocols/binding now compile). The remaining frozen/uncompiled
 # set keeps the harness honest in the punt direction.
 (def must-punt
-  ["(ns foo.bar)" "(defmacro m [x] x)" "(deftype T [a])"
+  ["(defmacro m [x] x)" "(deftype T [a])"
    "(set! *warn-on-reflection* true)" "(letfn [(f [n] (g n)) (g [n] (f n))] (f 1))"])
 
 (var fails @[])

test/spec/namespaces-spec.janet

@@ -16,6 +16,11 @@
 
 (defspec "namespaces / ns operations"
   ["in-ns switches"     "true"     "(do (in-ns 'my.ns) (symbol? 'x))"]
+  # ns is a macro over in-ns/require/use/import (Stage 2 jolt-eaa): the form sets
+  # the current ns and processes its clauses.
+  ["ns form + alias"    "\"HI\""   "(do (ns my.app (:require [clojure.string :as s])) (s/upper-case \"hi\"))"]
+  ["ns :use refers all" "9"        "(do (ns src.lib) (def helper 9) (ns dst.app (:use [src.lib])) helper)"]
+  ["standalone use"     "7"        "(do (ns src.l2) (def k 7) (in-ns 'dst.a2) (use '[src.l2]) k)"]
   ["ns-name"            "true"     "(do (require (quote [clojure.string])) (= 'clojure.string (ns-name (find-ns 'clojure.string))))"]
   ["find-ns existing"   "true"     "(some? (find-ns 'clojure.core))"]
   ["find-ns missing"    "nil"      "(find-ns 'does.not.exist)"]