core: close the compile-path gaps that broke uberscripting Selmer + config

Loading these libs via require worked (load-ns-source interprets, macros
expand lazily) but the same code inlined by uberscript routes through
eval-toplevel and compiled, surfacing four gaps:

- a ^{:map} metadata def name reads as (def (with-meta name m) v); the
  analyzer died extracting the name (config.core's defonce env). It now
  throws uncompilable so the interpreter, which handles it, takes over.
- declare was a no-op, so a compiled forward reference to a declared
  name that collides with a janet root binding bound to the host fn
  (selmer.parser's (declare parse) compiled to janet's 1-arg parse).
  declare now expands to no-init defs, the interpreter interns them,
  and the analyzer routes no-init def to the interpreter.
- class? was missing (selmer.util's exception macro calls it at
  expansion time). Always false, like ratio? — no Class objects here.
- require of an unlocatable namespace silently left an empty ns behind,
  deferring the failure to an unresolved symbol far from the cause. It
  now throws like Clojure's FileNotFoundException. Namespaces entered
  in-session count as loaded (Clojure puts them in *loaded-libs*), and
  the SCI bootstrap opts out via :lenient-require? since its
  clj-targeted requires can't all exist on this host.

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

@@ -116,9 +116,12 @@
                      `(~form ~x))]
       `(->> ~threaded ~@(rest forms)))))
 
-;; Forward declaration is a no-op on Jolt — the compiler resolves forward refs via
-;; pending cells (matching the prior Janet macro).
-(defmacro declare [& syms] `(do))
+;; Forward declaration interns unbound vars (Clojure semantics). The interpreter
+;; resolves forward refs lazily either way, but the COMPILER classifies globals at
+;; compile time: without the var, a declared name that collides with a Janet root
+;; binding (parse, hash, …) would compile to the host fn instead of the var.
+(defmacro declare [& syms]
+  `(do ~@(map (fn* [s] `(def ~s)) syms)))
 
 ;; destructure — Clojure's binding-vector expander, ported from the Janet seed
 ;; (was core-destructure). Turns a binding vector that may contain destructuring

jolt-core/clojure/core/20-coll.clj

@@ -83,6 +83,9 @@
 ;; Jolt has no ratio or bigdecimal types, so these are constants / reduce to int?.
 (defn ratio? [x] false)
 (defn decimal? [x] false)
+;; No first-class Class objects either: class names are symbols the evaluator
+;; handles in instance?/new positions, never values — so nothing is a class.
+(defn class? [x] false)
 (defn rational? [x] (int? x))
 (defn nat-int? [x] (and (int? x) (>= x 0)))
 (defn neg-int? [x] (and (int? x) (neg? x)))

jolt-core/jolt/analyzer.clj

@@ -140,11 +140,19 @@
                     (const nil)))
     "do" (analyze-seq ctx (rest items) env)
     "throw" (throw-node (analyze ctx (nth items 1) env))
-    "def" (let [name-sym (nth items 1)
-                nm (form-sym-name name-sym)
+    "def" (let [name-sym (nth items 1)]
+            ;; ^{:map} metadata reads as (def (with-meta name m) v) — the
+            ;; metadata is a runtime expression, so the interpreter evaluates
+            ;; the whole def (it unwraps the name and merges the meta).
+            (when-not (form-sym? name-sym)
+              (uncompilable "def name with map metadata"))
+            ;; (def name) with no init (declare) just interns — interpreter's job
+            (when (< (count items) 3)
+              (uncompilable "def with no init"))
+            (let [nm (form-sym-name name-sym)
                   cur (compile-ns ctx)]
               (host-intern! ctx cur nm)
-            (def-node cur nm (analyze ctx (nth items 2) env) (form-sym-meta name-sym)))
+              (def-node cur nm (analyze ctx (nth items 2) env) (form-sym-meta name-sym))))
     "let*" (let [bvec (vec (form-vec-items (nth items 1)))
                  r (analyze-bindings ctx bvec env)]
              (let-node (first r) (analyze-seq ctx (drop 2 items) (second r))))

src/jolt/evaluator.janet

@@ -340,10 +340,22 @@
   for ns-form-less stdlib files, changes it). No-op for already-loaded namespaces."
   [ctx ns-name]
   (let [ns (ctx-find-ns ctx ns-name)]
-    (when (and (= 0 (length (ns :mappings))) (not= ns-name "clojure.core"))
+    (when (and (= 0 (length (ns :mappings)))
+               (not (get (get (ctx :env) :loaded-namespaces @{}) ns-name))
+               (not= ns-name "clojure.core"))
       (let [path (find-ns-file ctx ns-name)
             embedded (get (get (ctx :env) :embedded-sources @{}) ns-name)
             stdlib? (not (nil? embedded))]
+        # Clojure throws FileNotFoundException here; succeeding silently leaves
+        # an empty namespace behind and defers the failure to the first
+        # unresolved symbol, far from the actual cause (a typo, a missing
+        # JOLT_PATH root). Best-effort loaders (the SCI bootstrap, which loads
+        # clj-targeted sources whose requires can't all exist on this host)
+        # opt out via :lenient-require? on the env.
+        (when (and (nil? path) (nil? embedded)
+                   (not (get (ctx :env) :lenient-require?)))
+          (error (string "Could not locate " ns-name
+                         " on the context's source paths (JOLT_PATH / :paths)")))
         (when (or path embedded)
           (let [saved (ctx-current-ns ctx)]
             # Stdlib files have no `ns` form, so switch into the target ns first
@@ -943,6 +955,13 @@
   [ctx sym]
   (def ns-name (if (and (struct? sym) (= :symbol (sym :jolt/type))) (sym :name) (string sym)))
   (def the-ns-obj (ctx-find-ns ctx ns-name))
+  # An ns entered in-session counts as loaded (Clojure's ns macro commutes the
+  # name into *loaded-libs*), so a later require/use of it must not try to load
+  # a file — see maybe-require-ns. Namespace objects are immutable structs, so
+  # the set lives on the env.
+  (def loaded (or (get (ctx :env) :loaded-namespaces)
+                  (let [t @{}] (put (ctx :env) :loaded-namespaces t) t)))
+  (put loaded ns-name true)
   (ctx-set-current-ns ctx ns-name)
   the-ns-obj)
 
@@ -1522,8 +1541,18 @@
                 ns-name (ctx-current-ns ctx)
                 ns (ctx-find-ns ctx ns-name)
                 # Create var first (unbound) so self-referencing defs resolve
-                v (ns-intern ns (name-sym :name))
-                # (def name docstring value): docstring is form 2, value form 3
+                v (ns-intern ns (name-sym :name))]
+            # (def name) with no init interns the var and leaves any existing
+            # root binding alone (Clojure semantics — this is what declare
+            # expands to, so compiled forward refs bind to the var instead of
+            # falling through to a like-named host builtin).
+            (if (= 2 (length form))
+              (do
+                (when (not (empty? name-meta))
+                  (put v :meta (merge (or (get v :meta) {}) name-meta)))
+                (when dynamic? (put v :dynamic true))
+                v)
+              (let [# (def name docstring value): docstring form 2, value form 3
                     has-doc (and (> (length form) 3) (string? (in form 2)))
                     val-form (in form (if has-doc 3 2))
                     val (eval-form ctx bindings val-form)]
@@ -1545,7 +1574,7 @@
                 (when dynamic?
                   (put v :dynamic true))
                 # def returns the var (Clojure semantics); REPL prints #'ns/name
-            v)
+                v)))
     "defmacro" (let [name-sym (in form 1)
                      rest-form (tuple/slice form 2)
                      # optional docstring

test/integration/compile-mode-test.janet

@@ -138,4 +138,31 @@
   (eval-string c "(defn g [] 2)")
   (assert (= 2 (ct-eval c "(calls-g)")) "compiled caller sees redefined global"))
 
+# Map-literal metadata on a def'd name reads as (def (with-meta name m) v); the
+# analyzer must route it to the interpreter (uncompilable), not die extracting
+# the name. Regression: yogthos/config's (defonce ^{:doc "…"} env …) broke
+# every load-string/uberscript path while loading fine through require.
+(let [c (init-cached {:compile? true})]
+  (assert (= 42 (do (eval-string c `(def ^{:doc "d"} md-def 42)`)
+                    (ct-eval c "md-def")))
+          "compile-mode def with ^{:map} metadata")
+  (assert (= "d" (ct-eval c "(:doc (meta (var md-def)))"))
+          "map metadata lands on the var")
+  (assert (= 7 (do (eval-string c `(defonce ^{:doc "o"} md-once 7)`)
+                   (ct-eval c "md-once")))
+          "compile-mode defonce with ^{:map} metadata"))
+
+# (declare name) must intern a var so a compiled forward reference binds to it —
+# not to a like-named Janet host builtin. Regression: selmer.parser's
+# (declare parse) + a (parse …) call compiled to janet's 1-arg `parse`.
+(let [c (init-cached {:compile? true})]
+  (eval-string c "(declare parse)")
+  (eval-string c "(defn callit [s] (parse s 1 2))")
+  (eval-string c "(defn parse [s a b] [s a b])")
+  (assert (deep= ["x" 1 2] (ct-eval c `(callit "x")`))
+          "compiled forward ref through declare beats host fallback")
+  (eval-string c "(def no-init-var)")
+  (assert (= true (ct-eval c "(do (def no-init-var 5) (= 5 no-init-var))"))
+          "(def name) with no init interns; later def binds"))
+
 (print "\nAll Phase 6 tests passed!")

test/integration/namespace-test.janet

@@ -53,6 +53,10 @@
 
 (print "5: require form (standalone)...")
 (let [ctx (fresh-ctx)]
+  # Populate other.lib first — require of an unlocatable ns now throws
+  # (Clojure's FileNotFoundException), see namespaces-spec.
+  (let [other-ns (ctx-find-ns ctx "other.lib")]
+    (ns-intern other-ns "f" (fn [x] x)))
   (eval-form ctx @{} (parse-string "(require '[other.lib :as o])"))
   (let [ns (ctx-find-ns ctx "user")
         aliased (ns-alias-lookup ns "o")]

test/integration/sci-bootstrap-test.janet

@@ -10,6 +10,10 @@
 (reader-features-set! ["jolt" "clj" "default"])
 
 (def ctx (init-cached))
+# Best-effort loading: SCI's clj-targeted requires (borkdude.graal.locking,
+# clojure.tools.reader.*) don't exist on this host; a strict require would fail
+# whole ns forms and cascade. See maybe-require-ns.
+(put (ctx :env) :lenient-require? true)
 
 (printf "Loading SCI stubs...\n")
 (defn load-stubs [ctx filepath]

test/spec/forms-spec.janet

@@ -73,6 +73,9 @@
   ["do nested"       "1"      "(do (do (do (do 1))))"]
   ["do returns last" "3"      "(do 1 2 3)"]
   ["def + deref var" "true"   "(var? (def one 1))"]
+  ["def no init interns var" "true" "(var? (def no-init))"]
+  ["def no init keeps existing root" "7" "(do (def kept 7) (def kept) kept)"]
+  ["declare interns var"     "true" "(do (declare fwd-declared) (var? (var fwd-declared)))"]
   ["def redefine"    "100"    "(do (def one 1) (def one 100) one)"]
   ["def in fn mutates" "[:default :meow]" "(do (def a :default) (def set-a (fn* [v] (def a v))) (let* [before a] (set-a :meow) [before a]))"]
   ["call literal fn" "1"      "((fn* [] 1))"]

test/spec/namespaces-spec.janet

@@ -34,7 +34,14 @@
   ["require clojure.set" "#{1 2 3}" "(do (require '[clojure.set :as set]) (set/union #{1 2} #{3}))"]
   ["require clojure.walk" "{:a 2}" "(do (require '[clojure.walk :as w]) (w/postwalk (fn [x] (if (number? x) (inc x) x)) {:a 1}))"]
   ["walk keywordize-keys" "{:a 1}" "(do (require '[clojure.walk :as w]) (w/keywordize-keys {\"a\" 1}))"]
-  ["walk stringify-keys" "true"    "(do (require '[clojure.walk :as w]) (= {\"a\" 1} (w/stringify-keys {:a 1})))"])
+  ["walk stringify-keys" "true"    "(do (require '[clojure.walk :as w]) (= {\"a\" 1} (w/stringify-keys {:a 1})))"]
+  # Clojure throws FileNotFoundException; silently succeeding masks typos and
+  # missing roots until the first unresolved-symbol error far from the cause.
+  ["require missing lib throws" :throws "(require '[no.such.lib])"]
+  ["use missing lib throws"     :throws "(use 'no.such.lib)"]
+  # …but an ns created in-session is in *loaded-libs* (the ns macro puts it
+  # there), so require/use of it must NOT hit the loader.
+  ["require of in-session ns ok" "1" "(do (ns made.here) (def x 1) (require '[made.here]) made.here/x)"])
 
 (defspec "namespaces / alias, ns-unalias, ns-publics"
   ["alias + use"        "\"1,2\"" "(do (require (quote clojure.string)) (alias (quote st) (quote clojure.string)) (st/join \",\" [1 2]))"]

test/spec/predicates-spec.janet

@@ -73,6 +73,11 @@
   ["simple-ident?"      "true"   "(simple-ident? :a)"]
   ["ratio?"             "false"  "(ratio? 3)"]
   ["decimal?"           "false"  "(decimal? 3)"]
+  # No first-class Class objects on this host (class names are symbols handled
+  # in instance?/new positions), so class? is always false — like Clojure's
+  # class? of a symbol. Selmer's `exception` macro calls it at expansion time.
+  ["class? of value"    "false"  "(class? \"s\")"]
+  ["class? of symbol"   "false"  "(class? 'java.lang.String)"]
   ["rational? int"      "true"   "(rational? 3)"]
   ["rational? float"    "false"  "(rational? 3.5)"]
   ["nat-int? zero"      "true"   "(nat-int? 0)"]