feat: java.io.File model + multimethod/assoc/defmulti fixes for migratus (jolt-hjw)

File API (jolt-hjw): io/file and (File. …) build a tagged :jolt/file value
(instance? File true) with a full method surface (isFile/isDirectory/exists/
getName/getPath/getAbsolutePath/listFiles/toPath/delete/createNewFile/…) backed
by os/ and file/. file-seq is File-aware (leaves are File values). str/slurp/spit
coerce :jolt/file to its path. ClassLoader/getSystemClassLoader + a classloader
stub whose getResource returns nil degrade migratus's classpath lookup to the
filesystem. java.nio.file Path/FileSystem/PathMatcher are shimmed just enough for
script-excluded?'s glob (recursive * / ? matcher).

Three bugs found getting migratus's migration discovery to work:
- (assoc nil k v) returned a raw janet table, not a map, so assoc-in built tables
  that count/seq rejected. Now returns an immutable map.
- methods/get-method resolved the multimethod symbol at runtime in the current
  ns, so a bare multifn ref in its defining ns saw an empty table once defmethods
  lived elsewhere. Now they take the multimethod VALUE and recover the var via a
  registry (Clojure semantics).
- defmulti now drops a leading docstring/attr-map (migratus's multimethods carry
  docstrings) instead of treating the docstring as the dispatch fn.

Conformance 335/335 x3, clojure-test-suite at baseline.

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

@@ -519,7 +519,11 @@
 ;; via the host dir primitives. Paths (strings), not File objects. (Lives below
 ;; tree-seq: forward references are analysis errors now — jolt-2o7.3.)
 (defn file-seq [root]
-  (tree-seq __dir? __list-dir root))
+  (if (__file? root)
+    ;; java.io.File tree: walk via the File method surface so leaves are File
+    ;; values callers can invoke .isFile/.getName/slurp on (jolt-hjw).
+    (tree-seq (fn [f] (.isDirectory f)) (fn [f] (seq (.listFiles f))) root)
+    (tree-seq __dir? __list-dir root)))
 
 ;; Canonical flatten via tree-seq: the leaves (non-sequential nodes) in order.
 ;; Flattens lists too (sequential?), matching Clojure/CLJS.

jolt-core/clojure/core/30-macros.clj

@@ -21,8 +21,15 @@
 ;; clojure.core fns) so they compile as plain invokes. name/mm are passed quoted;
 ;; the dispatch fn, options, and dispatch value evaluate normally, and the method
 ;; body becomes a compiled (fn …).
-(defmacro defmulti [name dispatch & opts]
+;; Clojure allows (defmulti name docstring? attr-map? dispatch-fn & options);
-  `(defmulti-setup (quote ~name) ~dispatch ~@opts))
+;; drop a leading docstring and/or attr-map so the dispatch fn isn't mistaken for
+;; one (migratus's multimethods carry docstrings).
+(defmacro defmulti [name & args]
+  (let [args (if (string? (first args)) (rest args) args)
+        args (if (and (map? (first args)) (not (symbol? (first args)))) (rest args) args)
+        dispatch (first args)
+        opts (rest args)]
+    `(defmulti-setup (quote ~name) ~dispatch ~@opts)))
 
 (defmacro defmethod [mm dispatch-val & fn-tail]
   `(defmethod-setup (quote ~mm) ~dispatch-val (fn ~@fn-tail)))
@@ -39,11 +46,14 @@
 (defmacro remove-all-methods [mm]
   `(remove-all-methods-setup (quote ~mm)))
 
+;; methods/get-method take the multimethod VALUE (Clojure semantics); the setup
+;; maps it back to its var via the registry, so a bare multifn ref works from a
+;; compiled fn in any namespace (jolt multimethod table-visibility fix).
 (defmacro get-method [mm dval]
-  `(get-method-setup (quote ~mm) ~dval))
+  `(get-method-setup ~mm ~dval))
 
 (defmacro methods [mm]
-  `(methods-setup (quote ~mm)))
+  `(methods-setup ~mm))
 
 ;; prefers reads the store off the VAR (the multifn value can't carry it) —
 ;; same symbol-passing shape as the other multimethod table ops.

src/jolt/clojure/java/io.clj

@@ -6,11 +6,13 @@
 ; …) won't work, but file/reader/writer/resource/copy/slurp do.
 
 (defn file
-  "A file path. With a parent and child, joins them with '/'."
+  "A java.io.File. With a parent and child, joins them with '/'. Returns a
-  ([path] (str path))
+  :jolt/file value (instance? File true) with the File method surface; str/slurp
-  ([parent child] (str parent "/" child)))
+  and io/reader coerce it back to its path."
+  ([path] (__make-file path))
+  ([parent child] (__make-file parent child)))
 
-(defn as-file [x] (str x))
+(defn as-file [x] (if (__file? x) x (__make-file x)))
 
 (defn reader [x]
   (cond

src/jolt/core.janet

@@ -541,7 +541,10 @@
             result)
         (do (var result @{}) (when m (each k (keys m) (put result k (get m k))))
           (var i 0) (while (< i (length kvs)) (let [k (kvs i) v (kvs (+ i 1))] (put result k v) (+= i 2)))
-          (if (struct? m) (table/to-struct result) result))))))
+          # nil assocs to a fresh immutable map ((assoc nil :a 1) => {:a 1}); a
+          # raw table here would not count?/seq like a Clojure map (assoc-in into
+          # an absent key recurses through nil — migratus's migration maps).
+          (if (or (struct? m) (nil? m)) (table/to-struct result) result))))))
 
 (defn core-dissoc [m & ks]
   (cond
@@ -1656,6 +1659,8 @@
       (if (v :ns) (string (v :ns) "/" (v :name)) (v :name))
     (and (struct? v) (= :jolt/uuid (v :jolt/type))) (v :str)
     (and (struct? v) (= :jolt/inst (v :jolt/type))) (inst->rfc3339 v)
+    # a java.io.File renders as its path (Clojure's File.toString)
+    (and (table? v) (= :jolt/file (get v :jolt/type))) (get v :path)
     (= :jolt/namespace (get v :jolt/type)) (ns-display-name v)
     (and (table? v) (= :jolt/var (get v :jolt/type))) (var-display v)
     (number? v) (fmt-number v)
@@ -1744,6 +1749,19 @@
 (defn core-jdbc-make-stmt [w]
   @{:jolt/type :jolt/jdbc-stmt :exec (get w :exec) :cmds @[]})
 
+# java.io.File model (jolt-hjw). io/file and (File. …) build a tagged :jolt/file
+# value so (instance? File x) works and migratus's File-vs-jar branching takes
+# the filesystem path. The File method surface + nio glob live in javatime; here
+# are the constructor/predicate builtins and the path coercion str/slurp use.
+(defn core-file-path
+  "The path string of a :jolt/file, or (string x) for anything else."
+  [x]
+  (if (and (table? x) (= :jolt/file (get x :jolt/type))) (get x :path) (string x)))
+(defn core-make-file [path &opt child]
+  (def base (core-file-path path))
+  @{:jolt/type :jolt/file :path (if child (string base "/" (core-file-path child)) base)})
+(defn core-file? [x] (and (table? x) (= :jolt/file (get x :jolt/type))))
+
 # newline lives in the Clojure collection tier (core/20-coll.clj).
 
 # Clojure 1.11 string->scalar parsers: nil on malformed input, throw on a
@@ -1787,6 +1805,7 @@
 # bodies, and the jolt Ring adapter hands those over as StringReaders.
 (defn core-slurp [src & opts]
   (cond
+    (core-file? src) (string (slurp (core-file-path src)))
     (and (table? src) (string? (get src :s)) (number? (get src :pos)))
       (let [s (src :s) p (src :pos)]
         (put src :pos (length s))
@@ -1799,7 +1818,7 @@
                      (when (and (= :append (in opts i)) (in opts (+ i 1))) (set a true))
                      (+= i 2))
                    a))
-  (def f (file/open path (if append? :a :w)))
+  (def f (file/open (core-file-path path) (if append? :a :w)))
   (file/write f (str-render-one content))
   (file/close f)
   nil)
@@ -2731,6 +2750,8 @@
     "__jdbc-wrap-conn" core-jdbc-wrap-conn
     "__jdbc-conn-raw" core-jdbc-conn-raw
     "__jdbc-make-stmt" core-jdbc-make-stmt
+    "__make-file" core-make-file
+    "__file?" core-file?
     "__pr-str1" core-pr-str1
     "__make-uuid" make-uuid
     "compare" core-compare

src/jolt/evaluator.janet

@@ -1197,6 +1197,13 @@
         (ns-unmap ns (if (and (struct? sym) (= :symbol (sym :jolt/type))) (sym :name) (string sym))))))
   nil)
 
+# Multimethod value -> its var. methods/get-method take the multimethod VALUE
+# (Clojure semantics) and recover the var (hence :jolt/methods) through this,
+# which works from a compiled fn in any namespace — resolving the symbol at call
+# time in the current ns did not (a bare multifn ref in its defining ns saw an
+# empty table once defmethods lived in other namespaces; migratus hit this).
+(def multi-registry @{})
+
 (defn defmulti-setup
   "(defmulti name dispatch & opts) — intern a multimethod var. A fn; name arrives
   quoted, dispatch + opts (:default key, :hierarchy h) arrive evaluated. The
@@ -1292,6 +1299,7 @@
   (put v :jolt/dispatch-cache dispatch-cache)
   (put v :jolt/default default-key)
   (when hierarchy (put v :jolt/hierarchy hierarchy))
+  (put multi-registry mm-fn v)
   (var-get v))
 
 (defn defmethod-setup
@@ -1301,9 +1309,11 @@
   [ctx mm-sym dispatch-val impl]
   (def mm-var
     (or (resolve-var ctx @{} mm-sym)
-        (let [ns (ctx-find-ns ctx (ctx-current-ns ctx))]
+        (let [ns (ctx-find-ns ctx (ctx-current-ns ctx))
-          (def v (ns-intern ns (mm-sym :name) (fn [& args] nil)))
+              stub (fn [& args] nil)]
+          (def v (ns-intern ns (mm-sym :name) stub))
           (put v :jolt/methods @{})
+          (put multi-registry stub v)
           v)))
   (def methods (or (get mm-var :jolt/methods) (let [m @{}] (put mm-var :jolt/methods m) m)))
   # nil is a legal dispatch value (ring's body-string keys a method on it);
@@ -1470,8 +1480,10 @@
       found
       (when auto-create?
         (def ns (ctx-find-ns ctx (ctx-current-ns ctx)))
-        (def nv (ns-intern ns (mm-sym :name) (fn [& args] nil)))
+        (def stub (fn [& args] nil))
+        (def nv (ns-intern ns (mm-sym :name) stub))
         (put nv :jolt/methods @{})
+        (put multi-registry stub nv)
         nv))))
   (def clear-dispatch-cache! (fn [mm-var]
     (let [dc (get mm-var :jolt/dispatch-cache)]
@@ -1510,16 +1522,21 @@
     (fn [mm-sym]
       (def mm-var (mm-var-of mm-sym false))
       (or (and mm-var (get mm-var :jolt/prefers)) {})))
+  # methods/get-method receive the multimethod VALUE (Clojure semantics): map it
+  # back to its var via multi-registry. A symbol arg still works (mm-var-of), for
+  # any caller that passes one.
+  (def mm-var-of-val (fn [mm]
+    (if (function? mm) (get multi-registry mm) (mm-var-of mm false))))
   (ns-intern core "get-method-setup"
-    (fn [mm-sym dval]
+    (fn [mm dval]
       (def dval (if (nil? dval) :jolt/nil-sentinel dval))
-      (def mm-var (mm-var-of mm-sym false))
+      (def mm-var (mm-var-of-val mm))
       (when mm-var
         (let [methods (get mm-var :jolt/methods)]
           (or (get methods dval) (get methods :default))))))
   (ns-intern core "methods-setup"
-    (fn [mm-sym]
+    (fn [mm]
-      (def mm-var (mm-var-of mm-sym false))
+      (def mm-var (mm-var-of-val mm))
       (when mm-var
         # a jolt map, not the live host table (and phm so vector dispatch
         # values look up by value, same reason build-eval-map promotes)
@@ -1588,6 +1605,10 @@
           # branch, so the wrapped conn must answer true here.
           "Connection" (and (table? val) (= :jolt/jdbc-conn (get val :jolt/type)))
           "java.sql.Connection" (and (table? val) (= :jolt/jdbc-conn (get val :jolt/type)))
+          # java.io.File model (jolt-hjw): io/file and (File. …) build :jolt/file,
+          # so migratus's (instance? File migration-dir) takes the filesystem path.
+          "File" (and (table? val) (= :jolt/file (get val :jolt/type)))
+          "java.io.File" (and (table? val) (= :jolt/file (get val :jolt/type)))
           # JVM char[] class — (Class/forName "[C"); jolt char arrays are Janet
           # arrays of char structs
           "[C" (and (array? val)

src/jolt/javatime.janet

@@ -537,6 +537,15 @@
   # that walks Thread/currentThread doesn't crash.
   (register-tagged-methods! :jolt/thread
     @{"getContextClassLoader" (fn [self] @{:jolt/type :jolt/classloader})})
+  # ClassLoader degrade (jolt-hjw): there is no classpath, so getResource returns
+  # nil and migratus's find-migration-dir falls through to the filesystem branch
+  # (resources/<dir>). getSystemClassLoader yields the same stub.
+  (each nm ["ClassLoader" "java.lang.ClassLoader"]
+    (register-class-statics! nm @{"getSystemClassLoader" (fn [] @{:jolt/type :jolt/classloader})}))
+  (register-tagged-methods! :jolt/classloader
+    @{"getResource" (fn [self path] nil)
+      "getResources" (fn [self path] nil)
+      "getResourceAsStream" (fn [self path] nil)})
   # next.jdbc host shims (paired with the __jdbc-* builtins in core.janet and the
   # instance? Connection case in evaluator.janet). The wrapped connection carries
   # a clj :exec callback (run one SQL string) and a :close callback.
@@ -563,7 +572,85 @@
                        (def out @[])
                        (each c (get self :cmds) (array/push out ((get self :exec) c)))
                        out)
-      "close" (fn [self] nil)}))
+      "close" (fn [self] nil)})
+  # java.io.File model (jolt-hjw). A :jolt/file carries its path; io/file and the
+  # File. ctor build it (see core.janet's __make-file). The method surface below
+  # is backed by os/ and file/. listFiles returns child :jolt/file values so
+  # file-seq (File-aware) yields :jolt/file leaves migratus can call methods on.
+  (defn- jfile-path [x]
+    (if (and (table? x) (= :jolt/file (get x :jolt/type))) (get x :path) (string x)))
+  (defn- make-jfile [path &opt child]
+    @{:jolt/type :jolt/file
+      :path (if child (string (jfile-path path) "/" (jfile-path child)) (jfile-path path))})
+  (defn- last-slash [p]
+    (var idx nil) (var i 0)
+    (while (< i (length p)) (when (= (p i) 47) (set idx i)) (++ i))
+    idx)
+  (defn- jfile-name [p]
+    (if-let [i (last-slash p)] (string/slice p (+ i 1)) p))
+  (defn- jfile-abs [p]
+    (if (string/has-prefix? "/" p) p (string (os/cwd) "/" p)))
+  (each nm ["File" "java.io.File"]
+    (register-class-ctor! nm make-jfile))
+  (register-tagged-methods! :jolt/file
+    @{"getPath" (fn [self] (get self :path))
+      "toString" (fn [self] (get self :path))
+      "getName" (fn [self] (jfile-name (get self :path)))
+      "getParent" (fn [self] (let [p (get self :path)]
+                               (if-let [i (last-slash p)] (string/slice p 0 i) nil)))
+      "getAbsolutePath" (fn [self] (jfile-abs (get self :path)))
+      "getCanonicalPath" (fn [self] (jfile-abs (get self :path)))
+      "getAbsoluteFile" (fn [self] (make-jfile (jfile-abs (get self :path))))
+      "exists" (fn [self] (not (nil? (os/stat (get self :path)))))
+      "isFile" (fn [self] (= :file (os/stat (get self :path) :mode)))
+      "isDirectory" (fn [self] (= :directory (os/stat (get self :path) :mode)))
+      "canRead" (fn [self] (not (nil? (os/stat (get self :path)))))
+      # listFiles: child File values, or nil when not a directory (Clojure null)
+      "listFiles" (fn [self]
+                    (let [p (get self :path)]
+                      (when (= :directory (os/stat p :mode))
+                        (map (fn [e] (make-jfile p e)) (os/dir p)))))
+      "list" (fn [self]
+               (let [p (get self :path)]
+                 (when (= :directory (os/stat p :mode)) (os/dir p))))
+      "toPath" (fn [self] @{:jolt/type :jolt/nio-path :s (get self :path)})
+      "toURI" (fn [self] (string "file:" (jfile-abs (get self :path))))
+      "toURL" (fn [self] @{:jolt/type :jolt/url :url (string "file:" (jfile-abs (get self :path)))})
+      "delete" (fn [self] (let [r (protect (os/rm (get self :path)))] (truthy? (r 0))))
+      "mkdir" (fn [self] (truthy? ((protect (os/mkdir (get self :path))) 0)))
+      "mkdirs" (fn [self] (truthy? ((protect (os/mkdir (get self :path))) 0)))
+      "createNewFile" (fn [self]
+                        (let [p (get self :path)]
+                          (if (os/stat p) false
+                            (do (def f (file/open p :w)) (file/close f) true))))
+      "equals" (fn [self o] (and (table? o) (= (get self :path) (get o :path))))
+      "hashCode" (fn [self] (hash (get self :path)))})
+  # java.nio.file degrade for migratus's script-excluded? glob check: just enough
+  # of Path / FileSystem / PathMatcher to match a filename against a glob, with a
+  # simple recursive * / ? matcher (no path-segment semantics — filenames only).
+  (defn- glob-matches? [glob s]
+    (defn m [gi si]
+      (cond
+        (= gi (length glob)) (= si (length s))
+        (= (glob gi) 42) # *
+          (or (m (+ gi 1) si)
+              (and (< si (length s)) (m gi (+ si 1))))
+        (and (< si (length s))
+             (or (= (glob gi) 63) (= (glob gi) (s si)))) # ? or literal
+          (m (+ gi 1) (+ si 1))
+        false))
+    (m 0 0))
+  (register-tagged-methods! :jolt/nio-path
+    @{"getFileSystem" (fn [self] @{:jolt/type :jolt/nio-fs})
+      "toString" (fn [self] (get self :s))})
+  (register-tagged-methods! :jolt/nio-fs
+    @{"getPath" (fn [self s & _] @{:jolt/type :jolt/nio-path :s s})
+      "getPathMatcher" (fn [self spec]
+                         @{:jolt/type :jolt/nio-matcher
+                           :glob (if (string/has-prefix? "glob:" spec)
+                                   (string/slice spec 5) spec)})})
+  (register-tagged-methods! :jolt/nio-matcher
+    @{"matches" (fn [self path] (glob-matches? (get self :glob) (get path :s)))}))
 
 (install!)
 (install-io!)