init.scm(re-export-public-interface): Syntax to re-export all defines.

Author: toothbrush

guile/spotiqueue/init.scm

@@ -20,6 +20,51 @@
   #:declarative? #f)
 (module-export-all! (current-module))
 
+;; Syntax transformer to re-export all public defines from a given module from this module.  Grabbed
+;; from https://www.mail-archive.com/bug-guile@gnu.org/msg10321.html
+;;
+;; What i want is, whenever someone imports (spotiqueue init), they should get whatever has been
+;; defined in (spotiqueue functions), too.  The latter is the "phantom module" created in Swift-land
+;; when Spotiqueue boots, exporting a few functions which are needed to sensibly be able to interact
+;; with the music player.
+(define-syntax re-export-public-interface
+  (syntax-rules ()
+    "Re-export the public interface of a module or modules. Invoked as
+@code{(re-export-public-interface (mod1) (mod2) ...)}."
+    ((_ (m0 m0* ...) (mn mn* ...) ...)
+     (let ((iface (module-public-interface (current-module))))
+       (define (r-e-p-i module)
+         (cond-expand
+          (guile-3
+           (module-for-each
+            (lambda (sym val)
+              (hashq-set! (module-replacements iface) sym #t)
+              (module-add! iface sym val))
+            (resolve-interface module)))
+          (else
+           (module-use! iface (resolve-interface module)))))
+       (r-e-p-i '(m0 m0* ...))
+       (r-e-p-i '(mn mn* ...))
+       ...))
+    ((_)
+     (syntax-error "must provide one or more module names"))
+    ((_ m m* ...)
+     (syntax-error "module names must look like lists"))))
+
+(re-export-public-interface (spotiqueue functions))
+
+;; The re-export thing should presumably be achievable with this snippet, from
+;; https://debbugs.gnu.org/cgi/bugreport.cgi?bug=47084, and it does seem to work, except that i feel
+;; like i can't really get my head around it.  Notably i don't understand the docstring of
+;; `module-use!`, which simply states, "Add interface [the second arg] to the front of the use-list
+;; of module [the first arg]. Both arguments should be module objects, and interface should very
+;; likely be a module returned by resolve-interface."  Also, (current-module) always resolves to
+;; (spotiqueue init), and not whatever is importing it...
+;;
+;;     (eval-when (expand load eval)
+;;       (module-use! (module-public-interface (current-module))
+;;                    (resolve-interface '(spotiqueue functions))))
+
 (format #t "guile ~s: Loading Spotiqueue bootstrap config...~%" (module-name (current-module)))
 
 ;; Define the key maps