scm: support configuration

Support a configuration function, with the system-configuration.

Update docs.

Add a tests for language, using the configuration to see if we support
it.

scm/mu-scm-store.cc

@@ -55,7 +55,8 @@ subr_cc_store_alist(SCM store_scm) try {
 			continue;
 
 		const auto str{conf.as_display_string(prop)};
-		const auto name{make_symbol(prop.name)};
+		const auto name{make_symbol(mu_format("{}{}", prop.name,
+						      prop.type == Type::Boolean ? "?" : ""))};
 		const auto val = std::invoke([&]() {
 			switch (prop.type) {
 			case Type::Number:

scm/mu-scm-test.scm

@@ -108,6 +108,10 @@
     (test-equal '((email . "anon@example.com") (name . "Mickey Mouse"))
       (car  (assoc-ref alist 'from)))
 
+    ;; language
+    (test-equal (language msg)
+      (if (assoc-ref (configuration) 'language-enabled?) 'en nil))
+
     ;; cc, bc, labels
     (test-equal '() (cc msg))
     (test-equal '() (bcc msg))

scm/mu-scm.cc

@@ -32,6 +32,8 @@
 
 #include "mu-scm-types.hh"
 
+#include "mu-config.hh"
+
 #ifdef HAVE_PTHREAD_SETNAME_NP
 #include <pthread.h>
 #endif
@@ -44,7 +46,7 @@ SCM mu_mod; // The mu module
 }
 
 /**
- * Create a plist for the relevant option items
+ * Create an alist for the relevant option items (i.e., command-line parameters)
  *
  * @param opts
  */
@@ -52,16 +54,51 @@ static void
 init_options(const Options& opts)
 {
 	SCM scm_opts = alist_add(SCM_EOL,
-				 make_symbol("verbose"), opts.verbose,
+				 make_symbol("verbose?"), opts.verbose,
-				 make_symbol("debug"), opts.debug,
+				 make_symbol("debug?"), opts.debug,
-				 make_symbol("quiet"), opts.quiet);
+				 make_symbol("quiet?"), opts.quiet);
 
 	if (opts.muhome.empty())
 		scm_opts = alist_add(scm_opts, make_symbol("mu-home"), SCM_BOOL_F);
 	else
 		scm_opts = alist_add(scm_opts, make_symbol("mu-home"), opts.muhome);
 
-	scm_c_define("%options", scm_opts);
+
+	scm_c_define("%options", scm_reverse_x(scm_opts, SCM_EOL));
+}
+
+/**
+ * Create an alist for the relevant system-configuration parameters
+ */
+static void
+init_configuration()
+{
+	SCM conf{SCM_EOL};
+
+	for (const auto& prop: Config::properties) {
+
+		if (none_of(prop.flags & Property::Flags::System))
+			continue;
+
+	        const auto val{Config::default_value(prop)};
+		if (!val)
+			continue;
+
+		switch(prop.type) {
+		case Config::Type::Boolean:
+			conf = alist_add(conf, make_symbol(mu_format("{}?", prop.name, "?")),
+					 Config::decode<Config::Type::Boolean>(*val));
+			break;
+		case Config::Type::String:
+			conf = alist_add(conf, make_symbol(prop.name), *val);
+			break;
+		default:
+			// other types are not used here yet.
+			break;
+		}
+        }
+
+	scm_c_define("%configuration", scm_reverse_x(conf, SCM_EOL));
 }
 
 static void
@@ -179,6 +216,7 @@ init_module_mu(void* data)
 	const ModMuData& conf{*reinterpret_cast<ModMuData*>(data)};
 
 	init_options(conf.opts);
+	init_configuration();
 	init_misc();
 	init_subrs();
 

scm/mu-scm.scm

@@ -1,4 +1,4 @@
-;; Copyright (C) 2025 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+;; Copyright (C) 2025-2026 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
 ;;
 ;; This program is free software; you can redistribute it and/or modify it
 ;; under the terms of the GNU General Public License as published by the
@@ -100,8 +100,10 @@
 	    ;; Other
 
 	    ;; misc
-	    %options
+            options
-	    ;;	    %preferences
+            configuration
+
+            %options  ;; deprecated, use (options)
 
 	    ;; logging
 	    debug
@@ -621,9 +623,20 @@ init'. Uses the default-store."
 ;;
 ;; The alist maps symbols to values; a value of #f indicates that the value is at
 ;; its default.
-%options ;; defined in c++
+%options ;; defined in c++ (public, but deprecated)
 (set-documentation! '%options
 		    "Alist with the command-line parameters.")
+(define (options)
+  "Get an alist with the options that \"mu\" started with. That as, command-line
+   arguments, defaults, environment."
+  %options)
+
+%configuration ;; defined in c++
+(set-documentation! '%configuration
+		    "Alist with the mu system configuration parameters.")
+(define (configuration)
+  "Alist with the mu system configuration parameters.."
+  %configuration)
 
 (define %preferences
   '( (short-date  . "%F %T")
@@ -684,7 +697,6 @@ UTC time.
 	  (strftime format t))
 	#f)))
 
-
 ;; Logging to mu's log
 
 (define (mlog level frmstr . args)

scm/mu-scm.texi

@@ -126,22 +126,20 @@ optional.
 To build @t{mu} with SCM support, first you need to ensure you have installed
 the required Guile development packages. The details of getting those vary
 across environments / distributions, e.g.: on Fedora (as root):
-
 @example
 # dnf install guile30-devel
 @end example
-
+or on Debian/Ubuntu and derivatives:
-or on Debian/Ubuntu:
 @example
 $ sudo apt install guile-3.0-dev
 @end example
 
-With those packages in place, you can (re)build @t{mu} and @t{mu-scm} should be
+With those packages in place, a (re)build @t{mu} and @t{mu-scm} should
-built automatically if you did @emph{not} explicitly disable it.
+automatically build the SCM-support, unless you explicitly disabled it.
 
-Parts of @t{mu-scm} depend on @t{mu} being @emph{installed}, not just built;
+By default,@t{mu-scm} expects @t{mu} being @emph{installed}, not just
-however, you can still use it un-installed as well by setting an environment
+@emph{built}; however, you can still use it un-installed as well by setting the
-variable @t{MU_SCM_DIR} to the source-directory, e.g.
+environment variable @t{MU_SCM_DIR} to the path to the source-directory, e.g.
 @t{/home/user/sources/mu/scm}.
 
 @node Starting the REPL
@@ -150,7 +148,9 @@ variable @t{MU_SCM_DIR} to the source-directory, e.g.
 After installing @t{mu}, you can check the output of @command{mu info}. If
 @t{mu-scm} is available, in the table you should find a line:
 @example
-| scm-support      | yes     | GNU Guile 3.x support (new)?          |
++------------------+-------------+--------------------------------------------+
+| scm-enabled      | yes         | Is SCM/Guile supported?                    |
++------------------+-------------+--------------------------------------------+
 @end example
 
 You can then start an interactive shell, also known as the
@@ -488,8 +488,8 @@ More fields may be added.
 @deffn {Scheme Procedure} root-maildir
 @end deffn
 
-Get the root maildir directory, that is, the root of under the directory under
+Get the root maildir directory, that is, the root directory under which all
-which all messages reside.
+messages reside.
 
 This is equivalent to @code{(assoc-ref (store->alist) 'root-maildir)}.
 
@@ -946,22 +946,34 @@ For example:
 @c Get the message's s-expression.
 
 @c @t{mu} caches an s-expression for each message; this was designed as an
-@c optimization for @code{mu4e}, but @t{mu-scm} uses it as well. The details of this
+@c optimization for @code{mu4e}, but @t{mu-scm} uses it as well. The details of
-@c s-expression (a property-list) are internal to @t{mu} (so do not base your next
+@c this s-expression (a property-list) are internal to @t{mu} (so do not base
-@c billion-dollar startup on it), but it can be useful for development and
+@c your next billion-dollar startup on it), but it can be useful for development
-@c debugging.
+@c and debugging.
 
 @node Miscellaneous
 @section Miscellaneous
 
-@defvar %options
+@deffn {Scheme Procedure} options
-@end defvar
+@end deffn
-
+Get an association-list (alist) of general options passed to @command{mu scm} or
-An association-list (alist) of general options passed to @command{mu scm} or
+their default values. This might look something like:
-their default values.
 @lisp
- %options
+(options)
-=> ((mu-home . #f) (quiet . #f) (debug . #f) (verbose . #f))
+=> ((verbose? . #f) (debug? . #f) (quiet? . #f) (mu-home . #f))
+@end lisp
+
+Other options may be added.
+
+@deffn {Scheme Procedure} configuration
+@end deffn
+
+An association-list (alist) of the @t{mu} system configuration. This might look
+something like:
+@lisp
+(configuration)
+((mu-version . "1.14.3") (xapian-version . "1.4.30") (glib-version . "2.88.2")
+ (gmime-version . "3.2.15") (scm-enabled? . #t) (language-enabled? . #t))
 @end lisp
 
 @c @defvar %preferences