[bug#41253] [PATCH] guix: add script execution to "guix repl"

[Konrad Hinsen <konrad.hinsen@fastmail.net>]

* guix/scripts/repl.scm: Add filename options for script execution.
* doc/guix.texi: Document script execution by "guix repl"
---
 doc/guix.texi         | 38 +++++++++++++++-----
 guix/scripts/repl.scm | 80 ++++++++++++++++++++++++++-----------------
 2 files changed, 78 insertions(+), 40 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index d6fbd85fde..68f1a8bba3 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -238,7 +238,7 @@ Programming Interface
 * Derivations::                 Low-level interface to package derivations.
 * The Store Monad::             Purely functional interface to the store.
 * G-Expressions::               Manipulating build expressions.
-* Invoking guix repl::          Fiddling with Guix interactively.
+* Invoking guix repl::          Programming Guix in Guile
 
 Defining Packages
 
@@ -5415,7 +5415,7 @@ package definitions.
 * Derivations::                 Low-level interface to package derivations.
 * The Store Monad::             Purely functional interface to the store.
 * G-Expressions::               Manipulating build expressions.
-* Invoking guix repl::          Fiddling with Guix interactively.
+* Invoking guix repl::          Programming Guix in Guile
 @end menu
 
 @node Package Modules
@@ -8134,12 +8134,31 @@ has an associated gexp compiler, such as a @code{<package>}.
 @node Invoking guix repl
 @section Invoking @command{guix repl}
 
-@cindex REPL, read-eval-print loop
-The @command{guix repl} command spawns a Guile @dfn{read-eval-print loop}
-(REPL) for interactive programming (@pxref{Using Guile Interactively,,, guile,
-GNU Guile Reference Manual}).  Compared to just launching the @command{guile}
+@cindex REPL, read-eval-print loop, script
+The @command{guix repl} command makes it easier to program Guix in Guile
+by launching a Guile @dfn{read-eval-print loop} (REPL) for interactive
+programming (@pxref{Using Guile Interactively,,, guile,
+GNU Guile Reference Manual}), or by running Guile scripts
+(@pxref{Running Guile Scripts,,, guile,
+GNU Guile Reference Manual}).
+Compared to just launching the @command{guile}
 command, @command{guix repl} guarantees that all the Guix modules and all its
-dependencies are available in the search path.  You can use it this way:
+dependencies are available in the search path.
+
+The general syntax is:
+
+@example
+guix repl @var{options} @var{files}
+@end example
+
+When at least one @var{files} argument is provided, @var{files} are
+executed as Guile scripts in the given order:
+
+@example
+$ guix repl my-script.scm
+@end example
+
+Otherwise a Guile REPL is started:
 
 @example
 $ guix repl
@@ -8188,11 +8207,12 @@ Add @var{directory} to the front of the package module search path
 (@pxref{Package Modules}).
 
 This allows users to define their own packages and make them visible to
-the command-line tool.
+the scripts or REPL.
 
 @item -q
 Inhibit loading of the @file{~/.guile} file.  By default, that
-configuration file is loaded when spawning a @code{guile} REPL.
+configuration file is loaded when executing scripts or spawning
+a @code{guile} REPL.
 @end table
 
 @c *********************************************************************
diff --git a/guix/scripts/repl.scm b/guix/scripts/repl.scm
index ff1f208894..f4cb744bbd 100644
--- a/guix/scripts/repl.scm
+++ b/guix/scripts/repl.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2020 Simon Tournier <zimon.toutoune@gmail.com>
+;;; Copyright © 2020 Konrad Hinsen <konrad.hinsen@fastmail.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -32,10 +33,12 @@
 
 ;;; Commentary:
 ;;;
-;;; This command provides a Guile REPL
+;;; This command provides a Guile script runner and REPL in an environment
+;;; that contains all the modules comprising Guix.
 
 (define %default-options
-  `((type . guile)))
+  `((scripts . ())
+    (type . guile)))
 
 (define %options
   (list (option '(#\h "help") #f #f
@@ -63,8 +66,9 @@
 
 
 (define (show-help)
-  (display (G_ "Usage: guix repl [OPTIONS...]
-Start a Guile REPL in the Guix execution environment.\n"))
+  (display (G_ "Usage: guix repl [OPTIONS...] [FILES...]
+In the Guix execution environment, run FILES as Guile scripts,
+or start a Guile REPL if no FILES are given,\n"))
   (display (G_ "
   -t, --type=TYPE        start a REPL of the given TYPE"))
   (display (G_ "
@@ -135,12 +139,13 @@ call THUNK."
 \f
 (define (guix-repl . args)
   (define opts
-    ;; Return the list of package names.
     (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (G_ "~A: unrecognized option~%") name))
                 (lambda (arg result)
-                  (leave (G_ "~A: extraneous argument~%") arg))
+                  (alist-cons 'scripts
+                              (cons arg (cdr (assq 'scripts result)))
+                              result))
                 %default-options))
 
   (define user-config
@@ -148,29 +153,42 @@ call THUNK."
            (lambda (home)
              (string-append home "/.guile"))))
 
+  (define (set-user-module)
+    (set-current-module user-module)
+    (when (and (not (assoc-ref opts 'ignore-dot-guile?))
+               user-config
+               (file-exists? user-config))
+      (load user-config)))
+
   (with-error-handling
-    (let ((type (assoc-ref opts 'type)))
-      (call-with-connection (assoc-ref opts 'listen)
-        (lambda ()
-          (case type
-            ((guile)
-             (save-module-excursion
-              (lambda ()
-                (set-current-module user-module)
-                (when (and (not (assoc-ref opts 'ignore-dot-guile?))
-                           user-config
-                           (file-exists? user-config))
-                  (load user-config))
-
-                ;; Do not exit repl on SIGINT.
-                ((@@ (ice-9 top-repl) call-with-sigint)
-                 (lambda ()
-                   (start-repl))))))
-            ((machine)
-             (machine-repl))
-            (else
-             (leave (G_ "~a: unknown type of REPL~%") type))))))))
-
-;; Local Variables:
-;; eval: (put 'call-with-connection 'scheme-indent-function 1)
-;; End:
+    (let ((scripts (reverse (assoc-ref opts 'scripts))))
+
+      (for-each (lambda (script)
+                  (save-module-excursion
+                   (lambda ()
+                     (set-user-module)
+                     (load script))))
+                scripts)
+
+      (when (null? scripts)
+        (let ((type (assoc-ref opts 'type)))
+          (call-with-connection (assoc-ref opts 'listen)
+            (lambda ()
+              (case type
+                ((guile)
+                 (save-module-excursion
+                  (lambda ()
+                    (set-user-module)
+                    ;; Do not exit repl on SIGINT.
+                    ((@@ (ice-9 top-repl) call-with-sigint)
+                     (lambda ()
+                       (start-repl))))))
+                ((machine)
+                 (machine-repl))
+                (else
+                 (leave (G_ "~a: unknown type of REPL~%") type)))))))))
+
+  ;; Local Variables:
+  ;; eval: (put 'call-with-connection 'scheme-indent-function 1)
+  ;; End:
+  )
-- 
2.26.2