gexp: Add '=>' syntax to import computed modules.

* guix/gexp.scm (imported-files)[file-pair]: Add case for pairs where
the cdr is not a string.
(imported-modules): Support '=>' syntax in MODULES.
* tests/gexp.scm ("imported-files with file-like objects")
("gexp->derivation & with-imported-module & computed module"): New tests.
* doc/guix.texi (G-Expressions): Document '=>' syntax for
'with-imported-modules'.

1 files changed, 16 insertions, 2 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 78bf03de9e..2e70848e55 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4347,8 +4347,22 @@ of the @code{gexp?} type (see below.)
 
 @deffn {Scheme Syntax} with-imported-modules @var{modules} @var{body}@dots{}
 Mark the gexps defined in @var{body}@dots{} as requiring @var{modules}
-in their execution environment.  @var{modules} must be a list of Guile
-module names, such as @code{'((guix build utils) (guix build gremlin))}.
+in their execution environment.
+
+Each item in @var{modules} can be the name of a module, such as
+@code{(guix build utils)}, or it can be a module name, followed by an
+arrow, followed by a file-like object:
+
+@example
+`((guix build utils)
+  (guix gcrypt)
+  ((guix config) => ,(scheme-file "config.scm"
+                                  #~(define-module @dots{}))))
+@end example
+
+@noindent
+In the example above, the first two modules are taken from the search
+path, and the last one is created from the given file-like object.
 
 This form has @emph{lexical} scope: it has an effect on the gexps
 directly defined in @var{body}@dots{}, but not on those defined, say, in