@@ -7105,20 +7105,42 @@ optional dependency, you can define a variant that removes that
dependency like so:
@lisp
-(use-modules (gnu packages gdb) ;for 'gdb'
- (srfi srfi-1)) ;for 'alist-delete'
+(use-modules (gnu packages gdb)) ;for 'gdb'
(define gdb-sans-guile
(package
(inherit gdb)
- (inputs (alist-delete "guile"
- (package-inputs gdb)))))
+ (inputs (modify-inputs (package-inputs gdb)
+ (delete "guile")))))
@end lisp
-The @code{alist-delete} call above removes the tuple from the
-@code{inputs} field that has @code{"guile"} as its first element
-(@pxref{SRFI-1 Association Lists,,, guile, GNU Guile Reference
-Manual}).
+The @code{modify-inputs} form above removes the @code{"guile"} package
+from the @code{inputs} field of @code{gdb}. The @code{modify-inputs}
+macro is a helper that can prove useful anytime you want to remove, add,
+or replace package inputs.
+
+@deffn {Scheme Syntax} modify-inputs @var{inputs} @var{clauses}
+Modify the given package inputs, as returned by @code{package-inputs} & co.,
+according to the given clauses. The example below removes the GMP and ACL
+inputs of Coreutils and adds libcap to the back of the input list:
+
+@lisp
+(modify-inputs (package-inputs coreutils)
+ (delete "gmp" "acl")
+ (append libcap))
+@end lisp
+
+The example below replaces the @code{guile} package from the inputs of
+@code{guile-redis} with @code{guile-2.2}:
+
+@lisp
+(modify-inputs (package-inputs guile-redis)
+ (replace "guile" guile-2.2))
+@end lisp
+
+The last type of clause is @code{prepend}, to add inputs to the front of
+the list.
+@end deffn
In some cases, you may find it useful to write functions
(``procedures'', in Scheme parlance) that return a package based on some
@@ -55,6 +55,7 @@
#:re-export (%current-system
%current-target-system
search-path-specification) ;for convenience
+ #:re-export-and-replace (delete) ;used as syntactic keyword
#:export (content-hash
content-hash?
content-hash-algorithm
@@ -113,6 +114,10 @@
lookup-package-propagated-input
lookup-package-direct-input
+ prepend ;syntactic keyword
+ replace ;syntactic keyword
+ modify-inputs
+
package-direct-sources
package-transitive-sources
package-direct-inputs
@@ -923,6 +928,69 @@ otherwise."
otherwise."
(lookup-input (package-direct-inputs package) name))
+(define (inputs-sans-labels inputs)
+ "Return INPUTS stripped of any input labels."
+ (map (match-lambda
+ ((label obj) obj)
+ ((label obj output) `(,obj ,output)))
+ inputs))
+
+(define (replace-input name replacement inputs)
+ "Replace input NAME by REPLACEMENT within INPUTS."
+ (map (lambda (input)
+ (match input
+ (((? string? label) . _)
+ (if (string=? label name)
+ (match replacement ;does REPLACEMENT specify an output?
+ ((_ _) (cons label replacement))
+ (_ (list label replacement)))
+ input))))
+ inputs))
+
+(define-syntax prepend
+ (lambda (s)
+ (syntax-violation 'prepend
+ "'prepend' may only be used within 'modify-inputs'"
+ s)))
+
+(define-syntax replace
+ (lambda (s)
+ (syntax-violation 'replace
+ "'replace' may only be used within 'modify-inputs'"
+ s)))
+
+(define-syntax modify-inputs
+ (syntax-rules (delete prepend append replace)
+ "Modify the given package inputs, as returned by 'package-inputs' & co.,
+according to the given clauses. The example below removes the GMP and ACL
+inputs of Coreutils and adds libcap:
+
+ (modify-inputs (package-inputs coreutils)
+ (delete \"gmp\" \"acl\")
+ (append libcap))
+
+Other types of clauses include 'prepend' and 'replace'."
+ ;; Note: This macro hides the fact that INPUTS, as returned by
+ ;; 'package-inputs' & co., is actually an alist with labels. Eventually,
+ ;; it will operate on list of inputs without labels.
+ ((_ inputs (delete name) clauses ...)
+ (modify-inputs (alist-delete name inputs)
+ clauses ...))
+ ((_ inputs (delete names ...) clauses ...)
+ (modify-inputs (fold alist-delete inputs (list names ...))
+ clauses ...))
+ ((_ inputs (prepend lst ...) clauses ...)
+ (modify-inputs (append (list lst ...) (inputs-sans-labels inputs))
+ clauses ...))
+ ((_ inputs (append lst ...) clauses ...)
+ (modify-inputs (append (inputs-sans-labels inputs) (list lst ...))
+ clauses ...))
+ ((_ inputs (replace name replacement) clauses ...)
+ (modify-inputs (replace-input name replacement inputs)
+ clauses ...))
+ ((_ inputs)
+ inputs)))
+
(define (package-direct-sources package)
"Return all source origins associated with PACKAGE; including origins in
PACKAGE's inputs."