packages: 'package-input-rewriting/spec' can rewrite implicit dependencies.

With this change, '--with-input', '--with-graft', etc. also apply to
implicit dependencies.  Thus, it's now possible to do:

  guix build python-itsdangerous --with-input=python-wrapper=python@2

or:

  guix build hello --with-graft=glibc=glibc@2.29

Additionally, before, implicit inputs were not rewritten, which could
lead to duplicates in the output of 'bag-transitive-inputs' (packages
that are not 'eq?' but lead to the same derivation).  This in turn would
lead to unnecessary rebuilds when using '--with-input' & co.  This
change fixes it by ensuring even implicit inputs are rewritten.

Fixes <https://bugs.gnu.org/42156>.

* guix/packages.scm (package-input-rewriting/spec): Add #:deep?
defaulting to #true, and pass it to 'package-mapping'.
[replacement-property]: New variable.
[rewrite]: Check that property and set it on the result of PROC.
[cut?]: New procedure.
* tests/packages.scm ("package-input-rewriting/spec"): Ensure implicit
inputs were unchanged.
("package-input-rewriting/spec, partial match"): Pass #:deep? #f.
("package-input-rewriting/spec, deep")
("package-input-rewriting/spec, no duplicates"): New tests.
(package/inherit): Move before use.
* tests/guix-build.sh: Add tests.
* tests/scripts-build.scm ("options->transformation, with-graft"):
Compare dependencies by package name or derivation file name.
* doc/guix.texi (Defining Packages): Adjust accordingly.

1 files changed, 11 insertions, 0 deletions

diff --git a/tests/guix-build.sh b/tests/guix-build.sh
index 6c08857358..ec2f736ccb 100644
--- a/tests/guix-build.sh
+++ b/tests/guix-build.sh
@@ -259,6 +259,17 @@ drv1=`guix build guile -d`
 drv2=`guix build guile --with-input=gimp=ruby -d`
 test "$drv1" = "$drv2"
 
+# See <https://bugs.gnu.org/42156>.
+drv1=`guix build glib -d`
+drv2=`guix build glib -d --with-input=libreoffice=inkscape`
+test "$drv1" = "$drv2"
+
+# Rewriting implicit inputs.
+drv1=`guix build hello -d`
+drv2=`guix build hello -d --with-input=gcc=gcc-toolchain`
+test "$drv1" != "$drv2"
+guix gc -R "$drv2" | grep `guix build -d gcc-toolchain`
+
 if guix build guile --with-input=libunistring=something-really-silly
 then false; else true; fi