From 97d615b1761c2054561057f6b56e2a0caed13aa4 Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Sat, 24 Apr 2021 06:43:46 +0100
Subject: inferior: Support querying package replacements.

I'm looking at this to help with adding support for looking up package
replacements to store in the Guix Data Service.

* guix/inferior.scm (inferior-package-replacement): New procedure.
* tests/inferior.scm ("inferior-package-replacement"): New test.
---
 guix/inferior.scm  | 22 ++++++++++++++++++++++
 tests/inferior.scm | 20 ++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/guix/inferior.scm b/guix/inferior.scm
index eb457f81f9..7c8e478f2a 100644
--- a/guix/inferior.scm
+++ b/guix/inferior.scm
@@ -90,6 +90,7 @@ (define-module (guix inferior)
             inferior-package-native-search-paths
             inferior-package-transitive-native-search-paths
             inferior-package-search-paths
+            inferior-package-replacement
             inferior-package-provenance
             inferior-package-derivation
 
@@ -462,6 +463,27 @@ (define inferior-package-search-paths
 (define inferior-package-transitive-native-search-paths
   (cut %inferior-package-search-paths <> 'package-transitive-native-search-paths))
 
+(define (inferior-package-replacement package)
+  "Return the replacement for PACKAGE.  This will either be an inferior
+package, or #f."
+  (match (inferior-package-field
+          package
+          '(compose (match-lambda
+                      ((? package? package)
+                       (let ((id (object-address package)))
+                         (hashv-set! %package-table id package)
+                         (list id
+                               (package-name package)
+                               (package-version package))))
+                      (#f #f))
+                    package-replacement))
+    (#f #f)
+    ((id name version)
+     (inferior-package (inferior-package-inferior package)
+                       name
+                       version
+                       id))))
+
 (define (inferior-package-provenance package)
   "Return a \"provenance sexp\" for PACKAGE, an inferior package.  The result
 is similar to the sexp returned by 'package-provenance' for regular packages."
diff --git a/tests/inferior.scm b/tests/inferior.scm
index f227e0b749..9992077cb2 100644
--- a/tests/inferior.scm
+++ b/tests/inferior.scm
@@ -26,6 +26,7 @@ (define-module (test-inferior)
   #:use-module (gnu packages)
   #:use-module (gnu packages bootstrap)
   #:use-module (gnu packages guile)
+  #:use-module (gnu packages sqlite)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-64)
@@ -260,6 +261,25 @@ (define result
          (list (inferior-package-derivation %store guile "x86_64-linux")
                (inferior-package-derivation %store guile "armhf-linux")))))
 
+(unless (package-replacement sqlite)
+  (test-skip 1))
+
+(test-equal "inferior-package-replacement"
+  (package-derivation %store
+                      (package-replacement sqlite)
+                      "x86_64-linux")
+  (let* ((inferior (open-inferior %top-builddir
+                                  #:command "scripts/guix"))
+         (packages (inferior-packages inferior)))
+    (match (lookup-inferior-packages inferior
+                                     (package-name sqlite)
+                                     (package-version sqlite))
+      ((inferior-sqlite rest ...)
+       (inferior-package-derivation %store
+                                    (inferior-package-replacement
+                                     inferior-sqlite)
+                                    "x86_64-linux")))))
+
 (test-equal "inferior-package->manifest-entry"
   (manifest-entry->list (package->manifest-entry
                          (first (find-best-packages-by-name "guile" #f))))
-- 
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