[bug#51319] [PATCH 1/2] build-system/julia: Enable Julia Pkg to find installed packages

[Jean-Baptiste Volatier]

* guix/build/julia-build-system.scm (link-depot): New phase.
Julia built-in package manager (Pkg) looks for packages in
JULIA_DEPOT_PATH/packages/PACKAGENAME/XXXX where XXXX is
a string encoding package UUID and SHA1 of files.
The link-depot phase creates a link at the correct location
to allow Pkg to find packages that were already installed by
Guix.
(%package-path): modified package path from packages/ to
loadpath/
(project.toml->uuid): retrive package uuid from TOML file

* gnu/packages/julia-xyz.scm: correct paths to reflect
change of %package-path

* gnu/packages/julia.scm: correct paths to reflect change of
%package-path
---
 gnu/packages/julia-xyz.scm        |  2 +-
 gnu/packages/julia.scm            |  2 +-
 guix/build/julia-build-system.scm | 46 ++++++++++++++++++++++++++++---
 3 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/gnu/packages/julia-xyz.scm b/gnu/packages/julia-xyz.scm
index c1ebc0fba1..1e407a2277 100644
--- a/gnu/packages/julia-xyz.scm
+++ b/gnu/packages/julia-xyz.scm
@@ -4610,7 +4610,7 @@ (define-public julia-uris
            (lambda* (#:key source outputs #:allow-other-keys)
              (let ((out (assoc-ref outputs "out")))
                (chdir
-                (string-append out "/share/julia/packages/URIs/test")))
+                (string-append out "/share/julia/loadpath/URIs/test")))
              #t)))))
     ;; required for tests
     (inputs `(("julia-json" ,julia-json)))
diff --git a/gnu/packages/julia.scm b/gnu/packages/julia.scm
index 411f2e2e10..5b9bf91ed6 100644
--- a/gnu/packages/julia.scm
+++ b/gnu/packages/julia.scm
@@ -673,7 +673,7 @@ (define-public julia
     (native-search-paths
       (list (search-path-specification
               (variable "JULIA_LOAD_PATH")
-              (files (list "share/julia/packages/")))
+              (files (list "share/julia/loadpath/")))
             (search-path-specification
               (variable "JULIA_DEPOT_PATH")
               (files (list "share/julia/")))))
diff --git a/guix/build/julia-build-system.scm 
b/guix/build/julia-build-system.scm
index d74acf2a05..c7f2119974 100644
--- a/guix/build/julia-build-system.scm
+++ b/guix/build/julia-build-system.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2019, 2020 Nicolò Balzarotti <nicolo@nixo.xyz>
+;;; Copyright © 2021 Jean-Baptiste Volatier <jbv@pm.me>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -20,10 +21,13 @@
 (define-module (guix build julia-build-system)
   #:use-module ((guix build gnu-build-system) #:prefix gnu:)
   #:use-module (guix build utils)
+  #:use-module (rnrs io ports)
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
   #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 popen)
   #:export (%standard-phases
+            %package-path
             julia-create-package-toml
             julia-build))

@@ -37,7 +41,7 @@ (define (invoke-julia code)
   (invoke "julia" "-e" code))

 ;; subpath where we store the package content
-(define %package-path "/share/julia/packages/")
+(define %package-path "/share/julia/loadpath/")

 (define (project.toml->name file)
   "Look for Julia package name in the TOML file FILE (usually named
@@ -51,6 +55,18 @@ (define (project.toml->name file)
               (if m (match:substring m 1)
                   (loop (read-line in 'concat)))))))))

+(define (project.toml->uuid file)
+  "Look for Julia package uuid in the TOML file FILE (usually named
+Project.toml)."
+  (call-with-input-file file
+    (lambda (in)
+      (let loop ((line (read-line in 'concat)))
+        (if (eof-object? line)
+            #f
+            (let ((m (string-match "uuid\\s*=\\s*\"(.*)\"" line)))
+              (if m (match:substring m 1)
+                  (loop (read-line in 'concat)))))))))
+
 (define* (install #:key source inputs outputs julia-package-name
                   #:allow-other-keys)
   (let* ((out (assoc-ref outputs "out"))
@@ -73,7 +89,7 @@ (define* (precompile #:key source inputs outputs 
julia-package-name
     (setenv "JULIA_DEPOT_PATH" builddir)
     ;; Add new package dir to the load path.
     (setenv "JULIA_LOAD_PATH"
-            (string-append builddir "packages/" ":"
+            (string-append builddir "loadpath/" ":"
                            (or (getenv "JULIA_LOAD_PATH")
                                "")))
     ;; Actual precompilation:
@@ -97,15 +113,36 @@ (define* (check #:key tests? source inputs outputs 
julia-package-name
       (setenv "SOURCE_DATE_EPOCH" "1")
       (setenv "JULIA_DEPOT_PATH" builddir)
       (setenv "JULIA_LOAD_PATH"
-              (string-append builddir "packages/" ":"
+              (string-append builddir "loadpath/" ":"
                              (or (getenv "JULIA_LOAD_PATH")
                                  "")))
       (setenv "HOME" "/tmp")
       (invoke "julia" "--depwarn=yes"
-              (string-append builddir "packages/"
+              (string-append builddir "loadpath/"
                              package "/test/runtests.jl"))))
   #t)

+(define* (link-depot #:key source inputs outputs julia-package-name
+                     #:allow-other-keys)
+  (let* ((out (assoc-ref outputs "out"))
+         (package-name (or
+                        julia-package-name
+                        (project.toml->name "Project.toml")))
+         (package-dir (string-append out %package-path package-name))
+         (uuid (project.toml->uuid "Project.toml"))
+         (pipe (open-pipe* OPEN_READ "julia" "-e"
+                           (format #f "using Pkg;
+println(Base.version_slug(Base.UUID(\"~a\"),
+                          Base.SHA1(Pkg.GitTools.tree_hash(\".\"))))" uuid 
package-dir)))
+         (slug (string-trim-right (get-string-all pipe))))
+    ;; When installing a package, julia looks first at in the JULIA_DEPOT_PATH
+    ;; for a path like packages/PACKAGE/XXXX
+    ;; Where XXXX is a slug encoding the package UUID and SHA1 of the files
+    ;; Here we create a link with the correct path to enable julia to find the 
package
+    (mkdir-p (string-append out "/share/julia/packages/" package-name))
+    (symlink package-dir (string-append out "/share/julia/packages/" 
package-name "/" slug)))
+  #t)
+
 (define (julia-create-package-toml outputs source
                                    name uuid version
                                    deps)
@@ -138,6 +175,7 @@ (define %standard-phases
     (delete 'check) ; tests must be run after installation
     (replace 'install install)
     (add-after 'install 'precompile precompile)
+    (add-after 'unpack 'link-depot link-depot)
     (add-after 'install 'check check)
     ;; TODO: In the future we could add a "system-image-generation" phase
     ;; where we use PackageCompiler.jl to speed up package loading times
--
2.33.1