Subject: Re: [PATCH] build-system: emacs: Add generation of -pkg.el files.

From: Liliana Marie Prikler <[email-masked]>
Date: Fri, 14 Jan 2022 21:56:56 +0100

Hi Andrew,

Am Donnerstag, dem 09.12.2021 um 12:01 +0300 schrieb Andrew Tropin:
> 
> * guix/build/emacs-build-system.scm (%default-exclude): Add
> generation of
> -pkg.el files for packages, which do not provide them.
> ---
> Implemented phase, which generates -pkg.el from comments in library
> file.  The solution for finding main el file of the package is a
> little hacky, because package name isn't available build time.
> 
> I took a part of the elisp implementation from melpa source code.
> https://github.com/melpa/melpa/blob/master/package-build/package-build.el#L553
As promised, I took a deeper look at your patch.  As already noted,
there were some clean-up actions I had to perform, such as keeping to
our line limit (it was not easy, I tell you) among other things.  Also,
confusingly, your condition-case code did not handle errors and wrong
handling of the version field blew up everything for me.  Did you test
this code?

In any case, attached is my revised patch.  I so far only checked it
with emacs-olivetti -- a package whose description is missing in
current Guix Emacs.  I'll give everyone some time to test things before
pushing this however; I don't want to break a bunch of Emacs packages
scattered around various files.

Cheers
From 9fa6a09a131cfe436ca053c960ed9625263bc650 Mon Sep 17 00:00:00 2001
From: Andrew Tropin <[email-masked]>
Date: Thu, 9 Dec 2021 12:01:46 +0300
Subject: [PATCH] build-system: emacs: Ensure that package descriptions are
 generated.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This patch addresses the second part of <https://bugs.gnu.org/48331>.
While existing -pkg.el files were previously installed, no such files
were generated for packages lacking them, resulting in packages not
being listed as installed and not being available towards
“describe-package”.

* guix/build/emacs-build-system.scm (find-root-library-file)
(ensure-package-description): New variables.
(%standard-phases): Add ‘ensure-package-description’.
---
 guix/build/emacs-build-system.scm | 77 ++++++++++++++++++++++++++++++-
 1 file changed, 76 insertions(+), 1 deletion(-)

diff --git a/guix/build/emacs-build-system.scm b/guix/build/emacs-build-system.scm
index ab77e57f33..58d2a9b9f4 100644
--- a/guix/build/emacs-build-system.scm
+++ b/guix/build/emacs-build-system.scm
@@ -140,6 +140,79 @@ (define (substitute-program-names)
           (substitute-program-names))))
     #t))
 
+(define (find-root-library-file name)
+  (let loop ((parts (string-split
+                     (package-name-version->elpa-name-version name) #\-))
+             (candidate ""))
+    (cond
+     ;; at least one version part is given, so we don't terminate "early"
+     ((null? parts) #f)
+     ((string-null? candidate) (loop (cdr parts) (car parts)))
+     ((file-exists? (string-append candidate ".el")) candidate)
+     (else
+      (loop (cdr parts) (string-append candidate "-" (car parts)))))))
+
+(define* (ensure-package-description #:key outputs #:allow-other-keys)
+  (define (write-pkg-file name)
+    (define summary-regexp
+      "^;;; [^ ]*\\.el ---[ \t]*\\(.*?\\)[ \t]*\\(-\\*-.*-\\*-[ \t]*\\)?$")
+    (define %write-pkg-file-form
+      `(progn
+        (require 'lisp-mnt)
+        (require 'package)
+
+        (defun build-package-desc-from-library (name)
+          (package-desc-from-define
+           name
+           ;; Workaround for malformed version string (for example "24 (beta)"
+           ;; in paredit.el), try to parse version obtained by lm-version,
+           ;; before trying to create package-desc.  Otherwis the whole process
+           ;; of generation -pkg.el will fail.
+           (condition-case
+            nil
+            (let ((version (lm-version)))
+              ;; raises an error if version is invalid
+              (and (version-to-list version) version))
+            (error "0.0.0"))
+           (or (save-excursion
+                (goto-char (point-min))
+                (and (re-search-forward ,summary-regexp nil t)
+                     (match-string-no-properties 1)))
+               package--default-summary)
+           (let ((require-lines (lm-header-multiline "package-requires")))
+             (and require-lines
+                  (package--prepare-dependencies
+                   (package-read-from-string
+                    (mapconcat 'identity require-lines " ")))))
+           :kind       'single
+           :url        (lm-homepage)
+           :keywords   (lm-keywords-list)
+           :maintainer (lm-maintainer)
+           :authors    (lm-authors)))
+
+        (defun generate-package-description-file (name)
+          (package-generate-description-file
+           (build-package-desc-from-library name)
+           (concat name "-pkg.el")))
+
+        (condition-case
+         err
+         (let ((name (file-name-base (buffer-file-name))))
+           (generate-package-description-file name)
+           (message (concat name "-pkg.el file generated.")))
+         (error
+          (message "There are some errors during generation of -pkg.el file:")
+          (message "%s" (error-message-string err))))))
+
+    (unless (file-exists? (string-append name "-pkg.el"))
+      (emacs-batch-edit-file (string-append name ".el")
+        %write-pkg-file-form)))
+
+  (let* ((out (assoc-ref outputs "out"))
+         (elpa-name-ver (store-directory->elpa-name-version out)))
+    (with-directory-excursion (elpa-directory out)
+      (and=> (find-root-library-file elpa-name-ver) write-pkg-file))))
+
 (define* (check #:key tests? (test-command '("make" "check"))
                 (parallel-tests? #t) #:allow-other-keys)
   "Run the tests by invoking TEST-COMMAND.
@@ -279,8 +352,10 @@ (define %standard-phases
     (add-after 'make-autoloads 'enable-autoloads-compilation
       enable-autoloads-compilation)
     (add-after 'enable-autoloads-compilation 'patch-el-files patch-el-files)
+    (add-after 'patch-el-files 'ensure-package-description
+      ensure-package-description)
     ;; The .el files are byte compiled directly in the store.
-    (add-after 'patch-el-files 'build build)
+    (add-after 'ensure-package-description 'build build)
     (add-after 'build 'validate-compiled-autoloads validate-compiled-autoloads)
     (add-after 'validate-compiled-autoloads 'move-doc move-doc)))
 
-- 
2.34.0