emacsql-pg: Require recent pg and disable on older Emacs releases

Makefile

@@ -19,6 +19,7 @@ TEST_ELS += tests/emacsql-tests.el
 TEST_ELCS = $(TEST_ELS:.el=.elc)
 
 DEPS  = pg
+DEPS += peg
 DEPS += sqlite3
 
 EMACS      ?= emacs

emacsql-pg.el

@@ -7,21 +7,24 @@
 ;; Homepage: https://github.com/magit/emacsql
 
 ;; Package-Version: 3.1.1.50-git
-;; Package-Requires: ((emacs "25.1") (emacsql "20230220") (pg "0.16"))
+;; Package-Requires: ((emacs "28.1") (emacsql "20240623") (pg "0.37"))
 ;; SPDX-License-Identifier: Unlicense
 
 ;;; Commentary:
 
 ;; This library provides an EmacSQL back-end for PostgreSQL, which
-;; uses the `pg' package to directly speak to the database.
+;; uses the `pg' package to directly speak to the database.  This
+;; library requires at least Emacs 28.1.
 
 ;; (For an alternative back-end for PostgreSQL, see `emacsql-psql'.)
 
 ;;; Code:
 
 (require 'emacsql)
 
-(require 'pg nil t)
+(if (>= emacs-major-version 28)
+    (require 'pg nil t)
+  (message "emacsql-pg.el requires Emacs 28.1 or later"))
 (declare-function pg-connect "pg"
                   ( dbname user &optional
                     (password "") (host "localhost") (port 5432) (tls nil)))

tests/emacsql-external-tests.el

@@ -20,10 +20,14 @@
 (require 'emacsql-mysql)
 (require 'emacsql-psql)
 ;; FIXME(CI) Broken and thus disabled in test.yml.
-(if (require 'pg nil t)
-    (require 'emacsql-pg)
-  (message "WARNING: Forgo testing `%s' because `%s' is unavailable"
-           'emacsql-pg 'pg))
+(cond
+ ((< emacs-major-version 28)
+  (message "WARNING: Forgo testing `%s' because it is unsupported on Emacs %s"
+           'emacsql-pg emacs-version))
+ ((require 'pg nil t)
+  (require 'emacsql-pg))
+ ((message "WARNING: Forgo testing `%s' because `%s' is unavailable"
+           'emacsql-pg 'pg)))
 
 (defvar emacsql-tests-timeout 4
   "Be aggressive about not waiting on subprocesses in unit tests.")