Introduce new function lm-package-requires

* lisp/emacs-lisp/package.el (package--prepare-dependencies): Move
from here...
* lisp/emacs-lisp/lisp-mnt.el (lm--prepare-package-dependencies):
...to here.
(lm-package-requires): New function.
(package-buffer-info): Use above new function.
* test/lisp/emacs-lisp/lisp-mnt-tests.el
(lm--tests-lm-package-requires): New test.

3 files changed, 54 insertions, 23 deletions

diff --git a/lisp/emacs-lisp/lisp-mnt.el b/lisp/emacs-lisp/lisp-mnt.el
index cb7cff43555..2c7c6816e9c 100644
--- a/lisp/emacs-lisp/lisp-mnt.el
+++ b/lisp/emacs-lisp/lisp-mnt.el
@@ -434,6 +434,38 @@ This can be found in an RCS or SCCS header."
              header-max t)
             (match-string-no-properties 1)))))))
 
+(defun lm--prepare-package-dependencies (deps)
+  "Turn DEPS into an acceptable list of dependencies.
+
+Any parts missing a version string get a default version string
+of \"0\" (meaning any version) and an appropriate level of lists
+is wrapped around any parts requiring it."
+  (cond
+   ((not (listp deps))
+    (error "Invalid requirement specifier: %S" deps))
+   (t (mapcar (lambda (dep)
+                (cond
+                 ((symbolp dep) `(,dep "0"))
+                 ((stringp dep)
+                  (error "Invalid requirement specifier: %S" dep))
+                 ((and (listp dep) (null (cdr dep)))
+                  (list (car dep) "0"))
+                 (t dep)))
+              deps))))
+
+(declare-function package-read-from-string "package" (str))
+
+(defun lm-package-requires (&optional file)
+  "Return dependencies listed in file FILE, or current buffer if FILE is nil.
+The return value is a list of elements of the form (PACKAGE VERSION)
+where PACKAGE is the package name (a symbol) and VERSION is the
+package version (a string)."
+  (require 'package)
+  (lm-with-file file
+    (and-let* ((require-lines (lm-header-multiline "package-requires")))
+      (lm--prepare-package-dependencies
+       (package-read-from-string (mapconcat #'identity require-lines " "))))))
+
 (defun lm-keywords (&optional file)
   "Return the keywords given in file FILE, or current buffer if FILE is nil.
 The return is a `downcase'-ed string, or nil if no keywords
diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index bed6e74c921..0e21f57fc3f 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -1149,27 +1149,8 @@ Signal an error if the entire string was not used."
                (error "Can't read whole string"))
       (end-of-file expr))))
 
-(defun package--prepare-dependencies (deps)
-  "Turn DEPS into an acceptable list of dependencies.
-
-Any parts missing a version string get a default version string
-of \"0\" (meaning any version) and an appropriate level of lists
-is wrapped around any parts requiring it."
-  (cond
-   ((not (listp deps))
-    (error "Invalid requirement specifier: %S" deps))
-   (t (mapcar (lambda (dep)
-                (cond
-                 ((symbolp dep) `(,dep "0"))
-                 ((stringp dep)
-                  (error "Invalid requirement specifier: %S" dep))
-                 ((and (listp dep) (null (cdr dep)))
-                  (list (car dep) "0"))
-                 (t dep)))
-              deps))))
-
 (declare-function lm-header "lisp-mnt" (header))
-(declare-function lm-header-multiline "lisp-mnt" (header))
+(declare-function lm-package-requires "lisp-mnt" (header))
 (declare-function lm-website "lisp-mnt" (&optional file))
 (declare-function lm-keywords-list "lisp-mnt" (&optional file))
 (declare-function lm-maintainers "lisp-mnt" (&optional file))
@@ -1212,9 +1193,7 @@ boundaries."
            (error "Package lacks a \"Version\" or \"Package-Version\" header")))
       (package-desc-from-define
        file-name pkg-version desc
-       (and-let* ((require-lines (lm-header-multiline "package-requires")))
-         (package--prepare-dependencies
-          (package-read-from-string (mapconcat #'identity require-lines " "))))
+       (lm-package-requires)
        :kind 'single
        :url website
        :keywords keywords
diff --git a/test/lisp/emacs-lisp/lisp-mnt-tests.el b/test/lisp/emacs-lisp/lisp-mnt-tests.el
index c056761f0f9..1418abf221f 100644
--- a/test/lisp/emacs-lisp/lisp-mnt-tests.el
+++ b/test/lisp/emacs-lisp/lisp-mnt-tests.el
@@ -30,6 +30,26 @@
                  '(("Bob Weiner" . "rsw@gnu.org")
                    ("Mats Lidell" . "matsl@gnu.org")))))
 
+(ert-deftest lm--tests-lm-package-requires ()
+  (with-temp-buffer
+    (insert ";; Package-Requires: ((emacs 29.1))")
+    (should (equal (lm-package-requires) '((emacs 29.1)))))
+  (with-temp-buffer
+    (insert ";; Package-Requires: ((emacs \"26.3\") (jsonrpc \"1.0.16\") (flymake \"1.2.1\") (project \"0.9.8\") (xref \"1.6.2\") (eldoc \"1.14.0\") (seq \"2.23\") (external-completion \"0.1\"))")
+    (should (equal (lm-package-requires)
+                   '((emacs "26.3") (jsonrpc "1.0.16") (flymake "1.2.1")
+                     (project "0.9.8") (xref "1.6.2") (eldoc "1.14.0")
+                     (seq "2.23") (external-completion "0.1")))))
+  (with-temp-buffer
+    (insert ";; Package-Requires: ((emacs \"26.3\") (jsonrpc \"1.0.16\") (flymake \"1.2.1\")\n"
+            ";;                    (project \"0.9.8\") (xref \"1.6.2\") (eldoc \"1.14.0\")\n"
+            ";;                    (seq \"2.23\") (external-completion \"0.1\"))")
+    (should (equal (lm-package-requires)
+                   '((emacs "26.3") (jsonrpc "1.0.16") (flymake "1.2.1")
+                     (project "0.9.8") (xref "1.6.2") (eldoc "1.14.0")
+                     (seq "2.23") (external-completion "0.1"))))))
+
+
 (ert-deftest lm--tests-lm-website ()
   (with-temp-buffer
     (insert ";; URL: https://example.org/foo")