Dissolve -util in favor of -mode and new -exec

The lean4-exec.el feature has been written from scratch.  Its logic is
simple: For Elan, Lake and Lean respectively, there is a hook of
functions which may return a path to the respective program.  Well,
there are some more details to it but its great at being minimalist
but scalable.

lean4-exec.el

@@ -0,0 +1,204 @@
+;;; lean4-exec.el --- Lean4-Mode Executable Location  -*- lexical-binding: t; -*-
+
+;; Copyright (c) 2024 Mekeor Melire
+
+;; This file is not part of GNU Emacs.
+
+;; Licensed under the Apache License, Version 2.0 (the "License"); you
+;; may not use this file except in compliance with the License.  You
+;; may obtain a copy of the License at
+;;
+;;     http://www.apache.org/licenses/LICENSE-2.0
+;;
+;; Unless required by applicable law or agreed to in writing, software
+;; distributed under the License is distributed on an "AS IS" BASIS,
+;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+;; implied.  See the License for the specific language governing
+;; permissions and limitations under the License.
+
+;;; Commentary:
+
+;; TODO
+
+;;; Code:
+
+;;;; Elan
+
+(defcustom lean4-exec-elan-base "elan"
+  "Basename of Elan executable (without suffixes, if any)."
+  :group 'lean4-exec
+  :type 'string)
+
+(defvar-local lean4-exec-elan-full nil
+  "Full name of Elan executable.
+
+It may be nil in which case Elan won't be used.  Otherwise it should be
+a list of strings, for example:
+
+    (\"docker\" \"compose\" \"ubuntu\" \"exec\" \"elan\")
+
+Member strings should not be quoted.  Consumers of this variable are
+expected to quote as needed, e.g. by using `combine-and-quote-strings'
+if necessary.")
+
+(defun lean4-exec-elan-executable-find ()
+  "Attempt to find Elan executable with `executable-find'."
+  (declare (side-effect-free t))
+  (ensure-list (executable-find lean4-exec-elan-base)))
+
+(defcustom lean4-exec-elan-hook
+  (list #'lean4-exec-elan-executable-find)
+  "Hook of functions to determine `lean4-exec-elan-full'.
+
+This hook is called from `lean4-exec-elan-init'.  Each member function
+represents a certain method of determining a value suitable for
+`lean4-exec-elan-full', which see.  If it does not find such a value, it
+should return nil.  It should probably use `lean4-exec-elan-base' (and
+maybe `executable-binary-suffixes') instead of a hard-coded basename for
+the Elan executable."
+  :group 'lean4-exec
+  :options '(lean4-exec-elan-executable-find)
+  :type 'hook)
+
+(defun lean4-exec-elan-init ()
+  "Buffer-locally set up `lean4-exec-elan-full'.
+
+Call functions from `lean4-exec-elan-hook' until one succeeds,
+i.e. returns non-nil.  `lean4-exec-elan-full' is then buffer-locally set
+to this value."
+  (setq-local lean4-exec-elan-full
+              (run-hook-with-args-until-success
+               'lean4-exec-elan-hook)))
+
+;;;; Lake
+
+(defcustom lean4-exec-lake-base "lake"
+  "Basename of Lake executable (without suffixes, if any)."
+  :group 'lean4-exec
+  :type 'string)
+
+(defvar-local lean4-exec-lake-full nil
+  "Full name of Lake executable.
+
+It may be nil in which case Lake won't be used.  Otherwise it should be
+a list of strings, for example:
+
+    (\"docker\" \"compose\" \"ubuntu\" \"exec\" \"lake\")
+
+Member strings should not be quoted.  Consumers of this variable are
+expected to quote as needed, e.g. by using `combine-and-quote-strings'
+if necessary.")
+
+(defun lean4-exec-lake-elan-which ()
+  "When `lean4-exec-elan-full', then attemp to find Lake with Elan."
+  (declare (side-effect-free t))
+  (when lean4-exec-elan-full
+    (ignore-errors
+      ;; This assumes that "elan which lake" outputs only a single
+      ;; line and a final newline.  In particular it assumes that the
+      ;; path to the Lake executable does not contain newlines.
+      (apply #'process-lines
+             (append lean4-exec-elan-full '("which" "lake"))))))
+
+(defun lean4-exec-lake-executable-find ()
+  "Attempt to find Lake executable with `executable-find'."
+  (declare (side-effect-free t))
+  (ensure-list (executable-find lean4-exec-lake-base)))
+
+(defcustom lean4-exec-lake-hook
+  (list
+   #'lean4-exec-lake-elan-which
+   #'lean4-exec-lake-executable-find)
+  "Hook of functions to determine `lean4-exec-lake-full'.
+
+This hook is called from `lean4-exec-lake-init'.  Each member function
+represents a certain method of determining a value suitable for
+`lean4-exec-lake-full', which see.  If it does not find such a value, it
+should return nil.  It should probably use `lean4-exec-lake-base' (and
+maybe `executable-binary-suffixes') instead of a hard-coded basename for
+the Lake executable."
+  :group 'lean4-exec
+  :options '(lean4-exec-lake-executable-find)
+  :type 'hook)
+
+(defun lean4-exec-lake-init ()
+  "Buffer-locally set up `lean4-exec-lake-full'.
+
+Call functions from `lean4-exec-lake-hook' until one succeeds,
+i.e. returns non-nil.  `lean4-exec-lake-full' is then buffer-locally set
+to this value."
+  (setq-local lean4-exec-lake-full
+              (run-hook-with-args-until-success
+               'lean4-exec-lake-hook)))
+
+;;;; Lean
+
+(defcustom lean4-exec-lean-base "lean"
+  "Basename of Lean4 executable (without suffixes, if any)."
+  :group 'lean4-exec
+  :type 'string)
+
+(defvar-local lean4-exec-lean-full nil
+  "Full name of Lean4 executable (without suffixes, if any).
+
+It should be a list of strings, e.g. (\"lake\" \"lean\").  Each string
+should not be shell-quoted; consumers of this variable
+should apply `shell-quote-argument' when necessary.")
+
+(defun lean4-exec-lean-getenv ()
+  "Attempt to find Lean4 executable per `LEAN' environment variable."
+  (declare (side-effect-free t))
+  (ensure-list (getenv "LEAN")))
+
+(defun lean4-exec-lean-elan-which ()
+  "When `lean4-exec-elan-full', then attemp to find Lean with Elan."
+  (declare (side-effect-free t))
+  (when lean4-exec-elan-full
+    (ignore-errors
+      ;; This assumes that "elan which lean" outputs only a single
+      ;; line and a final newline.  In particular it assumes that the
+      ;; path to the Lean executable does not contain newlines.
+      (apply #'process-lines
+             (append lean4-exec-elan-full '("which" "lean"))))))
+
+(defun lean4-exec-lean-lake ()
+  "When `lean4-exec-lake-full', return `lean' as its subcommand."
+  (declare (side-effect-free error-free))
+  (when lean4-exec-lake-full
+    (append lean4-exec-lake-full
+            ;; We do not use `lean4-exec-lean-base' here because a
+            ;; user could have set it to "lean4" but Lake only accepts
+            ;; "lean" as subcommand.
+            '("lake"))))
+
+(defcustom lean4-exec-lean-hook
+  (list
+   #'lean4-exec-lean-getenv
+   #'lean4-exec-lean-elan-which
+   #'lean4-exec-lean-lake)
+  "Hook of functions to determine `lean4-exec-lean-full'.
+
+This hook is called from `lean4-exec-lean-init'.  Each member function
+represents a certain method of determining a value suitable for
+`lean4-exec-lean-full', which see.  If it does not find such a value, it
+should return nil.  It should probably use `lean4-exec-lean-base' (and
+maybe `executable-binary-suffixes') instead of a hard-coded basename for
+the Lean4 executable."
+  :group 'lean4-exec
+  :options '(lean4-exec-lean-getenv
+             lean4-exec-lean-elan-which
+             lean4-exec-lean-lake)
+  :type 'hook)
+
+(defun lean4-exec-lean-init ()
+  "Buffer-locally set up `lean4-exec-lean-full'.
+
+Call functions from `lean4-exec-lean-hook' until one succeeds,
+i.e. returns non-nil.  `lean4-exec-lean-full' is then buffer-locally set
+to this value."
+  (setq-local lean4-exec-lean-full
+              (run-hook-with-args-until-success
+               'lean4-exec-lean-hook)))
+
+(provide 'lean4-exec)
+;;; lean4-exec.el ends here