bug#71655: Eshell external commands do not work under GNU Emacs for Windows

[Eli Zaretskii]

> Cc: 71655@debbugs.gnu.org
> Date: Wed, 19 Jun 2024 22:12:34 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
>   (Eshell) $ ls -l 
> C:/Users/MyUser/AppData/Local/Microsoft/WindowsApps/winget.exe
> 
> What do you see?  Does what you see explain the error?
> 
> I think this page explains what is going on:
> 
>   
> https://stackoverflow.com/questions/58296925/what-is-zero-byte-executable-files-in-windows

That being said, both M-! and call-process succeed in invoking this
"program" okay, so there's something Eshell does that gets in the way.
Here's the backtrace from the error:

  Debugger entered--Lisp error: (file-error "Opening input file" "Invalid 
argument" "C:/Users/EliZ/AppData/Local/Microsoft/WindowsApps/winget.exe")
    
insert-file-contents("C:/Users/EliZ/AppData/Local/Microsoft/WindowsApps/winget.exe"
 nil 0 256 nil)
    
insert-file-contents-literally("C:/Users/EliZ/AppData/Local/Microsoft/WindowsApps/winget.exe"
 nil 0 256)
    
eshell-script-interpreter("C:/Users/EliZ/AppData/Local/Microsoft/WindowsApps/winget.exe")
    eshell-find-interpreter("winget" ("--help") nil)
    eshell-connection-local-command("winget" ("--help"))
    eshell-external-command("winget" ("--help"))
    eshell-plain-command("winget" ("--help"))
    eshell-named-command("winget" ("--help"))
    eval((eshell-named-command '"winget" '("--help")))
    eshell-do-eval((eshell-named-command '"winget" '("--help")) nil)
    eshell-do-eval((unwind-protect (eshell-named-command '"winget" '("--help")) 
(mapc #'funcall eshell-this-command-hook)) nil)
    #f(compiled-function () #<bytecode -0x165be7c9ce9ef886>)()
    funcall(#f(compiled-function () #<bytecode -0x165be7c9ce9ef886>))
    (let ((eshell-this-command-hook '(ignore))) (funcall '#f(compiled-function 
() #<bytecode -0x165be7c9ce9ef886>)))
    eval((let ((eshell-this-command-hook '(ignore))) (funcall 
'#f(compiled-function () #<bytecode -0x165be7c9ce9ef886>))))
    eshell-do-eval((let ((eshell-this-command-hook '(ignore))) (unwind-protect 
(eshell-named-command '"winget" '("--help")) (mapc #'funcall 
eshell-this-command-hook))) nil)
    (condition-case err (eshell-do-eval '(let ((eshell-this-command-hook 
'(ignore))) (unwind-protect (eshell-named-command '"winget" '("--help")) (mapc 
#'funcall eshell-this-command-hook))) nil) ((debug error) (eshell-errorn 
(error-message-string err)) (eshell-close-handles 1)))
    eval((condition-case err (eshell-do-eval '(let ((eshell-this-command-hook 
'...)) (unwind-protect (eshell-named-command '"winget" '...) (mapc #'funcall 
eshell-this-command-hook))) nil) ((debug error) (eshell-errorn 
(error-message-string err)) (eshell-close-handles 1))))
    eshell-do-eval((condition-case err (eshell-do-eval '(let 
((eshell-this-command-hook '...)) (unwind-protect (eshell-named-command 
'"winget" '...) (mapc #'funcall eshell-this-command-hook))) nil) ((debug error) 
(eshell-errorn (error-message-string err)) (eshell-close-handles 1))) nil)
    eshell-do-eval((condition-case err (eshell-do-eval '(let 
((eshell-this-command-hook '...)) (unwind-protect (eshell-named-command 
'"winget" '...) (mapc #'funcall eshell-this-command-hook))) nil) ((debug error) 
(eshell-errorn (error-message-string err)) (eshell-close-handles 1))) nil)
    #f(compiled-function () #<bytecode -0x165be7c9ce9ef886>)()
    funcall(#f(compiled-function () #<bytecode -0x165be7c9ce9ef886>))
    (let ((eshell-current-handles '[nil (((t) . 2) t) (((t) . 2) t)])) (funcall 
'#f(compiled-function () #<bytecode -0x165be7c9ce9ef886>)))
    eval((let ((eshell-current-handles '[nil ((... . 2) t) ((... . 2) t)])) 
(funcall '#f(compiled-function () #<bytecode -0x165be7c9ce9ef886>))))
    eshell-do-eval((let ((eshell-current-handles '[nil ((... . 2) t) ((... . 2) 
t)])) (condition-case err (eshell-do-eval '(let ((eshell-this-command-hook 
...)) (unwind-protect (eshell-named-command ... ...) (mapc ... 
eshell-this-command-hook))) nil) ((debug error) (eshell-errorn 
(error-message-string err)) (eshell-close-handles 1)))) nil)
    eshell-do-eval((progn (let ((eshell-current-handles '[nil (... t) (... 
t)])) (condition-case err (eshell-do-eval '(let (...) (unwind-protect ... ...)) 
nil) ((debug error) (eshell-errorn (error-message-string err)) 
(eshell-close-handles 1))))) nil)
    eshell-do-eval((unwind-protect (progn (let ((eshell-current-handles '[nil 
... ...])) (condition-case err (eshell-do-eval '(let ... ...) nil) ((debug 
error) (eshell-errorn (error-message-string err)) (eshell-close-handles 1))))) 
(run-hooks 'eshell-post-command-hook)) nil)
    eshell-do-eval((progn 'nil (unwind-protect (progn (let 
((eshell-current-handles '...)) (condition-case err (eshell-do-eval '... nil) 
((debug error) (eshell-errorn ...) (eshell-close-handles 1))))) (run-hooks 
'eshell-post-command-hook))) nil)
    #f(compiled-function () #<bytecode -0x165be7c9ce9ef886>)()
    funcall(#f(compiled-function () #<bytecode -0x165be7c9ce9ef886>))
    (let ((eshell-current-handles '[nil (((t) . 2) t) (((t) . 2) t)]) 
(eshell-current-subjob-p 'nil)) (funcall '#f(compiled-function () #<bytecode 
-0x165be7c9ce9ef886>)))
    eval((let ((eshell-current-handles '[nil ((... . 2) t) ((... . 2) t)]) 
(eshell-current-subjob-p 'nil)) (funcall '#f(compiled-function () #<bytecode 
-0x165be7c9ce9ef886>))))
    eshell-do-eval((let ((eshell-current-handles '[nil ((... . 2) t) ((... . 2) 
t)]) eshell-current-subjob-p) (progn 'nil (unwind-protect (progn (let 
((eshell-current-handles ...)) (condition-case err (eshell-do-eval ... nil) 
(... ... ...)))) (run-hooks 'eshell-post-command-hook)))))
    eshell-resume-eval((nil (let ((eshell-current-handles '[nil (... t) (... 
t)]) eshell-current-subjob-p) (progn 'nil (unwind-protect (progn (let (...) 
(condition-case err ... ...))) (run-hooks 'eshell-post-command-hook)))) nil))
    eshell-eval-command((let ((eshell-current-handles '[nil ((... . 2) t) ((... 
. 2) t)]) eshell-current-subjob-p) (progn 'nil (unwind-protect (progn (let 
((eshell-current-handles ...)) (condition-case err (eshell-do-eval ... nil) 
(... ... ...)))) (run-hooks 'eshell-post-command-hook)))) "winget --help")
    eshell-send-input(nil)
    funcall-interactively(eshell-send-input nil)
    call-interactively(eshell-send-input nil nil)
    command-execute(eshell-send-input)

Jim, why does Eshell want to read the executable file winget.exe?  If
that's because it wants to find the signature by which it will deduce
the interpreter, then doing that for zero-size files is not useful,
and should probably be skipped?

This naïve patch fixes the problem:

diff --git a/lisp/eshell/esh-ext.el b/lisp/eshell/esh-ext.el
index 3c4deb3..d9631be 100644
--- a/lisp/eshell/esh-ext.el
+++ b/lisp/eshell/esh-ext.el
@@ -247,7 +247,8 @@ eshell-connection-local-command
                 ;; know the interpreter in that case, therefore the
                 ;; check is suppressed.
                 (or (and (stringp command) (file-remote-p command))
-                    (file-remote-p default-directory)))))
+                    (file-remote-p default-directory)
+                     (zerop (file-attribute-size (file-attributes 
(executable-find command))))))))
     (cl-assert interp)
     (if (functionp (car interp))
        (apply (car interp) (append (cdr interp) args))