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Simplify how Eshell's iterative evaluation handles 'if' forms

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The previous implementation used 'eshell-test-body' and
'eshell-command-body' to track the condition and the then/else forms,
but those special variables are only needed for looping.  'if' only
evaluates each form once at most (bug#61954).

* lisp/eshell/esh-cmd.el (Command evaluation macros): Remove 'if' from
the notes about 'eshell-test-body' and 'eshell-command-body'.
(eshell-do-eval): Reimplement evaluation of 'if' forms.
(eshell-eval-command): Don't let-bind 'eshell-command-body' and
'eshell-test-body'; they're no longer needed here.
This commit is contained in:
Jim Porter 2023-01-28 15:06:31 -08:00
parent 67a2b320f6
commit e01660ca50
1 changed files with 14 additions and 22 deletions
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36
lisp/eshell/esh-cmd.el
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@ -745,9 +745,9 @@ if none)."
;; `condition-case', `if', `let', `prog1', `progn', `quote', `setq',
;; `unwind-protect', and `while'.
;;
;; @ When using `if' or `while', first let-bind `eshell-test-body' and
;; @ When using `while', first let-bind `eshell-test-body' and
;; `eshell-command-body' to '(nil). Eshell uses these variables to
;; handle conditional evaluation.
;; handle evaluating its subforms multiple times.
;;
;; @ The two `special' variables are `eshell-current-handles' and
;; `eshell-current-subjob-p'. Bind them locally with a `let' if you
@ -1031,9 +1031,7 @@ produced by `eshell-parse-command'."
;; We can just stick the new command at the end of the current
;; one, and everything will happen as it should.
(setcdr (last (cdr eshell-current-command))
(list `(let ((here (and (eobp) (point)))
(eshell-command-body '(nil))
(eshell-test-body '(nil)))
(list `(let ((here (and (eobp) (point))))
,(and input
`(insert-and-inherit ,(concat input "\n")))
(if here
@ -1149,23 +1147,17 @@ have been replaced by constants."
(setcar eshell-test-body (copy-tree (car args))))
(setcar eshell-command-body nil))
((eq (car form) 'if)
;; `copy-tree' is needed here so that the test argument
;; doesn't get modified and thus always yield the same result.
(if (car eshell-command-body)
(progn
(cl-assert (not synchronous-p))
(eshell-do-eval (car eshell-command-body)))
(unless (car eshell-test-body)
(setcar eshell-test-body (copy-tree (car args))))
(setcar eshell-command-body
(copy-tree
(if (cadr (eshell-do-eval (car eshell-test-body)
synchronous-p))
(cadr args)
(car (cddr args)))))
(eshell-do-eval (car eshell-command-body) synchronous-p))
(setcar eshell-command-body nil)
(setcar eshell-test-body nil))
(eshell-manipulate "evaluating if condition"
(setcar args (eshell-do-eval (car args) synchronous-p)))
(eshell-do-eval
(cond
((eval (car args)) ; COND is non-nil
(cadr args))
((cdddr args) ; Multiple ELSE forms
`(progn ,@(cddr args)))
(t ; Zero or one ELSE forms
(caddr args)))
synchronous-p))
((eq (car form) 'setcar)
(setcar (cdr args) (eshell-do-eval (cadr args) synchronous-p))
(eval form))