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master e01660ca50a 2/3: Simplify how Eshell's iterative evaluation handl
From: |
Jim Porter |
Subject: |
master e01660ca50a 2/3: Simplify how Eshell's iterative evaluation handles 'if' forms |
Date: |
Fri, 17 Mar 2023 01:32:42 -0400 (EDT) |
branch: master
commit e01660ca50ad360db78e5a0206ed824465c2aada
Author: Jim Porter <jporterbugs@gmail.com>
Commit: Jim Porter <jporterbugs@gmail.com>
Simplify how Eshell's iterative evaluation handles 'if' forms
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.
---
lisp/eshell/esh-cmd.el | 36 ++++++++++++++----------------------
1 file changed, 14 insertions(+), 22 deletions(-)
diff --git a/lisp/eshell/esh-cmd.el b/lisp/eshell/esh-cmd.el
index 2dd8f5d6042..5dbbd770582 100644
--- a/lisp/eshell/esh-cmd.el
+++ b/lisp/eshell/esh-cmd.el
@@ -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@@ -1149,23 +1147,17 @@ have been replaced by constants."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))