Refactor lisp eval result printing

* lisp/simple.el (eval-expression-print-format): Don't check
`standard-output' or `current-prefix-arg'.
(eval-expression-get-print-arguments): New function, centralizes
decision about how to print results of `eval-expression' and
`eval-last-sexp'.
(eval-expression):
* lisp/progmodes/elisp-mode.el (elisp--eval-last-sexp-print-value):
Use it.

1 files changed, 30 insertions, 28 deletions

diff --git a/lisp/simple.el b/lisp/simple.el
index 7f13df5006d..3af62657dbf 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1456,16 +1456,14 @@ This string will typically look like \" (#o1, #x1, ?\\C-a)\".
 If VALUE is not an integer, nil is returned.
 This function is used by functions like `prin1' that display the
 result of expression evaluation."
-  (if (and (integerp value)
-	   (or (eq standard-output t)
-	       (zerop (prefix-numeric-value current-prefix-arg))))
-      (let ((char-string
-	     (if (and (characterp value)
-		      (char-displayable-p value))
-		 (prin1-char value))))
-        (if char-string
-            (format " (#o%o, #x%x, %s)" value value char-string)
-          (format " (#o%o, #x%x)" value value)))))
+  (when (integerp value)
+    (let ((char-string
+           (and (characterp value)
+                (char-displayable-p value)
+                (prin1-char value))))
+      (if char-string
+          (format " (#o%o, #x%x, %s)" value value char-string)
+        (format " (#o%o, #x%x)" value value)))))
 
 (defvar eval-expression-minibuffer-setup-hook nil
   "Hook run by `eval-expression' when entering the minibuffer.")
@@ -1484,9 +1482,21 @@ result of expression evaluation."
                             read-expression-map t
                             'read-expression-history))))
 
+(defun eval-expression-get-print-arguments (prefix-argument)
+  "Get arguments for commands that print an expression result.
+Returns a list (INSERT-VALUE NO-TRUNCATE CHAR-PRINT)
+based on PREFIX-ARG.  This function determines the interpretation
+of the prefix argument for `eval-expression' and
+`eval-last-sexp'."
+  (let ((num (prefix-numeric-value prefix-argument)))
+    (list (not (memq prefix-argument '(nil)))
+          (= num 0)
+          (cond ((not (memq prefix-argument '(0 nil))) nil)
+                (t t)))))
+
 ;; We define this, rather than making `eval' interactive,
 ;; for the sake of completion of names like eval-region, eval-buffer.
-(defun eval-expression (exp &optional insert-value)
+(defun eval-expression (exp &optional insert-value no-truncate char-print)
   "Evaluate EXP and print value in the echo area.
 When called interactively, read an Emacs Lisp expression and evaluate it.
 Value is also consed on to front of the variable `values'.
@@ -1507,8 +1517,8 @@ minibuffer.
 If `eval-expression-debug-on-error' is non-nil, which is the default,
 this command arranges for all errors to enter the debugger."
   (interactive
-   (list (read--expression "Eval: ")
-	 current-prefix-arg))
+   (cons (read--expression "Eval: ")
+         (eval-expression-get-print-arguments current-prefix-arg)))
 
   (if (null eval-expression-debug-on-error)
       (push (eval exp lexical-binding) values)
@@ -1523,23 +1533,15 @@ this command arranges for all errors to enter the debugger."
       (unless (eq old-value new-value)
 	(setq debug-on-error new-value))))
 
-  (let ((print-length (and (not (zerop (prefix-numeric-value insert-value)))
-			   eval-expression-print-length))
-	(print-level (and (not (zerop (prefix-numeric-value insert-value)))
-			  eval-expression-print-level))
+  (let ((print-length (unless no-truncate eval-expression-print-length))
+        (print-level  (unless no-truncate eval-expression-print-level))
         (deactivate-mark))
-    (if insert-value
-	(with-no-warnings
-	 (let ((standard-output (current-buffer)))
-	   (prog1
-	       (prin1 (car values))
-	     (when (zerop (prefix-numeric-value insert-value))
-	       (let ((str (eval-expression-print-format (car values))))
-		 (if str (princ str)))))))
+    (let ((out (if insert-value (current-buffer) t)))
       (prog1
-          (prin1 (car values) t)
-        (let ((str (eval-expression-print-format (car values))))
-          (if str (princ str t)))))))
+          (prin1 (car values) out)
+        (let ((str (and char-print
+                        (eval-expression-print-format (car values)))))
+          (when str (princ str out)))))))
 
 (defun edit-and-eval-command (prompt command)
   "Prompting with PROMPT, let user edit COMMAND and eval result.