Fix for python3.2

[patrikha]

Hi,

I think you should add an if statement for the config scripts when python3 is specified:

1. in pymac.el remove the lines (str objects are UTF-8 by default):
   (when multibyte
   (princ ".decode('UTF-8')"))
2. in Pymacs.py modify to (sys.exc_type and value are removed):
   value = traceback.format_exception_only(sys.exc_info()[0],
   sys.exc_info()[1])

[ufleisch]

I can confirm this issue. I have used the following patch as a workaround.

---

diff --git a/Pymacs.py.in b/Pymacs.py.in
index 808cfb2..787d0e7 100755
--- a/Pymacs.py.in
+++ b/Pymacs.py.in
@@ -232,8 +232,8 @@ class Protocol:
                     import traceback
                     action = 'raise'
                     if lisp.debug_on_error.value() is None:
-                        value = traceback.format_exception_only(sys.exc_type,
-                            sys.exc_value)
+                        value = traceback.format_exception_only(sys.exc_info()[0],
+                            sys.exc_info()[1])
                         value = ''.join(value).rstrip()
                     else:
                         value = traceback.format_exc()
diff --git a/pymacs.el.in b/pymacs.el.in
index 3deed86..1d9db35 100644
--- a/pymacs.el.in
+++ b/pymacs.el.in
@@ -488,6 +488,14 @@ The timer is used only if `post-gc-hook' is not available.")
       (pymacs-print-for-eval argument))
     (princ ")")))

+(defun pymacs-python3-p ()
+  "Return true if python command ends with '3'."
+  (let ((proc (get-buffer-process "*Pymacs*")))
+    (when (processp proc)
+      (let* ((cmd (process-command proc))
+             (exe (car cmd)))
+        (and (> (length exe) 0) (string= "3" (substring exe -1)))))))
+
 (defun pymacs-print-for-eval (expression)
   ;; This function prints a Python expression out of a Lisp EXPRESSION.
   (let (done)
@@ -511,7 +519,7 @@ The timer is used only if `post-gc-hook' is not available.")
                (princ (mapconcat 'identity
                                  (split-string (prin1-to-string text) "\n")
                                  "\\n"))
-               (when multibyte
+               (when (and multibyte (not (pymacs-python3-p)))
                  (princ ".decode('UTF-8')")))
              (setq done t)))
           ((symbolp expression)

---

The function "pymacs-python3-p" is just a quick hack to find out if Python 3 is running. Is there a function providing the Python version for Pymacs?

By the way: I could not "setup.py install" the current Git head, so I patched the 0.25 release. Is there an issue with the setup? If have a standard Ubuntu 12.04 Python installation and built the package using "make" (after modifying "PYTHON = python3" in the Makefile), followed by "python3 ./setup.py install --user".

[pinard]

Hi, Patrik and (?) ufleish.

Thanks for the note about sys.exc_info() in Python3, happily applied here.

About "an issue with the setup", Will Roberts submitted a correction in that area, I do not know if it addresses the issue you are reporting.

For the multibyte issue, I am still reluctant as I do not understand your comment. In Python3, str objects are not UTF-8, they are Unicode, which is not the same thing. But if Emacs transmits UTF-8 bytes, and are received on the Python side as bytes, it seems to me that decoding is still required to turn those bytes from UTF-8 into Unicode.

I'm not that assertive, however, as I do not swim often enough in these waters to feel solid in whatever I say.

François

[ufleisch]

Hi François,

Here is a simple test to reproduce the bug by passing a multibyte string to a Python function:

pymacstest.py:

def greet(name):
    return 'Hello ' + name

(pymacs-load "pymacstest")
(pymacstest-greet "François")

Debugger entered--Lisp error: (error "Python: Traceback (most recent call last):
  File \"/home/urs/python/packages/Pymacs-0.25-py3.2/Pymacs.py\", line 191, in loop
    value = eval(text)
  File \"<string>\", line 1, in <module>
AttributeError: 'str' object has no attribute 'decode'
")

*Pymacs*
>44 eval pymacs_load_helper("pymacstest", None)
<78 (return '(progn (pymacs-defuns '(8 pymacstest-greet nil)) (pymacs-python 9)))
>50 eval python[8]("Fran\303\247ois".decode('UTF-8'))
<22 (eval debug-on-error)
>15 return Lisp(0)
<263    (free (0) raise "Traceback (most recent call last):\n  File \"/home/urs/python/packages/Pymacs-0.25-py3.2/Pymacs.py\", line 191, in loop\n    value = eval(text)\n  File \"<string>\", line 1, in <module>\nAttributeError: 'str' object has no attribute 'decode'\n")

The problem is that str in Python 3 does not have a decode() method. Instead of a string, a byte array should be passed, so that the UTF-8 bytes are decoded to a correct unicode string.

So b"Fran\303\247ois".decode('UTF-8') should be passed instead of "Fran\303\247ois".decode('UTF-8'). Just omitting ".decode('UTF-8')" as suggested in the patch above is not correct since the UTF-8 bytes are not decoded. Byte array b"..." literals works since Python 2.6 (it is a no-op for Python 2), so the Elisp part of Pymacs does not have to know the Python version.

A patch is below.

Regards,
Urs

--- pymacs.el.orig  2012-06-26 17:58:18.785507900 +0200
+++ pymacs.el   2012-09-01 14:15:12.191417377 +0200
@@ -502,6 +502,8 @@
                               (encode-coding-string expression 'utf-8)
                             (copy-sequence expression))))
                (set-text-properties 0 (length text) nil text)
+               (when multibyte
+                 (princ "b"))
                (princ (mapconcat 'identity
                                  (split-string (prin1-to-string text) "\n")
                                  "\\n"))

[patrikha]

Sorry for the delay but your patch with using a byte array works fine!

[paparomeo]

This issue was closed but the patch provided by Urs ended up not being applied and so the problem remains in master. Shouldn't the patch be applied to master?