Extraneous line for multiline output in Sage command line

[kwankyu]

To reproduce it, run Sage in the terminal and evaluate the following code. Extra blank lines are printed before outputs as below:

class Foo(object):

    def __repr__(self):
        return "foo"


class Bar(object):

    def __repr__(self):
        return "bar\nbar"


sage: identity_matrix(QQ, 2)

[1 0]
[0 1]
sage: Foo()
foo
sage: Bar()

bar
bar

This was first discussed in https://groups.google.com/forum/#!topic/sage-devel/AYYaUb_9kjw

Upstream: Fixed upstream, but not in a stable release.

CC: @sagetrac-stakemori @tscrim

Component: user interface

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/22158

[kwankyu]

comment:1

The related upstream discussion is in ipython/ipython#10138

[sagetrac-stakemori]

comment:3

Thank you. I will try to make a patch this weekend.

[kwankyu]

comment:4

Replying to @sagetrac-stakemori:

Thank you. I will try to make a patch this weekend.

Did you see the comment posted in the upstream discussion? We may think that the bug is in IPython than in Sage. So we need a patch for IPython. You may submit a pull request of the patch to IPython Github repo.

[kwankyu]

comment:5

Fixed upstream in ipython/ipython#10146

[kwankyu]

Changed upstream from Reported upstream. No feedback yet. to Fixed upstream, but not in a stable release.

[sagetrac-stakemori]

comment:6

Replying to @kwankyu:

I saw the pull request. This has been fixed in IPython. But I think this can be fixed immediately in Sage (how long will it take before the fix will be merged into Sage?). Right now I have a fever, so I avoid coding.

[kwankyu]

comment:7

It will take some time for the fix in the upstream eventually to get into a release of Sage. For the impatient, copy and paste the following to replace the code for write_output_prompt method in sage/local/lib/python/site-packages/IPython/terminal.

    def write_output_prompt(self):
        sys.stdout.write(self.shell.separate_out)
        # If we're not displaying a prompt, it effectively ends with a newline,
        # because the output will be left-aligned.
        self.prompt_end_newline = True

        if self.do_full_cache:
            tokens = self.shell.prompts.out_prompt_tokens()
            prompt_txt = ''.join(s for t, s in tokens)
            if prompt_txt and not prompt_txt.endswith('\n'):
                # Ask for a newline before multiline output
                self.prompt_end_newline = False

            if self.shell.pt_cli:
                self.shell.pt_cli.print_tokens(tokens)
            else:
                sys.stdout.write(prompt_txt) 

[sagetrac-stakemori]

comment:8

For the impatient, copy and paste the following to replace the code for write_output_prompt method in sage/local/lib/python/site-packages/IPython/terminal.

The method write_output_prompt of the class RichPromptDisplayHook in $SAGE_ROOT/local/lib/python/site-packages/IPython/terminal/prompts.py more precisely.

[tscrim]

comment:9

We can just patch Sage's IPython in the meantime. This is the fastest fix, as we have to wait for the next version of IPython with the PR included.

I doubt Volker will let this ticket get into the 7.5 release though. :/

[jdemeyer]

comment:10

Replying to @tscrim:

as we have to wait for the next version of IPython with the PR included.

That would be a pity for such an important major bug like this one ;-)

[sagetrac-stakemori]

comment:11

I made a patch for this problem. I think the attribute prompt_end_newline should be always true.
https://gist.github.com/stakemori/68f42ba2f9ac6f6d581e9525c1c41e07

[kwankyu]

comment:12

Your patch will be redundant once the next release of IPython is incorporated to Sage. Note that the upstream patch was back ported to the current release, which means, I guess, that the fixed IPython would be available in Sage sooner than usual.

Your patch can be used as an (alternative) temporary measure to fix the issue, but should not be merged to Sage.

[kwankyu]

comment:13

As Sage's IPython was updated to version 5.5, this issue is now fixed. Nice!

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:14

Indeed!

[videlec]

comment:15

closing positively reviewed duplicates