Feature: magics always

[tinmarino]

Always prepend and append are implemented. As show and clear to inspect and remove them all. As conversed in issue #85
The first commit contains the real work. The rest is test and doc.

Note on t/20-end-to-end.t

(I renamed it : 10 -> 20 for it to stay the last when adding more test)

The client is not dying sometimes => address already in use (9103 iopub)
For example when my tests did freeze a Ctrl-C killed the kernel but not the client.

pkill raku
P6_JUPYTER_TEST_END_TO_END=1 ra t/20-end-to-end.t

Or more wisely

netstat -laputn | grep 9103   # to find its pid (here 666)
kill -15 666

[bduggan]

Very cool!

However, I think it should execute whatever is in the cell -- so that you can have something like

#% always
say "-----header-----"

This makes it useful in the notebook UI, e.g. to set up a cell that does several things

In this pr --

In [1]: #% always \
      : say "----"
Out[1]:

In [2]: 2
Out[2]: 2

However, it's cool that this works --

In [1]: #% always say 'hi'
Out[1]:

In [2]: 3
hi
Out[2]: 3

I suppose we can keep that even though it could potentially be ambiguous (e.g. if there is a prepend sub defined)

also +1 for nice tests

[tinmarino]

Awesome review : nice catch! I made a mistake for believing this was only a check:

my $magic-line = $code.lines[0] or return Nil;
$magic-line ~~ /^ [ '#%' | '%%' ] / or return Nil;

Fixed (c1e019d above):

In [6]: #% always 
      : say "-----header-----"               
Out[6]: 

In [7]: say "May the Magic be always with you"                                             
-----header-----
May the Magic be always with you

[bduggan]

Great!