Use Expect.jl for interactive tests?

[ThomasBreuer]

@fingolfin had listed Expect.jl as a tool for interactive tests. Examples where such tests are interesting are the GAP help system, functions that use GAP's Browse package, or Julia's terminal menus.

Here are my first experiments.
First we start a GAP session.

julia> using Expect

julia> proc = ExpectProc(`path-to-your-gaproot/bin/gap.sh`, 16 );   # start a GAP process

julia> bytesavailable( proc )   # it has printed the GAP banner (size depends on installed packages etc.)
913

julia> println(proc, "1 + 1;")   # compute something in the GAP session
7

julia> bytesavailable( proc )
920

julia> while bytesavailable( proc ) > 5   # remove the banner stuff
              global line = readline( proc )
              end

julia> line
"gap> 2"

julia> bytesavailable( proc )   # this is the current `gap> ` prompt (without newline)
5

julia> close( proc )   # kill the GAP process

We better start GAP without prompt (and without banner), and also without packages.

julia> proc = ExpectProc(`path-to-your-gaproot/bin/gap.sh -q -A`, 16 );

julia> bytesavailable( proc )
0

julia> print( proc, "for i in [1..3] do Print( i, \"\\n\" ); od;\n" );

julia> bytesavailable( proc )
6

julia> while bytesavailable( proc ) > 0
              println( readline( proc ) )
              end
1
2
3

This looks reasonable.
Now let us look at the GAP help. The Browse package was not loaded, thus we get just a pager.

julia> println(proc, "SizeScreen();"); readline(proc)   # the "terminal" has only 24 rows
"[ 80, 24 ]"

julia> bytesavailable(proc)
0

julia> println(proc, "?Size");   # show one screen of entries about `Size`

julia> bytesavailable( proc )
1084

julia> println(proc, "q" );   # quit the pager

julia> bytesavailable( proc )   # careful: there is no newline character in the end (and calling `readline` for the "last line" would trigger a timeout)
1294

julia> println(proc, "0+0;");   # make sure that there is a trailing newline

julia> while bytesavailable( proc ) > 0
              println( readline( proc ) )
              end
Help: several entries match this topic - type ?2 to get match [2]

[1] Reference: Size
[2] FinInG (not loaded): Size
[...]
[21] Reference: Size for a character table
[22] Reference: SizeScreen
0                                                                     

julia> println(proc, "?1" );   # show the first entry

julia> println(proc, "q" );   # quit the pager

julia> println(proc, "0+0;");   # make sure that there is a trailing newline

julia> while bytesavailable(proc) > 0 println(readline(proc)) end
  30.4-6 Size
  
  ‣ Size( listorcoll ) ───────────────────────────────────────────── attribute
  
[...]
  
  30.4-7 Representative
  
0                                           

With the Browse package, the expected behaviour of GAP is different, and different input is needed.

Here the idea is that the menu of choices opens in a Browse table, one can move the focus down to the entry in question, and then choose it by entering <Return> (the character \r).

Initially this seemed to work, but after some experiments the whole setup became unstable, and bytesavailable(proc) returned 0 from that point on.
Even after closing all GAP processses with close(proc) and leaving all Julia sessions, still two GAP processes were alive on my computer --I do not understand what is going on.
Here is some input that should work, but it doesn't work anymore.

using Expect
proc = ExpectProc(`path-to-your-gaproot/bin/gap.sh -q -A`, 16 )
bytesavailable(proc)
println(proc, "LoadPackage(\"browse\");")
readline(proc)   # some special characters plus the `true` output   <- leaving out this line may change the behaviour --why?
bytesavailable(proc)
println(proc, "?Size")   # open the Browse table
bytesavailable(proc)
println(proc, "ddd")   # navigate down three times
bytesavailable(proc)
println(proc, "\r")    # enter <Return>, this opens the pager with the help entry
bytesavailable(proc)
println(proc, "qq")   # quit the pager, quit the Browse table
bytesavailable(proc)
println(proc, "0+0;")   # make sure that there is a newline in the end
bytesavailable(proc)   # here I got 6186
while bytesavailable(proc) > 0 println(readline(proc)) end   # show the output (contents of the Browse table and contents of the help section)

[ThomasBreuer]

Update, after a discussion with @fingolfin :

First, the input lines println(proc, "ddd"), println(proc, "\r"), println(proc, "qq") in the above "bad" code example should be changed to print(proc, "ddd"), print(proc, "\r"), print(proc, "qq"), respectively, because the intended input does not contain newline characters.
(This does not change the behaviour because the Browse tables in question ignore the input \n.)

The really problematic part in the above input code is the println in the final code line.
That is, there is no problem to fetch the output lines with readline, but the attempt to print some of them with println causes severe problems --in my terminal, the cursor remains always in the last line, even after leaving Julia, such that the terminal window cannot be used properly anymore.
Thus one can in principle use Expect.jl in order to enter the inputs for the interactive help, and one can also evaluate GAP's outputs.
(But one should not try to print them in the Julia session.)
A Julia session for that could look as follows.

julia> using Expect

julia> proc = ExpectProc(`path-to-your-gaproot/bin/gap.sh -q -A`, 16);

julia> println(proc, "LoadPackage(\"browse\");");

julia> println(proc, "?Size");   # open the Browse table

julia> print(proc, "ddd");   # navigate down three times

julia> print(proc, "\r");    # enter <Return>, this opens the pager with the help entry

julia> print(proc, "qq");   # quit the pager, quit the Browse table

julia> println(proc, "0+0;");   # make sure that there is a newline in the end

julia> bytesavailable(proc)   # the value may depend on color settings etc.
6186

julia> output = [];

julia> while bytesavailable(proc) > 0 push!(output, readline(proc)) end

julia> length(output)
26

julia> close(proc)   # kill the GAP process