[Octave-bug-tracker] [bug #60723] subsagn raise error on .-indexing for table with subsref/subsasgn defined

[Andrew Janke]

URL:
  <https://savannah.gnu.org/bugs/?60723>

                 Summary: subsagn raise error on .-indexing for table with
subsref/subsasgn defined
                 Project: GNU Octave
            Submitted by: apjanke
            Submitted on: Wed 02 Jun 2021 08:51:10 PM EDT
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Unexpected Error or Warning
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: 6.2.0
         Discussion Lock: Any
        Operating System: Mac OS

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Details:

Hi folks. In my Tablicious package
(https://github.com/apjanke/octave-tablicious) I have defined a `table` class
using a classdef
(https://github.com/apjanke/octave-tablicious/blob/3b905b4d190d4869bb6cde2baa37b9273a61822b/inst/table.m),
and given it subsref and subsasgn methods, plus a lot of other
structure-and-size-related overridden methods. For .-indexing with these, the
intent is for you to be able to index a variable (aka "column") by name, and
either get the entire variable out, or assign a new array to the whole thing.

Reading the variables out works:


>> t = table([11;22;33], {'uno';'dos';'tres'}, 'VariableNames', {'X','S'});
>> t.X
ans =
   11
   22
   33


But attempting to assign to them errors out:


>> t.X = [1;2;3];
error: invalid dot name structure assignment because the structure array is
empty.  Specify a subscript on the structure array to resolve.
>> t.foobar = [1;2;3]
error: invalid dot name structure assignment because the structure array is
empty.  Specify a subscript on the structure array to resolve.


The error appears to be happening in the Octave interpreter before my subsasgn
method ever gets called: If I put a `keyboard` statement as the first line in
my table.subsasgn implementation, it never gets hit in this case.

Am I doing something wrong here? Or could this be an issue in the Octave
interpreter's handling of subsasgn/subsref on existing objects, maybe in
regards to how it interacts with numel or other size-related methods? Maybe
it's implicitly calling one of the size-related methods to get some info about
the assignment target and not happy with what it's hearing?

I've tried to come up with a minimal reproducible example, but haven't been
able to trigger this behavior with a simpler classdef. (See attached shtable.m
file.)

Original bug in the Tablicious project:
https://github.com/apjanke/octave-tablicious/issues/80



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File Attachments:


-------------------------------------------------------
Date: Wed 02 Jun 2021 08:51:10 PM EDT  Name: shtable.m  Size: 6KiB   By:
apjanke

<http://savannah.gnu.org/bugs/download.php?file_id=51510>

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