TODO.txt

# t/45_eol.t

strict_eol i.c.w. $csv->eol (undef);

Fix inconsistence between 1:0:1: and 1:0:1:"
Fix inconsistence between 1:1:1: and 1:1:1:"

# https://www.perlmonks.org/index.pl?node_id=11163264

It's the inconsistency of csv (in => ..., out => ...);

                       | in
                       +---------------------------------------------------------------
                       | Data Structure | Sub   | File Name            | File Handle
----+------------------+----------------+-------+----------------------+---------------
out | [Absent]         | Works          | Works | Works                | Works
    | Undefined Scalar | Works          | Works | Run-time error       | Run-time error
    | File Name        | Works          | Works | Instructs programmer | Run-time error
    | File Handle      | Works          | Works | Run-time error       | Run-time error
----+------------------+----------------+-------+----------------------+---------------

The instruction to the programmer is doubly weird because it could simply do what it would do if the programmer used the suggested code.

Current plan:

 Support for (in, out) : (file, file), (fh, fh), (file, fh), and (fh, file) with
 callback on the level of after_parse where after_parse then calls the inner CSV
 with the eol_type of the first line of in and then sets the record to \"skip".
 The CSV object is reused for in *and* out, so all settings are shared, including
 the errors.

 Document that when in this mode, on_in cannot be used.

 Advantages of the previous documented use of csv with an explicit csv call for
 out, is that the in-stream is completely parsed before the output is generated,
 so it won't output if the input is invalid (at row 12345).

 Trace why out => sub { ... } was not implemented and if this could be used for
 above plan. (likely because of the same reason why (in => "file", out => "file")
 was abandoned several times). Note that *all* attributes are shared. Now that we
 have strict_eol, and internal stored eol_type, the need for "eol" for output has
 gone. (we can alo use ->say, but reuse of eol_type is easier).

 We also need a read-only $csv->eol_type to check what was detected.

# https://www.perlmonks.org/index.pl?node_id=11163263

  The function csv () is streaming!

You can encode as a stream.
You can decode as a stream.

But you can't transform as a stream. The inner call (csv (in => "a.csv, ...)) loads the entire file into memory.