Re: parseCSV "name" . printCSV not idempotent

It is true, the fix may belong in CSV. I am recovering from my tendencies to go through contortions to work around issues that I could be solving at their source. Does CSV use line/unlines under the hood? I have heard that these do not perfectly round-trip. Antoine On Nov 8, 2010 1:33 AM, "Joachim Breitner" wrote:

Hi,

Am Sonntag, den 07.11.2010, 19:52 +0100 schrieb Antoine Latter:

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On Sun, Nov 7, 2010 at 10:43 AM, Joachim Breitner wrote:

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Hi Jaap,

your CSV library is used in the Hackage2 project. I found that backup and restore does not work with a pristine state, and the reason seems to be a problem with your library: It either adds unnecessary newlines or interprets empty lines at the end of the program for no apparent reason:

Prelude Text.CSV> (parseCSV "name" . printCSV) [] Right [[""]] Prelude Text.CSV> (parseCSV "name" . printCSV) [[]] Right [[""],[""]] Prelude Text.CSV> (parseCSV "name" . printCSV) [[],[]] Right [[""],[""]] Prelude Text.CSV> (parseCSV "name" . printCSV) [["hi"],["ho"]] Right [["hi"],["ho"],[""]] Prelude Text.CSV> (parseCSV "name" . printCSV) [["hi"]] Right [["hi"],[""]] Prelude Text.CSV>

At some point I had a hack in place to drop the last row of a parsed CSV file if it was nothing but an empty string. It may have gotten lost, or it may not be universally applied in hackage-server 2. This worked pretty well for most things, but I don't think I ever ran into the issue of an empty line in the middle of a CSV file.

correct, I later found that code as well. I’m not fully anymore that the issues I observed are caused by this bug. But nevertheless it’s better to fix the CSV module than work around it in hackage2.

Greetings, Joachim

-- Joachim "nomeata" Breitner mail: mail@joachim-breitner.de | ICQ# 74513189 | GPG-Key: 4743206C JID: nomeata@joachim-breitner.de | http://www.joachim-breitner.de/ Debian Developer: nomeata@debian.org