Incorrect error message when BUFR_TABLES environment variable is undefined

[Yves Pelletier]

Currently, if BUFR_TABLES is undefined, the libecbufr utility bufr_encoder will stop with an error message stating that the template is not defined properly. This is because bufr_encoder cannot find the tables and therefore is unable to read the template. The template is probably just fine. So the message is erroneous and could be considered a bug. The root cause of the issue is that the BUFR_TABLES variable is undefined - this is what needs to be reported to the user in order to take proper action.

[cpb (chris-beauregard)]

Strictly speaking, BUFR_TABLES doesn't *need* to be defined for bufr_encoder to work... one could imagine a template using purely local descriptors and -ltableb/-ltabled arguments (actually, I think that would fail in some situations; I can't decide if it's a bug or just good taste ;)

And (this is the real gotcha) local and master tables can be defined within a template file (LOCAL_TABLEB, MASTER_TABLED, etc), the interpretation of which is buried in the API call bufr_load_template() called by bufr_encoder to handle the -template command-line argument.

In other words, if bufr_encoder has no tables defined via BUFR_TABLES or the command line switches, it's not necessarily a usage error and isn't guaranteed to fail.

The design of the API is such that it turns out that bufr_encoder still can't expect when trying to load a template file that not having tables set/provided will be an error, or the precise nature of the error (i.e. distinguishing between missing tables or templates using descriptors not found in the tables provided/available).

In other words, from the perspective of the encoder and API, not having any tables provided is exactly the same situation as a template using descriptors not available in the various provided tables. The real problem, in a sense, is that the error from the API level is actually buried in the various debug messages.

I don't have a solution to propose off hand. I touched on this problem somewhat in bug #697746 , and it's a bit of a can of worms.

[cpb (chris-beauregard)]

<sigh> And in the process of looking at this, I noticed bug #1253128

[Yves Pelletier (yves-pelletier)]

`Chris,

I understand that, given certain usage scenarios, the use of BUFR_TABLES to define the location of the BUFR tables is not essential. And I think I made a point approaching what you say in my bug submission. But my main point is that in its current form, in what we bill as the default usage scenario, when BUFR_TABLES is undefined the resulting error message is misleading and unhelpful. I would be happy with a simple warning that BUFR_TABLES is undefined, alongside (not replacing) the other message suggesting that there is an issue in the template. Last week I watched (and helped) as 20 people who were familiarizing themselves with libecbufr struggled to fix perfectly good templates, when all they needed to do is set the BUFR_TABLES variable in their environment.

Yves

-----Message d'origine-----
De : <email address hidden> [mailto:<email address hidden>] De la part de cpb
Envoyé : 20 November, 2013 10:30
À : Pelletier,Yves [CMC]
Objet : [Bug 1250947] Re: Incorrect error message when BUFR_TABLESenvironment variable is undefined

Strictly speaking, BUFR_TABLES doesn't *need* to be defined for bufr_encoder to work... one could imagine a template using purely local descriptors and -ltableb/-ltabled arguments (actually, I think that would fail in some situations; I can't decide if it's a bug or just good taste ;)

And (this is the real gotcha) local and master tables can be defined within a template file (LOCAL_TABLEB, MASTER_TABLED, etc), the interpretation of which is buried in the API call bufr_load_template() called by bufr_encoder to handle the -template command-line argument.

In other words, if bufr_encoder has no tables defined via BUFR_TABLES or the command line switches, it's not necessarily a usage error and isn't guaranteed to fail.

The design of the API is such that it turns out that bufr_encoder still can't expect when trying to load a template file that not having tables set/provided will be an error, or the precise nature of the error (i.e.
distinguishing between missing tables or templates using descriptors not found in the tables provided/available).

In other words, from the perspective of the encoder and API, not having any tables provided is exactly the same situation as a template using descriptors not available in the various provided tables. The real problem, in a sense, is that the error from the API level is actually buried in the various debug messages.

I don't have a solution to propose off hand. I touched on this problem somewhat in bug #697746 , and it's a bit of a can of worms.

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https://bugs.launchpad.net/bugs/1250947

Title:
  Incorrect error message when BUFR_TABLES environment variable is
  undefined

Status in Environment Canada BUFR Library:
  New

Bug description:
  Currently, if BUFR_TABLES is undefined, the libecbufr utility
  bufr_encoder will stop with an error message stating that the template
  is not defined properly. This is because bufr_encoder cannot find the
  tables and therefore is unable to read the template. The template is
  probably just fine. So the message ...

[cpb (chris-beauregard)]

On 11/20/13 10:54, Yves Pelletier wrote:
> Last
> week I watched (and helped) as 20 people who were familiarizing
> themselves with libecbufr struggled to fix perfectly good templates,
> when all they needed to do is set the BUFR_TABLES variable in their
> environment.

That does sound like an annoying experience.

One "quick hack" to fix what you encountered there is to have the
libecbufr .deb add a BUFR_TABLES environment setting to the stock config
(in /etc/profile.d/ on Ubuntu and I believe newer Debian's).

Wouldn't necessarily fix the underlying problem of an unhelpful error
message, but it would at least ensure that typical libecbufr
installations don't normally lack BUFR_TABLES.

c.

[vanh souvanlasy (vanh-souvanlasy)]

Added an error message saying :
Warning: env.var. BUFR_TABLES not defined
when trying to run decoder or encoder without defining this env. variable