Michael Stone wrote:
I've continued playing with Ur/Web over the last few days and I'm
fairly happy with the results I'm getting. The manual and demos have
both been exceptionally helpful.
Now, for what they're worth, here is a report of a few of the rough
edges that I've bumped up against recently, in case you're interested
in polishing a few of them off.
I sure am! Several of these issues are covered in the manual, which I
know is an impractical thing to read through and digest in full. I'll
try to point to the manual sections relevant to the different issues.
script tags
: I wanted to use the jQuery "quicksearch" library. The natural way
to do this seemed to be to add a few script tags to my document. To do
this, I added a script tag admissible in the "head" context with a
"src : url" attr. (I don't need bodies for to do what I want.)
I think what you're looking for is the "script" .urp directive, as
described in 3.1.
documentation of the { eqNullable' (SQL table.Field) xyz } construction
: An additional demo would have helped here.
Does reading the function's implementation help explain it? Is the
issue with the (SQL ...) syntax?
ability to COUNT( table.Field ) vs. COUNT( * )
: this is mainly a source of confusion; thus far, it's been easy to
work around with views
I'd been thinking that these forms are equivalent, but now I've read the
Postgres manual and seen the error of my ways. I'll add the first form
in the basis library for the next release.
syntax for specifying indices on tables
: I can post-process the generated SQL, but this will eventually get annoying
My current model is that indices are added in an out-of-band way, but I
know that doesn't play so well with modularity, if you think of the
presence of an index as an important part of the module. For now,
though, I'm not planning to add any support for this, since adding
indices manually doesn't seem like that big of a deal, and is probably
even the optimal solution for many applications with changing data
distributions and performance requirements.
compiler/build flags for debug outputs
: It would be easier to understand the compiler internals if I could
see the output of each phase. I'm particularly interested in the
output of the earliest phases.
I do this sort of thing in SML/NJ, as described in 2. I hope that
looking at src/compiler.sig suffices for learning about the relevant
instrumentation.
an API for reading files
: I'm basically working on a syntax highlighter and statistics
viewer for the contents of a small file system
: At the moment, I'm using a combination of a pre-seeded database
(to inform the web-app of the contents of the filesystem) and a C FFI
module (to read the files) to work around this.
I expect folks to use the C FFI for this sort of thing. I don't want to
provide a conventional "file IO library" out of the box, because this
isn't so compatible with the transactional world-view. Ur/Web programs
_will_ break horribly if you use the FFI to execute actions that aren't
rolled back on failure.
error-handling idioms in the C FFI
: While writing my C module, I need to ensure that I close files
that I open. This makes the raw uw_error() primitive hard to use
safely. Is there, for example, a way to hook into urweb's region-based
control flow logic?
I suggest uw_register_transactional(), as documented in 11.1. This is
assuming you only open a few files per HTTP request and don't mind
having them all open until the request is fully processed. (Though you
could also include an explicit close function in your FFI module.)
uw_malloc
: uw_malloc is doing something that I don't understand, in that the
following approximate snippet:
size_t len = ...
char* c = uw_malloc(ctx, len);
if (!c) uw_error(ctx, FATAL, "couldn't allocate %d bytes", len);
memset(c, 0, len);
sometimes segfaults on the memset. (I was able to work around this
problem by using a fixed-size stack-allocated array.)
That is definitely not supposed to happen. Would you mind reducing this
to a minimal example that still exhibits the problem and then submitting
the source code in a Mantis bug report?
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