On Tue, 14 Jun 2011 09:53:16 -0400, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
http://www.wikiservice.at/d/wiki.cgi?LanguageDevel/DIPs/DIP11
Destroy.
I put this as replies in several threads, but I'll throw it out there as
its own thread:
* You already agree that having the fetching done by a separate program
(possibly written in d) makes the solution cleaner (i.e. you are not
infiltrating the code that actually does compiling with code that does
network fetching).
* I think specifying the entire url in the pragma is akin to specifying
the full path of a given module on your local disk. I think it's not the
right place for it, the person who is building the code should be
responsible for where the modules come from, and import should continue to
specify the module relative to the include path.
* A perfect (IMO) way to configure the fetch tool is by using the same
mechanism that configures dmd on how to get modules -- the include path.
For instance -Ihttp://xxx.yyy.zzz/package can be passed to the compiler or
put into the dmd.conf.
* DMD already has a good mechanism to specify configuration and you would
barely have to change anything internally.
Here's how it would work. I'll specify how it goes from command line to
final (note the http path is not a valid path, it's just an example):
dmd -Ihttp://www.dsource.org/projects/dcollections/import testproj.d
1. dmd recognizes the url pattern and stores this as an 'external' path
2. dmd reads the file testproj.d and sees that it imports
dcollections.TreeMap
3. Using it's non-external paths, it cannot find the module.
4. It calls:
dget -Ihttp://www.dsource.org/projects/dcollections/import
dcollections.TreeMap
5. dget checks its internal cache to see if the file
dcollections/TreeMap.[d|di] already exists -- not found
6. dget uses internal logic to generate a request to download either
a. an entire package which contains the requested import (preferred)
b. just the specific file dcollections/TreeMap.d
7. Using the url as a key, it stores the TreeMap.d file in a cache so it
doesn't have to download it again (can be stored globally or local to the
user/project)
8. Pipes the file to stdout, dmd reads the file, and returns 0 for success
9. dmd finishes compiling.
On a second run to dmd, it would go through the same process, but dget
succeeds on step 5 of finding it in the cache and pipes it to stdout.
Some issues with this scheme:
1. dependency checking would be difficult for a build tool (like make) for
doing incremental builds. However, traditionally one does not specify
standard library files as dependencies, so downloaded files would probably
be under this same category. I.e. if you need to rebuild, you'd have to
clear the cache and do a make clean (or equivalent). Another option is to
have dget check to see if the file on the server has been modified.
2. It's possible that dget fetches files one at a time, which might be
very slow (on the first build). However, one can trigger whole package
downloads easily enough (for example, by making the include path entry
point at a zip file or tarball). dget should be smart enough to handle
extracting packages.
I can't really think of any other issues.
-Steve
