Ya'll need true packages

FeepingCreature feepingcreature at gmail.com
Fri Oct 29 06:59:31 UTC 2021

On Tuesday, 19 October 2021 at 04:03:38 UTC, Mathias LANG wrote:
> I was looking at a few packages recently, and noticed a 
> bothering trend: Single-module libraries ending up at the top 
> level.
> Why is it bothering ? Well, here's a little puzzle: Does the 
> following code compile?
> ```D
> import std.stdio;
> void main ()
> {
>     writeln(foo.stringof);
> }
> ```
> The answer is "maybe". In most case, it will not. However, if 
> the file this resides in is named `foo.d`, it will compile. 
> Because the module name accounts for an identifier that can be 
> addressed in the scope of the module (and other modules that 
> import it).

This is ultimately because D modules just reuse the notion of 
import paths from C. I had to find a better way in my language in 
order to handle self-rebuilds, where there's name collisions 
between compiler runtime and compiled runtime packages, but the 
same approach would also solve the issue in D, so let me outline 

Basically, we replace import paths (`-I~/.dub/packages/bla/src`) 
with package paths:


As you can see, each package is named. This allows us to 
explicitly specify which packages a package can see and access:


As it walks imports, the compiler tracks each module's package. 
When evaluating an import statement, only files in the current 
package or a direct dependency of the current package are 

Thus, your 'foo' problem will only happen if you directly depend 
on package "foo" in your dub.json.

This approach is fully backwards compatible with include paths. 
It also allows other funky things, such as per-package settings 
(-i, -deps, -g, -debug etc) which solves a whole host of problems 
with dub. For instance, a static library can safely be used, even 
if the main program's source is being built with different flags.

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