Rust @programming.dev jpfreely @programming.dev 1 yr. ago

Do you use mod.rs, the module name, or does it vary? How do you decide?

I started off avoiding mod.rs because it's the old way and I prefer having the module name as the filename. However, if the module needs a folder for submodules anyway, then there's a reason to tuck it away as mod.rs, especially if not doing so leaves lots of duplicate names (a.rs, b.rs, c.rs, ..., a/, b/, c/).

But then I don't really like to have much else in mod.rs other than mod declarations and pub use. Maybe a utility fn or a not-unwieldly implementation of struct "Foo", the module's namesake.

8 comments

I avoid using mod.rs because then I'll have a bazillion mod.rs files. It's what I hate about python modules. I would rather have a thingy.rs and then a thingy folder than many files named the same thing distinct only by their path.
I use mod.rs because I prefer having all the module’s files in the same folder. But I don’t do that unless a module is multiple files.
I use mod.rs because I like having a module entirely contained in its own directory, rather than having part of it in the parent one. Obvious exception is when the module does not have submodules.

It also follows the same structure of crates, where mod.rs maps to lib.rs. It has the (minor) advantage that I can trivially extract a module into its own crate by copying the module's directory and renaming mod.rs to lib.rs, but more than anything I like the homogeneity.

But then I don’t really like to have much else in mod.rs other than mod declarations and pub use. Maybe a utility fn or a not-unwieldly implementation of struct “Foo”, the module’s namesake.

Same.

My mod.rs only contains a sequence of pub use self::...;.
But then I don't really like to have much else in mod.rs other than mod declarations and pub use.

You can always inline the mod.rs contents in its parent module and have one fewer file overall. Not every module needs to be in its own file.

But generally when working in an IDE I don't like to see a bunch of mod.rs files in the tabs as it just makes it harder to jump to the right one.
- I did that at work and people had a heart attack lol. Which i thought was silly because the mod literally had no code in it besides module file declarations. /shrug
For a moment in time, I rather disliked mod.rs files.

Then my editor got an update to show the folder name in tabs, when two files were named the same.

Now I am using mod.rs in my own code bases, because I want all related files in one place. ¯\_(ツ)_/¯
It varies, depending on if I have submodules or not. I see no reason to have a folder with a single mod.rs.
- @snaggen @jpfreely Why you need dir “name” with “mod.rs” without other submodules? Why not just “name.rs” instead?
  
  Or you can describe hierarchy of submodules in the parent module instead of same in “mod.rs” like this:
  mod name { mod sub; }
I use mod.rs all over the place because it entirely encapsulates a module in a folder. But since the name of the file is fairly obtuse and doesn't say what it is, I usually only re-export other better named files that also exist in that folder.

I'm the case that I want a module with content, and then more further nested content that may use pub(super), I will use a module named file and a separate folder to hold it's children modules.

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