post: compact module decalration

_posts/2023-09-27-compact-module-declaration.md

@@ -0,0 +1,59 @@
+---
+title: Compact module declaration
+date: 2023-09-27
+author: m
+tags: [cairo]
+---
+
+Here's a cool technique how to declare all of a project's modules inside the project root (typically `src/lib.cairo`) without any intermediary module files.
+
+Let's say we have a project where `src/` looks something like this:
+
+```
+.
+├── core
+│   ├── m1.cairo
+│   ├── m2.cario
+│   └── m3.cairo
+├── lib.cairo
+├── tests
+│   ├── core
+│   │   ├── test_m1.cairo
+│   │   ├── test_m2.cairo
+│   │   └── test_m3.cairo
+│   └── utils
+└── utils
+    ├── common.cairo
+    └── conv.cairo
+```
+
+Instead of having additional files like `core.cairo` and `utils.cairo` on the same level as `lib.cairo` that just declare the inner modules, we can put everything in `lib.cairo`:
+
+```rust
+mod core {
+    mod m1;
+    mod m2;
+    mod m3;
+}
+
+mod utils {
+    mod commmon;
+    mod conv;
+}
+
+#[cfg(test)]
+mod tests {
+    mod core {
+        mod test_m1;
+        mod test_m2;
+        mod test_m3;
+    }
+}
+```
+{: .nolineno }
+
+They're the same picture!
+
+To get a better sense of the improvement, let's have a look at some real world examples. Compare the original, verbose style that's used in [Pragma](https://github.com/Astraly-Labs/pragma-oracle/blob/fe22f63188416b5f9810f8c6b93f095a20e31c9a/src/lib.cairo) with the compact one used in [Satoru](https://github.com/keep-starknet-strange/satoru/blob/fad9f1d6b7f5d8fcf1093b873f89d2241983424e/src/lib.cairo). Notice the additional files in Pragma's `src` dir like `admin.cairo` that are there only to declare `mod admin`. I definitely like the compact one better.
+
+Shout out to [gaetbout](https://twitter.com/gaetbout/) for showing me the way.