Merge pull request #20 from MidasLamb/patskov-compile-time-macro

Compile time macro

Author: MidasLamb

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.2.6](https://github.com/MidasLamb/non-empty-string/compare/v0.2.5...v0.2.6) - 2025-04-09
+
+### Added
+
+- `non_empty_string!()` macro to create a `NonEmptyString` at compile time , thanks @patskovn in #19 (requires `macros` feature flag)
+
 ## [0.2.5](https://github.com/MidasLamb/non-empty-string/compare/v0.2.4...v0.2.5) - 2024-10-15
 
 ### Added

Cargo.toml

@@ -25,6 +25,7 @@ serde = { version = "1", features = ["derive"] }
 
 [features]
 default = []
+macros = []
 serde = ["dep:serde"]
 
 

src/lib.rs

@@ -17,6 +17,9 @@ use delegate::delegate;
 #[cfg(feature = "serde")]
 mod serde_support;
 
+#[cfg(feature = "macros")]
+mod macros;
+
 mod trait_impls;
 
 /// A simple String wrapper type, similar to NonZeroUsize and friends.

src/macros.rs

@@ -0,0 +1,57 @@
+#[macro_export]
+/// Creates a `NonEmptyString` from a string literal at compile time.
+///
+/// This macro ensures that the provided string is **not empty** at compile time,
+/// preventing runtime errors due to empty strings.
+///
+/// # Examples
+///
+/// ```
+/// use non_empty_string::{non_empty_string, NonEmptyString};
+///
+/// let s: NonEmptyString = non_empty_string!("Hello, Rust!");
+/// assert_eq!(s, NonEmptyString::new("Hello, Rust!".to_string()).unwrap());
+/// ```
+///
+/// # Compile-time Failure
+///
+/// If an empty string is provided, this macro will cause a **compile-time error**.
+///
+/// ```compile_fail
+/// use non_empty_string::non_empty_string;
+///
+/// let s = non_empty_string!("");
+/// ```
+macro_rules! non_empty_string {
+    ($s:expr) => {{
+        // Compile-time assertion to ensure the string is non-empty
+        const _: () = assert!(!$s.is_empty(), "String cannot be empty");
+
+        // Create a NonEmptyString, unsafely wrapping since we've checked it's valid
+        unsafe { $crate::NonEmptyString::new_unchecked($s.to_string()) }
+    }};
+}
+
+#[cfg(test)]
+mod tests {
+    // We explicitely DO NOT do `use crate::NonEmptyString` or anything of the sorts to ensure the macro has proper hygiene.
+    // Otherwise tests might pass, but if a user does `non_empty_string::non_empty_string!("A")`, they might get compilation
+    // errors that `NonEmptyString` is not in scope.
+
+    const NON_EMPTY_STRING: &'static str = "non-empty-string";
+
+    #[test]
+    fn test_const_non_empty_string_macro_valid() {
+        let s = non_empty_string!(NON_EMPTY_STRING);
+        assert_eq!(
+            s,
+            crate::NonEmptyString::try_from(NON_EMPTY_STRING).unwrap()
+        );
+    }
+
+    #[test]
+    fn test_inline_non_empty_string_macro_valid() {
+        let s = non_empty_string!("Test String");
+        assert_eq!(s, crate::NonEmptyString::try_from("Test String").unwrap());
+    }
+}