feat(error): add custom error

Signed-off-by: Taylan Dogan <git@taylandogan.info>

Cargo.lock

@@ -84,6 +84,9 @@ dependencies = [
 [[package]]
 name = "gitolith-core"
 version = "0.1.0"
+dependencies = [
+ "thiserror",
+]
 
 [[package]]
 name = "heck"
@@ -284,6 +287,26 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e0f4a65597094d4483ddaed134f409b2cb7c1beccf25201a9f73c719254fa98e"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7765189610d8241a44529806d6fd1f2e0a08734313a35d5b3a556f92b381f3c0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "unicode-segmentation"
 version = "1.7.1"

gitolith-core/Cargo.toml

@@ -13,3 +13,4 @@ categories = []
 edition = "2018"
 
 [dependencies]
+thiserror = "1.0"

gitolith-core/src/error.rs

@@ -0,0 +1,29 @@
+use thiserror::Error as ThisError;
+
+/// Githolit-core related errors that we are exposing to the rest of the
+/// workspaces.
+#[derive(Debug, ThisError, PartialEq)]
+pub enum Error {
+	/// When commit's not follow the conventional commit structure we throw this
+	/// error.
+	#[error("Cannot parse the commit")]
+	ParseError,
+}
+
+/// Result type of the githolit-core libraries.
+pub type Result<T> = core::result::Result<T, Error>;
+
+#[cfg(test)]
+mod test {
+	use super::*;
+	fn mock_function() -> super::Result<()> {
+		return Err(Error::ParseError);
+	}
+
+	#[test]
+	fn throw_parse_error() {
+		let actual_error = mock_function().unwrap_err();
+		let expected_error = Error::ParseError;
+		assert_eq!(actual_error, expected_error);
+	}
+}

gitolith-core/src/lib.rs

@@ -1,7 +1 @@
-#[cfg(test)]
-mod tests {
-	#[test]
-	fn it_works() {
-		assert_eq!(2 + 2, 4);
-	}
-}
+pub mod error;