Impl new fn CrateName::dedup

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

src/helpers/crate_name.rs

@@ -1,8 +1,8 @@
-use std::convert::Infallible;
-use std::fmt;
-use std::str::FromStr;
+use std::{convert::Infallible, fmt, str::FromStr};
 
-#[derive(Debug, Clone)]
+use itertools::Itertools;
+
+#[derive(Debug, Clone, Eq, PartialEq)]
 pub struct CrateName {
     pub name: String,
     pub version: Option<String>,
@@ -37,3 +37,71 @@ impl FromStr for CrateName {
         })
     }
 }
+
+impl CrateName {
+    pub fn dedup(mut crate_names: Vec<Self>) -> impl Iterator<Item = Self> {
+        crate_names.sort_by(|x, y| x.name.cmp(&y.name));
+        crate_names.into_iter().coalesce(|previous, current| {
+            if previous.name == current.name {
+                Ok(current)
+            } else {
+                Err((previous, current))
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    macro_rules! assert_dedup {
+        ([ $( ( $input_name:expr, $input_version:expr ) ),*  ], [ $( ( $output_name:expr, $output_version:expr ) ),*  ]) => {
+            let input_crate_names = vec![$( CrateName {
+                name: $input_name.into(),
+                version: Some($input_version.into())
+            }, )*];
+
+            let mut output_crate_names: Vec<CrateName> = vec![$( CrateName {
+                name: $output_name.into(), version: Some($output_version.into())
+            }, )*];
+            output_crate_names.sort_by(|x, y| x.name.cmp(&y.name));
+
+            let crate_names: Vec<_> = CrateName::dedup(input_crate_names).collect();
+            assert_eq!(crate_names, output_crate_names);
+        };
+    }
+
+    #[test]
+    fn test_dedup() {
+        // Base case 0: Empty input
+        assert_dedup!([], []);
+
+        // Base case 1: With only one input
+        assert_dedup!([("a", "1")], [("a", "1")]);
+
+        // Base Case 2: Only has duplicate names
+        assert_dedup!([("a", "1"), ("a", "2")], [("a", "2")]);
+
+        // Complex Case 0: Having two crates
+        assert_dedup!(
+            [("a", "10"), ("b", "3"), ("a", "0"), ("b", "0"), ("a", "1")],
+            [("a", "1"), ("b", "0")]
+        );
+
+        // Complex Case 1: Having three crates
+        assert_dedup!(
+            [
+                ("d", "1.1"),
+                ("a", "10"),
+                ("b", "3"),
+                ("d", "230"),
+                ("a", "0"),
+                ("b", "0"),
+                ("a", "1"),
+                ("d", "23")
+            ],
+            [("a", "1"), ("b", "0"), ("d", "23")]
+        );
+    }
+}