save Link as a different format in toml

src/types/link.rs

@@ -1,15 +1,16 @@
+use serde::{
+    Deserialize, Deserializer, Serialize, Serializer,
+    de::{self, Visitor},
+};
 use std::{
-    fmt::Debug,
+    fmt::{self, Debug},
     path::{Path, PathBuf},
 };
 
-use serde::{Deserialize, Serialize};
-
 use crate::types::mod_file::ModFile;
 
 /// A link between a file from a mod and a destination in a ModdedInstance
-#[derive(Clone, Deserialize, Serialize, PartialEq, Eq, Hash)]
-#[serde(from = "(PathBuf, PathBuf)", into = "(PathBuf,PathBuf)")]
+#[derive(Clone, PartialEq, Eq, Hash)]
 pub struct Link {
     src: PathBuf,
     dst: PathBuf,
@@ -36,18 +37,46 @@ impl Link {
     }
 }
 
-impl From<(PathBuf, PathBuf)> for Link {
-    fn from(value: (PathBuf, PathBuf)) -> Self {
-        Self {
-            src: value.0,
-            dst: value.1,
+impl Serialize for Link {
+    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        if self.src == self.dst {
+            serializer.serialize_str(&self.src.to_string_lossy())
+        } else {
+            serializer.serialize_str(&format!(
+                "{} -> {}",
+                self.src.to_string_lossy(),
+                self.dst.to_string_lossy()
+            ))
         }
     }
 }
 
-impl From<Link> for (PathBuf, PathBuf) {
-    fn from(value: Link) -> Self {
-        (value.src, value.dst)
+impl<'de> Deserialize<'de> for Link {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        struct LinkVisitor;
+
+        impl<'de> Visitor<'de> for LinkVisitor {
+            type Value = Link;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str(r#"a string like "src -> dst" or "path" if they are the same"#)
+            }
+
+            fn visit_str<E: de::Error>(self, value: &str) -> Result<Link, E> {
+                match value.split_once(" -> ") {
+                    Some((src, dst)) => Ok(Link {
+                        src: PathBuf::from(src),
+                        dst: PathBuf::from(dst),
+                    }),
+                    None => Ok(Link {
+                        src: PathBuf::from(value),
+                        dst: PathBuf::from(value),
+                    }),
+                }
+            }
+        }
+
+        deserializer.deserialize_str(LinkVisitor)
     }
 }