radicle-surf: serialize type for any kind of line

To help frontends with figuring out what kind of line is being talked
about for added and deleted files, the serialization of `Addition` and
`Deletion` always include a type. This mirrors the serialization of
the `Modification` type, which is tagged because it's an enum.

The serialization is hand-rolled since it is desirable to make sure
that added files and deleted files are only ever composed of lines
that are not modified.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

radicle-surf/src/diff.rs

@@ -238,23 +238,15 @@ impl Serialize for Line {
 
 /// Either the modification of a single [`Line`], or just contextual
 /// information.
-#[cfg_attr(
-    feature = "serde",
-    derive(Serialize),
-    serde(tag = "type", rename_all = "camelCase")
-)]
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Modification {
     /// A lines is an addition in a file.
-    #[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
     Addition(Addition),
 
     /// A lines is a deletion in a file.
-    #[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
     Deletion(Deletion),
 
     /// A contextual line in a file, i.e. there were no changes to the line.
-    #[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
     Context {
         line: Line,
         line_no_old: u32,
@@ -262,22 +254,96 @@ pub enum Modification {
     },
 }
 
+#[cfg(feature = "serde")]
+impl Serialize for Modification {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use serde::ser::SerializeMap as _;
+
+        const NAME: &str = "Modification";
+        const ADDITION: &str = "Addition";
+        const DELETION: &str = "Deletion";
+        const CONTEXT: &str = "Context";
+
+        match self {
+            Modification::Addition(addition) => {
+                let mut map = serializer.serialize_map(Some(3))?;
+                map.serialize_entry("line", &addition.line)?;
+                map.serialize_entry("lineNo", &addition.line_no)?;
+                map.serialize_entry("type", "addition")?;
+                map.end()
+            },
+            Modification::Deletion(deletion) => {
+                let mut map = serializer.serialize_map(Some(3))?;
+                map.serialize_entry("line", &deletion.line)?;
+                map.serialize_entry("lineNo", &deletion.line_no)?;
+                map.serialize_entry("type", "deletion")?;
+                map.end()
+            },
+            Modification::Context {
+                line,
+                line_no_old,
+                line_no_new,
+            } => {
+                let mut map = serializer.serialize_map(Some(4))?;
+                map.serialize_entry("line", line)?;
+                map.serialize_entry("lineNoOld", line_no_old)?;
+                map.serialize_entry("lineNoNew", line_no_new)?;
+                map.serialize_entry("type", "context")?;
+                map.end()
+            },
+        }
+    }
+}
+
 /// A addition of a [`Line`] at the `line_no`.
-#[cfg_attr(feature = "serde", derive(Serialize), serde(rename_all = "camelCase"))]
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Addition {
     pub line: Line,
     pub line_no: u32,
 }
 
+#[cfg(feature = "serde")]
+impl Serialize for Addition {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use serde::ser::SerializeStruct as _;
+
+        let mut s = serializer.serialize_struct("Addition", 3)?;
+        s.serialize_field("line", &self.line)?;
+        s.serialize_field("lineNo", &self.line_no)?;
+        s.serialize_field("type", "addition")?;
+        s.end()
+    }
+}
+
 /// A deletion of a [`Line`] at the `line_no`.
-#[cfg_attr(feature = "serde", derive(Serialize), serde(rename_all = "camelCase"))]
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Deletion {
     pub line: Line,
     pub line_no: u32,
 }
 
+#[cfg(feature = "serde")]
+impl Serialize for Deletion {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use serde::ser::SerializeStruct as _;
+
+        let mut s = serializer.serialize_struct("Deletion", 3)?;
+        s.serialize_field("line", &self.line)?;
+        s.serialize_field("lineNo", &self.line_no)?;
+        s.serialize_field("type", "deletion")?;
+        s.end()
+    }
+}
+
 impl Modification {
     pub fn addition(line: impl Into<Line>, line_no: u32) -> Self {
         Self::Addition(Addition {

radicle-surf/t/src/git/diff.rs

@@ -5,6 +5,8 @@ use radicle_surf::{
     diff::{
         Added,
         Addition,
+        Deleted,
+        Deletion,
         Diff,
         EofNewLine,
         FileDiff,
@@ -160,7 +162,17 @@ fn test_diff_serde() {
                 }].into()
             }
         }],
-        deleted: vec![],
+        deleted: vec![ Deleted {
+            path: Path::new("DCO").to_path_buf(),
+            diff: FileDiff::Plain {
+                hunks: vec![Hunk {
+                    header: Line::from(b"@@ -0,0 +1,1".to_vec()),
+                    lines: vec![
+                        Deletion { line: Line::from(b"TODO".to_vec()), line_no: 1 }
+                    ]
+                }].into()
+            }
+        }],
         moved: vec![ Moved {
             old_path: Path::new("CONTRIBUTING").to_path_buf(),
             new_path: Path::new("CONTRIBUTING.md").to_path_buf(),
@@ -199,11 +211,25 @@ fn test_diff_serde() {
                     "lines": [{
                         "line": "MIT",
                         "lineNo": 1,
+                        "type": "addition",
+                    }]
+                }]
+            },
+        }],
+        "deleted": [{
+            "path": "DCO",
+            "diff": {
+                "type": "plain",
+                "hunks": [{
+                    "header": "@@ -0,0 +1,1",
+                    "lines": [{
+                        "line": "TODO",
+                        "lineNo": 1,
+                        "type": "deletion",
                     }]
                 }]
             },
         }],
-        "deleted": [],
         "moved": [{ "oldPath": "CONTRIBUTING", "newPath": "CONTRIBUTING.md" }],
         "copied": [],
         "modified": [{