Implement support for turning .json files into Lua modules (#308)

* Stub implementation

* Flesh out feature and add tests. Other snapshots currently failing.

* Blacklist .meta.json in JSON handler

* Write to correct property (Source) instead of Value

* Update changelog

src/snapshot_middleware/error.rs

@@ -7,30 +7,36 @@ pub enum SnapshotError {
     #[error("file name had malformed Unicode")]
     FileNameBadUnicode { path: PathBuf },
 
-    #[error("file had malformed Unicode contents")]
+    #[error("file had malformed Unicode contents at path {}", .path.display())]
     FileContentsBadUnicode {
         source: std::str::Utf8Error,
         path: PathBuf,
     },
 
-    #[error("malformed project file")]
+    #[error("malformed project file at path {}", .path.display())]
     MalformedProject {
         source: serde_json::Error,
         path: PathBuf,
     },
 
-    #[error("malformed .model.json file")]
+    #[error("malformed .model.json file at path {}", .path.display())]
     MalformedModelJson {
         source: serde_json::Error,
         path: PathBuf,
     },
 
-    #[error("malformed .meta.json file")]
+    #[error("malformed .meta.json file at path {}", .path.display())]
     MalformedMetaJson {
         source: serde_json::Error,
         path: PathBuf,
     },
 
+    #[error("malformed JSON at path {}", .path.display())]
+    MalformedJson {
+        source: serde_json::Error,
+        path: PathBuf,
+    },
+
     #[error(transparent)]
     Io {
         #[from]
@@ -76,4 +82,11 @@ impl SnapshotError {
             path: path.into(),
         }
     }
+
+    pub(crate) fn malformed_json(source: serde_json::Error, path: impl Into<PathBuf>) -> Self {
+        Self::MalformedJson {
+            source,
+            path: path.into(),
+        }
+    }
 }