Fix malformed meta files causing panics.

Fixes #280.

src/snapshot_middleware/csv.rs

@@ -46,8 +46,8 @@ impl SnapshotMiddleware for SnapshotCsv {
                     .relevant_paths(vec![path.to_path_buf(), meta_path.clone()]),
             );
 
-        if let Some(meta_contents) = vfs.read(meta_path).with_not_found()? {
+        if let Some(meta_contents) = vfs.read(&meta_path).with_not_found()? {
-            let mut metadata = AdjacentMetadata::from_slice(&meta_contents);
+            let mut metadata = AdjacentMetadata::from_slice(&meta_contents, &meta_path)?;
             metadata.apply_all(&mut snapshot);
         }
 

src/snapshot_middleware/dir.rs

@@ -73,8 +73,8 @@ impl SnapshotMiddleware for SnapshotDir {
                     .context(context),
             );
 
-        if let Some(meta_contents) = vfs.read(meta_path).with_not_found()? {
+        if let Some(meta_contents) = vfs.read(&meta_path).with_not_found()? {
-            let mut metadata = DirectoryMetadata::from_slice(&meta_contents);
+            let mut metadata = DirectoryMetadata::from_slice(&meta_contents, &meta_path)?;
             metadata.apply_all(&mut snapshot);
         }
 

src/snapshot_middleware/error.rs

@@ -63,6 +63,13 @@ impl SnapshotError {
             path: Some(path.into()),
         }
     }
+
+    pub(crate) fn malformed_meta_json(source: serde_json::Error, path: impl Into<PathBuf>) -> Self {
+        Self {
+            detail: SnapshotErrorDetail::MalformedMetaJson { source },
+            path: Some(path.into()),
+        }
+    }
 }
 
 impl Error for SnapshotError {
@@ -114,6 +121,9 @@ pub enum SnapshotErrorDetail {
 
     #[snafu(display("malformed .model.json file"))]
     MalformedModelJson { source: serde_json::Error },
+
+    #[snafu(display("malformed .meta.json file"))]
+    MalformedMetaJson { source: serde_json::Error },
 }
 
 impl From<io::Error> for SnapshotErrorDetail {

src/snapshot_middleware/lua.rs

@@ -87,8 +87,8 @@ fn snapshot_lua_file(context: &InstanceContext, vfs: &Vfs, path: &Path) -> Snaps
                 .context(context),
         );
 
-    if let Some(meta_contents) = vfs.read(meta_path).with_not_found()? {
+    if let Some(meta_contents) = vfs.read(&meta_path).with_not_found()? {
-        let mut metadata = AdjacentMetadata::from_slice(&meta_contents);
+        let mut metadata = AdjacentMetadata::from_slice(&meta_contents, &meta_path)?;
         metadata.apply_all(&mut snapshot);
     }
 

src/snapshot_middleware/meta_file.rs

@@ -1,4 +1,4 @@
-use std::{borrow::Cow, collections::HashMap};
+use std::{borrow::Cow, collections::HashMap, path::Path};
 
 use rbx_dom_weak::UnresolvedRbxValue;
 use rbx_reflection::try_resolve_value;
@@ -6,6 +6,8 @@ use serde::{Deserialize, Serialize};
 
 use crate::snapshot::InstanceSnapshot;
 
+use super::error::SnapshotError;
+
 /// Represents metadata in a sibling file with the same basename.
 ///
 /// As an example, hello.meta.json next to hello.lua would allow assigning
@@ -21,10 +23,9 @@ pub struct AdjacentMetadata {
 }
 
 impl AdjacentMetadata {
-    pub fn from_slice(slice: &[u8]) -> Self {
+    pub fn from_slice(slice: &[u8], path: &Path) -> Result<Self, SnapshotError> {
         serde_json::from_slice(slice)
-            // TODO: Turn into error type
+            .map_err(|source| SnapshotError::malformed_meta_json(source, path))
-            .expect(".meta.json file was malformed")
     }
 
     pub fn apply_ignore_unknown_instances(&mut self, snapshot: &mut InstanceSnapshot) {
@@ -74,10 +75,9 @@ pub struct DirectoryMetadata {
 }
 
 impl DirectoryMetadata {
-    pub fn from_slice(slice: &[u8]) -> Self {
+    pub fn from_slice(slice: &[u8], path: &Path) -> Result<Self, SnapshotError> {
         serde_json::from_slice(slice)
-            // TODO: Turn into error type
+            .map_err(|source| SnapshotError::malformed_meta_json(source, path))
-            .expect("init.meta.json file was malformed")
     }
 
     pub fn apply_all(&mut self, snapshot: &mut InstanceSnapshot) {

src/snapshot_middleware/txt.rs

@@ -52,8 +52,8 @@ impl SnapshotMiddleware for SnapshotTxt {
                     .context(context),
             );
 
-        if let Some(meta_contents) = vfs.read(meta_path).with_not_found()? {
+        if let Some(meta_contents) = vfs.read(&meta_path).with_not_found()? {
-            let mut metadata = AdjacentMetadata::from_slice(&meta_contents);
+            let mut metadata = AdjacentMetadata::from_slice(&meta_contents, &meta_path)?;
             metadata.apply_all(&mut snapshot);
         }