Add utility for working with file names, port JSON model to use it

src/snapshot_middleware/json_model.rs

@@ -10,8 +10,8 @@ use crate::{
 };
 
 use super::{
-    error::SnapshotError,
     middleware::{SnapshotFileResult, SnapshotInstanceResult, SnapshotMiddleware},
+    util::match_file_name,
 };
 
 pub struct SnapshotJsonModel;
@@ -25,15 +25,8 @@ impl SnapshotMiddleware for SnapshotJsonModel {
             return Ok(None);
         }
 
-        let file_name = entry
-            .path()
-            .file_name()
-            .unwrap()
-            .to_str()
-            .ok_or_else(|| SnapshotError::file_name_bad_unicode(entry.path()))?;
-
-        let instance_name = match match_trailing(&file_name, ".model.json") {
-            Some(name) => name.to_owned(),
+        let instance_name = match match_file_name(entry.path(), ".model.json") {
+            Some(name) => name,
             None => return Ok(None),
         };
 
@@ -58,7 +51,7 @@ impl SnapshotMiddleware for SnapshotJsonModel {
             }
         }
 
-        let mut snapshot = instance.core.into_snapshot(instance_name);
+        let mut snapshot = instance.core.into_snapshot(instance_name.to_owned());
 
         snapshot.metadata.instigating_source = Some(entry.path().to_path_buf().into());
         snapshot.metadata.relevant_paths = vec![entry.path().to_path_buf()];

src/snapshot_middleware/mod.rs

@@ -16,6 +16,7 @@ mod rbxlx;
 mod rbxm;
 mod rbxmx;
 mod txt;
+mod util;
 
 pub use self::error::*;
 

src/snapshot_middleware/util.rs

@@ -0,0 +1,20 @@
+use std::path::Path;
+
+/// If the given string ends up with the given suffix, returns the portion of
+/// the string before the suffix.
+pub fn match_trailing<'a>(input: &'a str, suffix: &str) -> Option<&'a str> {
+    if input.ends_with(suffix) {
+        let end = input.len().saturating_sub(suffix.len());
+        Some(&input[..end])
+    } else {
+        None
+    }
+}
+
+/// If the given path has a file name, and that file name ends with the given
+/// suffix, returns the portion of the file name before the given suffix.
+pub fn match_file_name<'a>(path: &'a Path, suffix: &str) -> Option<&'a str> {
+    let file_name = path.file_name()?.to_str()?;
+
+    match_trailing(&file_name, suffix)
+}