Fix snapshot & module name extraction (#483)

insta/src/snapshot.rs

@@ -323,31 +323,11 @@ impl Snapshot {
             buf.push_str(&line);
         }
 
-        let module_name = p
-            .file_name()
-            .unwrap()
-            .to_str()
-            .unwrap_or("")
-            .split("__")
-            .next()
-            .unwrap_or("<unknown>")
-            .to_string();
-
-        let snapshot_name = p
-            .file_name()
-            .unwrap()
-            .to_str()
-            .unwrap_or("")
-            .split('.')
-            .next()
-            .unwrap_or("")
-            .splitn(2, "__")
-            .nth(1)
-            .map(|x| x.to_string());
+        let (snapshot_name, module_name) = names_of_path(p);
 
         Ok(Snapshot::from_components(
             module_name,
-            snapshot_name,
+            Some(snapshot_name),
             metadata,
             buf.into(),
         ))
@@ -630,6 +610,53 @@ fn normalize_inline_snapshot(snapshot: &str) -> String {
         .join("\n")
 }
 
+/// Extracts the module and snapshot name from a snapshot path
+fn names_of_path(path: &Path) -> (String, String) {
+    // The final part of the snapshot file name is the test name; the
+    // initial parts are the module name
+    let parts: Vec<&str> = path
+        .file_stem()
+        .unwrap()
+        .to_str()
+        .unwrap_or("")
+        .rsplitn(2, "__")
+        .collect();
+
+    match parts.as_slice() {
+        [snapshot_name, module_name] => (snapshot_name.to_string(), module_name.to_string()),
+        [snapshot_name] => (snapshot_name.to_string(), String::new()),
+        _ => (String::new(), "<unknown>".to_string()),
+    }
+}
+
+#[test]
+fn test_names_of_path() {
+    assert_debug_snapshot!(
+        names_of_path(Path::new("/src/snapshots/insta_tests__tests__name_foo.snap")), @r###"
+    (
+        "name_foo",
+        "insta_tests__tests",
+    )
+    "###
+    );
+    assert_debug_snapshot!(
+        names_of_path(Path::new("/src/snapshots/name_foo.snap")), @r###"
+    (
+        "name_foo",
+        "",
+    )
+    "###
+    );
+    assert_debug_snapshot!(
+        names_of_path(Path::new("foo/src/snapshots/go1.20.5.snap")), @r###"
+    (
+        "go1.20.5",
+        "",
+    )
+    "###
+    );
+}
+
 /// Helper function that returns the real inline snapshot value from a given
 /// frozen value string.  If the string starts with the '⋮' character
 /// (optionally prefixed by whitespace) the alternative serialization format