move empty index filtering into affected test

Author: ntBre

crates/ruff/src/cache.rs

@@ -547,7 +547,7 @@ mod tests {
                     continue;
                 }
 
-                let diagnostics = lint_path(
+                let mut diagnostics = lint_path(
                     &path,
                     Some(PackageRoot::root(&package_root)),
                     &settings.linter,
@@ -557,7 +557,14 @@ mod tests {
                     UnsafeFixes::Enabled,
                 )
                 .unwrap();
-                if !diagnostics.inner.is_empty() {
+                if diagnostics.inner.is_empty() {
+                    // We won't load a notebook index from the cache for files without diagnostics,
+                    // so remove them from `expected_diagnostics` too. This allows us to keep the
+                    // full equality assertion below.
+                    diagnostics
+                        .notebook_indexes
+                        .remove(&path.to_string_lossy().to_string());
+                } else {
                     paths_with_diagnostics.push(path.clone());
                 }
                 paths.push(path);

crates/ruff/src/diagnostics.rs

@@ -329,17 +329,10 @@ pub(crate) fn lint_path(
         cache.set_linted(relative_path.to_owned(), &key, linted);
     }
 
-    // Avoid constructing a map when there are no diagnostics. The index is only used for rendering
-    // diagnostics anyway. This mirrors our caching behavior, which does not preserve an empty index
-    // either.
-    let notebook_indexes = if diagnostics.is_empty() {
-        FxHashMap::default()
+    let notebook_indexes = if let SourceKind::IpyNotebook(notebook) = transformed {
+        FxHashMap::from_iter([(path.to_string_lossy().to_string(), notebook.into_index())])
     } else {
-        if let SourceKind::IpyNotebook(notebook) = transformed {
-            FxHashMap::from_iter([(path.to_string_lossy().to_string(), notebook.into_index())])
-        } else {
-            FxHashMap::default()
-        }
+        FxHashMap::default()
     };
 
     Ok(Diagnostics {
@@ -477,19 +470,13 @@ pub(crate) fn lint_stdin(
             (result, transformed, fixed)
         };
 
-    // Avoid constructing a map when there are no diagnostics. The index is only used for rendering
-    // diagnostics anyway.
-    let notebook_indexes = if diagnostics.is_empty() {
-        FxHashMap::default()
+    let notebook_indexes = if let SourceKind::IpyNotebook(notebook) = transformed {
+        FxHashMap::from_iter([(
+            path.map_or_else(|| "-".into(), |path| path.to_string_lossy().to_string()),
+            notebook.into_index(),
+        )])
     } else {
-        if let SourceKind::IpyNotebook(notebook) = transformed {
-            FxHashMap::from_iter([(
-                path.map_or_else(|| "-".into(), |path| path.to_string_lossy().to_string()),
-                notebook.into_index(),
-            )])
-        } else {
-            FxHashMap::default()
-        }
+        FxHashMap::default()
     };
 
     Ok(Diagnostics {