[ty] Remove FileLookupError (#19323)

## Summary

This PR removes the `FileLookupError` as it's not really required. The
original intention was that this would be returned from the `.file`
lookup to the different handlers but we've since moved the logic of
"lookup file and add trace message if file unavailable with the reason"
under the `file_ok` method which all of the handlers use.

crates/ty_server/src/server/api/requests/completion.rs

@@ -38,7 +38,7 @@ impl BackgroundDocumentRequestHandler for CompletionRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/server/api/requests/goto_type_definition.rs

@@ -34,7 +34,7 @@ impl BackgroundDocumentRequestHandler for GotoTypeDefinitionRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/server/api/requests/hover.rs

@@ -34,7 +34,7 @@ impl BackgroundDocumentRequestHandler for HoverRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/server/api/requests/inlay_hints.rs

@@ -33,7 +33,7 @@ impl BackgroundDocumentRequestHandler for InlayHintRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/server/api/requests/semantic_tokens.rs

@@ -30,7 +30,7 @@ impl BackgroundDocumentRequestHandler for SemanticTokensRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/server/api/requests/semantic_tokens_range.rs

@@ -32,7 +32,7 @@ impl BackgroundDocumentRequestHandler for SemanticTokensRangeRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/server/api/requests/signature_help.rs

@@ -36,7 +36,7 @@ impl BackgroundDocumentRequestHandler for SignatureHelpRequestHandler {
             return Ok(None);
         }
 
-        let Some(file) = snapshot.file_ok(db) else {
+        let Some(file) = snapshot.file(db) else {
             return Ok(None);
         };
 

crates/ty_server/src/session.rs

@@ -508,35 +508,25 @@ impl DocumentSnapshot {
         self.document_query_result.as_ref()
     }
 
-    pub(crate) fn file_ok(&self, db: &dyn Db) -> Option<File> {
-        match self.file(db) {
-            Ok(file) => Some(file),
-            Err(err) => {
-                tracing::debug!("Failed to resolve file: {}", err);
-                None
-            }
-        }
-    }
-
-    fn file(&self, db: &dyn Db) -> Result<File, FileLookupError> {
+    pub(crate) fn file(&self, db: &dyn Db) -> Option<File> {
         let document = match self.document() {
             Ok(document) => document,
-            Err(err) => return Err(FileLookupError::DocumentQuery(err.clone())),
+            Err(err) => {
+                tracing::debug!("Failed to resolve file: {}", err);
+                return None;
+            }
         };
-        document
-            .file(db)
-            .ok_or_else(|| FileLookupError::NotFound(document.file_path().clone()))
+        let file = document.file(db);
+        if file.is_none() {
+            tracing::debug!(
+                "Failed to resolve file: file not found for path `{}`",
+                document.file_path()
+            );
+        }
+        file
     }
 }
 
-#[derive(Debug, thiserror::Error)]
-pub(crate) enum FileLookupError {
-    #[error("file not found for path `{0}`")]
-    NotFound(AnySystemPath),
-    #[error(transparent)]
-    DocumentQuery(DocumentQueryError),
-}
-
 /// An immutable snapshot of the current state of [`Session`].
 pub(crate) struct SessionSnapshot {
     projects: Vec<ProjectDatabase>,