lsp: Update contents before diagnosticRequestFile

One of the main causes for the 'empty module' error stemmed from the
sending of diagnosticRequestFile events with no content.

One solution would have been to fetch the content when processing
events on the diagnosticRequestFile channel, however it felt like the
publisher had more knowledge of how to do this correctly and
processing diagnosticRequestFile was getting unwieldy.

I have removed the content from diagnosticRequestFile, and these events
will just update the parse and send diagnostics. This should be less
surprising.

Signed-off-by: Charlie Egan <charlie@styra.com>

internal/lsp/server.go

@@ -115,9 +115,8 @@ type LanguageServer struct {
 
 // fileUpdateEvent is sent to a channel when an update is required for a file.
 type fileUpdateEvent struct {
-	Reason  string
-	URI     string
-	Content string
+	Reason string
+	URI    string
 }
 
 func (l *LanguageServer) Handle(
@@ -212,9 +211,11 @@ func (l *LanguageServer) StartDiagnosticsWorker(ctx context.Context) {
 		case <-ctx.Done():
 			return
 		case evt := <-l.diagnosticRequestFile:
-			err := l.processTextContentUpdate(ctx, evt.URI, evt.Content)
+			// updateParse will not return an error when the parsing failed,
+			// but only when it was impossible
+			_, err := updateParse(ctx, l.cache, l.regoStore, evt.URI)
 			if err != nil {
-				l.logError(fmt.Errorf("failed to process text content update: %w", err))
+				l.logError(fmt.Errorf("failed to update module for %s: %w", evt.URI, err))
 
 				continue
 			}
@@ -223,11 +224,15 @@ func (l *LanguageServer) StartDiagnosticsWorker(ctx context.Context) {
 			err = updateFileDiagnostics(ctx, l.cache, l.loadedConfig, evt.URI, l.workspaceRootURI)
 			if err != nil {
 				l.logError(fmt.Errorf("failed to update file diagnostics: %w", err))
+
+				continue
 			}
 
 			err = l.sendFileDiagnostics(ctx, evt.URI)
 			if err != nil {
 				l.logError(fmt.Errorf("failed to send diagnostic: %w", err))
+
+				continue
 			}
 
 			// if the file has agg diagnostics, we trigger a run for the workspace as by changing this file,
@@ -260,9 +265,42 @@ func (l *LanguageServer) StartHoverWorker(ctx context.Context) {
 		case <-ctx.Done():
 			return
 		case evt := <-l.builtinsPositionFile:
-			err := l.processHoverContentUpdate(ctx, evt.URI, evt.Content)
+			fileURI := evt.URI
+
+			if l.ignoreURI(fileURI) {
+				continue
+			}
+
+			if _, ok := l.cache.GetFileContents(fileURI); !ok {
+				// If the file is not in the cache, exit early or else
+				// we might accidentally put it in the cache after it's been
+				// deleted: https://github.com/StyraInc/regal/issues/679
+				continue
+			}
+
+			success, err := updateParse(ctx, l.cache, l.regoStore, fileURI)
+			if err != nil {
+				l.logError(fmt.Errorf("failed to update parse: %w", err))
+
+				continue
+			}
+
+			if !success {
+				continue
+			}
+
+			err = hover.UpdateBuiltinPositions(l.cache, fileURI)
+			if err != nil {
+				l.logError(fmt.Errorf("failed to update builtin positions: %w", err))
+
+				continue
+			}
+
+			err = hover.UpdateKeywordLocations(ctx, l.cache, fileURI)
 			if err != nil {
-				l.logError(fmt.Errorf("failed to process builtin and keyword positions update: %w", err))
+				l.logError(fmt.Errorf("failed to update keyword positions: %w", err))
+
+				continue
 			}
 		}
 	}
@@ -813,9 +851,8 @@ func (l *LanguageServer) StartTemplateWorker(ctx context.Context) {
 
 			// finally, trigger a diagnostics run for the new file
 			updateEvent := fileUpdateEvent{
-				Reason:  "internal/templateNewFile",
-				URI:     fileURI,
-				Content: newContents,
+				Reason: "internal/templateNewFile",
+				URI:    fileURI,
 			}
 
 			l.diagnosticRequestFile <- updateEvent
@@ -1012,33 +1049,6 @@ func (l *LanguageServer) fixRenameParams(
 	}, nil
 }
 
-// processTextContentUpdate updates the cache with the new content for the file at the given URI, attempts to parse the
-// file, and returns whether the parse was successful. If it was not successful, the parse errors will be sent
-// on the diagnostic channel.
-func (l *LanguageServer) processTextContentUpdate(
-	ctx context.Context,
-	fileURI string,
-	content string,
-) error {
-	if l.ignoreURI(fileURI) {
-		return nil
-	}
-
-	currentContent, ok := l.cache.GetFileContents(fileURI)
-	if ok && currentContent == content {
-		return nil
-	}
-
-	l.cache.SetFileContents(fileURI, content)
-
-	_, err := updateParse(ctx, l.cache, l.regoStore, fileURI)
-	if err != nil {
-		return fmt.Errorf("failed to update parse: %w", err)
-	}
-
-	return nil
-}
-
 // processHoverContentUpdate updates information about built in, and keyword
 // positions in the cache for use when handling hover requests.
 func (l *LanguageServer) processHoverContentUpdate(ctx context.Context, fileURI string, content string) error {
@@ -1617,10 +1627,11 @@ func (l *LanguageServer) handleTextDocumentDidOpen(
 		return struct{}{}, nil
 	}
 
+	l.cache.SetFileContents(params.TextDocument.URI, params.TextDocument.Text)
+
 	evt := fileUpdateEvent{
-		Reason:  "textDocument/didOpen",
-		URI:     params.TextDocument.URI,
-		Content: params.TextDocument.Text,
+		Reason: "textDocument/didOpen",
+		URI:    params.TextDocument.URI,
 	}
 
 	l.diagnosticRequestFile <- evt
@@ -1674,10 +1685,15 @@ func (l *LanguageServer) handleTextDocumentDidChange(
 		return struct{}{}, nil
 	}
 
+	if len(params.ContentChanges) < 1 {
+		return struct{}{}, nil
+	}
+
+	l.cache.SetFileContents(params.TextDocument.URI, params.ContentChanges[0].Text)
+
 	evt := fileUpdateEvent{
-		Reason:  "textDocument/didChange",
-		URI:     params.TextDocument.URI,
-		Content: params.ContentChanges[0].Text,
+		Reason: "textDocument/didChange",
+		URI:    params.TextDocument.URI,
 	}
 
 	l.diagnosticRequestFile <- evt
@@ -1819,10 +1835,11 @@ func (l *LanguageServer) handleTextDocumentFormatting(
 
 		l.cache.ClearFileDiagnostics()
 
+		l.cache.SetFileContents(params.TextDocument.URI, newContent)
+
 		updateEvent := fileUpdateEvent{
-			Reason:  "internal/templateFormattingFallback",
-			URI:     params.TextDocument.URI,
-			Content: newContent,
+			Reason: "internal/templateFormattingFallback",
+			URI:    params.TextDocument.URI,
 		}
 
 		l.diagnosticRequestFile <- updateEvent
@@ -2031,9 +2048,8 @@ func (l *LanguageServer) handleWorkspaceDidRenameFiles(
 		l.cache.SetFileContents(renameOp.NewURI, content)
 
 		evt := fileUpdateEvent{
-			Reason:  "textDocument/didRename",
-			URI:     renameOp.NewURI,
-			Content: content,
+			Reason: "textDocument/didRename",
+			URI:    renameOp.NewURI,
 		}
 
 		l.diagnosticRequestFile <- evt
@@ -2206,7 +2222,18 @@ func (l *LanguageServer) loadWorkspaceContents(ctx context.Context, newOnly bool
 		}
 
 		// if the caller has requested only new files, then we can exit early
-		if _, ok := l.cache.GetFileContents(fileURI); newOnly && ok {
+		if contents, ok := l.cache.GetFileContents(fileURI); newOnly && ok {
+			diskContents, err := os.ReadFile(fileURI)
+			if err != nil {
+				// then there is nothing we can do here
+				return nil
+			}
+
+			if string(diskContents) == "" && contents == "" {
+				// then there is nothing to be gained from loading from disk
+				return nil
+			}
+
 			return nil
 		}