Better cancellation token error suppression (#268)

Author: kddejong

src/handlers/DocumentHandler.ts

@@ -12,6 +12,7 @@ import { LintTrigger } from '../services/cfnLint/CfnLintService';
 import { ValidationTrigger } from '../services/guard/GuardService';
 import { publishValidationDiagnostics } from '../stacks/actions/StackActionOperations';
 import { LoggerFactory } from '../telemetry/LoggerFactory';
+import { CancellationError } from '../utils/Delayer';
 
 const log = LoggerFactory.getLogger('DocumentHandler');
 
@@ -36,8 +37,8 @@ export function didOpenHandler(components: ServerComponents): (event: TextDocume
 
         components.cfnLintService.lintDelayed(content, uri, LintTrigger.OnOpen).catch((reason) => {
             // Handle cancellation gracefully - user might have closed/changed the document
-            if (reason instanceof Error && reason.message.includes('Request cancelled')) {
-                // Do nothing
+            if (reason instanceof CancellationError) {
+                // Do nothing - cancellation is expected behavior
             } else {
                 log.error(reason, `Linting error for ${uri}`);
             }
@@ -105,8 +106,8 @@ export function didChangeHandler(
         // Trigger cfn-lint validation
         components.cfnLintService.lintDelayed(content, documentUri, LintTrigger.OnChange, true).catch((reason) => {
             // Handle both getTextDocument and linting errors
-            if (reason instanceof Error && reason.message.includes('Request cancelled')) {
-                // Do nothing
+            if (reason instanceof CancellationError) {
+                // Do nothing - cancellation is expected behavior
             } else {
                 log.error(reason, `Error in didChange processing for ${documentUri}`);
             }
@@ -172,8 +173,8 @@ export function didSaveHandler(components: ServerComponents): (event: TextDocume
 
         // Trigger cfn-lint validation
         components.cfnLintService.lintDelayed(documentContent, documentUri, LintTrigger.OnSave).catch((reason) => {
-            if (reason instanceof Error && reason.message.includes('Request cancelled')) {
-                // Do nothing
+            if (reason instanceof CancellationError) {
+                // Do nothing - cancellation is expected behavior
             } else {
                 log.error(reason, `Linting error for ${documentUri}`);
             }

src/services/DiagnosticCoordinator.ts

@@ -6,7 +6,7 @@ import { LspDiagnostics } from '../protocol/LspDiagnostics';
 import { ValidationManager } from '../stacks/actions/ValidationManager';
 import { CFN_VALIDATION_SOURCE } from '../stacks/actions/ValidationWorkflow';
 import { LoggerFactory } from '../telemetry/LoggerFactory';
-import { Delayer } from '../utils/Delayer';
+import { CancellationError, Delayer } from '../utils/Delayer';
 
 type SourceToDiagnostics = Map<string, Diagnostic[]>;
 
@@ -54,6 +54,10 @@ export class DiagnosticCoordinator {
             // Debounce the actual LSP publishing to avoid spam on keystrokes
             await this.delayer.delay(uri, () => this.publishToLsp(uri));
         } catch (error) {
+            // Suppress cancellation errors as they are expected behavior
+            if (error instanceof CancellationError) {
+                return;
+            }
             this.log.error(error, `Failed to publish diagnostics for source ${source}, URI ${uri}`);
             throw error;
         }

src/services/cfnLint/CfnLintService.ts

@@ -12,7 +12,7 @@ import { LoggerFactory } from '../../telemetry/LoggerFactory';
 import { ScopedTelemetry } from '../../telemetry/ScopedTelemetry';
 import { Count, Telemetry } from '../../telemetry/TelemetryDecorator';
 import { Closeable } from '../../utils/Closeable';
-import { Delayer } from '../../utils/Delayer';
+import { CancellationError, Delayer } from '../../utils/Delayer';
 import { extractErrorMessage } from '../../utils/Errors';
 import { byteSize } from '../../utils/String';
 import { DiagnosticCoordinator } from '../DiagnosticCoordinator';
@@ -632,12 +632,20 @@ export class CfnLintService implements SettingsConfigurable, Closeable {
         }
 
         // Service is ready, process based on trigger type
-        if (trigger === LintTrigger.OnSave) {
-            // For save operations: execute immediately (0ms delay)
-            await this.delayer.delay(uri, () => this.lint(content, uri, forceUseContent), 0);
-        } else {
-            // For other triggers: use normal delayed execution
-            await this.delayer.delay(uri, () => this.lint(content, uri, forceUseContent));
+        try {
+            if (trigger === LintTrigger.OnSave) {
+                // For save operations: execute immediately (0ms delay)
+                await this.delayer.delay(uri, () => this.lint(content, uri, forceUseContent), 0);
+            } else {
+                // For other triggers: use normal delayed execution
+                await this.delayer.delay(uri, () => this.lint(content, uri, forceUseContent));
+            }
+        } catch (error) {
+            // Suppress cancellation errors as they are expected behavior
+            if (error instanceof CancellationError) {
+                return;
+            }
+            throw error;
         }
     }
 

src/services/guard/GuardService.ts

@@ -10,7 +10,7 @@ import { LoggerFactory } from '../../telemetry/LoggerFactory';
 import { ScopedTelemetry } from '../../telemetry/ScopedTelemetry';
 import { Count, Telemetry } from '../../telemetry/TelemetryDecorator';
 import { Closeable } from '../../utils/Closeable';
-import { Delayer } from '../../utils/Delayer';
+import { CancellationError, Delayer } from '../../utils/Delayer';
 import { extractErrorMessage } from '../../utils/Errors';
 import { readFileIfExistsAsync } from '../../utils/File';
 import { byteSize } from '../../utils/String';
@@ -377,9 +377,8 @@ export class GuardService implements SettingsConfigurable, Closeable {
                 await this.delayer.delay(uri, () => this.validate(content, uri, forceUseContent));
             }
         } catch (error) {
-            const errorMessage = extractErrorMessage(error);
-            // Check if this is a cancellation error - these are normal during rapid typing
-            if (errorMessage.includes('Request cancelled') || errorMessage.includes('cancelled')) {
+            // Suppress cancellation errors as they are expected behavior
+            if (error instanceof CancellationError) {
                 return;
             }
             // For other errors, re-throw to be handled by caller

src/utils/Delayer.ts

@@ -1,3 +1,10 @@
+export class CancellationError extends Error {
+    constructor(key: string) {
+        super(`Request cancelled for key: ${key}`);
+        this.name = 'CancellationError';
+    }
+}
+
 interface DelayedRequest<T> {
     executor: () => Promise<T>;
     resolve: (result: T) => void;
@@ -142,7 +149,7 @@ export class Delayer<T> {
 
         if (request) {
             this.pendingRequests.delete(key);
-            request.reject(new Error(`Request cancelled for key: ${key}`));
+            request.reject(new CancellationError(key));
         }
 
         // Note: We don't cancel running requests as they can't be safely cancelled
@@ -163,7 +170,7 @@ export class Delayer<T> {
 
         // Reject all pending requests
         for (const [key, request] of this.pendingRequests.entries()) {
-            request.reject(new Error(`Request cancelled for key: ${key}`));
+            request.reject(new CancellationError(key));
         }
         this.pendingRequests.clear();