prompt validator: improve error reporting

[aeschli]

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[github-actions]

Screenshot Changes

Base: 200fb2ed Current: 879cb04f

Changed (2)

chat/aiCustomizations/aiCustomizationManagementEditor/McpBrowseMode/Light

Before	After

agentSessionsViewer/NeedsInput/Dark

Before	After

[Copilot]

Pull request overview

Improves prompt file validation diagnostics by making file-reference checks more precise and adding logging for unexpected failures during existence checks.

Changes:

• Inject ILogService into PromptValidator to enable logging.
• Only emit a “file not found” marker when fileService.exists(...) returns false (avoids false positives).
• Add a warning log when file existence checks throw.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/common/promptSyntax/languageProviders/promptValidator.ts	Refines file-reference validation logic and logs failures during existence checks.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

The catch here swallows exceptions from fileService.exists and only logs a generic string. Please capture the error (e.g. catch (err)) and pass it to ILogService.warn so stack/details are preserved; additionally consider reporting a marker when the existence check fails so users still get feedback when validation can’t be performed.

Suggested change

	} catch {
	this.logger.warn(`Error checking existence of file reference '${ref.content}' resolved to '${resolved.toString()}' in prompt file '${promptAST.uri.toString()}'`);
	} catch (err) {
	this.logger.warn(`Error checking existence of file reference '${ref.content}' resolved to '${resolved.toString()}' in prompt file '${promptAST.uri.toString()}'`, err);
	report(toMarker(localize('promptValidator.fileReferenceValidationFailed', "Could not validate file reference '{0}'.", ref.content), ref.range, MarkerSeverity.Warning));