feat: make logger injectable in ResponsiveTable class (#628)

- Add optional logger parameter to TableOptions type
- Update ResponsiveTable constructor to accept injected logger function
- Replace hardcoded logger.warn call with injected logger instance
- Default to logger.warn when no custom logger is provided
- Update test to use mock logger function instead of spying on global logger

This change improves testability by allowing tests to inject custom loggers
and increases flexibility by enabling different logging behaviors per table
instance. The change is backward compatible as the logger parameter is
optional and defaults to the existing behavior.

Resolves dependency injection concerns and enhances unit test isolation
by removing reliance on global logger state in tests.

Author: ryoppippi

src/_table.ts

@@ -29,6 +29,7 @@ export type TableOptions = {
 	compactColAligns?: TableCellAlign[];
 	compactThreshold?: number;
 	forceCompact?: boolean;
+	logger?: (message: string) => void;
 };
 
 /**
@@ -46,6 +47,7 @@ export class ResponsiveTable {
 	private compactThreshold: number;
 	private compactMode = false;
 	private forceCompact: boolean;
+	private logger: (message: string) => void;
 
 	/**
 	 * Creates a new responsive table instance
@@ -60,6 +62,7 @@ export class ResponsiveTable {
 		this.compactColAligns = options.compactColAligns;
 		this.compactThreshold = options.compactThreshold ?? 100;
 		this.forceCompact = options.forceCompact ?? false;
+		this.logger = options.logger ?? logger.warn;
 	}
 
 	/**
@@ -105,7 +108,7 @@ export class ResponsiveTable {
 			const index = this.head.indexOf(compactHeader);
 			if (index < 0) {
 				// Log warning for debugging configuration issues
-				logger.warn(`Warning: Compact header "${compactHeader}" not found in table headers [${this.head.join(', ')}]. Using first column as fallback.`);
+				this.logger(`Warning: Compact header "${compactHeader}" not found in table headers [${this.head.join(', ')}]. Using first column as fallback.`);
 				return 0; // fallback to first column if not found
 			}
 			return index;
@@ -711,15 +714,15 @@ if (import.meta.vitest != null) {
 			});
 
 			it('should fallback to first column for non-existent headers and log warning', () => {
+				// Mock logger.warn to capture warning
+				const mockLogger = vi.fn();
 				const table = new ResponsiveTable({
 					head: ['Date', 'Model', 'Input', 'Output', 'Cost'],
 					compactHead: ['Date', 'NonExistent', 'Cost'],
 					compactThreshold: 100,
+					logger: mockLogger,
 				});
 
-				// Mock logger.warn to capture warning
-				const mockWarn = vi.spyOn(logger, 'warn');
-
 				// Mock process.env.COLUMNS to simulate narrow terminal
 				const originalColumns = process.env.COLUMNS;
 				process.env.COLUMNS = '80';
@@ -733,12 +736,11 @@ if (import.meta.vitest != null) {
 				expect(indices).toEqual([0, 0, 4]); // Date (0), fallback to first (0), Cost (4)
 
 				// Verify warning was logged
-				expect(mockWarn).toHaveBeenCalledWith(
+				expect(mockLogger).toHaveBeenCalledWith(
 					'Warning: Compact header "NonExistent" not found in table headers [Date, Model, Input, Output, Cost]. Using first column as fallback.',
 				);
 
-				// Restore original values
-				mockWarn.mockRestore();
+				// Restore original value
 				process.env.COLUMNS = originalColumns;
 			});