Fix console output suppression when happy-dom overrides console

Fixes #6044

When DOM libraries like happy-dom override globalThis.console with their
VirtualConsole implementation, console output was silently suppressed
during tests because the VirtualConsole doesn't print to stdout/stderr
by default.

This fix implements console preservation by:
1. Storing the original Bun console when tests start
2. Setting up a property interceptor for globalThis.console
3. When a non-Bun console is assigned, replacing it with a bridged
   console that forwards all calls to Bun's original console

The solution maintains compatibility with DOM libraries while ensuring
console output remains visible during test execution.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/bun.js/test/jest.zig

@@ -355,6 +355,12 @@ pub const Jest = struct {
         else
             .{ TestScope, DescribeScope };
 
+        // Preserve console functionality for test environment
+        // This ensures that DOM libraries like happy-dom don't break console output
+        if (!outside_of_test) {
+            preserveConsoleForTests(globalObject);
+        }
+
         const module = JSValue.createEmptyObject(globalObject, 14);
 
         const test_fn = jsc.host_fn.NewFunction(globalObject, ZigString.static("test"), 2, ThisTestScope.call, false);
@@ -451,6 +457,69 @@ pub const Jest = struct {
         return module;
     }
 
+    /// Preserve console functionality for test environments when DOM libraries override it
+    fn preserveConsoleForTests(globalObject: *JSGlobalObject) void {
+        // Execute JavaScript code to set up console preservation
+        const console_preserve_code =
+            \\(() => {
+            \\  // Store the original Bun console
+            \\  const originalConsole = globalThis.console;
+            \\  const bunConsoleSymbol = Symbol.for('Bun.originalConsole');
+            \\  originalConsole[bunConsoleSymbol] = true;
+            \\  
+            \\  // Create a bridged console that always forwards to Bun's console
+            \\  const bridgedMethods = ['log', 'error', 'warn', 'info', 'debug', 'trace', 'assert', 'clear', 'count', 'countReset', 'dir', 'dirxml', 'group', 'groupCollapsed', 'groupEnd', 'table', 'time', 'timeEnd', 'timeLog'];
+            \\  const bridgedConsole = {};
+            \\  
+            \\  for (const method of bridgedMethods) {
+            \\    bridgedConsole[method] = function(...args) {
+            \\      return originalConsole[method](...args);
+            \\    };
+            \\  }
+            \\  
+            \\  // Copy Console constructor and other properties
+            \\  bridgedConsole.Console = originalConsole.Console;
+            \\  
+            \\  // Set up property descriptor to intercept console assignment
+            \\  const descriptor = Object.getOwnPropertyDescriptor(globalThis, 'console');
+            \\  let currentConsole = originalConsole;
+            \\  
+            \\  Object.defineProperty(globalThis, 'console', {
+            \\    get() {
+            \\      return currentConsole;
+            \\    },
+            \\    set(newConsole) {
+            \\      // Check if this is not Bun's original console (e.g., happy-dom's VirtualConsole)
+            \\      const isBunConsole = newConsole && newConsole[bunConsoleSymbol];
+            \\      
+            \\      if (!isBunConsole && newConsole && typeof newConsole.log === 'function') {
+            \\        // Use bridged console that forwards to Bun's original console
+            \\        currentConsole = bridgedConsole;
+            \\      } else {
+            \\        currentConsole = newConsole || originalConsole;
+            \\      }
+            \\    },
+            \\    configurable: true,
+            \\    enumerable: true
+            \\  });
+            \\})();
+        ;
+
+        // Execute the console preservation code
+        var exception: JSValue = .zero;
+        _ = jsc.JSModuleLoader.evaluate(
+            globalObject,
+            console_preserve_code.ptr,
+            console_preserve_code.len,
+            "bun:test:console-preserve".ptr,
+            "bun:test:console-preserve".len,
+            "".ptr,
+            0,
+            globalObject.toJSValue(),
+            @ptrCast(&exception),
+        );
+    }
+
     fn createMockObjects(globalObject: *JSGlobalObject, module: JSValue) void {
         const setSystemTime = jsc.host_fn.NewFunction(globalObject, ZigString.static("setSystemTime"), 0, JSMock__jsSetSystemTime, false);
         module.put(

test/regression/issue/6044.test.ts

@@ -0,0 +1,41 @@
+// Regression test for issue #6044: happy-dom causes console.log() to not print during tests
+// https://github.com/oven-sh/bun/issues/6044
+
+import { test, expect, describe } from "bun:test";
+import { Window } from "happy-dom";
+
+describe("Console preservation with happy-dom", () => {
+  test("console.log should work when happy-dom overrides console", () => {
+    const window = new Window();
+    globalThis.window = window;
+    globalThis.document = window.document;
+    globalThis.console = window.console; // This previously broke console output
+    
+    // These console calls should now appear in the output thanks to the fix
+    console.log("console.log works with happy-dom override");
+    console.error("console.error works with happy-dom override");
+    
+    expect(true).toBe(true);
+  });
+
+  test("console works with multiple happy-dom instances", () => {
+    // Test with multiple DOM setups that override console
+    for (let i = 0; i < 2; i++) {
+      const window = new Window();
+      globalThis.console = window.console;
+      console.log(`Console works with happy-dom instance ${i}`);
+    }
+    
+    expect(true).toBe(true);
+  });
+
+  test("console methods with complex arguments", () => {
+    const window = new Window();
+    globalThis.console = window.console;
+    
+    console.log("Complex object:", { key: "value", nested: { prop: 123 } });
+    console.log("Multiple arguments:", "string", 42, true, null);
+    
+    expect(true).toBe(true);
+  });
+});