fix(ext/console): prevent duplicate error printing when the cause is assigned (#25327)

This commit fixes the error format when the cause is assigned
separately, ensuring that the cause is only printed once instead of
twice.

The fix addresses issue
[#21651](https://github.com/denoland/deno/issues/21651).

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/unit/console_test.ts b/tests/unit/console_test.ts
index 63ffff0dc..201d18f00 100644
--- a/tests/unit/console_test.ts
+++ b/tests/unit/console_test.ts
@@ -1894,6 +1894,25 @@ Deno.test(function consoleLogShouldNotThrowErrorWhenInputIsProxiedTypedArray() {
   });
 });
 
+Deno.test(function consoleLogWhenCauseIsAssignedShouldNotPrintCauseTwice() {
+  mockConsole((console, out) => {
+    const typeError = new TypeError("Type incorrect");
+    const syntaxError = new SyntaxError("Improper syntax");
+    typeError.cause = syntaxError;
+    console.log(typeError);
+    const result = stripAnsiCode(out.toString());
+    // Filter out stack trace lines, keeping only the first line and the cause line
+    const filteredOutput = result
+      .split("\n")
+      .filter((line) => !line.trim().startsWith("at"))
+      .join("\n");
+
+    const expectedResult =
+      "TypeError: Type incorrect\nCaused by SyntaxError: Improper syntax\n";
+    assertEquals(filteredOutput.trim(), expectedResult.trim());
+  });
+});
+
 // console.log(new Proxy(new RegExp(), {}))
 Deno.test(function consoleLogShouldNotThrowErrorWhenInputIsProxiedRegExp() {
   mockConsole((console, out) => {