[test] Pretty print object properties on assert failure

Because I don't get much out of "Object() != Object()"

Change-Id: I5a765b9cb0a272d30edcd834ec7b60d2fd03190b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3497352Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79370}

test/message/mjsunit/fail/assert_not_same.out

@@ -3,7 +3,7 @@ test/mjsunit/mjsunit.js:{NUMBER}: Failure: expected <not same as 1> found <1>
 Stack: MjsUnitAssertionError
     at assertNotSame *mjsunit.js {NUMBER}:{NUMBER}
     at               *%(basename)s 7:1
-    throw new MjsUnitAssertionError(message);
+    throw new MjsUnitAssertionError(
     ^
 MjsUnitAssertionError
     at assertNotSame *mjsunit.js {NUMBER}:{NUMBER}

test/message/mjsunit/fail/assert_true.out

@@ -3,7 +3,7 @@ test/mjsunit/mjsunit.js:{NUMBER}: Failure: expected <true> found <false>
 Stack: MjsUnitAssertionError
     at assertTrue *mjsunit.js {NUMBER}:{NUMBER}
     at            *%(basename)s 7:1
-    throw new MjsUnitAssertionError(message);
+    throw new MjsUnitAssertionError(
     ^
 MjsUnitAssertionError
     at assertTrue *mjsunit.js {NUMBER}:{NUMBER}

test/mjsunit/mjsunit.js

@@ -25,8 +25,12 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-function MjsUnitAssertionError(message) {
-  this.message = message;
+var MjsUnitAssertionError = class MjsUnitAssertionError {
+  #cached_message = undefined;
+  #message_func = undefined;
+
+  constructor(message_func) {
+    this.#message_func = message_func;
     // Temporarily install a custom stack trace formatter and restore the
     // previous value.
     let prevPrepareStackTrace = Error.prepareStackTrace;
@@ -37,6 +41,18 @@ function MjsUnitAssertionError(message) {
     } finally {
       Error.prepareStackTrace = prevPrepareStackTrace;
     }
+  }
+
+  get message() {
+    if (this.#cached_message === undefined) {
+      this.#cached_message = this.#message_func();
+    }
+    return this.#cached_message
+  }
+
+  toString() {
+    return this.message + "\n\nStack: " + this.stack;
+  };
 }
 
 /*
@@ -45,11 +61,6 @@ function MjsUnitAssertionError(message) {
  * the f-word and ignore all other lines.
  */
 
-MjsUnitAssertionError.prototype.toString = function () {
-  return this.message + "\n\nStack: " + this.stack;
-};
-
-
 // Expected and found values the same objects, or the same primitive
 // values.
 // For known primitive values, please use assertEquals.
@@ -258,6 +269,9 @@ var prettyPrinted;
 
 
   prettyPrinted = function prettyPrinted(value) {
+    let visited = new Set();
+    function prettyPrint(value) {
+      try {
         switch (typeof value) {
           case "string":
             return JSONStringify(value);
@@ -273,6 +287,9 @@ var prettyPrinted;
             return String(value);
           case "object":
             if (value === null) return "null";
+            // Guard against re-visiting.
+            if (visited.has(value)) return "<...>";
+            visited.add(value);
             var objectClass = classOf(value);
             switch (objectClass) {
               case "Number":
@@ -280,12 +297,15 @@ var prettyPrinted;
               case "String":
               case "Boolean":
               case "Date":
-            return objectClass + "(" + prettyPrinted(ValueOf(value)) + ")";
+                return objectClass + "(" + prettyPrint(ValueOf(value)) + ")";
               case "RegExp":
                 return RegExpPrototypeToString.call(value);
               case "Array":
                 var mapped = ArrayPrototypeMap.call(
-                value, prettyPrintedArrayElement);
+                    value, (v,i,array)=>{
+                      if (v === undefined && !(i in array)) return "";
+                      return prettyPrint(v, visited);
+                    });
                 var joined = ArrayPrototypeJoin.call(mapped, ",");
                 return "[" + joined + "]";
               case "Uint8Array":
@@ -304,23 +324,27 @@ var prettyPrinted;
                 return objectClass + "(" + String(value) + ")";
             }
             // classOf() returned "Object".
-        var name = value.constructor.name;
-        if (name) return name + "()";
-        return "Object()";
+            var name = value.constructor?.name ?? "Object";
+            var pretty_properties = [];
+            for (let [k,v] of Object.entries(value)) {
+              ArrayPrototypePush.call(
+                  pretty_properties, `${k}:${prettyPrint(v, visited)}`);
+            }
+            var joined = ArrayPrototypeJoin.call(pretty_properties, ",");
+            return `${name}({${joined}})`;
           default:
             return "-- unknown value --";
         }
+      } catch (e) {
+        // Guard against general exceptions (especially stack overflows).
+        return "<error>"
       }
-
-
-  function prettyPrintedArrayElement(value, index, array) {
-    if (value === undefined && !(index in array)) return "";
-    return prettyPrinted(value);
     }
-
+    return prettyPrint(value);
+  }
 
   failWithMessage = function failWithMessage(message) {
-    throw new MjsUnitAssertionError(message);
+    throw new MjsUnitAssertionError(()=>message);
   }
 
   formatFailureText = function(expectedText, found, name_opt) {
@@ -340,7 +364,8 @@ var prettyPrinted;
   }
 
   function fail(expectedText, found, name_opt) {
-    return failWithMessage(formatFailureText(expectedText, found, name_opt));
+    throw new MjsUnitAssertionError(
+        ()=>formatFailureText(expectedText, found, name_opt));
   }