JSON.stringify safely

lib/bunyan.js

@@ -69,7 +69,7 @@ if (!format) {
       switch (x) {
         case '%s': return String(args[i++]);
         case '%d': return Number(args[i++]);
-        case '%j': return JSON.stringify(args[i++]);
+        case '%j': return JSON.stringify(args[i++], safeCycles());
         case '%%': return '%';
         default:
           return x;
@@ -672,24 +672,7 @@ Logger.prototype._emit = function (rec) {
   // Stringify the object. Attempt to warn/recover on error.
   var str;
   if (this.haveNonRawStreams) {
-    try {
-      str = JSON.stringify(obj) + '\n';
-    } catch (e) {
-      var src = ((obj.src && obj.src.file) ? obj.src : getCaller3Info());
-      var emsg = format('bunyan: ERROR: could not stringify log record from '
-        + '%s:%d: %s', src.file, src.line, e);
-      var eobj = objCopy(rec[0]);
-      eobj.bunyanMsg = emsg;
-      eobj.msg = obj.msg;
-      eobj.time = obj.time;
-      eobj.v = LOG_VERSION;
-      _warn(emsg, src.file, src.line);
-      try {
-        str = JSON.stringify(eobj) + '\n';
-      } catch (e2) {
-        str = JSON.stringify({bunyanMsg: emsg});
-      }
-    }
+    str = JSON.stringify(obj, safeCycles()) + '\n';
   }
 
   for (i = 0; i < this.streams.length; i++) {
@@ -1022,6 +1005,21 @@ var errSerializer = Logger.stdSerializers.err = function err(err) {
   return obj;
 };
 
+// A JSON stringifier that handles cycles safely.
+// Usage: JSON.stringify(obj, safeCycles())
+function safeCycles() {
+  var seen = [];
+  return function(key, val) {
+    if (!val || typeof val !== 'object') {
+      return val;
+    }
+    if (seen.indexOf(val) !== -1) {
+      return '[Circular]';
+    }
+    seen.push(val);
+    return val;
+  };
+}
 
 /**
  * RingBuffer is a Writable Stream that just stores the last N records in

test/cycles.test.js

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2012 Trent Mick. All rights reserved.
+ *
+ * Make sure cycles are safe.
+ */
+
+var test = require('tap').test;
+var Logger = require('../lib/bunyan.js');
+
+var Stream = require('stream').Stream;
+var outstr = new Stream;
+outstr.writable = true;
+var output = [];
+outstr.write = function (c) {
+  output.push(JSON.parse(c + ''));
+};
+outstr.end = function (c) {
+  if (c) this.write(c);
+  this.emit('end');
+};
+
+// these are lacking a few fields that will probably never match
+var expect =
+    [
+      {
+        "name": "blammo",
+        "level": 30,
+        "msg": "bango { bang: 'boom', KABOOM: [Circular] }",
+        "v": 0
+      },
+      {
+        "name": "blammo",
+        "level": 30,
+        "msg": "kaboom { bang: 'boom', KABOOM: [Circular] }",
+        "v": 0
+      },
+      {
+        "name": "blammo",
+        "level": 30,
+        "bang": "boom",
+        "KABOOM": {
+          "bang": "boom",
+          "KABOOM": "[Circular]"
+        },
+        "msg": "",
+        "v": 0
+      }
+    ];
+
+var log = new Logger({
+  name: 'blammo',
+  streams: [
+    {
+      type: 'stream',
+      level: 'info',
+      stream: outstr
+    }
+  ]
+});
+
+test('cycles', function (t) {
+  outstr.on('end', function () {
+    output.forEach(function (o, i) {
+      t.has(o, expect[i], 'log item ' + i + ' matches');
+    });
+    t.end();
+  });
+
+  var obj = { bang: 'boom' };
+  obj.KABOOM = obj;
+  log.info('bango', obj);
+  log.info('kaboom', obj.KABOOM);
+  log.info(obj);
+  outstr.end();
+  t.pass('did not throw');
+});