From 34c02357ff8e00c35e493754943f599dba0b0f29 Mon Sep 17 00:00:00 2001
From: Xavier Shay <xavier@rhnh.net>
Date: Tue, 1 Dec 2009 21:20:14 +1100
Subject: [PATCH] sys.inspect is totally more awesome now

- No longer relies on JSON.stringify, so it can output nulls and functions
- Handles circular references better
- Has tests
---
 lib/sys.js               | 84 ++++++++++++++++++++++++++++++----------
 test/mjsunit/test-sys.js | 26 +++++++++++++
 2 files changed, 90 insertions(+), 20 deletions(-)
 create mode 100644 test/mjsunit/test-sys.js

diff --git a/lib/sys.js b/lib/sys.js
index f755d71638..9c4dc6d944 100644
--- a/lib/sys.js
+++ b/lib/sys.js
@@ -17,26 +17,11 @@ exports.error = function (x) {
 /**
  * Echos the value of a value. Trys to print the value out
  * in the best way possible given the different types.
- * 
+ *
  * @param {Object} value The object to print out
  */
 exports.inspect = function (value) {
-  if (value === 0) return "0";
-  if (value === false) return "false";
-  if (value === "") return '""';
-  if (typeof(value) == "function") return "[Function]";
-  if (value === undefined) return;
-  
-  try {
-    return JSON.stringify(value, undefined, 1);
-  } catch (e) {
-    // TODO make this recusrive and do a partial JSON output of object.
-    if (e.message.search("circular")) {
-      return "[Circular Object]";
-    } else {
-      throw e;
-    }
-  }
+  return formatter(value, '', []);
 };
 
 exports.p = function (x) {
@@ -50,13 +35,13 @@ exports.exec = function (command) {
   var promise = new process.Promise();
 
   child.addListener("output", function (chunk) {
-    if (chunk) stdout += chunk; 
+    if (chunk) stdout += chunk;
   });
 
   child.addListener("error", function (chunk) {
-    if (chunk) stderr += chunk; 
+    if (chunk) stderr += chunk;
   });
-  
+
   child.addListener("exit", function (code) {
     if (code == 0) {
       promise.emitSuccess(stdout, stderr);
@@ -82,3 +67,62 @@ exports.exec = function (command) {
  * @param {function} superCtor Constructor function to inherit prototype from
  */
 exports.inherits = process.inherits;
+
+/**
+ * A recursive function to format an object - used by inspect.
+ *
+ * @param {Object} value
+ *   the value to format
+ * @param {String} indent
+ *   the indent level of any nested objects, since they are formatted over
+ *   more than one line
+ * @param {Array} parents
+ *   contains all objects above the current one in the heirachy, used to
+ *   prevent getting stuck in a loop on circular references
+ */
+var formatter = function(value, indent, parents) {
+  switch(typeof(value)) {
+    case 'string':    return '"' + value + '"';
+    case 'number':    return '' + value;
+    case 'function':  return '[Function]';
+    case 'boolean':   return '' + value;
+    case 'undefined': return 'undefined';
+    case 'object':
+      if (value == null) return 'null';
+      if (parents.indexOf(value) >= 0) return '[Circular]';
+      parents.push(value);
+
+      if (value instanceof Array) {
+        return formatObject(value, indent, parents, '[]', function(x, f) {
+          return f(value[x]);
+        });
+      } else {
+        return formatObject(value, indent, parents, '{}', function(x, f) {
+          return f(x) + ': ' + f(value[x]);
+        });
+      }
+      return buffer;
+    default:
+      throw('inspect unimplemented for ' + typeof(value));
+  }
+}
+
+/**
+ * Helper function for formatting either an array or an object, used internally by formatter
+ */
+var formatObject = function(obj, indent, parents, parenthesis, entryFormatter) {
+  var buffer = parenthesis[0];
+  var values = [];
+
+  var localFormatter = function(value) {
+    return formatter(value, indent + ' ', parents);
+  };
+  for (x in obj) {
+    values.push(indent + ' ' + entryFormatter(x, localFormatter));
+  }
+  if (values.length > 0) {
+    buffer += "\n" + values.join(",\n") + "\n" + indent;
+  }
+  buffer += parenthesis[1];
+  return buffer;
+}
diff --git a/test/mjsunit/test-sys.js b/test/mjsunit/test-sys.js
new file mode 100644
index 0000000000..14ce55157b
--- /dev/null
+++ b/test/mjsunit/test-sys.js
@@ -0,0 +1,26 @@
+process.mixin(require("./common"));
+process.mixin(require("sys"));
+
+assert.equal("0", inspect(0));
+assert.equal("1", inspect(1));
+assert.equal("false", inspect(false));
+assert.equal('""', inspect(""));
+assert.equal('"hello"', inspect("hello"));
+assert.equal("[Function]", inspect(function() {}));
+assert.equal('undefined', inspect(undefined));
+assert.equal('null', inspect(null));
+
+assert.equal('[]', inspect([]));
+assert.equal('[\n 1,\n 2\n]', inspect([1, 2]));
+assert.equal('[\n 1,\n [\n  2,\n  3\n ]\n]', inspect([1, [2, 3]]));
+
+assert.equal('{}', inspect({}));
+assert.equal('{\n "a": 1\n}', inspect({a: 1}));
+assert.equal('{\n "a": [Function]\n}', inspect({a: function() {}}));
+assert.equal('{\n "a": 1,\n "b": 2\n}', inspect({a: 1, b: 2}));
+assert.equal('{\n "a": {}\n}', inspect({'a': {}}));
+assert.equal('{\n "a": {\n  "b": 2\n }\n}', inspect({'a': {'b': 2}}));
+
+var value = {}
+value['a'] = value;
+assert.equal('{\n "a": [Circular]\n}', inspect(value));