Added more typechecking functions and unit tests for existing code.

remoting/webapp/crd/js/typecheck.js

Index: remoting/webapp/crd/js/typecheck.js
diff --git a/remoting/webapp/crd/js/typecheck.js b/remoting/webapp/crd/js/typecheck.js
index b44df12c4fe6e51aad0d4b765e5783edd33dd929..1329f4834a2e976f719ba241763cf03fb02fdbc4 100644
--- a/remoting/webapp/crd/js/typecheck.js
+++ b/remoting/webapp/crd/js/typecheck.js
@@ -3,6 +3,107 @@
 // found in the LICENSE file.
 
 /**
+ * @param {*} value the value to check; must be an object
+ * @return {*} the argument
+ */
+function assertDefined(value) {
+  if (value !== undefined) {
+    return value;
+  } else {
+    throw new Error('Undefined value');

[kelvinp, 2015/03/17 21:41:48]

we have a function base.debug.assert which current doesn't throw but only logs
an error message.

I think we can probably modify that function to throw and use base.debug.assert
here.

Same for the functions below.

In general, we are moving away from global functions so please add the new
functions to the base namespace.

[John Williams, 2015/03/18 17:23:01]

I tried rewriting in terms of assert, but it won't make the code any shorter
without sacrificing informative error messages.
Done.

+  }
+}
+
+/**
+ * @param {*} value the value to check; must be an object
+ * @return {!Array} the argument
+ */
+function assertArray(value) {
+  if (value instanceof Array) {

[kelvinp, 2015/03/17 21:41:48]

Nit: Array.isArray(value) as it is more robust across iframes.
http://stackoverflow.com/questions/22289727/difference-between-using-array-is...

[John Williams, 2015/03/18 17:23:01]

Done.

+    return /** @type {!Array} */ (value);
+  } else {
+    throw new Error('Invalid data type' +
+                    ' (expected: array, actual: ' + typeof value + ')');
+  }
+}
+
+/**
+ * @param {*} value the value to check; must be a boolean
+ * @return {boolean} the argument
+ */
+function assertBoolean(value) {
+  if (typeof value == 'boolean') {
+    return /** @type {boolean} */ (value);
+  } else {
+    throw new Error('Invalid data type' +
+                    ' (expected: boolean, actual: ' + typeof value + ')');
+  }
+}
+
+/**
+ * @param {*} value the value to check; must be a number
+ * @return {number} the argument
+ */
+function assertNumber(value) {
+  if (typeof value == 'number') {
+    return /** @type {number} */ (value);
+  } else {
+    throw new Error('Invalid data type' +
+                    ' (expected: number, actual: ' + typeof value + ')');
+  }
+}
+
+/**
+ * @param {*} value the value to check; must be an object
+ * @return {!Object} the argument
+ */
+function assertObject(value) {
+  if (value instanceof Object && !(value instanceof Array)) {
+    return /** @type {!Object} */ (value);
+  } else {
+    throw new Error('Invalid data type' +
+                    ' (expected: object, actual: ' + typeof value + ')');
+  }
+}
+
+/**
+ * @param {*} value the value to check; must be a string
+ * @return {string} the argument
+ */
+function assertString(value) {
+  if (typeof value == 'string') {
+    return /** @type {string} */ (value);
+  } else {
+    throw new Error('Invalid data type' +
+                    ' (expected: string, actual: ' + typeof value + ')');
+  }
+}
+
+/**
+ * Get the |key| attribute in the given |dict| and verify that it is an
+ * array value.

[kelvinp, 2015/03/17 21:41:48]

comment needs update. array value no longer applies.

[John Williams, 2015/03/18 17:23:01]

I just got rid of this function entirely.

+ *
+ * If the attribute is not an array, then an exception will be thrown unless
+ * a default value is specified in |opt_default|.
+ *
+ * @param {Object<string,*>} dict The dictionary containing the |key|
+ * @param {string} key The key to typecheck in the |dict|.
+ * @param {*=} opt_default The value to return if the key is not a bool.
+ * @return {*} The |key| attribute value as an object.
+ */
+function getAttr(dict, key, opt_default) {
+  var value = /** @type {*} */ (dict[key]);
+  if (value === undefined) {
+    if (opt_default === undefined) {
+      throw new Error('Undefined value for ' + key);
+    } else {
+      return opt_default;
+    }
+  }
+  return value;
+}
+
+/**
  * Get the |key| attribute in the given |dict| and verify that it is an
  * array value.
  *
@@ -18,8 +119,8 @@ function getArrayAttr(dict, key, opt_default) {
   var value = /** @type {Array} */ (dict[key]);
   if (!(value instanceof Array)) {
     if (opt_default === undefined) {
-      throw 'Invalid data type for ' + key +
-          ' (expected: array, actual: ' + typeof value + ')';
+      throw new Error('Invalid data type for ' + key +
+                      ' (expected: array, actual: ' + typeof value + ')');
     } else {
       return opt_default;
     }
@@ -46,8 +147,8 @@ function getBooleanAttr(dict, key, opt_default) {
   }
   if (typeof value !== 'boolean') {
     if (opt_default === undefined) {
-      throw 'Invalid data type for ' + key +
-          ' (expected: boolean, actual: ' + typeof value + ')';
+      throw new Error('Invalid data type for ' + key +
+                      ' (expected: boolean, actual: ' + typeof value + ')');
     } else {
       return opt_default;
     }
@@ -71,8 +172,8 @@ function getNumberAttr(dict, key, opt_default) {
   var value = /** @type {number} */(dict[key]);
   if (typeof value != 'number') {
     if (opt_default === undefined) {
-      throw 'Invalid data type for ' + key +
-          ' (expected: number, actual: ' + typeof value + ')';
+      throw new Error('Invalid data type for ' + key +
+                      ' (expected: number, actual: ' + typeof value + ')');
     } else {
       return opt_default;
     }
@@ -94,10 +195,10 @@ function getNumberAttr(dict, key, opt_default) {
  */
 function getObjectAttr(dict, key, opt_default) {
   var value = /** @type {Object} */ (dict[key]);
-  if (typeof value != 'object') {
+  if (!(value instanceof Object) || value instanceof Array) {
     if (opt_default === undefined) {
-      throw 'Invalid data type for ' + key +
-          ' (expected: object, actual: ' + typeof value + ')';
+      throw new Error('Invalid data type for ' + key +
+                      ' (expected: object, actual: ' + typeof value + ')');
     } else {
       return opt_default;
     }
@@ -121,8 +222,8 @@ function getStringAttr(dict, key, opt_default) {
   var value =  /** @type {string} */ (dict[key]);
   if (typeof value != 'string') {
     if (opt_default === undefined) {
-      throw 'Invalid data type for ' + key +
-          ' (expected: string, actual: ' + typeof value + ')';
+      throw new Error('Invalid data type for ' + key +
+                      ' (expected: string, actual: ' + typeof value + ')');
     } else {
       return opt_default;
     }
@@ -142,7 +243,8 @@ function getStringAttr(dict, key, opt_default) {
 function getJsonObjectFromString(jsonString) {
   var value = base.jsonParseSafe(jsonString);
   if (typeof value != 'object') {
-    throw 'Invalid data type (expected: Object, actual: ' + typeof value + ')';
+    throw new Error('Invalid data type (expected: Object, actual: ' +
+                    typeof value + ')');
   }
   return value;
 }