Throw on warnings by default; Add onWarning loader option

Related to issue #121

README.md

@@ -103,8 +103,8 @@ options:
 
 - `filename` _(default: null)_ - string to be used as a file path in
   error/warning messages.
-- `strict` _(default - false)_ makes the loader to throw errors instead of
-  warnings.
+- `onWarning` _(default: null)_ - function to call on warning messages.
+  Loader will throw on warnings if this function is not provided.
 - `schema` _(default: `DEFAULT_SAFE_SCHEMA`)_ - specifies a schema to use.
   - `FAILSAFE_SCHEMA` - only strings, arrays and plain objects:
     http://www.yaml.org/spec/1.2/spec.html#id2802346

lib/js-yaml/loader.js

@@ -103,15 +103,15 @@ function simpleEscapeSequence(c) {
 
 
 function State(input, options) {
-  this.input    = input;
+  this.input = input;
 
-  this.filename = options['filename'] || null;
-  this.schema   = options['schema']   || DEFAULT_FULL_SCHEMA;
-  this.strict   = options['strict']   || false;
-  this.legacy   = options['legacy']   || false;
+  this.filename  = options['filename']  || null;
+  this.schema    = options['schema']    || DEFAULT_FULL_SCHEMA;
+  this.onWarning = options['onWarning'] || null;
+  this.legacy    = options['legacy']    || false;
 
-  this.implicitTypes     = this.schema.compiledImplicit;
-  this.typeMap           = this.schema.compiledTypeMap;
+  this.implicitTypes = this.schema.compiledImplicit;
+  this.typeMap       = this.schema.compiledTypeMap;
 
   this.length     = input.length;
   this.position   = 0;
@@ -145,10 +145,10 @@ function throwError(state, message) {
 function throwWarning(state, message) {
   var error = generateError(state, message);
 
-  if (state.strict) {
-    throw error;
+  if (state.onWarning) {
+    state.onWarning.call(null, error);
   } else {
-    console.warn(error.toString());
+    throw error;
   }
 }