Remove throws in function evaluation and handle color function arguments

correctly.

lib/carto/functions.js

@@ -7,6 +7,7 @@ tree.functions = {
     rgba: function (r, g, b, a) {
         var rgb = [r, g, b].map(function (c) { return number(c); });
         a = number(a);
+        if (rgb.some(isNaN) || isNaN(a)) return null;
         return new tree.Color(rgb, a);
     },
     hsl: function (h, s, l) {
@@ -15,9 +16,10 @@ tree.functions = {
     hsla: function (h, s, l, a) {
         h = (number(h) % 360) / 360;
         s = number(s); l = number(l); a = number(a);
+        if ([h, s, l, a].some(isNaN)) return null;
 
-        var m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s;
-        var m1 = l * 2 - m2;
+        var m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s,
+            m1 = l * 2 - m2;
 
         return this.rgba(hue(h + 1/3) * 255,
                          hue(h)       * 255,
@@ -154,8 +156,8 @@ tree.functions['agg-stack-blur'] = function(x, y) {
     return new tree.ImageFilter('agg-stack-blur', [x, y]);
 };
 
-function hsla(hsla) {
-    return tree.functions.hsla(hsla.h, hsla.s, hsla.l, hsla.a);
+function hsla(h) {
+    return tree.functions.hsla(h.h, h.s, h.l, h.a);
 }
 
 function number(n) {
@@ -164,7 +166,7 @@ function number(n) {
     } else if (typeof(n) === 'number') {
         return n;
     } else {
-        throw new Error('Color functions take numbers as parameters.');
+        return NaN;
     }
 }
 

lib/carto/renderer.js

@@ -84,7 +84,7 @@ carto.Renderer.prototype.render = function render(m, callback) {
     var rulesets = _(m.Stylesheet).chain()
         .map(function(s) {
             if (typeof s == 'string') {
-               throw new Error("Stylesheet object is expected not a string: '" + s + "'");
+               callback(new Error("Stylesheet object is expected not a string: '" + s + "'"));
             }
             // Passing the environment from stylesheet to stylesheet,
             // allows frames and effects to be maintained.

lib/carto/tree/call.js

@@ -30,7 +30,17 @@ tree.Call.prototype = {
 
         if (this.name in tree.functions) {
             if (tree.functions[this.name].length === args.length) {
-                return tree.functions[this.name].apply(tree.functions, args);
+                var val = tree.functions[this.name].apply(tree.functions, args);
+                if (val == null) {
+                    env.error({
+                        message: 'incorrect arguments given to ' + this.name + '()',
+                        index: this.index,
+                        type: 'runtime',
+                        filename: this.filename
+                    });
+                    return { is: 'undefined', value: 'undefined' };
+                }
+                return val;
             } else {
                 env.error({
                     message: 'incorrect number of arguments for ' + this.name +

test/errorhandling/color_functions.mml

@@ -0,0 +1,15 @@
+{
+    "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+    "Stylesheet": [
+        "color_functions.mss"
+    ],
+    "Layer": [{
+        "id": "world",
+        "name": "world",
+        "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+        "Datasource": {
+            "file": "http://tilemill-data.s3.amazonaws.com/test_data/shape_demo.zip",
+            "type": "shape"
+        }
+    }]
+}

test/errorhandling/color_functions.mss

@@ -0,0 +1,4 @@
+@foo: 'bar';
+#world {
+  polygon-fill: hsl(1, @foo, 3);
+}

test/errorhandling/color_functions.result

@@ -0,0 +1 @@
+color_functions.mss:3:31 incorrect arguments given to hsl()