Add advanced field test, fixes for combining fields with colors that otherwise go back to mapnik

lib/carto/tree/dimension.js

@@ -25,7 +25,7 @@ tree.Dimension.prototype = {
         return new tree.Color([this.value, this.value, this.value]);
     },
     toString: function() {
-        return this.value;
+        return this.value.toString();
     },
 
     // In an operation between two Dimensions,

lib/carto/tree/literal.js

@@ -1,3 +1,6 @@
+// A literal is a literal string for Mapnik - the
+// result of the combination of a `tree.Field` with any
+// other type.
 (function(tree) {
 
 tree.Literal = function Field(content) {

lib/carto/tree/operation.js

@@ -46,9 +46,23 @@ tree.Operation.prototype.eval = function(env) {
         };
     }
 
+    // Fields, literals, dimensions, and quoted strings can be combined.
     if (a instanceof tree.Field || b instanceof tree.Field ||
         a instanceof tree.Literal || b instanceof tree.Literal) {
-        return new tree.Literal(a.eval(env).toString(true) + this.op + b.eval(env).toString(true));
+        if (a.is === 'color' || b.is === 'color') {
+            env.error({
+               message: "Can't subtract, divide, or multiply colors in expressions.",
+               index: this.index,
+               type: 'runtime',
+               filename: this.filename
+            });
+            return {
+                is: 'undefined',
+                value: 'undefined'
+            };
+        } else {
+            return new tree.Literal(a.eval(env).toString(true) + this.op + b.eval(env).toString(true));
+        }
     }
 
     return a.operate(this.op, b);

test/rendering/field_advanced.mml

@@ -0,0 +1,23 @@
+{
+    "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": [
+        "field_advanced.mss"
+    ],
+    "Layer": [{
+        "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"
+        }
+    },
+    {
+        "class": "new",
+        "name": "countries",
+        "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/rendering/field_advanced.mss

@@ -0,0 +1,6 @@
+#world {
+  text-name: "hello " + [NAME] + " hello" + 2;
+  text-size: 11;
+  text-face-name: "Georgia Regular", "Arial Italic";
+}
+

test/rendering/field_advanced.result

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE Map[]>
+<Map 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" maximum-extent="-20037508.34,-20037508.34,20037508.34,20037508.34">
+
+<FontSet name="fontset-0">
+  <Font face-name="Georgia Regular"/>
+  <Font face-name="Arial Italic"/>
+</FontSet>
+<Style name="world" filter-mode="first" >
+  <Rule>
+    <TextSymbolizer size="11" fontset-name="fontset-0" ><![CDATA['hello '+[NAME]+' hello'+2]]></TextSymbolizer>
+  </Rule>
+</Style>
+<Layer 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">
+    <StyleName>world</StyleName>
+    <Datasource>
+       <Parameter name="file"><![CDATA[[absolute path]]]></Parameter>
+       <Parameter name="type"><![CDATA[shape]]></Parameter>
+    </Datasource>
+  </Layer>
+
+</Map>