Did you mean for properties, with proper levenstein distance for

better matching. Fixes #199

lib/carto/tree/call.js

@@ -22,7 +22,7 @@ tree.Call.prototype = {
     // we try to pass a variable to a function, like: `saturate(@color)`.
     // The function should receive the value, not the variable.
     //
-    eval: function(env) {
+    'eval': function(env) {
         var args = this.args.map(function(a) { return a.eval(env); });
 
         for (var i = 0; i < args.length; i++) {
@@ -55,11 +55,11 @@ tree.Call.prototype = {
             if (!fn) {
                 var functions = tree.Reference.mapnikFunctions();
                 // cheap closest, needs improvement.
-                var name_array = this.name.split('');
+                var name = this.name;
                 var mean = functions.map(function(f) {
-                    return [f[0], _.intersection(name_array, f[0].split('')).length, f[1]];
+                    return [f[0], tree.Reference.editDistance(name, f[0]), f[1]];
                 }).sort(function(a, b) {
-                    return b[1] - a[1];
+                    return a[1] - b[1];
                 });
                 env.error({
                     message: 'unknown function ' + this.name + '(), did you mean ' +

lib/carto/tree/reference.js

@@ -138,6 +138,31 @@ tree.Reference.isFont = function(selector) {
     return tree.Reference.selector(selector).validate == 'font';
 };
 
+// https://gist.github.com/982927
+tree.Reference.editDistance = function(a, b){
+    if (a.length === 0) return b.length;
+    if (b.length === 0) return a.length;
+
+    var matrix = [];
+
+    for (var i = 0; i <= b.length; i++) { matrix[i] = [i]; }
+    for (var j = 0; j <= a.length; j++) { matrix[0][j] = j; }
+
+    for (i = 1; i <= b.length; i++) {
+        for (j = 1; j <= a.length; j++) {
+            if (b.charAt(i-1) == a.charAt(j-1)) {
+                matrix[i][j] = matrix[i-1][j-1];
+            } else {
+                matrix[i][j] = Math.min(matrix[i-1][j-1] + 1, // substitution
+                    Math.min(matrix[i][j-1] + 1, // insertion
+                    matrix[i-1][j] + 1)); // deletion
+            }
+        }
+    }
+
+    return matrix[b.length][a.length];
+};
+
 tree.Reference.validValue = function(env, selector, value) {
     var i, j;
     // TODO: handle in reusable way

lib/carto/tree/rule.js

@@ -39,8 +39,18 @@ tree.Rule.prototype.toString = function() {
 // properties in reference.json which specify serialization=content
 tree.Rule.prototype.toXML = function(env, content, sep, format) {
     if (!tree.Reference.validSelector(this.name)) {
+        var name = this.name;
+        var mean = tree.Reference.selectors.map(function(f) {
+            return [f, tree.Reference.editDistance(name, f)];
+        }).sort(function(a, b) {
+            return a[1] - b[1];
+        });
+        var mean_message = '';
+        if (mean[0][1] < 3) {
+            mean_message = '. Did you mean ' + mean[0][0] + '?';
+        }
         return env.error({
-            message: "Unrecognized rule: " + this.name,
+            message: "Unrecognized rule: " + this.name + mean_message,
             index: this.index,
             type: 'syntax',
             filename: this.filename

test/errorhandling/invalid_property.result

@@ -1 +1 @@
-invalid_property.mss:3:2 Unrecognized rule: polygonopacity
+invalid_property.mss:3:2 Unrecognized rule: polygonopacity. Did you mean polygon-opacity?