Support for if-else-endif.

lib/preprocess.js

@@ -162,15 +162,27 @@ function preprocessor(src, context, opts, noRestoreEol) {
 
   if (opts.type.if) {
     rv = replaceRecursive(rv, opts.type.if, function (startMatches, endMatches, include, recurse) {
+	  // I need to recurse first, so I don't catch "inner" else-directives
+      var recursed = recurse(include);
+
+	  // look for the first else-directive
+	  var matches = opts.type.else && recursed.match(new RegExp(opts.type.else));
+      var match = (matches || [""])[0];
+      var index = match ? recursed.indexOf(match) : recursed.length;
+
+      var ifBlock = recursed.substring(0, index);
+      var elseBlock = recursed.substring(index + match.length); // empty string if no else-directive
+
       var variant = startMatches[1];
       var test = (startMatches[2] || '').trim();
+
       switch(variant) {
         case 'if':
-          return testPasses(test,context) ? recurse(include) : '';
+          return testPasses(test,context) ? ifBlock : elseBlock;
         case 'ifdef':
-          return typeof getDeepPropFromObj(context, test) !== 'undefined' ? recurse(include) : '';
+          return typeof getDeepPropFromObj(context, test) !== 'undefined' ? ifBlock : elseBlock;
         case 'ifndef':
-          return typeof getDeepPropFromObj(context, test) === 'undefined' ? recurse(include) : '';
+          return typeof getDeepPropFromObj(context, test) === 'undefined' ? ifBlock : elseBlock;
         default:
           throw new Error('Unknown if variant ' + variant + '.');
       }

lib/regexrules.js

@@ -24,6 +24,7 @@ module.exports = {
       start : "[ \t]*<!--[ \t]*@(ifndef|ifdef|if)[ \t]+(.*?)[ \t]*(?:-->|!>)(?:[ \t]*\n+)?",
       end   : "[ \t]*<!(?:--)?[ \t]*@endif[ \t]*(?:-->|!>)(?:[ \t]*\n)?"
     },
+    else : "[ \t]*<!(?:--)?[ \t]*@else[ \t]*(?:-->|!>)(?:[ \t]*\n)?",
     foreach : {
       start : "[ \t]*<!--[ \t]*@foreach[ \t]+(.*?)[ \t]*(?:-->|!>)(?:[ \t]*\n+)?",
       end   : "[ \t]*<!(?:--)?[ \t]*@endfor[ \t]*(?:-->|!>)(?:[ \t]*\n)?"
@@ -56,6 +57,7 @@ module.exports = {
       start : "[ \t]*(?://|/\\*)[ \t]*@(ifndef|ifdef|if)[ \t]+([^\n*]*)(?:\\*(?:\\*|/))?(?:[ \t]*\n+)?",
       end   : "[ \t]*(?://|/\\*)[ \t]*@endif[ \t]*(?:\\*(?:\\*|/))?(?:[ \t]*\n)?"
     },
+    else : "[ \t]*(?://|/\\*)[ \t]*@else[ \t]*(?:\\*(?:\\*|/))?(?:[ \t]*\n)?",
     foreach : {
       start : "[ \t]*(?://|/\\*)[ \t]*@foreach[ \t]+([^\n*]*)(?:\\*(?:\\*|/))?(?:[ \t]*\n+)?",
       end   : "[ \t]*(?://|/\\*)[ \t]*@endfor[ \t]*(?:\\*(?:\\*|/))?(?:[ \t]*\n)?"
@@ -79,6 +81,7 @@ module.exports = {
       start : "^[ \t]*#+[ \t]*@(ifndef|ifdef|if)[ \t]+(.*?)[ \t]*\n+",
       end   : "^[ \t]*#+[ \t]*@endif[ \t]*\n?"
     },
+    else : "^[ \t]*#+[ \t]*@else[ \t]*\n?",
     foreach : {
       start : "^[ \t]*#+[ \t]*@foreach[ \t]+(.*?)[ \t]*\n+",
       end   : "^[ \t]*#+[ \t]*@endfor[ \t]*\n?"

test/if-else.spec.js

@@ -0,0 +1,52 @@
+'use strict';
+
+var chai = require('chai'),
+  pp = require('../lib/preprocess');
+
+chai.should();
+
+describe('@if/@else directive shall be preprocessed', function () {
+  describe('in html', function () {
+
+    ['=', '==', '==='].forEach(function (equalsOp) {
+      describe('and should work with unequality operator `' + equalsOp + '`', function () {
+
+        describe('with common comment syntax', function () {
+          var input = "a\n" +
+            "<!-- @if NODE_ENV" + equalsOp + "'production' -->\n" +
+            "b\n" +
+            "<!-- @else -->\n" +
+            "c\n" +
+            "<!-- @endif -->\n" +
+            "d";
+
+          it('and exclude second block if condition evals to true', function () {
+            pp.preprocess(input, {NODE_ENV: 'production'}).should.equal("a\nb\nd");
+          });
+
+          it('and exclude first block if condition evals to false', function () {
+            pp.preprocess(input, {NODE_ENV: 'dev'}).should.equal("a\nc\nd");
+          });
+        });
+
+      });
+    });
+
+    it('should support nesting', function () {
+      var input = "a\n" +
+        "// @ifdef FLAG\n" +
+        "b\n" +
+        "//   @ifdef FLAG2\n" +
+        "bad\n" +
+        "//   @else\n" +
+        "c\n" +
+        "//   @endif\n" +
+        "d\n" +
+        "// @else\n" +
+        "equally bad\n" +
+        "// @endif\n" +
+        "e";
+      pp.preprocess(input, {FLAG: 1}, 'js').should.equal("a\nb\nc\nd\ne");
+    });
+  });
+});