Sub variable expansion

README.md

@@ -56,6 +56,14 @@ Use fancy operators in assignment.
 {% assign title_text += ' →' if linkpost %}
 ```
 
+Use variables in assignment.
+
+```
+{% assign my_data = site.data.{{ data_file_name }} %}
+{% assign name = site.name | append:page.{{ product_name }} | downcase %}
+{% assign stupid_example = (page.{{ product_name }} == null ? 'no-product' : 'product-{{ page.product_code }} | downcase }}') %}
+```
+
 ## Contributing
 
 1. Fork it ( https://github.com/octopress/assign-tag/fork )

lib/octopress-assign-tag.rb

@@ -7,6 +7,8 @@ module Tags
     module Assign
       class Tag < Liquid::Tag
         SYNTAX = /([[:word:]]+)\s*(=|\+=|\|\|=)\s*(.*)\s*/o
+        VAR_MATCH = /([^{]*)({{(.*)}})(.*)/o
+        SUB_VARS = /([^{]*)({{\s([^}]*)\s}})/o
 
         def initialize(tag_name, markup, tokens)
           @markup = markup
@@ -22,7 +24,22 @@ def render(context)
             operator = $2
             value    = $3
 
+            if value =~ VAR_MATCH 
+              first_part = $1
+              evaluate_part = $2
+              last_part = $4
+              new_value = ""
+
+              evaluate_part.scan (SUB_VARS) {
+                pre_value = $1
+                evaluated_var = TagHelpers::Var.get_value($3, context)
+                new_value = new_value + pre_value + evaluated_var
+              }
+              value = first_part + new_value + last_part
+            end
+
             value = TagHelpers::Var.get_value(value, context)
+
             return if value.nil?
 
             context = TagHelpers::Var.set_var(var, operator, value, context)

lib/octopress-assign-tag/version.rb

@@ -1,7 +1,7 @@
 module Octopress
   module Tags
     module Assign
-      VERSION = "1.0.3"
+      VERSION = "1.0.4"
     end
   end
 end

test/_expected/index.html

@@ -21,5 +21,15 @@
 AWESOME → AWESOME
 whatever-man → whatever-man
 
+## Assignment with sub variables
+sub_var1 → sub_var1
+sub_var2 → sub_var2
+hello → hello
+HELLO → HELLO
+hello-goodbye → hello-goodbye
+HELLO-GOODBYE → HELLO-GOODBYE
+COMPLEX-HELLO-GOODBYE → COMPLEX-HELLO-GOODBYE
+complex-hello-GOODBYE → complex-hello-GOODBYE
+
 ## Filters on non-string variables
 ABab

test/index.html

@@ -1,6 +1,8 @@
 ---
 layout: null
 test_array: [a, b, A, B]
+sub_var1: hello
+sub_var2: goodbye
 ---
 ## Simple assign
 yep → {% assign var1 = 'yep' %}{{ var1 }}
@@ -25,5 +27,15 @@
 AWESOME → {% assign var10 = var9 | upcase %}{{ var10 }}
 whatever-man → {% assign var11 = 'whatever man' || nil | replace:' ','-' %}{{ var11 }}
 
+## Assignment with sub variables
+sub_var1 → {% assign test_var1 = 'sub_var1' %}{{ test_var1 }}
+sub_var2 → {% assign test_var2 = 'sub_var2' %}{{ test_var2 }}
+hello → {% assign var12 = page.{{ test_var1 }} %}{{ var12 }}
+HELLO → {% assign var13 = page.{{ test_var1 }} | upcase %}{{ var13 }}
+hello-goodbye → {% assign var15 = page.{{ test_var1 }} | append:'-' | append:page.{{ test_var2 }} %}{{ var15 }}
+HELLO-GOODBYE → {% assign var16 = page.{{ test_var1 }} | append:'-' | append:page.{{ test_var2 }} | upcase %}{{ var16 }}
+COMPLEX-HELLO-GOODBYE → {% assign var17 = (page.{{ test_var1 }} == 'hello' ? 'complex-{{ page.sub_var1 }}-{{ page.sub_var2 }}' : 'lame' ) | upcase %}{{ var17 }}
+complex-hello-GOODBYE → {% assign var17 = (page.{{ test_var1 }} == null ? 'lame' : 'complex-{{ page.sub_var1 }}-{{ page.sub_var2 | upcase }}') %}{{ var17 }}
+
 ## Filters on non-string variables
 {% assign items = page.test_array | sort %}{{ items }}