Allow live collections based on generic data. Helps with #1527

middleman-core/features/collections.feature

@@ -193,3 +193,44 @@ Feature: Collections
     When I go to "2.html"
     Then I should see 'Again'
 
+  Scenario: Arbitrary live datasets
+    Given a fixture app "collections-app"
+    And a file named "config.rb" with:
+      """
+      live {
+        Dir["descriptions/*.txt"]
+      }.each do |description_name|
+        base = File.basename(description_name, '.txt')
+        proxy "#{base}.html", "/description_template.html", locals: {
+          contents: File.read(description_name)
+        }, ignore: true
+      end
+      """
+    And a file named "source/description_template.html.erb" with:
+      """
+      <%= contents %>
+      """
+    And a file named "descriptions/test1.txt" with:
+      """
+      Test1
+      """
+    Given the Server is running at "collections-app"
+    When I go to "test1.html"
+    Then I should see 'Test1'
+    When I go to "test2.html"
+    Then I should see 'Not Found'
+
+    When the file "descriptions/test2.txt" has the contents
+      """
+      Test2
+      """
+    When I go to "test1.html"
+    Then I should see 'Test1'
+    When I go to "test2.html"
+    Then I should see 'Test2'
+
+    When the file "descriptions/test1.txt" is removed
+    When I go to "test1.html"
+    Then I should see 'Not Found'
+    When I go to "test2.html"
+    Then I should see 'Test2'

middleman-core/lib/middleman-core/core_extensions/collections.rb

@@ -16,12 +16,13 @@ module Middleman
         # gets a chance to modify any new resources that get added.
         self.resource_list_manipulator_priority = 110
 
-        attr_accessor :sitemap_collector, :data_collector, :leaves
+        attr_accessor :leaves
 
         # Expose `resources`, `data`, and `collection` to config.
         expose_to_config resources: :sitemap_collector,
                          data: :data_collector,
-                         collection: :register_collector
+                         collection: :register_collector,
+                         live: :live_collector
 
         # Exposes `collection` to templates
         expose_to_template collection: :collector_value
@@ -39,8 +40,7 @@ module Middleman
           @collectors_by_name = {}
           @values_by_name = {}
 
-          @sitemap_collector = LazyCollectorRoot.new(self)
+          @collector_roots = []
-          @data_collector = LazyCollectorRoot.new(self)
         end
 
         def before_configuration
@@ -52,6 +52,28 @@ module Middleman
           @collectors_by_name[label] = endpoint
         end
 
+        Contract LazyCollectorRoot
+        def sitemap_collector
+          live_collector { |_, resources| resources }
+        end
+
+        Contract LazyCollectorRoot
+        def data_collector
+          live_collector { |app, _| app.data }
+        end
+
+        Contract Proc => LazyCollectorRoot
+        def live_collector(&block)
+          root = LazyCollectorRoot.new(self)
+
+          @collector_roots << {
+            root: root,
+            block: block
+          }
+
+          root
+        end
+
         Contract Symbol => Any
         def collector_value(label)
           @values_by_name[label]
@@ -59,8 +81,10 @@ module Middleman
 
         Contract ResourceList => ResourceList
         def manipulate_resource_list(resources)
-          @sitemap_collector.realize!(resources)
+          @collector_roots.each do |pair|
-          @data_collector.realize!(app.data)
+            dataset = pair[:block].call(app, resources)
+            pair[:root].realize!(dataset)
+          end
 
           ctx = StepContext.new
           leaves = @leaves.dup

middleman-core/lib/middleman-core/step_definitions/middleman_steps.rb

@@ -1,9 +1,15 @@
 Then /^the file "([^\"]*)" has the contents$/ do |path, contents|
   write_file(path, contents)
-  @server_inst.files.find_new_files!
+
+  in_current_dir do
+    @server_inst.files.find_new_files!
+  end
 end
 
 Then /^the file "([^\"]*)" is removed$/ do |path|
   step %Q{I remove the file "#{path}"}
-  @server_inst.files.find_new_files!
+
+  in_current_dir do
+    @server_inst.files.find_new_files!
+  end
 end

middleman-core/lib/middleman-core/step_definitions/server_steps.rb

@@ -33,7 +33,6 @@ end
 Given /^the Server is running$/ do
   root_dir = File.expand_path(current_dir)
 
-
   if File.exists?(File.join(root_dir, 'source'))
     ENV['MM_SOURCE'] = 'source'
   else
@@ -53,10 +52,10 @@ Given /^the Server is running$/ do
         instance_exec(&p)
       end
     end
-  end
 
-  rack = ::Middleman::Rack.new(@server_inst)
+    rack = ::Middleman::Rack.new(@server_inst)
-  @browser = ::Rack::MockRequest.new(rack.to_app)
+    @browser = ::Rack::MockRequest.new(rack.to_app)
+  end
 end
 
 Given /^the Server is running at "([^\"]*)"$/ do |app_path|