- Support ability to interpret multiple DSL expression hierarchies, b…

…y suspending interpretation of a hierarchy, interpreting another until done, and then resuming interpretation of previous hierarchy until done too. That is done by starting a new expression hierarchy interpretation using `Glimmer::DSL::Engine::new_parent_stack` in the middle of interpreting another expression hierarchy.

- Refactor/rename `Glimmer::DSL::Engine::parent_stacks` to `Glimmer::DSL::Engine::dsl_parent_stacks` and have it include an `Array` of `Array`s of parent stacks per DSL.

CHANGELOG.md

@@ -3,6 +3,11 @@
 Related Change Logs:
 - [glimmer-dsl-swt/CHANGELOG.md](https://github.com/AndyObtiva/glimmer-dsl-swt/blob/master/CHANGELOG.md)
 
+### 2.8.0
+
+- Support ability to interpret multiple DSL expression hierarchies, by suspending interpretation of a hierarchy, interpreting another until done, and then resuming interpretation of previous hierarchy until done too. That is done by starting a new expression hierarchy interpretation using `Glimmer::DSL::Engine::new_parent_stack` in the middle of interpreting another expression hierarchy.
+- Refactor/rename `Glimmer::DSL::Engine::parent_stacks` to `Glimmer::DSL::Engine::dsl_parent_stacks` and have it include an `Array` of `Array`s of parent stacks per DSL.
+
 ### 2.7.9
 
 - Optimize performance of `Glimmer::DataBinding::ObservableModel#add_observer` by removing `OpenStruct` constant check.

README.md

@@ -1,4 +1,4 @@
-# [<img src="https://raw.githubusercontent.com/AndyObtiva/glimmer/master/images/glimmer-logo-hi-res.png" height=85 style="position: relative; top: 20px;" />](https://rubygems.org/gems/glimmer) Glimmer 2.7.9
+# [<img src="https://raw.githubusercontent.com/AndyObtiva/glimmer/master/images/glimmer-logo-hi-res.png" height=85 style="position: relative; top: 20px;" />](https://rubygems.org/gems/glimmer) Glimmer 2.8.0
 ## DSL Framework for Ruby GUI and More
 [![Gem Version](https://badge.fury.io/rb/glimmer.svg)](http://badge.fury.io/rb/glimmer)
 [![rspec](https://github.com/AndyObtiva/glimmer/workflows/rspec/badge.svg)](https://github.com/AndyObtiva/glimmer/actions?query=workflow%3Arspec)
@@ -268,7 +268,7 @@ end
 ### Setup
 
 Follow these steps to author a [Glimmer](https://rubygems.org/gems/glimmer) DSL:
-- Add `gem 'glimmer', '~> 2.7.9'` to `Gemfile` and run `bundle` or run `gem install glimmer -v2.7.9` and add `require 'glimmer'`
+- Add `gem 'glimmer', '~> 2.8.0'` to `Gemfile` and run `bundle` or run `gem install glimmer -v2.8.0` and add `require 'glimmer'`
 - Create `glimmer/dsl/[dsl_name]/dsl.rb`, which requires and adds all dynamic expressions for the [dsl_name] Glimmer DSL module as per the code shown in the previous section (or [Official DSLs](#official-dsls) as examples)
 - Create `glimmer/dsl/[dsl_name]/[expresion_name]_expresion.rb` for every [expresion_name] expression needed, whether dynamic or static
 

TODO.md

@@ -14,7 +14,7 @@ Related TODO files:
 - Observe multiple attributes (e.g. observe(@game, [:width, :height]) returns |value, attribute_name|)
 - Fix issue with computed data-binding when combined with nested/indexed data-binding (it looks up computed attributes on root object instead of nested object, it seems)
 - Support nested computed attributes (e.g. computed_by: {address1: [:street, :city, :state, :zip]})
-- Consider the idea of having Observer#observe accept an optional block to do observation without implementing `call` (kinda like when using the `observe` keyword in the Glimmer DSL). 
+- Consider the idea of having Observer#observe accept an optional block to do observation without implementing `call` (kinda like when using the `observe` keyword in the Glimmer DSL).
 - Ensure removing observers from hash in ObservableModel when removed from observable
 - Avoid `< Struct.new` in specs (tests)
 - Add built-in support to Glimmer::DSL::Engine to memoize/cache expressions similar to how that is supported for StaticExpression (but allowing an outside keyword and non-static expression to be used)
@@ -57,6 +57,7 @@ Related TODO files:
 - Support `recursive: true` with models that have nested models
 - Observe multiple attributes or indexed/keyed/nested attribute expressions with a single observer
 - Consider the idea of having before_read and before_write support cancelling a data-binding operation by returning `false`, returning `:cancel`, Or by receiving an extra arg that enables calling arg.cancel on or something similar to avoid having normal code cancel the data-binding operation just because it returns nil.
+- Consider supporting concurrent/parallel interpretation of expression hierarchies by assigning each one an ID that is used to identify it if multiple hierarchies were interpreted in multiple concurrent/parallel threads.
 
 ### Miscellaneous
 

VERSION

@@ -1 +1 @@
-2.7.9
+2.8.0

lib/glimmer/dsl/engine.rb

@@ -103,7 +103,7 @@ def enabled_dsls=(dsl_names)
 
         # Resets Glimmer's engine activity and configuration. Useful in rspec before or after blocks in tests.
         def reset
-          parent_stacks.values.each do |a_parent_stack|
+          dsl_parent_stacks.values.each do |a_parent_stack|
             a_parent_stack.clear
           end
           dsl_stack.clear
@@ -230,11 +230,11 @@ def interpret_expression(expression, keyword, *args, &block)
         def add_content(new_parent, expression, keyword, *args, &block)
           if block_given? && expression.is_a?(ParentExpression)
             dsl_stack.push(expression.class.dsl)
-            parent_stack.push(new_parent)
+            push_parent_into_parent_stack(new_parent)
             begin
               expression.add_content(new_parent, keyword, *args, &block)
             ensure
-              parent_stack.pop
+              pop_parent_from_parent_stack
               dsl_stack.pop
             end
           end
@@ -244,14 +244,34 @@ def add_content(new_parent, expression, keyword, *args, &block)
         #
         # Parents are maintained in a stack while evaluating Glimmer DSL
         # to ensure properly ordered interpretation of DSL syntax
-        def_delegator :parent_stack, :last, :parent
+        def parent
+          parent_stack.last
+        end
+
+        def push_parent_into_parent_stack(parent)
+          parent_stack.push(parent)
+        end
 
+        def pop_parent_from_parent_stack
+          parent_stack.pop
+          parent_stacks.pop if parent_stacks.size > 1 && parent_stacks.last.empty?
+        end
+
         def parent_stack
-          parent_stacks[dsl] ||= Concurrent::Array.new
+          new_parent_stack if parent_stacks.last.nil?
+          parent_stacks.last
+        end
+
+        def new_parent_stack
+          parent_stacks.push(Concurrent::Array.new)
         end
 
         def parent_stacks
-          @parent_stacks ||= Concurrent::Hash.new
+          dsl_parent_stacks[dsl] ||= Concurrent::Array.new # TODO insted of having one array, we need to nest it within an array of arrays
+        end
+
+        def dsl_parent_stacks
+          @dsl_parent_stacks ||= Concurrent::Hash.new
         end
 
         # Enables multiple DSLs to play well with each other when mixing together

spec/lib/glimmer/dsl/engine_spec.rb

@@ -61,6 +61,24 @@ module GlimmerSpec
         expect(GLIMMER_TOP_LEVEL_TARGET.to_s).to eq('SWT shell { SWT Dynamic browser(XML html { XML Dynamic body { XML Dynamic input({:type=>"text", :value=>"Hello, World!"}) } }) }')
       end
 
+      it 'interprets another expression hierarchy in the middle of interpreting an expression hierarchy' do
+        @target1 = shell {
+          spinner {
+            # start a second hierarchy
+            Glimmer::DSL::Engine.new_parent_stack
+            @target2 = shell {
+              table {
+              }
+            }
+            # continue back in first hierarchy
+            progress
+          }
+        }
+
+        expect(@target1.to_s).to eq('SWT shell { SWT Dynamic spinner { SWT Dynamic progress } }')
+        expect(@target2.to_s).to eq('SWT shell { SWT Dynamic table }')
+      end
+
       it 'standard static expression' do
         @target = shell {
         }