Use a separate DSL class for Layer evaluation

Author: gravitystorm

lib/glug.rb

@@ -11,3 +11,4 @@ module Glug # :nodoc:
 require_relative 'glug/layer'
 require_relative 'glug/extensions'
 require_relative 'glug/stylesheet_dsl'
+require_relative 'glug/layer_dsl'

lib/glug/layer.rb

@@ -78,12 +78,17 @@ def initialize(stylesheet, args = {})
       @kv[:source] ||= stylesheet.sources.find { |_k, v| v[:default] }[0]
       @kv[:source_layer] ||= args[:id] if stylesheet.sources[@kv[:source]][:type] == 'vector'
       @child_num = 0	# incremented sublayer suffix
+      @dsl = LayerDSL.new(self)
+    end
+
+    def dsl_eval(&block)
+      @dsl.instance_eval(&block)
     end
 
     # Handle all missing 'method' calls
     # If we can match it to a GL property, it's an assignment:
     # otherwise it's an OSM key
-    def method_missing(method_sym, *arguments)
+    def add_property(method_sym, *arguments)
       if EXPRESSIONS.include?(method_sym)
         Condition.new.from_list(method_sym, arguments)
       elsif LAYOUT.include?(method_sym) || PAINT.include?(method_sym) || TOP_LEVEL.include?(method_sym)
@@ -135,7 +140,7 @@ def on(*args, &block)
         sub_cond = nilsafe_merge(sub_cond, @condition)
       end
       r._set_filter(nilsafe_merge(sub_cond, @uncascaded))
-      r.instance_eval(&block)
+      r.dsl_eval(&block)
       @stylesheet._add_layer(r)
 
       # Create cascaded layers
@@ -159,7 +164,7 @@ def nilsafe_merge(a, b) # rubocop:disable Naming/MethodParameterName
     def cascade(*args, &block)
       cond = args.length == 1 ? args[0] : Condition.new.from_list(:any, args)
       @cascade_cond = cond
-      instance_eval(&block)
+      dsl_eval(&block)
       @cascade_cond = nil
     end
 

lib/glug/layer_dsl.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Glug
+  # Defines the methods available to the DSL
+  class LayerDSL
+    def initialize(impl)
+      @__impl = impl
+    end
+
+    def literal(*args)
+      @__impl.literal(*args)
+    end
+
+    def current_value(key)
+      @__impl.current_value(key)
+    end
+
+    def on(*args, &block)
+      @__impl.on(*args, &block)
+    end
+
+    def cascade(*args, &block)
+      @__impl.cascade(*args, &block)
+    end
+
+    def uncascaded(*args)
+      @__impl.uncascaded(*args)
+    end
+
+    def filter(*args)
+      @__impl.filter(*args)
+    end
+
+    def id(name)
+      @__impl.id(name)
+    end
+
+    def suppress
+      @__impl.suppress
+    end
+
+    def any
+      @__impl.any
+    end
+
+    def all
+      @__impl.all
+    end
+
+    def respond_to_missing?(*)
+      true
+    end
+
+    def method_missing(method_sym, *arguments)
+      @__impl.add_property(method_sym, *arguments)
+    end
+  end
+end

lib/glug/stylesheet.rb

@@ -30,7 +30,7 @@ def source(source_name, opts = {})
     def layer(id, opts = {}, &block)
       r = Layer.new(self, id: id, kv: opts)
       @layers << r
-      r.instance_eval(&block)
+      r.dsl_eval(&block)
     end
 
     # Assemble into GL JSON format

spec/lib/glug/layer_spec.rb

@@ -7,7 +7,7 @@
         source :osm_data, type: 'vector', url: 'http://example.com/osm.tilejson', default: true
       end
       l = described_class.new(stylesheet, { zoom: 7 })
-      l.line_width 1
+      l.add_property(:line_width, 1)
 
       h = l.to_hash
       expect(h['minzoom']).to be(7)
@@ -19,7 +19,7 @@
         source :osm_data, type: 'vector', url: 'http://example.com/osm.tilejson', default: true
       end
       l = described_class.new(stylesheet, { zoom: 1..5 })
-      l.line_width 1
+      l.add_property(:line_width, 1)
 
       h = l.to_hash
       expect(h['minzoom']).to be(1)
@@ -32,7 +32,7 @@
           source :osm_data, type: 'vector', url: 'http://example.com/osm.tilejson', default: true
         end
         l = described_class.new(stylesheet, { zoom: 1.. })
-        l.line_width 1
+        l.add_property(:line_width, 1)
 
         h = l.to_hash
         expect(h).to have_key('minzoom')
@@ -45,7 +45,7 @@
           source :osm_data, type: 'vector', url: 'http://example.com/osm.tilejson', default: true
         end
         l = described_class.new(stylesheet, { zoom: ..5 })
-        l.line_width 1
+        l.add_property(:line_width, 1)
 
         h = l.to_hash
         expect(h).not_to have_key('minzoom')