feat: Add before_render, around_render and after_render (#90)

spec/blueprint/html/hooks_spec.cr

@@ -0,0 +1,77 @@
+require "../../spec_helper"
+
+private class ExampleWithBlock
+  include Blueprint::HTML
+
+  private def blueprint(&)
+    h1 { yield }
+  end
+
+  private def before_render(&)
+    span { "Before render" }
+  end
+
+  private def around_render(&)
+    span { "Around start" }
+    yield
+    span { "Around end" }
+  end
+
+  private def after_render(&)
+    span { "After render" }
+  end
+end
+
+private class ExampleWithoutBlock
+  include Blueprint::HTML
+
+  private def blueprint
+    h1 "Without block"
+  end
+
+  private def before_render(&)
+    span { "Before render" }
+  end
+
+  private def around_render(&)
+    span { "Around start" }
+    yield
+    span { "Around end" }
+  end
+
+  private def after_render(&)
+    span { "After render" }
+  end
+end
+
+describe "hooks" do
+  context "with block" do
+    it "allows defining hooks before_render, around_render, after_render" do
+      actual_html = ExampleWithBlock.new.to_s { "With block" }
+      expected_html = normalize_html <<-HTML
+        <span>Before render</span>
+        <span>Around start</span>
+        <h1>With block</h1>
+        <span>Around end</span>
+        <span>After render</span>
+      HTML
+
+      actual_html.should eq expected_html
+    end
+  end
+
+  context "without block" do
+    it "allows defining hooks before_render, around_render, after_render" do
+      actual_html = ExampleWithoutBlock.new.to_s
+      expected_html = normalize_html <<-HTML
+        <span>Before render</span>
+        <span>Around start</span>
+        <h1>Without block</h1>
+        <span>Around end</span>
+        <span>After render</span>
+      HTML
+
+      actual_html.should eq expected_html
+    end
+  end
+end

src/blueprint/html.cr

@@ -39,24 +39,44 @@ module Blueprint::HTML
 
     @buffer = buffer
 
-    envelope { blueprint }
+    {% if @type.has_method?(:before_render) %}
+      before_render { }
+    {% end %}
+
+    {% if @type.has_method?(:around_render) %}
+      around_render { blueprint }
+    {% else %}
+      blueprint
+    {% end %}
+
+    {% if @type.has_method?(:after_render) %}
+      after_render { }
+    {% end %}
   end
 
   def to_s(buffer : String::Builder, &) : Nil
     return unless render?
 
     @buffer = buffer
 
-    envelope do
+    {% if @type.has_method?(:before_render) %}
+      before_render { yield }
+    {% end %}
+
+    {% if @type.has_method?(:around_render) %}
+      around_render do
+        blueprint { capture_content { yield } }
+      end
+    {% else %}
       blueprint { capture_content { yield } }
-    end
+    {% end %}
+
+    {% if @type.has_method?(:after_render) %}
+      after_render { yield }
+    {% end %}
   end
 
   private def render? : Bool
     true
   end
-
-  private def envelope(&) : Nil
-    yield
-  end
 end