Add support for virtual columns (#163)

One of these changes was support for [virtual/generated
columns](https://guides.rubyonrails.org/active_record_postgresql.html#generated-columns).
At the moment, the following table would create a slightly confusing
annotation
```ruby
create_table :users do |t|
  t.string :name
  t.virtual :name_upcased, type: :string, as: "upper(name)", stored: true
end
```

```ruby
# Table name: users
#
#  name                :string
#  name_upcased :string
class User < ApplicationRecord
```

With these changes, this would generate the following:
```ruby
# Table name: users
#
#  name                :string
#  name_upcased :virtual(string)
class User < ApplicationRecord
```

I wasn't a 100% sure where you'd want these changes exactly. I'm happy
to make further changes, or add some more tests.

One additional change could be to also place the function in the
annotation, but this would maybe better in a further PR. I've tried this
in the past and noticed that it can become unwieldy once the function
becomes more complicated
```ruby
# Table name: users
#
#  name.                :string
#  name_upcased :virtual(string)    upcase(name)
class User < ApplicationRecord
```

---------

Co-authored-by: Andrew W. Lee <[email protected]>

lib/annotate_rb/model_annotator/column_annotation/attributes_builder.rb

@@ -78,6 +78,12 @@ def build
             end
           end
 
+          # Check if the column is a virtual column and print the function
+          if @options[:show_virtual_columns] && @column.virtual?
+            # Any whitespace in the function gets reduced to a single space
+            attrs << @column.default_function.gsub(/\s+/, " ").strip
+          end
+
           attrs
         end
 

lib/annotate_rb/model_annotator/column_annotation/column_wrapper.rb

@@ -85,6 +85,14 @@ def name
           @column.name
         end
 
+        def virtual?
+          @column.respond_to?(:virtual?) && @column.virtual?
+        end
+
+        def default_function
+          @column.default_function
+        end
+
         private
 
         # Simple quoting for the default column value

lib/annotate_rb/model_annotator/column_annotation/type_builder.rb

@@ -25,6 +25,8 @@ def build
 
           if is_decimal_type
             formatted_column_type = "decimal(#{@column.precision}, #{@column.scale})"
+          elsif @options[:show_virtual_columns] && @column.virtual?
+            formatted_column_type = "virtual(#{column_type})"
           elsif is_special_type
             # Do nothing. Kept as a code fragment in case we need to do something here.
           elsif @column.limit && !@options[:format_yard]

lib/annotate_rb/options.rb

@@ -48,6 +48,7 @@ def from(options = {}, state = {})
       show_check_constraints: false, # ModelAnnotator
       show_foreign_keys: true, # ModelAnnotator
       show_indexes: true, # ModelAnnotator
+      show_virtual_columns: false, # ModelAnnotator
       simple_indexes: false, # ModelAnnotator
       sort: false, # ModelAnnotator
       timestamp: false, # RouteAnnotator

spec/lib/annotate_rb/model_annotator/column_annotation/attributes_builder_spec.rb

@@ -210,6 +210,26 @@
       it { is_expected.to match_array(expected_result) }
     end
 
+    context "when the show_virtual_columns option is false with a virtual column" do
+      let(:column) { mock_column("name", :string, virtual?: true, default_function: "first_name || ' ' || last_name") }
+      let(:options) do
+        AnnotateRb::Options.new({show_virtual_columns: false})
+      end
+      let(:expected_result) { ["not null"] }
+
+      it { is_expected.to match_array(expected_result) }
+    end
+
+    context "when the show_virtual_columns option is true with a virtual column" do
+      let(:column) { mock_column("name", :string, virtual?: true, default_function: "first_name || ' ' || last_name") }
+      let(:options) do
+        AnnotateRb::Options.new({show_virtual_columns: true})
+      end
+      let(:expected_result) { ["first_name || ' ' || last_name", "not null"] }
+
+      it { is_expected.to match_array(expected_result) }
+    end
+
     context "column defaults in sqlite" do
       # Mocked representations when using the sqlite adapter
       context "with an integer default value of 0" do

spec/lib/annotate_rb/model_annotator/column_annotation/type_builder_spec.rb

@@ -77,6 +77,28 @@
       it { is_expected.to eq(expected_result) }
     end
 
+    context "with a virtual column without option enabled" do
+      context "when show_virtual_columns if false" do
+        let(:column) { mock_column("name", :string, virtual?: true) }
+        let(:options) do
+          AnnotateRb::Options.new({show_virtual_columns: false})
+        end
+        let(:expected_result) { "string" }
+
+        it { is_expected.to eq(expected_result) }
+      end
+
+      context "when show_virtual_columns if true" do
+        let(:column) { mock_column("name", :string, virtual?: true) }
+        let(:options) do
+          AnnotateRb::Options.new({show_virtual_columns: true})
+        end
+        let(:expected_result) { "virtual(string)" }
+
+        it { is_expected.to eq(expected_result) }
+      end
+    end
+
     context 'when "format_yard" is specified in options' do
       context "with a string column with a limit" do
         let(:column) { mock_column("name", :string, limit: 50) }