Support Ruby 2.7+ Pattern Matching

Add `#deconstruct_keys` to `Expression::Base` and `Schedule` so that
they can be used in pattern matches.

In our products, we've been using `#to_h` for this, and it would be
nice sugar to have it built in.

A common example we've used in our products is building a
humanized-readable version of a schedule. An extremely stripped down
version might look something like this

```ruby
case existing_user_schedule
in weekday: { weekday: }
  "Every #{weekday}"
in day_in_month: { day: }
  "Last #{day} of every month"
end
```

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ### Unreleased
 
+Changes:
+
+* Support pattern matching for `Expression` and `Schedule`
+
 [Commits](https://github.com/molawson/repeatable/compare/v1.1.0...main)
 
 ### 1.1.0 (2022-02-25)

lib/repeatable/expression/base.rb

@@ -26,6 +26,11 @@ def to_h
         {hash_key => hash_value}
       end
 
+      sig { params(_keys: T.nilable(T::Array[Symbol])).returns(T::Hash[Symbol, T.any(Types::SymbolHash, T::Array[Types::SymbolHash])]) }
+      def deconstruct_keys(_keys)
+        to_h
+      end
+
       sig { params(other: Expression::Base).returns(Expression::Union) }
       def union(other)
         Union.new(self, other)

lib/repeatable/schedule.rb

@@ -54,6 +54,11 @@ def to_h
       expression.to_h
     end
 
+    sig { params(_keys: T.nilable(T::Array[Symbol])).returns(T::Hash[Symbol, T.any(Types::SymbolHash, T::Array[Types::SymbolHash])]) }
+    def deconstruct_keys(_keys)
+      to_h
+    end
+
     sig { params(other: Object).returns(T::Boolean) }
     def ==(other)
       other.is_a?(self.class) && expression == other.expression

spec/repeatable/schedule_spec.rb

@@ -328,6 +328,14 @@ module Repeatable
       end
     end
 
+    describe "pattern matching" do
+      let(:arg) { nested_set_expression_hash }
+
+      it "can #deconstruct_keys" do
+        expect(subject.deconstruct_keys(nil)).to eq subject.to_h
+      end
+    end
+
     describe "#==" do
       it "returns true if the schedules have the same identity" do
         schedule = described_class.new(nested_set_expression_object)

spec/support/expression_examples.rb

@@ -11,4 +11,10 @@
       expect { subject.to_h }.not_to raise_error
     end
   end
+
+  describe "pattern matching" do
+    it "can #deconstruct_keys" do
+      expect(subject.deconstruct_keys(nil)).to be_a(Hash)
+    end
+  end
 end