Enum string parsing (#639)

* Treat string enum values as their to_s representation

* Try to coerce to an integer first, then try parsing

A valid enum value name can't start with a digit, so theoretically this is safe.
Integers will only have digits (and a leading digit), so the two are mutually exclusive.

* Add tests for parsing enum values

spec/type_extensions/enum_spec.cr

@@ -43,6 +43,16 @@ describe "Enum" do
     Issue::Status.new(:closed).enum.should eq(Issue::Status::Closed)
   end
 
+  it "parses the enum value name" do
+    Issue::Status.new("Closed").should eq(Issue::Status.new(:closed))
+    Issue::Status.new("Opened").should eq(Issue::Status.new(:opened))
+  end
+
+  it "parses the enum value integer when a string" do
+    Issue::Status.new("0").should eq(Issue::Status.new(:opened))
+    Issue::Status.new("1").should eq(Issue::Status.new(:closed))
+  end
+
   it "implements case equality" do
     case Issue::Status.new(:closed).value
     when Issue::Status.new(:closed)

src/avram/charms/enum_extensions.cr

@@ -34,7 +34,12 @@ macro avram_enum(enum_name, &block)
     end
 
     def initialize(enum_value : String)
-      @enum = Avram{{ enum_name }}.from_value(enum_value.to_i)
+      int_value = enum_value.to_i?
+      @enum = if int_value
+                Avram{{ enum_name }}.from_value(int_value)
+              else
+                Avram{{ enum_name }}.parse(enum_value)
+              end
     end
 
     delegate :===, to_s, to_i, to: @enum
@@ -58,7 +63,7 @@ macro avram_enum(enum_name, &block)
       end
 
       def parse(value : String)
-        SuccessfulCast({{ enum_name }}).new({{ enum_name }}.new(value.to_i))
+        SuccessfulCast({{ enum_name }}).new({{ enum_name }}.new(value))
       end
 
       def parse(value : Int32)