Deprecate constructor as a block

So far, we have been accepting both a block and the `constructor:`
keyword argument for providing a constructor. The former will not be
available in 1.0, so we're deprecating it now.

We also prepare the test suite for the change and make naming consistent
using "constructor" where we were using "pre-processor."

docsite/source/index.html.md

@@ -28,7 +28,7 @@ class App
   end
   # Defaults to nil if no default value is given
   setting :adapter
-  # Pre-process values
+  # Construct values
   setting(:path, 'test') { |value| Pathname(value) }
   # Passing the reader option as true will create attr_reader method for the class
   setting :pool, 5, reader: true

lib/dry/configurable/dsl.rb

@@ -49,6 +49,8 @@ def setting(name, *args, &block)
           if block.arity.zero?
             ast << [:nested, [node, DSL.new(&block).ast]]
           else
+            # TODO: [Before 1.0] Remove constructor-as-block
+            warn '[dry-configurable] Passing a constructor as a bloc is deprecated, please use the `constructor:` kwarg instead', uplevel: 1
             ast << [:constructor, [node, block]]
           end
         else

spec/integration/dry/configurable/setting_spec.rb

@@ -97,9 +97,9 @@
       end
     end
 
-    context 'with a value pre-processor' do
-      it 'pre-processes the value with nil default' do
-        klass.setting(:path, nil) { |value| "test:#{value || "fallback"}" }
+    context 'with a value constructor' do
+      it 'constructs the value with nil default' do
+        klass.setting(:path, nil, constructor: ->(value) { "test:#{value || "fallback"}" })
 
         expect(object.config.path).to eql("test:fallback")
 
@@ -110,22 +110,20 @@
         expect(object.config.path).to eql('test:foo')
       end
 
-      it 'pre-processes the value with undefined default' do
-        klass.setting(:path) { |value| "test:#{value || "fallback"}" }
+      it 'constructs the value with undefined default' do
+        klass.setting(:path, constructor: ->(value) { "test:#{value || "fallback"}" })
 
         expect(object.config.path).to eql('test:fallback')
       end
 
-      it 'pre-processes the value with non-nil default' do
-        klass.setting(:path, 'test') { |value| Pathname(value) }
+      it 'constructs the value with non-nil default' do
+        klass.setting(:path, 'test', constructor: ->(value) { Pathname(value) })
 
         expect(object.config.path).to eql(Pathname('test'))
       end
 
-      it 'raises pre-processor errors immediately' do
-        klass.setting :failable do |value|
-          value.to_sym unless value.nil?
-        end
+      it 'raises constructor errors immediately' do
+        klass.setting(:failable, constructor: ->(value) { value.to_sym unless value.nil? })
 
         expect {
           object.config.failable = 12
@@ -316,7 +314,7 @@
     end
 
     it 'creates distinct setting values across instances' do
-      klass.setting(:path, 'test') { |m| Pathname(m) }
+      klass.setting(:path, 'test', constructor: ->(m) { Pathname(m) })
 
       new_object = klass.new
 

spec/unit/dry/configurable/dsl_spec.rb

@@ -43,6 +43,14 @@
   end
 
   it 'compiles a setting with a constructor' do
+    setting = dsl.setting(:dsn, 'sqlite', constructor: ->(value) { "jdbc:#{value}" })
+
+    expect(setting.name).to be(:dsn)
+    expect(setting.value).to eql('jdbc:sqlite')
+  end
+
+  it 'supports but deprecates giving a constructor as a block' do
+
     setting = dsl.setting(:dsn, 'sqlite') { |value| "jdbc:#{value}" }
 
     expect(setting.name).to be(:dsn)