From cecd2464de18c792b1538b90dca18da259975ac7 Mon Sep 17 00:00:00 2001
From: Michael Miller <icy.arctic.fox@gmail.com>
Date: Sun, 3 Jul 2022 13:40:29 -0600
Subject: [PATCH] Initial code for StubbedType

---
 spec/spectator/mocks/double_spec.cr | 29 +++++++++++++
 src/spectator/mocks/stubbable.cr    |  8 ++++
 src/spectator/mocks/stubbed_type.cr | 66 +++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 src/spectator/mocks/stubbed_type.cr

diff --git a/spec/spectator/mocks/double_spec.cr b/spec/spectator/mocks/double_spec.cr
index 008320a..841d8e4 100644
--- a/spec/spectator/mocks/double_spec.cr
+++ b/spec/spectator/mocks/double_spec.cr
@@ -270,6 +270,35 @@ Spectator.describe Spectator::Double do
     end
   end
 
+  context "class method stubs" do
+    Spectator::Double.define(ClassDouble) do
+      stub def self.foo
+        :stub
+      end
+
+      stub def self.bar(arg)
+        arg
+      end
+
+      stub def self.baz
+        yield
+      end
+    end
+
+    subject(dbl) { ClassDouble }
+    let(foo_stub) { Spectator::ValueStub.new(:foo, :override) }
+
+    after_each { dbl._spectator_clear_stubs }
+
+    it "overrides an existing method" do
+      expect { dbl._spectator_define_stub(foo_stub) }.to change { dbl.foo }.from(:stub).to(:override)
+    end
+
+    it "doesn't affect other methods" do
+      expect { dbl._spectator_define_stub(foo_stub) }.to_not change { dbl.bar(42) }
+    end
+  end
+
   describe "#_spectator_define_stub" do
     subject(dbl) { FooBarDouble.new }
     let(stub3) { Spectator::ValueStub.new(:foo, 3) }
diff --git a/src/spectator/mocks/stubbable.cr b/src/spectator/mocks/stubbable.cr
index d3e1a1f..2dca87f 100644
--- a/src/spectator/mocks/stubbable.cr
+++ b/src/spectator/mocks/stubbable.cr
@@ -2,6 +2,7 @@ require "../dsl/reserved"
 require "./arguments"
 require "./method_call"
 require "./stub"
+require "./stubbed_type"
 require "./typed_stub"
 
 module Spectator
@@ -380,5 +381,12 @@ module Spectator
         end
       end
     end
+
+    # Automatically extend `StubbedType` when a type is made stubbable.
+    macro included
+      extend StubbedType
+
+      private class_getter _spectator_stubs : Array(::Spectator::Stub) = [] of ::Spectator::Stub
+    end
   end
 end
diff --git a/src/spectator/mocks/stubbed_type.cr b/src/spectator/mocks/stubbed_type.cr
new file mode 100644
index 0000000..23a4342
--- /dev/null
+++ b/src/spectator/mocks/stubbed_type.cr
@@ -0,0 +1,66 @@
+require "./method_call"
+require "./stub"
+
+module Spectator
+  # Defines stubbing functionality at the type level (classes and structs).
+  #
+  # This module is intended to be extended from when a type includes `Stubbable`.
+  module StubbedType
+    private abstract def _spectator_stubs : Array(Stub)
+
+    def _spectator_find_stub(call : MethodCall) : Stub?
+      _spectator_stubs.find &.===(call)
+    end
+
+    def _spectator_stub_for_method?(method : Symbol) : Bool
+      _spectator_stubs.any? { |stub| stub.method == method }
+    end
+
+    def _spectator_define_stub(stub : Stub) : Nil
+      _spectator_stubs.unshift(stub)
+    end
+
+    def _spectator_clear_stubs : Nil
+      _spectator_stubs.clear
+    end
+
+    def _spectator_record_call(call : MethodCall) : Nil
+      _spectator_calls << call
+    end
+
+    def _spectator_calls
+      [] of MethodCall
+    end
+
+    def _spectator_stub_fallback(call : MethodCall, &)
+      Log.trace { "Fallback for #{call} - call original" }
+      yield
+    end
+
+    def _spectator_stub_fallback(call : MethodCall, type, &)
+      _spectator_stub_fallback(call) { yield }
+    end
+
+    def _spectator_abstract_stub_fallback(call : MethodCall)
+      Log.info do
+        break unless _spectator_stub_for_method?(call.method)
+
+        "Stubs are defined for #{call.method.inspect}, but none matched (no argument constraints met)."
+      end
+
+      raise UnexpectedMessage.new("#{_spectator_stubbed_name} received unexpected message #{call}")
+    end
+
+    def _spectator_abstract_stub_fallback(call : MethodCall, type)
+      _spectator_abstract_stub_fallback(call)
+    end
+
+    def _spectator_stubbed_name : String
+      {% if anno = @type.annotation(StubbedName) %}
+        "#<Stubbed " + {{(anno[0] || :Anonymous.id).stringify}} + ">"
+      {% else %}
+        "#<Stubbed " + {{@type.name.stringify}} + ">"
+      {% end %}
+    end
+  end
+end