ensure spec files are *_spec.rb, fixes SD-594

test plan:
* see test commit

Change-Id: I8483b6979629642f9524f4fa7fecd17e402d56b4
Reviewed-on: https://gerrit.instructure.com/72669
Tested-by: Jenkins
Reviewed-by: Jon Jensen <jon@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>
QA-Review: Landon Wilkins <lwilkins@instructure.com>

Author: Landon Wilkins

gems/rubocop-canvas/lib/rubocop_canvas.rb

@@ -7,13 +7,15 @@
 require 'rubocop_canvas/helpers/comments'
 require 'rubocop_canvas/helpers/consts'
 require 'rubocop_canvas/helpers/diff_parser'
+require 'rubocop_canvas/helpers/file_meta'
 require 'rubocop_canvas/helpers/file_sieve'
 require 'rubocop_canvas/helpers/git_proxy'
 require 'rubocop_canvas/helpers/migration_tags'
 
 # cops
 require 'rubocop_canvas/cops/datafixup/find_ids'
 require 'rubocop_canvas/cops/lint/freeze_constants'
+require 'rubocop_canvas/cops/lint/specs_ensure_spec_extension'
 require 'rubocop_canvas/cops/lint/specs_f_over_fj'
 require 'rubocop_canvas/cops/migration/concurrent_index'
 require 'rubocop_canvas/cops/migration/primary_key'

gems/rubocop-canvas/lib/rubocop_canvas/cops/lint/specs_ensure_spec_extension.rb

@@ -0,0 +1,57 @@
+module RuboCop
+  module Cop
+    module Lint
+      # most of this has been stolen from:
+      # https://github.com/nevir/rubocop-rspec/blob/master/lib/rubocop/rspec/top_level_describe.rb
+      # https://github.com/nevir/rubocop-rspec/blob/9aa33ee7014e8d6d580b12fe2651b32ccdaa7a92/lib/rubocop/cop/rspec/file_path.rb
+      class SpecsEnsureSpecExtension < Cop
+        include RuboCop::Cop::FileMeta
+
+        MSG = "Spec files need to end with \"_spec.rb\" for rspec to find and run them."
+        METHODS = [:context, :describe].freeze
+        SPEC_FILE_NAME_REGEX = /_spec\.rb$/
+
+        def on_send(node)
+          return unless top_level_describe?(node)
+          return if file_name =~ SPEC_FILE_NAME_REGEX
+          add_offense node, :expression, MSG
+        end
+
+        private
+
+        def top_level_describe?(node)
+          _receiver, method_name, *_args = *node
+          return false unless METHODS.include?(method_name)
+          top_level_nodes.include?(node)
+        end
+
+        def top_level_nodes
+          nodes = describe_statement_children(root_node)
+          # If we have no top level describe statements, we need to check any
+          # blocks on the top level (e.g. after a require).
+          if nodes.empty?
+            nodes = node_children(root_node).map do |child|
+              describe_statement_children(child) if child.type == :block
+            end.flatten.compact
+          end
+
+          nodes
+        end
+
+        def describe_statement_children(node)
+          node_children(node).select do |element|
+            element.type == :send && METHODS.include?(element.children[1])
+          end
+        end
+
+        def node_children(node)
+          node.children.select { |e| e.is_a? Parser::AST::Node }
+        end
+
+        def root_node
+          processed_source.ast
+        end
+      end
+    end
+  end
+end

gems/rubocop-canvas/lib/rubocop_canvas/helpers/file_meta.rb

@@ -0,0 +1,9 @@
+module RuboCop
+  module Cop
+    module FileMeta
+      def file_name
+        processed_source.buffer.name.split('/').last
+      end
+    end
+  end
+end