Merge pull request #467 from composerinteralia/custom-errors

Raise custom error on empty join

6 files changed, 27 insertions, 2 deletions

diff --git a/lib/arel.rb b/lib/arel.rb
index e04999ed92..710914a2e3 100644
--- a/lib/arel.rb
+++ b/lib/arel.rb
@@ -1,3 +1,5 @@
+require 'arel/errors'
+
 require 'arel/crud'
 require 'arel/factory_methods'
 
diff --git a/lib/arel/errors.rb b/lib/arel/errors.rb
new file mode 100644
index 0000000000..c8a6af9f77
--- /dev/null
+++ b/lib/arel/errors.rb
@@ -0,0 +1,7 @@
+module Arel
+  class ArelError < StandardError
+  end
+
+  class EmptyJoinError < ArelError
+  end
+end
diff --git a/lib/arel/select_manager.rb b/lib/arel/select_manager.rb
index eae3bc8cbc..6af9b6fbe6 100644
--- a/lib/arel/select_manager.rb
+++ b/lib/arel/select_manager.rb
@@ -106,7 +106,7 @@ module Arel
 
       case relation
       when String, Nodes::SqlLiteral
-        raise if relation.empty?
+        raise EmptyJoinError if relation.empty?
         klass = Nodes::StringJoin
       end
 
diff --git a/lib/arel/table.rb b/lib/arel/table.rb
index 3e06f94272..130b7ea028 100644
--- a/lib/arel/table.rb
+++ b/lib/arel/table.rb
@@ -37,7 +37,7 @@ module Arel
 
       case relation
       when String, Nodes::SqlLiteral
-        raise if relation.empty?
+        raise EmptyJoinError if relation.empty?
         klass = Nodes::StringJoin
       end
 
diff --git a/test/test_select_manager.rb b/test/test_select_manager.rb
index 9a225edeec..e88f0e8e11 100644
--- a/test/test_select_manager.rb
+++ b/test/test_select_manager.rb
@@ -618,6 +618,16 @@ module Arel
         manager   = Arel::SelectManager.new
         manager.join(nil).must_equal manager
       end
+
+      it 'raises EmptyJoinError on empty' do
+        left      = Table.new :users
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        assert_raises(EmptyJoinError) do
+          manager.join("")
+        end
+      end
     end
 
     describe 'outer join' do
diff --git a/test/test_table.rb b/test/test_table.rb
index 168fde370d..e36a6e3a41 100644
--- a/test/test_table.rb
+++ b/test/test_table.rb
@@ -71,6 +71,12 @@ module Arel
           mgr.to_sql.must_be_like %{ SELECT FROM "users" }
         end
 
+        it 'raises EmptyJoinError on empty' do
+          assert_raises(EmptyJoinError) do
+            @relation.join ""
+          end
+        end
+
         it 'takes a second argument for join type' do
           right     = @relation.alias
           predicate = @relation[:id].eq(right[:id])