Improve handling of boolean type casts

Edited By: Lukas Fittl <[email protected]>

lib/pg_query/deparse.rb

@@ -1268,10 +1268,30 @@ def deparse_update(node)
       output.join(' ')
     end
 
-    def deparse_typecast(node) # rubocop:disable Metrics/CyclomaticComplexity
-      if deparse_item(node['typeName']) == 'boolean' || deparse_item(node['typeName']) == 'bool'
-        return 'true' if deparse_item(node['arg']) == "'t'" || deparse_item(node['arg']) == 'true'
-        return 'false' if deparse_item(node['arg']) == "'f'" || deparse_item(node['arg']) == 'false'
+    # Builds a properly-qualified reference to a built-in Postgres type.
+    #
+    # Inspired by SystemTypeName in Postgres' gram.y, but without node name
+    # and locations, to simplify comparison.
+    def make_system_type_name(name)
+      {
+        'names' => [
+          { 'String' => { 'str' => 'pg_catalog' } },
+          { 'String' => { 'str' => name } }
+        ],
+        'typemod' => -1
+      }
+    end
+
+    def make_string(str)
+      { 'String' => { 'str' => str } }
+    end
+
+    def deparse_typecast(node)
+      # Handle "bool" or "false" in the statement, which is represented as a typecast
+      # (other boolean casts should be represented as a cast, i.e. don't need special handling)
+      if node['arg'][A_CONST] && node['typeName'][TYPE_NAME].slice('names', 'typemod') == make_system_type_name('bool')
+        return 'true' if node['arg'][A_CONST]['val'] == make_string('t')
+        return 'false' if node['arg'][A_CONST]['val'] == make_string('f')
       end
 
       context = true if node['arg']['A_Expr']

spec/lib/pg_query/deparse_spec.rb

@@ -595,11 +595,30 @@
         it { is_expected.to eq query }
       end
 
-      context 'boolean' do
+      context 'boolean column reference' do
         let(:query) { "SELECT \"table_field\"::bool, \"table_field\"::boolean FROM \"t\"" }
 
         it { is_expected.to eq query }
       end
+
+      context 'boolean bool value cast' do
+        let(:query) { "SELECT true, false" }
+
+        it { is_expected.to eq query }
+      end
+
+      context 'boolean string value cast' do
+        let(:query) { "SELECT 't'::boolean, 'f'::boolean" }
+
+        # The AST is identical to the more common "SELECT true" case, which is why we return the short-form in that case
+        it { is_expected.to eq "SELECT true, false" }
+      end
+
+      context 'boolean integer value cast' do
+        let(:query) { "SELECT 1::boolean, 0::boolean" }
+
+        it { is_expected.to eq query }
+      end
     end
 
     context 'param ref' do