X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FSQL%2FAbstract%2FTree.pm;h=0db1757bfa417638338cd6d81031b2a90bd040da;hb=bb54fcb44cb8362f47b6b1f5c26427b4204d0caa;hp=9536ce9c92eedea91f2b40ef643e5565416a2091;hpb=257ecc8a4f33c53c658100982c39f27c736e4423;p=dbsrgits%2FSQL-Abstract.git

diff --git a/lib/SQL/Abstract/Tree.pm b/lib/SQL/Abstract/Tree.pm
index 9536ce9..0db1757 100644
--- a/lib/SQL/Abstract/Tree.pm
+++ b/lib/SQL/Abstract/Tree.pm
@@ -461,6 +461,7 @@ sub fill_in_placeholder {
 # FIXME - terrible name for a user facing API
 sub unparse {
   my ($self, $tree, $bindargs) = @_;
+  $self->_parenthesis_unroll($tree);
   $self->_unparse($tree, [@{$bindargs||[]}], 0);
 }
 
@@ -519,6 +520,135 @@ sub _unparse {
   }
 }
 
+# All of these keywords allow their parameters to be specified with or without parenthesis without changing the semantics
+my @unrollable_ops = (
+  'ON',
+  'WHERE',
+  'GROUP \s+ BY',
+  'HAVING',
+  'ORDER \s+ BY',
+);
+my $unrollable_ops_re = join ' | ', @unrollable_ops;
+$unrollable_ops_re = qr/$unrollable_ops_re/xi;
+
+sub _parenthesis_unroll {
+  my $self = shift;
+  my $ast = shift;
+
+  #return if $self->parenthesis_significant;
+  return unless (ref $ast and ref $ast->[1]);
+
+  my $changes;
+  do {
+    my @children;
+    $changes = 0;
+
+    for my $child (@{$ast->[1]}) {
+      # the current node in this loop is *always* a PAREN
+      if (not ref $child or not $child->[0] eq 'PAREN') {
+        push @children, $child;
+        next;
+      }
+
+      # unroll nested parenthesis
+      while ( @{$child->[1]} && $child->[1][0][0] eq 'PAREN') {
+        $child = $child->[1][0];
+        $changes++;
+      }
+
+      # if the parenthesis are wrapped around an AND/OR matching the parent AND/OR - open the parenthesis up and merge the list
+      if (
+        ( $ast->[0] eq 'AND' or $ast->[0] eq 'OR')
+            and
+          $child->[1][0][0] eq $ast->[0]
+      ) {
+        push @children, @{$child->[1][0][1]};
+        $changes++;
+      }
+
+      # if the parent operator explcitly allows it nuke the parenthesis
+      elsif ( $ast->[0] =~ $unrollable_ops_re ) {
+        push @children, $child->[1][0];
+        $changes++;
+      }
+
+      # only *ONE* LITERAL or placeholder element
+      elsif (
+        @{$child->[1]} == 1 && (
+          $child->[1][0][0] eq 'LITERAL'
+            or
+          $child->[1][0][0] eq 'PLACEHOLDER'
+        )
+      ) {
+        push @children, $child->[1][0];
+        $changes++;
+      }
+
+      # only one element in the parenthesis which is a binary op
+      # and has exactly two grandchildren
+      # the only time when we can *not* unroll this is when both
+      # the parent and the child are mathops (in which case we'll
+      # break precedence) or when the child is BETWEEN (special
+      # case)
+      elsif (
+        @{$child->[1]} == 1
+          and
+        $child->[1][0][0] =~ SQL::Abstract::Tree::_binary_op_re()
+          and
+        $child->[1][0][0] ne 'BETWEEN'
+          and
+        @{$child->[1][0][1]} == 2
+          and
+        ! (
+          $child->[1][0][0] =~ SQL::Abstract::Tree::_math_op_re()
+            and
+          $ast->[0] =~ SQL::Abstract::Tree::_math_op_re()
+        )
+      ) {
+        push @children, $child->[1][0];
+        $changes++;
+      }
+
+      # a function binds tighter than a mathop - see if our ancestor is a
+      # mathop, and our content is:
+      # a single non-mathop child with a single PAREN grandchild which
+      # would indicate mathop ( nonmathop ( ... ) )
+      # or a single non-mathop with a single LITERAL ( nonmathop foo )
+      # or a single non-mathop with a single PLACEHOLDER ( nonmathop ? )
+      elsif (
+        @{$child->[1]} == 1
+          and
+        @{$child->[1][0][1]} == 1
+          and
+        $ast->[0] =~ SQL::Abstract::Tree::_math_op_re()
+          and
+        $child->[1][0][0] !~ SQL::Abstract::Tree::_math_op_re
+          and
+        (
+          $child->[1][0][1][0][0] eq 'PAREN'
+            or
+          $child->[1][0][1][0][0] eq 'LITERAL'
+            or
+          $child->[1][0][1][0][0] eq 'PLACEHOLDER'
+        )
+      ) {
+        push @children, $child->[1][0];
+        $changes++;
+      }
+
+
+      # otherwise no more mucking for this pass
+      else {
+        push @children, $child;
+      }
+    }
+
+    $ast->[1] = \@children;
+
+  } while ($changes);
+
+}
+
 sub format { my $self = shift; $self->unparse($self->parse($_[0]), $_[1]) }
 
 1;