support stringify for plain CTE

Altered the compilation for the :class:`.CTE` construct so that a string is
returned representing the inner SELECT statement if the :class:`.CTE` is
stringified directly, outside of the context of an enclosing SELECT; This
is the same behavior of :meth:`_FromClause.alias` and
:meth:`_SelectStatement.subquery`. Previously, a blank string would be
returned as the CTE is normally placed above a SELECT after that SELECT has
been generated, which is generally misleading when debugging.

Change-Id: Id3007c28e4a7a56d867e850bb890752946bd8f6f
References: #5988

diff --git a/doc/build/changelog/unreleased_14/cte_str.rst b/doc/build/changelog/unreleased_14/cte_str.rst
new file mode 100644 (file)
index 0000000..1dfaad2
--- /dev/null
+++ b/doc/build/changelog/unreleased_14/cte_str.rst
@@ -0,0 +1,11 @@
+.. change::
+    :tags: change, sql
+
+    Altered the compilation for the :class:`.CTE` construct so that a string is
+    returned representing the inner SELECT statement if the :class:`.CTE` is
+    stringified directly, outside of the context of an enclosing SELECT; This
+    is the same behavior of :meth:`_FromClause.alias` and
+    :meth:`_SelectStatement.subquery`. Previously, a blank string would be
+    returned as the CTE is normally placed above a SELECT after that SELECT has
+    been generated, which is generally misleading when debugging.
+

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 763b4cabbd7cbfd404ef40870300d56c590652bb..ff1eb686bcaaec848d5fce992b0a62ca69e6e154 100644 (file)
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -2550,12 +2550,23 @@ class SQLCompiler(Compiled):
                     kwargs["positional_names"] = self.cte_positional[cte] = []
 
                 assert kwargs.get("subquery", False) is False
-                text += " AS %s\n(%s)" % (
-                    self._generate_prefixes(cte, cte._prefixes, **kwargs),
-                    cte.element._compiler_dispatch(
+
+                if not self.stack:
+                    # toplevel, this is a stringify of the
+                    # cte directly.  just compile the inner
+                    # the way alias() does.
+                    return cte.element._compiler_dispatch(
+                        self, asfrom=asfrom, **kwargs
+                    )
+                else:
+                    prefixes = self._generate_prefixes(
+                        cte, cte._prefixes, **kwargs
+                    )
+                    inner = cte.element._compiler_dispatch(
                         self, asfrom=True, **kwargs
-                    ),
-                )
+                    )
+
+                    text += " AS %s\n(%s)" % (prefixes, inner)
 
                 if cte._suffixes:
                     text += " " + self._generate_prefixes(

diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index 140de8622305dc1d5d28619d564f5c9708469875..acf16ca1c314e7cf614bf5d4d4efaadac747b284 100644 (file)
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -4309,6 +4309,17 @@ class StringifySpecialTest(fixtures.TestBase):
             "SELECT anon_1.myid FROM anon_1",
         )
 
+    @testing.combinations(("cte",), ("alias",), ("subquery",))
+    def test_grouped_selectables_print_alone(self, modifier):
+        stmt = select(table1).where(table1.c.myid == 10)
+
+        grouped = getattr(stmt, modifier)()
+        eq_ignore_whitespace(
+            str(grouped),
+            "SELECT mytable.myid, mytable.name, "
+            "mytable.description FROM mytable WHERE mytable.myid = :myid_1",
+        )
+
     def test_next_sequence_value(self):
         # using descriptive text that is intentionally not compatible
         # with any particular backend, since all backends have different