avoid recursion (#36)

* avoid recursion, fix #35

* fix imports

buildpg/components.py

@@ -12,6 +12,7 @@
     'Values',
     'MultipleValues',
     'SetValues',
+    'JoinComponent',
 )
 
 NOT_WORD = re.compile(r'[^\w.*]', flags=re.A)
@@ -146,3 +147,14 @@ def render(self):
         for k, v in iter_:
             yield RawDangerous(', ')
             yield from self._yield_pairs(k, v)
+
+
+class JoinComponent(Component):
+    __slots__ = 'sep', 'items'
+
+    def __init__(self, items, sep=RawDangerous(', ')):
+        self.items = items
+        self.sep = sep
+
+    def render(self):
+        yield from yield_sep(self.items, self.sep)

buildpg/funcs.py

@@ -1,4 +1,5 @@
 from . import logic
+from .components import JoinComponent
 
 
 def AND(arg, *args):
@@ -16,10 +17,7 @@ def OR(arg, *args):
 
 
 def comma_sep(arg, *args):
-    v = logic.as_sql_block(arg)
-    for a in args:
-        v = v.comma(a)
-    return v
+    return JoinComponent((arg,) + args)
 
 
 def count(expr):

buildpg/logic.py

@@ -1,7 +1,7 @@
 from enum import Enum, unique
 from typing import Union
 
-from .components import Component, RawDangerous, VarLiteral, check_word, yield_sep
+from .components import Component, JoinComponent, RawDangerous, VarLiteral, check_word, yield_sep
 
 __all__ = ('LogicError', 'SqlBlock', 'Func', 'Not', 'Var', 'S', 'V', 'select_fields', 'Empty')
 
@@ -317,10 +317,7 @@ def __init__(self, v1, *, op: Operator = None, v2=None):
 
 
 def select_fields(arg, *args):
-    v = as_var(arg)
-    for a in args:
-        v = v.comma(as_var(a))
-    return v
+    return JoinComponent([as_var(v) for v in (arg,) + args])
 
 
 class Empty(SqlBlock):

tests/test_logic.py

@@ -164,3 +164,13 @@ def test_simple_blocks(block, expected_query):
 )
 def test_block_repr(block, s):
     assert s == repr(block())
+
+
+def test_recursion():
+    # without JoinComponent this would cause a recursion error, see #35
+    values = [f'foo_{i}' for i in range(5000)]
+    query, query_args = render(':t', t=funcs.comma_sep(*values))
+
+    assert query.startswith('$1, $2')
+    assert query.endswith('$4998, $4999, $5000')
+    assert len(query_args) == 5000