bpo-38870: Simplify sequence interleaves in ast.unparse (GH-17892)
diff --git a/Lib/ast.py b/Lib/ast.py
index 2719f6f..9a3d380 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -613,6 +613,16 @@
inter()
f(x)
+ def items_view(self, traverser, items):
+ """Traverse and separate the given *items* with a comma and append it to
+ the buffer. If *items* is a single item sequence, a trailing comma
+ will be added."""
+ if len(items) == 1:
+ traverser(items[0])
+ self.write(",")
+ else:
+ self.interleave(lambda: self.write(", "), traverser, items)
+
def fill(self, text=""):
"""Indent a piece of text and append it, according to the current
indentation level"""
@@ -1020,11 +1030,7 @@
value = node.value
if isinstance(value, tuple):
with self.delimit("(", ")"):
- if len(value) == 1:
- self._write_constant(value[0])
- self.write(",")
- else:
- self.interleave(lambda: self.write(", "), self._write_constant, value)
+ self.items_view(self._write_constant, value)
elif value is ...:
self.write("...")
else:
@@ -1116,12 +1122,7 @@
def visit_Tuple(self, node):
with self.delimit("(", ")"):
- if len(node.elts) == 1:
- elt = node.elts[0]
- self.traverse(elt)
- self.write(",")
- else:
- self.interleave(lambda: self.write(", "), self.traverse, node.elts)
+ self.items_view(self.traverse, node.elts)
unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
unop_precedence = {
@@ -1264,12 +1265,7 @@
if (isinstance(node.slice, Index)
and isinstance(node.slice.value, Tuple)
and node.slice.value.elts):
- if len(node.slice.value.elts) == 1:
- elt = node.slice.value.elts[0]
- self.traverse(elt)
- self.write(",")
- else:
- self.interleave(lambda: self.write(", "), self.traverse, node.slice.value.elts)
+ self.items_view(self.traverse, node.slice.value.elts)
else:
self.traverse(node.slice)
@@ -1296,12 +1292,7 @@
self.traverse(node.step)
def visit_ExtSlice(self, node):
- if len(node.dims) == 1:
- elt = node.dims[0]
- self.traverse(elt)
- self.write(",")
- else:
- self.interleave(lambda: self.write(", "), self.traverse, node.dims)
+ self.items_view(self.traverse, node.dims)
def visit_arg(self, node):
self.write(node.arg)
diff --git a/Lib/test/test_unparse.py b/Lib/test/test_unparse.py
index d33f32e..3d87cfb 100644
--- a/Lib/test/test_unparse.py
+++ b/Lib/test/test_unparse.py
@@ -280,6 +280,20 @@
self.check_ast_roundtrip(r"""{**{'y': 2}, 'x': 1}""")
self.check_ast_roundtrip(r"""{**{'y': 2}, **{'x': 1}}""")
+ def test_ext_slices(self):
+ self.check_ast_roundtrip("a[i]")
+ self.check_ast_roundtrip("a[i,]")
+ self.check_ast_roundtrip("a[i, j]")
+ self.check_ast_roundtrip("a[()]")
+ self.check_ast_roundtrip("a[i:j]")
+ self.check_ast_roundtrip("a[:j]")
+ self.check_ast_roundtrip("a[i:]")
+ self.check_ast_roundtrip("a[i:j:k]")
+ self.check_ast_roundtrip("a[:j:k]")
+ self.check_ast_roundtrip("a[i::k]")
+ self.check_ast_roundtrip("a[i:j,]")
+ self.check_ast_roundtrip("a[i:j, k]")
+
def test_invalid_raise(self):
self.check_invalid(ast.Raise(exc=None, cause=ast.Name(id="X")))
@@ -310,6 +324,12 @@
# check as Module docstrings for easy testing
self.check_ast_roundtrip(f"'{docstring}'")
+ def test_constant_tuples(self):
+ self.check_src_roundtrip(ast.Constant(value=(1,), kind=None), "(1,)")
+ self.check_src_roundtrip(
+ ast.Constant(value=(1, 2, 3), kind=None), "(1, 2, 3)"
+ )
+
class CosmeticTestCase(ASTTestCase):
"""Test if there are cosmetic issues caused by unnecesary additions"""
@@ -344,20 +364,6 @@
self.check_src_roundtrip("call((yield x))")
self.check_src_roundtrip("return x + (yield x)")
- def test_subscript(self):
- self.check_src_roundtrip("a[i]")
- self.check_src_roundtrip("a[i,]")
- self.check_src_roundtrip("a[i, j]")
- self.check_src_roundtrip("a[()]")
- self.check_src_roundtrip("a[i:j]")
- self.check_src_roundtrip("a[:j]")
- self.check_src_roundtrip("a[i:]")
- self.check_src_roundtrip("a[i:j:k]")
- self.check_src_roundtrip("a[:j:k]")
- self.check_src_roundtrip("a[i::k]")
- self.check_src_roundtrip("a[i:j,]")
- self.check_src_roundtrip("a[i:j, k]")
-
def test_docstrings(self):
docstrings = (
'"""simple doc string"""',