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gh-99606: Make code generated for an empty f-string identical to that of a normal empty string #112407

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merged 5 commits into from
Nov 26, 2023
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gh-99606: Make code generated for an empty f-string identical to that of a normal empty string #112407

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cc370d7
gh-99606: Make code generated for an empty f-string identical to that…
iritkatriel Nov 25, 2023
8e15f08
fix magic number
iritkatriel Nov 25, 2023
c1924e4
Merge branch 'main' into gh-99606
iritkatriel Nov 26, 2023
21eedf4
Update _bootstrap_external.py
iritkatriel Nov 26, 2023
c5c1d96
Update _bootstrap_external.py
iritkatriel Nov 26, 2023
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10 changes: 10 additions & 0 deletions Lib/test/test_fstring.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
# Unicode identifiers in tests is allowed by PEP 3131.

import ast
import dis
import os
import re
import types
Expand Down Expand Up @@ -1738,5 +1739,14 @@ def test_syntax_warning_infinite_recursion_in_file(self):
self.assertIn(rb'\1', stdout)
self.assertEqual(len(stderr.strip().splitlines()), 2)

def test_fstring_without_formatting_bytecode(self):
# f-string without any formatting should emit the same bytecode
# as a normal string. See gh-99606.
def get_code(s):
return [(i.opname, i.oparg) for i in dis.get_instructions(s)]

for s in ["", "some string"]:
self.assertEqual(get_code(f"'{s}'"), get_code(f"f'{s}'"))

if __name__ == '__main__':
unittest.main()
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-11-25-20-36-38.gh-issue-99606.fDY5hK.rst
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@@ -0,0 +1,2 @@
Make code generated for an empty f-string identical to the code of an empty
normal string.
8 changes: 6 additions & 2 deletions Python/compile.c
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Expand Up @@ -5042,8 +5042,12 @@ compiler_joined_str(struct compiler *c, expr_ty e)
}
else {
VISIT_SEQ(c, expr, e->v.JoinedStr.values);
if (asdl_seq_LEN(e->v.JoinedStr.values) != 1) {
ADDOP_I(c, loc, BUILD_STRING, asdl_seq_LEN(e->v.JoinedStr.values));
if (value_count > 1) {
ADDOP_I(c, loc, BUILD_STRING, value_count);
}
else if (value_count == 0) {
_Py_DECLARE_STR(empty, "");
ADDOP_LOAD_CONST_NEW(c, loc, Py_NewRef(&_Py_STR(empty)));
}
}
return SUCCESS;
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