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bpo-47129: Add more informative messages to f-string syntax errors (32127)

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* Add more informative messages to f-string syntax errors

* 📜🤖 Added by blurb_it.

* Fix whitespaces

* Change error message

* Remove the 'else' statement (as sugested in review)

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
This commit is contained in:
Maciej Górski 2022-03-28 23:08:36 +02:00 committed by GitHub
parent 15ba8167d7
commit 7b44ade018
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 35 additions and 11 deletions
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40
Lib/test/test_fstring.py
View File

@ -628,16 +628,27 @@ x = (
["f'{}'",
"f'{ }'"
"f' {} '",
"f'{!r}'",
"f'{ !r}'",
"f'{10:{ }}'",
"f' { } '",
# The Python parser ignores also the following
# whitespace characters in additional to a space.
"f'''{\t\f\r\n}'''",
])
# Catch the empty expression before the
# Different error messeges are raised when a specfier ('!', ':' or '=') is used after an empty expression
self.assertAllRaise(SyntaxError, "f-string: expression required before '!'",
["f'{!r}'",
"f'{ !r}'",
"f'{!}'",
"f'''{\t\f\r\n!a}'''",
# Catch empty expression before the
# missing closing brace.
"f'{!'",
"f'{!s:'",
# Catch empty expression before the
# invalid conversion.
"f'{!x}'",
"f'{ !xr}'",
@ -645,16 +656,23 @@ x = (
"f'{!x:a}'",
"f'{ !xr:}'",
"f'{ !xr:a}'",
])
"f'{!}'",
"f'{:}'",
# We find the empty expression before the
# missing closing brace.
"f'{!'",
"f'{!s:'",
self.assertAllRaise(SyntaxError, "f-string: expression required before ':'",
["f'{:}'",
"f'{ :!}'",
"f'{:2}'",
"f'''{\t\f\r\n:a}'''",
"f'{:'",
"f'{:x'",
])
self.assertAllRaise(SyntaxError, "f-string: expression required before '='",
["f'{=}'",
"f'{ =}'",
"f'{ =:}'",
"f'{ =!}'",
"f'''{\t\f\r\n=}'''",
"f'{='",
])
# Different error message is raised for other whitespace characters.

1
Misc/NEWS.d/next/Core and Builtins/2022-03-26-16-35-57.bpo-47129.hDg2Vt.rst Normal file
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@ -0,0 +1 @@
Improve error messages in f-string syntax errors concerning empty expressions.

5
Parser/string_parser.c
View File

@ -357,7 +357,12 @@ fstring_compile_expr(Parser *p, const char *expr_start, const char *expr_end,
break;
}
}
if (s == expr_end) {
if (*expr_end == '!' || *expr_end == ':' || *expr_end == '=') {
RAISE_SYNTAX_ERROR("f-string: expression required before '%c'", *expr_end);
return NULL;
}
RAISE_SYNTAX_ERROR("f-string: empty expression not allowed");
return NULL;
}