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bpo-36817: Add f-string debugging using '='. (GH-13123)

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If a "=" is specified a the end of an f-string expression, the f-string will evaluate to the text of the expression, followed by '=', followed by the repr of the value of the expression.
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Eric V. Smith 2019-05-08 16:28:48 -04:00 • committed by GitHub
parent 65d98d0f53
commit 9a4135e939
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GPG key ID: 4AEE18F83AFDEB23
11 changed files with 286 additions and 49 deletions
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112
Python/ast.c
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@ -4854,7 +4854,8 @@ fstring_compile_expr(const char *expr_start, const char *expr_end,
assert(expr_end >= expr_start);
assert(*(expr_start-1) == '{');
assert(*expr_end == '}' || *expr_end == '!' || *expr_end == ':');
assert(*expr_end == '}' || *expr_end == '!' || *expr_end == ':' ||
*expr_end == '=');
/* If the substring is all whitespace, it's an error. We need to catch this
here, and not when we call PyParser_SimpleParseStringFlagsFilename,
@ -4997,9 +4998,9 @@ fstring_parse(const char **str, const char *end, int raw, int recurse_lvl,
struct compiling *c, const node *n);
/* Parse the f-string at *str, ending at end. We know *str starts an
expression (so it must be a '{'). Returns the FormattedValue node,
which includes the expression, conversion character, and
format_spec expression.
expression (so it must be a '{'). Returns the FormattedValue node, which
includes the expression, conversion character, format_spec expression, and
optionally the text of the expression (if = is used).
Note that I don't do a perfect job here: I don't make sure that a
closing brace doesn't match an opening paren, for example. It
@ -5016,7 +5017,12 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
const char *expr_end;
expr_ty simple_expression;
expr_ty format_spec = NULL; /* Optional format specifier. */
int conversion = -1; /* The conversion char. -1 if not specified. */
int conversion = -1; /* The conversion char. Use default if not
specified, or !r if using = and no format
spec. */
int equal_flag = 0; /* Are we using the = feature? */
PyObject *expr_text = NULL; /* The text of the expression, used for =. */
const char *expr_text_end;
/* 0 if we're not in a string, else the quote char we're trying to
match (single or double quote). */
@ -5033,7 +5039,7 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
/* Can only nest one level deep. */
if (recurse_lvl >= 2) {
ast_error(c, n, "f-string: expressions nested too deeply");
return -1;
goto error;
}
/* The first char must be a left brace, or we wouldn't have gotten
@ -5061,7 +5067,7 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
ast_error(c, n,
"f-string expression part "
"cannot include a backslash");
return -1;
goto error;
}
if (quote_char) {
/* We're inside a string. See if we're at the end. */
@ -5106,7 +5112,7 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
} else if (ch == '[' || ch == '{' || ch == '(') {
if (nested_depth >= MAXLEVEL) {
ast_error(c, n, "f-string: too many nested parenthesis");
return -1;
goto error;
}
parenstack[nested_depth] = ch;
nested_depth++;
@ -5114,22 +5120,38 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
/* Error: can't include a comment character, inside parens
or not. */
ast_error(c, n, "f-string expression part cannot include '#'");
return -1;
goto error;
} else if (nested_depth == 0 &&
(ch == '!' || ch == ':' || ch == '}')) {
/* First, test for the special case of "!=". Since '=' is
not an allowed conversion character, nothing is lost in
this test. */
if (ch == '!' && *str+1 < end && *(*str+1) == '=') {
/* This isn't a conversion character, just continue. */
continue;
(ch == '!' || ch == ':' || ch == '}' ||
ch == '=' || ch == '>' || ch == '<')) {
/* See if there's a next character. */
if (*str+1 < end) {
char next = *(*str+1);
/* For "!=". since '=' is not an allowed conversion character,
nothing is lost in this test. */
if ((ch == '!' && next == '=') || /* != */
(ch == '=' && next == '=') || /* == */
(ch == '<' && next == '=') || /* <= */
(ch == '>' && next == '=') /* >= */
) {
*str += 1;
continue;
}
/* Don't get out of the loop for these, if they're single
chars (not part of 2-char tokens). If by themselves, they
don't end an expression (unlike say '!'). */
if (ch == '>' || ch == '<') {
continue;
}
}
/* Normal way out of this loop. */
break;
} else if (ch == ']' || ch == '}' || ch == ')') {
if (!nested_depth) {
ast_error(c, n, "f-string: unmatched '%c'", ch);
return -1;
goto error;
}
nested_depth--;
int opening = parenstack[nested_depth];
@ -5141,7 +5163,7 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
"f-string: closing parenthesis '%c' "
"does not match opening parenthesis '%c'",
ch, opening);
return -1;
goto error;
}
} else {
/* Just consume this char and loop around. */
@ -5154,12 +5176,12 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
let's just do that.*/
if (quote_char) {
ast_error(c, n, "f-string: unterminated string");
return -1;
goto error;
}
if (nested_depth) {
int opening = parenstack[nested_depth - 1];
ast_error(c, n, "f-string: unmatched '%c'", opening);
return -1;
goto error;
}
if (*str >= end)
@ -5170,7 +5192,22 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
conversion or format_spec. */
simple_expression = fstring_compile_expr(expr_start, expr_end, c, n);
if (!simple_expression)
return -1;
goto error;
/* Check for =, which puts the text value of the expression in
expr_text. */
if (**str == '=') {
*str += 1;
equal_flag = 1;
/* Skip over ASCII whitespace. No need to test for end of string
here, since we know there's at least a trailing quote somewhere
ahead. */
while (Py_ISSPACE(**str)) {
*str += 1;
}
expr_text_end = *str;
}
/* Check for a conversion char, if present. */
if (**str == '!') {
@ -5182,13 +5219,19 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
*str += 1;
/* Validate the conversion. */
if (!(conversion == 's' || conversion == 'r'
|| conversion == 'a')) {
if (!(conversion == 's' || conversion == 'r' || conversion == 'a')) {
ast_error(c, n,
"f-string: invalid conversion character: "
"expected 's', 'r', or 'a'");
return -1;
goto error;
}
}
if (equal_flag) {
Py_ssize_t len = expr_text_end-expr_start;
expr_text = PyUnicode_FromStringAndSize(expr_start, len);
if (!expr_text)
goto error;
}
/* Check for the format spec, if present. */
@ -5202,7 +5245,7 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
/* Parse the format spec. */
format_spec = fstring_parse(str, end, raw, recurse_lvl+1, c, n);
if (!format_spec)
return -1;
goto error;
}
if (*str >= end || **str != '}')
@ -5213,20 +5256,31 @@ fstring_find_expr(const char **str, const char *end, int raw, int recurse_lvl,
assert(**str == '}');
*str += 1;
/* If we're in = mode, and have no format spec and no explict conversion,
set the conversion to 'r'. */
if (equal_flag && format_spec == NULL && conversion == -1) {
conversion = 'r';
}
/* And now create the FormattedValue node that represents this
entire expression with the conversion and format spec. */
*expression = FormattedValue(simple_expression, conversion,
format_spec, LINENO(n), n->n_col_offset,
n->n_end_lineno, n->n_end_col_offset,
c->c_arena);
format_spec, expr_text, LINENO(n),
n->n_col_offset, n->n_end_lineno,
n->n_end_col_offset, c->c_arena);
if (!*expression)
return -1;
goto error;
return 0;
unexpected_end_of_string:
ast_error(c, n, "f-string: expecting '}'");
/* Falls through to error. */
error:
Py_XDECREF(expr_text);
return -1;
}
/* Return -1 on error.